EPA-600/2-77-139
August 1977
Environmental Protection Technology Series
        PHYSICAL AND ENGINEERING  PROPERTIES  OF
    HAZARDOUS INDUSTRIAL  WASTES AND SLUDGES
                                  Municip
       icipal Environmental Research Laboratory
          Office of Research and Development
         U.S. Environmental Protection Agency
                 Cincinnati, Ohio 45268

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                 RESEARCH  REPORTING SERIES

 Research reports of the Office of Research and Development, U.S. Environmental
 Protection Agency, have been grouped into nine series. These nine broad cate-
 gories were established to facilitate further development and application of en-
 vironmental technology. Elimination  of traditional grouping was consciously
 planned to foster technology transfer and a maximum interface in related fields.
 The nine series are:

       1.  Environmental Health Effects Research
       2.  Environmental Protection Technology
       3.  Ecological Research
       4.  Environmental Monitoring
       5.  Socioeconomic Environmental Studies
       6.  Scientific and Technical Assessment Reports (STAR)
       7.  Interagency Energy-Environment Research and  Development
       8.  "Special" Reports
       9.  Miscellaneous Reports

 This report has been assigned to the ENVIRONMENTAL  PROTECTION TECH-
 NOLOGY series. This series describes research performed to develop and dem-
 onstrate instrumentation, equipment, and methodology to repair or prevent en-
 vironmental degradation from point and non-point sources  of pollution. This work
 provides the new or improved technology required for the control and treatment
 of pollution sources to  meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia  22161.

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                                   EPA-600/2-77-139
                                   August 1977
    PHYSICAL AND ENGINEERING PROPERTIES OF
    HAZARDOUS INDUSTRIAL WASTES AND SLUDGES
                       by

      M. J. Bartos, Jr. and M. R. Palermo
        Environmental Effects Laboratory
U.S. Army Engineer Waterways Experiment Station
         Vicksburg, Mississippi  39180
   Interagency Agreement No. EPA-IAG-D4-0569
                Project Officer

               Robert E. Landreth
  Solid and Hazardous Waste Research Division
  Municipal Environmental Research Laboratory
            Cincinnati, Ohio  45268
  MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
       OFFICE OF RESEARCH AND DEVELOPMENT
      U.S. ENVIRONMENTAL PROTECTION AGENCY
            CINCINNATI, OHIO  45268

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                                  DISCLAIMER
      This report has been reviewed by the Municipal Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publica-
tion.  Approval does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or re-
commendation for use.
                                    11

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                                   FOREWORD
      The Environmental Protection Agency was created because of increasing
public and government concern about the dangers of pollution to the health
and welfare of the American people.  Noxious air, foul water, and spoiled
land are tragic testimony to the deterioration of our natural environment.
The complexity of that environment and the interplay between its components
require a concentrated and integrated attack on the problem.

      Research and development is that necessary first step in problem sol-
ution and it involves defining the problem, measuring its impact, and search-
ing for solutions.  The Municipal Environmental Research Laboratory develops
new and improved technology and systems for the prevention, treatment, and
management of wastewater and solid and hazardous waste pollutant discharges
from municipal and community sources, for the preservation and treatment of
public drinking water supplies, and to minimize the adverse economic, social,
health, and aesthetic effects of pollution.  This publication is one of the
products of that research; a most vital communications link between the research-
er and the user community.

      This research was supported by the U.S. Environmental Protection Agency
to develop a data base in the event guidelines become necessary for stabili-
zation technology and for potential utilization of sludges in a productive
venture.
                                       Francis T. Mayo, Director
                                       Municipal Environmental Research
                                        Laboratory
                                       111

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                                  ABSTRACT
      This report presents the results of a laboratory testing program to in-
vestigate the properties of raw and chemically fixed hazardous industrial
wastes and flue gas desulfurization (FGD) sludges.

      Samples of hazardous wastes and FGD sludges were obtained and divided
into several portions.  Some portions of each sample were designated for
testing to characterize each of the raw sludges.  The remaining portions of
each sample were chemically fixed at the Waterways Experiment Station by
representatives of the respective processors.

      Specimens of raw and fixed sludges were subjected to a variety of tests
commonly used in soils engineering.  The grain-size distributions, Atterberg
limits, specific gravities, volume-weight-moisture relationships and per-
meabilities of raw and fixed sludges were determined.  Selected fixed sludges
were subjected to appropriate engineering properties (compaction and uncon-
fined compression) tests and durability (wet-dry and freeze-thaw) tests.

      Test results show that fixing can cause significant changes in the
properties of sludge, that fixed sludges are similar to soil, soil-cement, or
low-strength concrete, and that properties are process-dependent.  On the
basis of test specimen behavior, fixed sludges can be expected to exhibit
substantial engineering strength and suitability for landfill and embankment
construction, although the durability tests show that weathering can be a
problem unless the fixed sludges are protected by an earth cover.  No leach-
ing studies were conducted as a part of this phase of the stabilization study.
Information and data on leaching are available in the interim report.

      This report was submitted in partial fulfillment of Interagency Agree-
ment Number EPA-IAG-D4-0569 by the U. S. Army Engineer Waterways Experiment
Station under the sponsorship of the U. S. Environmental Protection Agency.
This report covers the period from January 1975 to August 1976.
                                      iv

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                                  CONTENTS
Foreword	ill
Abstract	iv
Figures	vi
Tables	ix
Conversion Factors 	   x
Acknowledgment	xi

   1.  Introduction	   1
   2.  Conclusions 	   3
   3.  Recommendations 	   5
   4.  Materials and Methods 	   6
   5.  Properties of Raw and Fixed Sludges	31
   6.  Disposal and Productive use of Raw and
         Fixed Sludges	73

References	76
                                     v

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                                  FIGURES

Number                                                                 Page

   1   Raw and fixed sludges, number 100	   8

   2   Raw and fixed sludges, number 200	   9

   3   Raw and fixed sludges, number 300	10

   4   Raw and fixed sludges, number 400	11

   5   Raw and fixed sludges, number 500	12

   6   Raw and fixed sludges, number 600	13

   7   Raw and fixed sludges, number 700	14

   8   Raw and fixed sludges, number 800	15

   9   Raw and fixed sludges, number 900	  16

  10   Raw and fixed sludges, number 1000	17

  11   Schematic diagram of falling head permeability test
         set-up used for raw sludges	  27

  12   Grain-size distributions, raw and fixed sludges 	  32

  13   Grain-size distributions, raw and fixed sludges 	  33

  14   Grain-size distributions, raw and fixed sludges 	  34

  15   Plasticity chart for  raw sludges and sludges fixed
         by process B	37

  16   Specific gravities of common minerals compared to those
         of raw and fixed sludges	38

  17   Void ratio and porosity of common soils compared to those
         of fixed sludges	42

  18   Compaction curves for sludges fixed by process B  	  44

  19   Composite stress-strain curves for fixed sludges  	  45
                                    vi

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                             FIGURES (continued)
Number                                                                 Page

  20   Composite stress-strain curves for fixed sludges  	  46

  21   Photographs of specimens after unconfined compression
         test, FGD sludges fixed by process A	47

  22   Photographs of specimens after unconfined compression
         test, industrial sludges fixed by process A 	  48

  23   Photographs of specimens after unconfined compression
         test, FGD sludges fixed-by process B	49

  24   Photographs of specimens after unconfined compression
         test, industrial sludges fixed by process B 	  50

  25   Photograph of specimen during unconfined compression
         test, industrial sludge (200) fixed by process D  	  51

  26   Photograph of specimens after unconfined compression
         test, FGD sludge fixed by process E	51

  27   Photographs of specimens after unconfined compression
         test, FGD sludges fixed by process G	52

  28   Elasticities of common materials compared to those of
         fixed sludges	53

  29   Influence of pore size on the permeability of raw
         sludges	60

  30   Influence of pore size on the permeability of sludges
         fixed by process A or B	61

  31   Influence of pore size on the permeability of sludges
         fixed by process C, E, F, or G	62

  32   Summary of durability testing of fixed sludges  	  65

  33   Photographs of test specimens after four wet-dry test
         cycles, sludges fixed by process C or E	66

  34   Photographs of test specimens after 12 wet-dry test
         cycles, sludges fixed by process C or E	67

  35   Influence of permeability on the durability of sludges
         fixed by process E	69
                                    vii

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                             FIGURES (Continued)

Number                                                                Page

  36   Influence of permeability on the durability of fixed
         sludges	   70

  37   Influence of compressive strength on the durability of
         fixed sludges	   72
                                   viii

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                                   TABLES
Number                                                                 Page

   1   Sludge Code Number Assignment .................   6

   2   Sludge Fixation Process Assignments ..............   7

   3   Test Schedule for Raw and Fixed Sludges ............  18

   4   The Unified Soil Classification System  ............  23

   5   USCS Soil Types:  Characteristics Pertinent to
         Foundations and Embankments .................  24

   6   USCS Soil Types:  Characteristics Pertinent to
         Roads and Airfields .....................  25

   7   Physical Properties of Raw Sludges and Sludges
         Fixed by Process B  .....................  36

   8   Comparison of Specific Gravities of Raw and
         Fixed Sludges ........................  39
   9   Physical Properties of Fixed Sludges
  10   Changes in Dry Unit Weight After Compaction of
         Sludges Fixed by Process B  .................   54

  11   Summary of Unconfined Compression Test Data ..........   55

  12   Consistency of Clay in Terms of Unconfined
         Compressive Strength  ....................   56

  13   Summary of Permeability Test Data for Raw Sludges .......   57

  14   Summary of Permeability Test Data for Fixed Sludges ......   58

  15   Summary of Durability Testing of Fixed Sludges  ........   64
                                     ix

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                             CONVERSION FACTORS
      All measurements In EPA documents are to be expressed in metric (SI)
units.  In this report, however, implementing this practice sometimes affects
clarity adversely.   Factors for converting British units of measurements to
SI units are given as follows:

                 British                         Metric

                 1 in	   2.5 4 cm
                 1 Ib	   0.454 kg
                 1 cu ft	 .   0.0283 cu meter
                 1 Ib/sq in	   0.690 N/sq cm
                 1 Ib/cu ft 	  16.042 kg/cu meter
                 1 ft-lb/cu ft   	  47.928 N-m/cu meter
                                     x

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                               ACKNOWLEDGMENT
      The assistance of the firms and companies that provided sludge samples
or that performed fixation on these samples is gratefully acknowledged.
Without the continued support of these companies, research projects of this
nature could not be successfully performed.

      The guidance and support of Mr. Robert E. Landreth, Mr. Norbert L.
Schomaker, and the Solid and Hazardous Waste Research Division, Municipal
Environmental Research Laboratory, U. S. Environmental Protection Agency are
greatly appreciated.

      This project was conducted at the U. S. Army Engineer Waterways Ex-
periment Station under the general supervision of Dr. John Harrison, Chief,
Environmental Effects Laboratory (EEL), Mr. Andrew J. Green, Chief, Environ-
mental Engineering Division (EED), EEL, and Mr. Raymond L. Montgomery, Chief,
Design and Concept Development Branch, EED.  The Soils and Pavements Labora-
tory performed the laboratory testing under the direction of Mr. G. P. Hale;
Directors of WES during the course of this study were COL G. H. Hilt, CE,
and COL J. L. Cannon, CE.  Technical Director was Mr. F. R. Brown.
                                     xi

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                                 SECTION 1

                                INTRODUCTION
BACKGROUND

     Pollution control systems are in widespread use to protect the environ-
ment from damage resulting from the release of contaminants into the air and
water.  These systems have become developed to the point where they are now
capable of removing most contaminants from liquid industrial waste streams
and flue gases before discharge into the environment.  The end product of many
pollution control systems is a sludge in which pollutants are highly concen-
trated.  These sludges are potentially hazardous because the concentrated
pollutants may cause environmental damage upon disposal.  To allow the product
of pollution control systems to damage the environment would reduce the func-
tion of such systems from pollution control to pollution postponement; there-
fore, the ultimate disposal of hazardous sludges must be accomplished without
adverse environmental impact.

     Landfilling and ponding are common methods for the ultimate disposal of
hazardous waste sludges, but groundwater contamination problems can result.
As liquid percolates through the sludge, pollutants may be leached; and if the
leachate is allowed to migrate from the sludge into the surrounding environ-
ment, the leachate will contaminate the groundwater.  Groundwater contamina-
tion by leachate can be prevented by lining the disposal site with a material
impermeable to leachate, although liners are somewhat expensive and potential
difficulties include leakage and deterioration caused by chemical reactions
between the liner and the sludge.

     Alternatively, pollution of groundwater by leachate can sometimes be
lessened or prevented by sludge fixation, retarding pollutant migration from
sludges.  Chemical fixation alters the chemical and physical properties of
hazardous sludges, resulting in the formation of materials which may have any
of a wide range of consistencies.  While some fixation processes result in
the formation of soil-like materials with discrete particles, other processes
produce hard and rigid concrete-like materials of significant strength and
integrity.

     The U. S. Army Engineer Waterways Experiment Station  (WES) is investi-
gating the feasibility of using chemical fixation to reduce the pollution
potential and to increase the stability and durability of hazardous sludges
placed in landfills or used for productive purposes.  An interim report  of
the pollution potential of raw and chemically fixed hazardous industrial
wastes and flue gas desulfurization (FGD) sludges has been published by the

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U. S. Environmental Protection Agency (EPA), sponsor of the investigation.
The interim report presents limited data concerning the physical and engineer-
ing properties and the durability of raw and fixed sludges.

PURPOSE

     The purpose of this report is to describe laboratory tests appropriate
for raw and fixed sludges and to present detailed information concerning the
properties of these sludges.  Investigation of the test procedures used to
determine the sludge properties presented in the interim report revealed that
some of the test conditions (notably the temperature used for oven drying)
altered the properties of the test specimens during testing, and that incorrect
test values had been reported.  Consequently, test conditions were modified
to preserve the properties of the test specimens, and the sludges were re-
tested.

SCOPE

     This report is an expansion of Sections III and V of the interim report
and provides more detailed descriptions of tests modified for this study and
includes additional test results.  The report contains the meaningful data
presented in the interim report, modified as necessary, and also includes
permeability, durability and other test data not previously available.

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                                 SECTION 2

                                CONCLUSIONS

     Raw and fixed sludges can be successfully tested by methods currently
used in soils engineering.  The data resulting from such testing are meaning-
ful and show that raw and fixed sludges exhibit a wide range of properties,
many of which are material- and/or process-dependent.  Sludges fixed by
process B or F resembled cemented soils and could be crushed into individual
particles with moderate effort.  Sludges fixed by process A, C, E, or G are
hard materials resembling soil-cement mixtures or low-strength concrete.
Sludge fixed by process D is a hard material covered with 1/4 inch of plastic.

     Grain-size analyses indicate that raw sludges have grain-size distribu-
tions similar to those of silty soils and that the grain size distributions
of sludges are not substantially affected by process B.  Attempts to determine
the grain size distribution of sludge fixed by process F were only partially
successful due to flocculation during the hydrometer analysis.  Since raw
sludge of the same type was successfully tested, test failure is attributed
to the fixing process.

     Atterberg limit tests indicate that raw sludges are similar to silts of
low plasticity and that fixation generally reduces plasticity.  Since raw
sludges and sludges fixed by process B exhibit grain size distributions and
plasticity properties characteristic of silty soils, the behavior of these  ,
sludges is expected to be similar to that of silty soils.

     The specific gravities of the raw sludges range generally higher than
those of soils.  Changes in specific gravity due to fixation are process-
dependent .

     Moisture-volume-weight relationships for fixed sludges are process-
dependent.  Three fixed sludges exhibited a marked loss of water after 60 C
oven drying, while the majority exhibited little or no loss.  Void ratios,
porosities, and bulk and dry unit weights for the fixed sludges are generally
within the ranges typical of soils.

     The compactive effort of the 15-blow compaction test did not increase the
dry unit weight of sludges fixed by process B to values significantly higher
than those of samples of the same material after air drying.  It may be con-
cluded from these data that to achieve significant increases in dry unit
weight the application of a compactive effort considerably higher than that
of the 15-blow compaction test will be required; this usually requires the use
of modern compaction equipment.

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     Results from the unconfined compression tests indicate that the com-
pressive strengths of fixed sludges are highly dependent on fixation process
and sludge type.   Sludges fixed by one fixation process exhibited compressive
strengths typical of silts and clays.   Most of the fixation processes produced
fixed sludges having strengths comparable to those of soil-cement mixtures or
of low-strength concrete.

     Based on the results of unconfined compression testing, the performance
of soil-like fixed sludges should be satisfactory in bearing capacity and em-
bankment construction for most landfill applications.  Fixed sludges resembling
soil cement mixtures or low-strength concretes should perform very well in
landfill or embankment construction.

     The durability of fixed sludges is a function of the fixation process
rather than sludge type.  With the exception of sludges fixed by process D or
E, fixed sludges are generally unable to withstand 12 durability test cycles.
However, since no long-term data concerning the field durability of fixed
sludges exist, no prediction of field durability can be made on the basis of
laboratory test results.  Data from field studies of fixed sludge landfills
are needed to develop relationships between laboratory testing and field per-
formance.

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                                 SECTION 3

                              RECOMMENDATIONS

     It is recommended that landfills constructed of fixed sludge be care-
fully monitored to permit correlation with experimental results and to faci-
litate the prediction of field performance on the basis of laboratory test
results.

     Some fixed sludges are like soil-cement or concrete,  and their potential
for use in landfill and embankment construction should be  investigated further
in hopes of reducing disposal area requirements.

     It is recommended that a manual describing recommended test procedures
for evaluating the physical and engineering properties and the durability of
raw and fixed sludges be prepared.  The manual should emphasize evaluation of
sludge properties that influence the behavior of landfills of raw or fixed
sludge.  The manual could be synthesized from the procedures specified by
various organizations for use in testing materials other than sludge; the
experience of various investigators that have tested sludge could be used as
the basis for modification of standard procedures.  The manual would serve to
consolidate under one cover test procedures for sludge testing, making Corps
of Engineers test procedures, which were used during this  study, more readily
available to the private sector.

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                                 SECTION A

                           MATERIALS  AND METHODS
MATERIALS

Sludges

     Sludge samples from five coal-burning electric power "enerating plants
and from five industrial manufacturing plants  were obtained and assigned code
numbers as shown in Table 1.   The sludges were sampled by WES personnel and
brought to WES for chemical fixation and laboratory testing.


	TABLE 1.  SLUDGE CODE NUMBER ASSIGNMENT	

Code Number                                    Sludge

    100                          FGD, lime process, eastern coal
    200                          Electroplating
    300                          Nickel/cadmium battery
    400                          FGD, limestone process,  eastern coal
    500                          FGD, double alkali process,  eastern coal
    600                          FGD, limestone process,  western coal
    700                          Inorganic pigment
    800                          Chlorine production, brine sludge
    900                          Calcium fluoride
   1000                          FGD, double alkali process,  western coal

Note:  Information from Reference 1.
Chemical Fixation

     The samples of each type of sludge (100, 200, etc.) were divided into
several portions.  Some portions of each sludge type were designated for test-
ing to characterize each raw sludge.  The remaining portions of each sludge
type were chemically fixed at the WES by representatives of the respective
processors.  Each process was assigned a code letter, and Table 2 shows the
process(es) used to fix each type of sludge.

     Each sludge sample is identified by a code consisting of a letter  to
represent the fixation process (Table 2) followed by a number to specify the
sludge type (Table 1).  The identification codes of samples of unfixed  (raw)
sludge are prefixed by the letter R.

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               TABLE 2.  SLUDGE FIXATION PROCESS ASSIGNMENTS
Sludge
type
100
200
300
400
500
600
700
800
900
1000

A
X
X
X
X
X
X

X
X
X

B
X
X
X
X
X
X

X
X
X
Fixation processes
C D E F
X
X X

X
X
X X
X


X

G

X

X
X
X



X
Note:  Information from Reference 1.
LABORATORY TESTS

     Tests commonly used in determining the properties of soil and/or concrete
were performed on the raw and fixed sludges to determine their physical and
engineering properties and durability.  The use of standard tests and proce-
dures allows the comparison of sludge properties with those of common materials
whose properties are described in the literature.  The various fixation pro-
cesses  (described in Reference 1) produce sludges of different appearances and
characteristics (Figures 1-10); some are similar in appearance to cemented
soil and others are hard and brittle, like concrete..  One process included
coating the sludge with plastic (Figure 2).  Procedures used to test raw and
fixed sludges were selected on the basis of the appearance of the material
(i.e., soil-like, etc.), and the testing schedule is shown in Table 3.

     To prevent the alteration of sludge properties during testing and to ac-
commodate non-standard test specimens, standard test procedures were modified
as necessary.  Specific deviations from standard procedures and the justifi-
cation for such deviations are presented in appropriate parts of the remainder
of this section.

Physical Properties Tests

Grain-size Analysis—

     The particle-size distributions of samples of raw and fixed sludges were
determined by combined grain-size analysis.  A sieve analysis was performed on
that fraction of each sludge sample larger than 0.074 mm (#200 sieve); and a
hydrometer analysis was performed on the finer fraction.  Test procedures are
described in Appendix V of Engineer Manual (EM) 1110-2-1906  and in American
Society for Testing and Materials (ASTM)3 standard test D422-63.

     Samples whose grain size distributions were determined were prepared in

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••--•
                        SLUDGE  NO. 1  1OO
                              PROCESS  F
              Figure 1. Raw and fixed sludges, Number 100 (from Reference 1)

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.
                 SLUDGE NO.I 20O
         RAW SLUDGE
PROCESS  A
            PROCESS C
         Figure 2.  Raw and fixed sludges, Number 200 (from Reference 1),

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           SLUDGE  NO. I 300
                                           "
     PROCESS
Figure 3, Raw and fixed sludges, Number 300 (from Reference 1),

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      SLUDGE  NO.  400
                       PROCESS G
Figure 4. Raw and fixed sludges, Number 400 (from Reference 1).

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                   LUDGE  NO.! 500

                                     ^
           RAW  SLUDGE ^*-   -^ PROCESS  B
                        PROCESS A
3
                                 PROCESS G
             Figure 5. Raw and fixed sludges, Number 500 (from Reference 1)

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       SLUDGE  NO.  600
Figure 6.  Raw and fixed sludges, Number 600 (from Reference 1)

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       SLUDGE NO.1 700
Figure 7. Raw and fixed sludges, Number 700 (from Reference 1)

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                   SLUDGE  NO.  800
Ln

              Figure 8. Raw and fixed sludges, Number 800 (from Reference 1)

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     SLUDGE  NO.  900

Figure 9. Raw and fixed sludges, Number 900 (from Reference 1).

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    SLUDGE  NO. 1000
Figure 10.  Raw and fixed sludges, Number 1000 (from Reference 1).

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                              TABLE 3.  TEST SCHEDULE FOR RAW AND FIXED  SLUDGES
00

Type of Test
ASTM** Method
Raw
Sludge
Fixation Processes*
A
B
C
D
E
F
G

Grain-size analysis
Specific gravity of solids
Water content
Bulk and dry unit weight
Porosity and void ratio
Liquid limit
Plastic limit
Compaction test (15-blow)
Unconfined compression test
Permeability test
Freeze-thaw test
Wet-dry test
D422-63
D854-58
D2216-71
t
t
D423-66
D424-59
D698-70//
D2166-66
t
D560-57
D559-57
X
X
X
X
X
X
X


X



X
X
X
X



X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X

X
X
X
X



X
X
X
X

X
X
X
X



X
X
X
X

X
X
X
X



X
X
X
X
X
X
X
X
X



X
X
X
X

X
X
X
X



X
X
X
X

        *    The sludge types fixed by each processor are listed in Table  2.




        t    No  ASTM standard method available.



        #    Modified procedure,  see text.




        **   American Society for Testing and Materials.

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accordance with the specifications of ASTM D421-58.  Figures 1-10 show that
the individual particles of the fixed sludges were bound together to form a
semi-continuous mass.  Using a rubber tipped pestle, the samples were ground
into their individual particles in a. mortar.

     A sieve analysis consists of passing a sample through a set of sieves
and weighing the portion of material retained on each sieve.  The hydrometer
analysis is based on Stoke1s Law and involves preparation of a dilute suspen-
sion of fine sludge particles in water; measurement of the specific gravity
of the suspension at specified time intervals; and correlation of settling
velocity, particle diameter, and time to determine grain-size distribution.
Dispersing agents were used in the hydrometer analysis to prevent the floc-
culation of fine particles during the test.

Specific Gravity of Solids—

     The specific gravity of solids (Gs) for raw and fixed sludges is1defined
as the ratio of the unit weight of dry sludge solids to that of water.   The
test procedure used to determine Gs is given in Appendix IV of EM 1110-2-1906
and in ASTM D854-58.  A volumetric flask was used to measure precisely the
volume of a suspension of sludge particles in water.  Later determination of
constituent weights allowed computation of Gs.  Tests were originally performed
using an oven drying temperature of 110+5°C.  It was later discovered that
hydration water was lost at this temperature, significantly affecting Gs values.
Consequently, the tests were repeated using an oven drying temperature of 60 C.

Water Content—

     The water content (w) of a sludge sample is defined as the ratio of the
weight of water to the weight of solids in the sample and is normally ex-
pressed as a percentage.  This value is termed dry weight basis water content.
The values of w of fixed sludges were determined by the method presented in
Appendix I of EM 1110-2-1906 and in ASTM D2216-71.  A sludge sample of known
weight was oven dried at 60°C and the weight loss upon drying was attributed
to loss of interstitial water.

Bulk and Dry Unit Weight—

     The bulk unit weight (y^) of a sludge sample is defined as the ratio of
total weight (solids and water) to total volume.  Dry unit weight (yd) is de-
fined as the ratio of oven dried (60 C) weight to total volume.  Values are
expressed in Ib/cu ft*.  The standard procedures for both tests are found in
Appendix II of EM 1110-2-1906.  No ASTM test procedures have been established
specifically for determining y^ or j^.  Although several ASTM test procedures
(e.g., D698-70, D2166-66) include provision for determining the y^ or yd °f
the test specimen, the method varies from test to test.  Volumes were computed
using linear measurements of a regularly shaped mass obtained by trimming or
cutting.


*A table of factors for converting British units of measurement to SI units
 of measurement appears on page x.

                                      19

-------
Porosity and Void Ratio —

     The void ratio (e) of a sludge sample is defined as the ratio of the vol-
ume of voids to the volume of solids and is normally expressed as a decimal.
Porosity (n) is defined as the ratio of the volume of voids to the total vol-
ume and is normally expressed as a percentage.  The standard test procedure
for determining e and n is found in Appendix II of EM 1110-2-1906.  No ASTM
standard test procedure exists; e and n are computed from test specimen weight
and volume measurements as part of other standard test procedures (e.g., D
2435-70) .  The volume of solids was computed from the dry weight and G , and
the total volume was determined during the test to determine y .

     The moisture-volume-weight values are related by the following set of
equations :

          V-V                                    W
                                            Y=                 (5)
                        (2)
          W                                       V
      w = ^ x 100%     (3)                  S = ^- x 100%     (7)
           s                                        s

           W                                     W
     Gs = V~7~          (4)           % Solids = ^T x 100%
           S W

where

      V = total volume of sample, cu ft

     V  = volume of solids, cu ft
      S

     V  = volume of water, cu ft
      w

      W = total weight of sample, Ib

     W  = weight of solids, Ib
      S

     W  = weight of water, Ib
      Vt

      e = void ratio

     Y, = dry unit weight, Ib/cu ft

     Y,  = bulk unit weight, Ib/cu ft

     Yw = unit weight  of water,  usually taken as 62.4 Ib/cu ft

                                     20

-------
          n = porosity, %

          w = water content  (dry weight basis), %

         GS = specific gravity of solids

          S = degree of saturation, %

     Values of w determined  on a dry weight basis can be converted to a wet
weight basis (m) or to percent solids by weight using the following relation-
ships :

                           m = ,„»... x 100%

and
                           % solids = .^17, x 100%           (10)
                                      XUUTW
where m = water content  (wet weight basis), %

Atterberg Limits—

     Atterberg limit tests were performed on samples of raw and fixed sludge
to determine the plasticity of the materials.  The tests are designed to de-
termine the limiting water contents, termed the plastic limit (PL) and liquid
limit (LL), at which the material exhibits plastic and liquid behavior.  The
plasticity index (PI) or range of plastic behavior is defined as the differ-
ence between the LL and PL and is normally expressed as a percentage.  Arbi-
trary tests have been developed to determine the Atterberg limits and are used
as standard reference tests for the comparison of soil properties.  Test pro-
cedures for determining the PL and LL are presented in Appendix III and IIIA
of EM 1110-2-1906 and ASTM standard tests D424-59 and D423-66.  The PL is
defined as the w at which the sludge will start to crumble when rolled into a
1/8 in thread under the palm of the hand.  The tests were conducted by taking
a small specimen of sludge at a w at which a ball could be shaped easily with-
out sticking to the fingers.  The ball was then rolled into a thread on a
piece of ground glass.  If the thread diameter became 1/8 in without crumbling,
the procedure was repeated until drying caused the thread to break at 1/8 in
diameter.  The w was then determined; a check test was performed; and the ave-
rage w was taken as the PL.

     The LL is defined as the lowest w at which the sludge will flow as a vis-
cous liquid, arbitrarily defined as the w at which two halves of a soil speci-
men separated by a groove of standard dimensions will close along a distance
of 1/2 in under the impact of 25 blows of a standard device.  The standard
device cited in the definition consists of a brass cup and a cam mechanism,
which is used to drop the cup a distance of 10 mm onto a base of a known dy-
namic resilience.  A specimen of sludge was placed in the cup at a w higher
than the LL.  A standard tool was used to shape a groove of known dimensions
through the specimen.  The cup was then dropped onto the base a number of
times until the groove closed 1/2 in, with the required number of blows re-
corded.   The w of the specimen was then determined.  This procedure was

                                      21

-------
repeated several times as the material dried slightly until the number of
blows to close the groove exceeded 25.  The results were plotted on a graph of
w versus number of blows and the w corresponding to 25 blows was termed the LL.

Classification—

     Soils engineers use classification systems to group together soils that
exhibit similar properties, and use the classification of a soil as an aid to
describe the soil properties in a general way.  The Unified Soil Classifica-
tion System (USCS) is a widely used system "based on the identification of
soils according to their textural and plasticity qualities and on their group-
ing with respect to behavior."   Using the results of the grain-size analyses
and the Atterberg limits, raw and soil-like fixed sludges were classified ac-
cording to the USCS.  Table 4 outlines the procedure used to classify the
sludge samples in accordance with the USCS, and Tables 5 and 6 summarize some
of the general characteristics of each type of soil.  The procedure for class-
ifying soil by the USCS is ASTM standard method D2487-69, and further infor-
mation concerning the USCS and the properties of soils in each group is avail-
able in References 4 through 7.

Engineering Properties Tests

Compaction Test—

     The 15-blow compaction test was performed on fixed sludge samples to de-
termine the optimum water content (CMC) for compaction and the unit weights
which could be expected from field compaction of the fixed sludge when used
as a construction material.  The test procedure is presented in Appendix VI
of EM 1110-2-1906 and is identical to the procedure of ASTM D698-70, except
that 15 (as opposed to 25 or 56) blows are used to compact each layer.  A 4
in diameter, 1/30 cu ft cylindrical mold was filled with three equal layers
of sludge.  Each layer was compacted with 15 uniformly distributed blows using
a 5.5 Ib hammer with 12 in drop.  Following compaction the specimen was
weighed and the y, and the w were determined.  The entire test was then re-
peated with a small amount of water added to the specimen to increase the w.
Results of the test were expressed as a plot of j  versus w.  The OMC for com-
paction was considered to be that at which the maximum j . was achieved.  The
15-blow test described above has a laboratory compactive effort of 7400
ft-lbs/cu ft and simulates conditions encountered when material is placed in a
landfill using available equipment such as bulldozers, etc. for compaction,
rather than using more sophisticated compaction equipment.  Also available is
the Standard Proctor test, which has a laboratory compactive effort of 12,400
ft-lbs/cu ft and simulates the compactive effort required for fill placed in
roadway subgrades or dams.  The Modified Proctor test has a laboratory com-
pactive effort of 56,000 ft-lb/cu ft and is designed to simulate the com-
pactive effort of several passes using modern compaction equipment.  Such
compaction is necessary in large scale highway construction projects.  The
15-blow test was selected for fixed sludge testing because the lower compac-
tive effort is more representative of the field compaction necessary for
general landfill applications using fixed sludges.
                                     22

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                                        TABLE 4.   THE UNIFIED  SOIL  CLASSIFICATION  SYSTEM
ro
OJ
Major Division
Coarse-grained
(over 50% by
weight coarser
than No. 200
sieve)
Fine-grained
(over 50° o by
weight finer
than No. 200
sieve)
Gravelly
soils (over
half of
coarse
fraction
larger
than No. 4)
Sandy soils
(over half
of coarse
fraction
finer than
No. 4)
Low com-
pressibility
(liquid
limit less
than 50)
High com-
pressibility
(liquid
limit more
than 50)
Soils with fibrous
organic matter
Group
Symbol
GW
GP
GM
GC
sw
SP
SM
SC
ML
CL
OL
MH
CH
OH
Pt
Laboratory Classification Criteria
Finer than
200 Sieve
%
0-5*
0-5*
1 2 or more*
12 or more*
0-5*
0-5*
12 or more*
12 or more*
Supplementary Requirements
DmjDw greater than 4,
DxfKDw x Dw) between 1 & 3
Not meeting above gradation for GW
PI less than 4 or below A-line
PI over 7 and above A-line
DtolDw greater than 4,
Dm'KDea x £>,„) between 1 & 3
Not meeting above gradation
requirements
PI less than 4 or below A-line
PI over 1 and above A-line
Plasticity chart
Plasticity chart
Plasticity chart, organic odor or color
Plasticity chart
Plasticity chart
Plasticity chart, organic odor or color
Fibrous organic matter; will char, burn, or glow
Soil Description
Well-graded gravels, sandy gravels
Gap-graded or uniform gravels, sandy
gravels
Silty gravels, silty sandy gravels,
Clayey gravels, clayey sandy gravels
Well-graded sands, gravelly sands
Gap-graded or uniform sands, gravelly
sands
Silty sands, silty gravelly sands
Clayey sands, clayey gravelly sands
Silts, very fine sands, silty or clayey fine
sands, micaceous silts
Low plasticity clays, sandy or silty clays
Organic silts and clays of low plasticity
Micaceous silts, diatomaceous silts,
volcanic ash
Highly plastic clays and sandy clays
Organic silts and clays of high plasticity
Peat, sandy peats, and clayey peat
                * For soils having 5 to 12 per cent passing the No. 200 sieve, use a dual symbol such as GW-GC.

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        TABLE 5.  USCS SOIL TYPES:  CHARACTERISTICS PERTINENT TO FOUNDATIONS AND EMBANKMENTS  (After  Reference  4)
Symbol
GW
GP
GM
GC

SW
SP
SM
sc

ML
Name
Well-graded gravels or
gravel-sand mixtures,
little or no fines
Poorly-graded gravel or
gravel-sand mixtures,
little or no fines
Silty gravels, gravel-
sand-silt mixtures
Clayey gravels, gravel-
sand-clay mixtures

Well-graded sands or
gravelly sands, little
or no fines
Poorly-graded sands or
gravelly sands, little
or no fines
Silty sands, sand-silt
mixtures
Clayey sands, sand-
clay mixtures

Inorganic silts and
very fine sands, rock
flour, silty or clayey
Value for
embankments
Very stable, pervious
shells of dikes and
dams
Reasonably stable,
pervious shells of
dikes and dams
Reasonably stable, not
particularly suited to
shells, but may be used
for impervious cores or
blankets
Fairly stable, may be
used for impervious
core
Very stable, pervious
sections, slope pro-
tection required
Reasonably stable, may
be used in. dike section
with flat slopes
Fairly stable, not par-
ticularly suited to
shells, but may be used
for impervious cores or
dikes
Fairly stable, use for
impervious core for
flood control struc-
tures
Poor stability, may
be used for embank-
ments with proper con-
Compaction
characteristics*
Good , tractor, rubber-
tired, steel-wheeled
roller
Good , tractor , rubber-
tired, steel-wheeled
roller
Good, with close con-
trol , rubber-tired ,
sheepsfoot roller
Fair, rubber-tired,
sheepsfoot roller

Good, tractor
Good, tractor
Good, with close con-
trol, rubber-tired,
sheepsfoot roller
Fair , sheepsfoot
roller, rubber-tired
roller

Good to poor, close
control essential,
rubber-tired roller,
Value for
foundations
Good bearing value
Good bearing value
Good bearing value
Good bearing value

Good bearing value
Good to poor bea'r-
ing value depending
on density
Good to poor bear-
ing value depend-
ing on density
Good to poor bear-
ing value

Very poor, suscep-
tible to liquefac-
tion
Requirements
for seepage
control
Positive cutoff
Positive cutoff
Toe trench to
none
None

Upstream blanket
and toe drain-
age or wells
Upstream blanket
and toe drain-
age or wells
Upstream blanket
and toe drain-
age or wells
None

Toe trench to
none
        fine sands or clayey
        silts with slight
        plasticity

CL      Inorganic clays of low
        to medium plasticity,
        gravelly clays, sandy
        clays, silty clays,
        lean clays

OL      Organic silts and or-
        ganic silt-clays of
        low plasticity
                                  trol
                                  Stable, impervious
                                  cores and blankets
                                  Not suitable for em-
                                  bankments
                                                           sheepsfoot roller
Fair to good, sheeps-
foot roller, rubber-
tired roller
Fair to poor, sheeps-
foot roller
Good to poor bear-    None
ing
Fair to poor bear-    None
ing, may have ex-
cessive settlements
MH




CH



OH


Pt

Inorganic silts, mica-
ceous or dlatomaceous
fine sandy or silty
soils, elastic silts

Inorganic clays of
high plasticity, fat
clays

Organic clays of med-
ium to high plasticity,
organic silts
Peat and other highly
organic soils
Poor stability, core
of hydraulic fill dam,
not desirable in
rolled fill construc-
tion
Fair stability with
flat slopes, thin
cores, blankets and
dike sections
Not suitable for em-
bankments

Not used for con-
struction
Poor to very poor,
sheepsfoot roller



Fair to poor, sheeps-
foot roller


Poor to very poor,
sheepsfoot roller

Compaction not
practical
Poor bearing None




Fair to poor bear- None
Ing


Very poor bearing None


Remove from foundations

*The equipment listed will usually produce the desired densities with a reasonable number of passes when moisture conditions
 and thickness of lift are properly controlled.
                                                            24

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                                                                   TABLE 6.   USCS SOIL TYPES:   CHARACTERISTICS PERTINENT TO ROADS AND AIRFIELDS (After Reference 4)
ro
Ln
Symbol
GW
GP
GM
GC
SW
SP
SM
SC
ML
CL
OL
KH
CH
OH
Pt
Name
Well-graded gravels or gravel-
sand mixtures, little or no
fines
Poorly graded gravels or
gravel-sand mixtures, little
or no fines
Sllty gravels, gravel-sand-
silt mixtures
Clayey gravels, gravel-sand-
clay mixtures
Well-graded sands or gravelly
sands, little or no fines
Poorly graded sands or
gravelly sands, little or
no fines
Silty sands, sand-silt mix-
tures
Clayey sands, sand-clay mix-
tures
Inorganic silts and very
fine sands, rock flour, sllty
or clayey fine sands or
clayey silts with slight
plasticity
Inorganic clays of low to
medium plasticity, gravelly
clays, sandy clays, silty
clays, lean clays
Organic silts and organic silt-
clays of low plasticity
Inorganic silts, micaceous or
diatomaceous fine sandy or
silty soils, elastic silts
city, fat clays
Organic clays of medium to high
plasticity, organic silts
Peat and other highly organic
soils
Value as
subgrade
when not
subject
to frost
action
Excellent
Good to
excellent
Good to
excellent
Good
Good
Fair to
good
Fair to
good
Poor to
fair
Poor to
fair
Poor to
fair
Poor
Poor
Poor to
fair
Poor to
very poor
Not
suitable
Value aa
sub-base
when not
subject
to frost
action
Excellent
Good
Good to
fair
Fair
Fair to
good
Pair
Fair to
good
Poor
Not
suitable
Not
suitable
Not
suitable
Not
suitable
Hot
suitable
Not
suitable
Hot
suitable
Value as
base when
not sub-
ject to
frost
action
Good
Fair to
good
Fair to
good
Poor to
not
suitable
Poor
Poor to
not
suitable
Poor
Not
suitable
Not
suitable
Not
suitable
Not
suitable
Not
suitable
Not
suitable
Not
suitable
Not
suitable
Potential
frost
action
None to very
slight
None to very
alight
Slight to
medium
Slight to
medium
None to
very
slight
None to
very
slight
Slight to
high
Slight to
high
Medium to
very high
Medium to
high
Medium to
high
Medium to
very high
Medium
Medium
Slight
Compress i-
expansion
Almost none
Almost none
Slight
Slight
Almost none
Almost none
Slight to
medium
Slight to
medium
Slight to
medium
Medium
Medium to
high
High
High
High
Very high
Drainage
istics
Excellent
Excellent
Fair to
poor
Poor to
practi-
cally im-
pervious
Excellent
Excellent
Fair to
poor
Poor to
practi-
cally im-
pervious
Fair to
poor
Practi-
cally im-
pervious
Poor
Fair to
poor
Practi-
cally im-
pervious
Practi-
cally im-
pervious
Fair to
poor
Compaction
equipment*
Crawler-type tractor, rubber-
tired roller, steel-wheeled
roller
Crawler-type tractor, rubber-
tired roller, steel-wheeled
roller
Rubber-tired roller, sheeps-
foot roller; close control of
moisture
Rubber-tired roller, sheeps-
foot roller
"Crawler-type tractor , rubber-
tired roller
Crawler-type tractor, rubber-
tired roller
Rubber-tired roller, sheeps-
of moisture
Rubber-tired roller, sheeps-
foot roller
Rubber-tired roller, sheeps-
of moisture
Rubber-tired roller, sheepa-
foot roller
Rubber-tired roller, sheeps-
foot roller
Sheepsfoot roller, rubber-
tired roller
Sheepsfoot roller, rubber-
tired roller
Sheep s foot roller, rubber-
tired roller
Compaction not practical
                                      *The  equipment  listed will  usually  produce  the desired densities with a reasonable number of passes when moisture conditions and thickness of lift -are
                                       properly  controlled.

-------
Unconfined Compression Test—

     The unconfined compression test is used to determine the uniaxial, uncon-
fined compressive strength of a cohesive or cemented material.  The tests were
performed on fixed sludges to determine their relative strength for bearing
capacity or embankment construction.  A cylindrical specimen of the sludge was
prepared and loaded axially until failure.  The test load was applied using a
controlled rate of strain (1 percent/min), and compressive stresses were re-
corded as the loading progressed.  The peak compressive stress sustained by
the specimen was considered the unconfined compressive strength of the material.
The undrained shear strength (T) is approximately one-half the unconfined com-
pressive strength of cohesive soil, and was determined for soil-like samples.
Multiple specimens were used for each test and results were averaged to con-
struct a composite stress-strain curve.  Young's modulus of elasticity, de-
fined as the slope of the stress-strain curve, was determined from the com-
posite stress-strain curves.  The standard test procedure, found in Appendix
XI of EM 1110-2-1906 and in ASTM standard method D2166-66, was followed except
that a specimen height-to-diameter ratio of 2.0 was used instead of the normal
2.1.

Permeability Tests—

     Two types of tests, both applicable for determining the coefficient of
permeability (k) of fine-grained soil, were used to determine the k of raw and
fixed sludges.  A falling head permeability test was used for the raw sludges,
while fixed sludges were tested in a triaxial compression chamber with back
pressure used to ensure complete saturation.  Test descriptions are presented
below.

     Permeability Test for Raw Sludges—The following permeameter, sample pre-
paration, procedure, and calculations were used to determine the k of samples
of raw sludge.  The test is a falling head test and is appropriate for testing
fine-grained material having k less than 10~^ cm/sec.

     Permeameter—Figure 11 shows a schematic diagram of the test set-up.  The
permeameter was constructed of plastic tubing with an inside diameter of 12.7
cm, and ports were provided to allow water to enter into the upper chamber and
to exit from the lower chamber.  The permeameter was constructed of clear plas-
tic so that the lengths of the samples could be measured during the tests.

     Support for the samples was provided by four sheets of filter paper rest-
ing on a No. 200 mesh (200 openings per linear inch) wire screen.  The filter
paper was provided to prevent the migration of fine particles from the sludge.
The k of the support system was 1.100 x 10"^ cm/sec, greater than the antici-
pated permeability of the sludges, so that any flow restriction would not in-
fluence the determination of the k of the sludges.

     The samples were topped with No. 200 mesh wire screen and 5 cm of Ottawa
sand to maintain a uniform sludge surface.  While the k of the Ottawa sand
layer was not quantified, this material was selected because it is known to  be
several orders of magnitude more permeable than the sludge.  The Ottawa sand
did not restrict the flow of water to the sludge samples.  Prior to beginning


                                      26

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                          CYLINDRICAL
                         PERMEAMETER
                      DIAMETER =12.7 cm
       FLOW
                                          >  UPPER CHAMBER
                                             OTTAWA  SAND
                                             #200 MESH
                                             WIRE SCREEN

                                             RAW SLUDGE SAMPLE

                                             4 SHEETS FILTER
                                             PAPER ON * 200
                                             MESH WIRE SCREEN


                                             LOWER CHAMBER
Figure 11.  Schematic diagram of falling head permeability test set-up used
          for raw sludges.
                               27

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the tests, the lower chamber was filled with deaired distilled water and the
4  sheets of  filter paper were saturated.

      Sample  preparation—A slurry was prepared by mixing sludge with deaired
distilled water in a mixer bowl so that the particles in the slurry were com-
pletely dispersed.  Sludge slurry was then poured into the permeameter until
a  column 7 to 10 cm in height was obtained.  The column was then gently rod-
ded to release entrapped air, thus ensuring complete saturation.  The No. 200
screen and the 5 cm of Ottawa sand were placed in the column, completing the
sample preparation.  The Y
-------
where

                                                        °
       ^20 = coefficient of permeability for water at 20C, cm/sec

     2.303 = factor for converting logarithms from natural base to base 10.

         L = length of sample at time of test, cm

        R  = Viscosity correction factor, determined by dividing the viscosity
             of water at the test temperature by the viscosity of water at
             20°C

         t = time for head to fall from h  to h,., sec
                                         o     t
        h  = head at start of test, cm

        hf = head at finish of test, cm

     Permeability test for fixed sludges—Accurate determinations of the k of
porous materials can be obtained only by testing samples that are completely
saturated.  The complete saturation of cohesive soils, concrete, and other
materials with low permeability is difficult to ensure; and for this reason
the application of pressure is used to saturate samples as much as possible.
During this study samples of fixed sludge were tested using a falling head
permeability test conducted in a triaxial compression chamber with back pres-
sure to increase saturation.  The difference between the chamber pressure and
the back pressure was 10 Ib/sq in.

     The test procedure itself is complex and requires considerable care and
experience.  The exact test procedure, including sample preparation, equipment
and calculations is fully described in Reference 2.  The only deviation from
the procedure cited therein was specimen diameter.  Standard specimen diameter
is 2.8 in, but the specimens tested were 3 in in diameter.  The ASTM has not
published a standard method suitable for determining the permeability of
fixed sludge.

Durability Tests

     Samples of fixed sludge were subjected to freeze-thaw tests and to wet-
dry tests to evaluate the resistance of these fixed sludges to natural weather-
ing stresses.  The 2 tests are standard ASTM tests used to estimate the dura-
bility of soil-cement mixtures.

Freeze-Thaw Test —

     Properly cured fixed sludge samples were subjected to the standard freez-
ing and thawing test of compacted soil-cement mixtures, ASTM test D560-57.
This test calls for cylindrical samples to be subjected to 12 test cycles,
each consisting of freezing for 24 hours, thawing for 23 hours, and 2 firm
strokes on all surface areas with a wire scratch brush.  Performance is eval-
uated by determining the weight loss after 12 cycles or the number of cycles
to cause disintegration, whichever occurs first.

                                      29

-------
     The procedure specified in ASTM D560-57 was followed except that test
specimens were 3 in in diameter and 4 to 6 in in height,  rather than 4 in in
diameter and 4.5 in in height.   Specimens for all properties tests were 3 in
in diameter to accomodate WES specifications for leaching column tests.

Wet-Dry Test—

     The wet-dry test is similar to the freeze-thaw test.  Cured cylinders of
fixed sludge were subjected to  12 test cycles, each consisting of 5 hours of
submergence in water, 42 hours  of oven drying, and 2 firm strokes on all sur-
face areas with a wire scratch  brush.  Test results are presented as weight
loss after 12 cycles or the number of cycles causing sample disintegration,
whichever occurs first.  A detailed test procedure is given in ASTM D559-57,
which is the standard wetting and drying test of compacted soil-cement mix-
tures.  As in the case of the freeze-thaw test, specimens were 3 in in diameter
and 4 to 6 in in height, rather than 4 in in diameter and 4.5 in in height.
                                     30

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                                 SECTION 5

                    PROPERTIES OF RAW AND FIXED SLUDGES
PHYSICAL PROPERTIES

Grain-size Analysis

     Results from the combined sieve and hydrometer analyses were used to de-
termine the grain-size distributions of 9 raw sludges, 9 sludges fixed by pro-
cess B, and 1 sludge fixed by process F.  No other fixed sludges exhibited
soil-like characteristics; therefore no other fixed sludges were tested.  The
grain-size distributions are presented in Figures 12, 13, and 14 as grain size
in mm versus percent finer by weight.  Results of testing raw and fixed sam-
ples of the respective sludge types are presented on the same figure, and some
typical grain-size distributions for common soils are included for comparison.

     Median grain sizes as determined by the grain size analyses ranged be-
tween 0.0076 and 0.125 mm.  The sludges are generally well-graded with a smooth
distribution of grain sizes.  A high percentage of the particles of raw sludges
and sludges fixed by process B pass the #200 sieve (.074mm), usually indicative
of low permeability, low strength, and high compressibility. '

     Comparison of the grain-size distributions of raw sludges with correspond-
ing sludges fixed by process B shows that fixation had only a slight effect on
the distribution of particle sizes.  There was essentially no change in grada-
tion for sludge 800; the fixation process resulted in a generally finer grada-
tion for sludges 100, 400, 500, and 600; and sludges 200, 300, 900, and 1000
exhibited generally coarser gradations after fixation.  It was anticipated
that a particular fixation process would have a consistent effect on the grain-
size distribution of the various sludges; however, effects on gradation were
not uniform for all sludges fixed by process B.  Differences in gradation can
be partially attributed to the imprecision inherent in the sample preparation
procedure.  Grinding in a mortar using a rubber coated pestle may not separate
all agglomerated particles and may break some individual particles into smaller
particles.  In general, sludges fixed with process B exhibited gradations in
the same ranges as the corresponding raw sludges and very similar to those of
silty soils.

     Grain-size analyses for sludge 600 fixed by process F were only partially
successful due to flocculation of the sludge suspension during the hydrometer
analysis.  Several attempts were made to run the test using the deflocculants
tetraphosphate and sodium oxalate; however, in all cases flocculation occurred
after four minutes at a grain size of 0.02 mm.  Flocculation of fixed sludge
F-600 was apparently caused by the chemical fixing agent, since the raw type

                                      31

-------
                                GRAIN Sift IN MILLIMETERS
                               SLUDGE  100
                                GRAIN SIZE IN MILLIMETERS



                              SLUDGE 200
                                GRAIN SKI IN MILLIMETERS-
                              SLUDGE 300
Figure 12.   Grain-size  distributions, raw and fixed sludges.




                                  32

-------
                              SLUDGE  400
                                GRAIN SIZE IN MILLIMETERS
                              SLUDGE  500
             U. S. STANDARD SEW OFENMG M
                                GIU1N SIZE IN MILLIMETERS
                              SLUDGE 600
Figure 13,   Grain-size distributions,  raw and  fixed  sludges,
                                 33

-------
                100  SO
                                   CRNN Silt IN MLUMCTEAS



                                 SLUDGE  800
                                   GRAIN SUE IN MILLIMETERS




                                 SLUDGE  900






                                  U. S. STANDARD SIEVE NUMBERS
                                   GRMN SIZE IN MtUJMfTERS



                                SLUDGE 1000
Figure  14.   Grain-size distributions, raw and fixed  sludges.




                                   34

-------
600 sludge was successfully tested.  Results of these tests are presented in
Figure 13.

Atterberg Limits

     The Atterberg limits of eight raw sludges and seven fixed sludges (pro-
cess B) were determined.  Values for the liquid limit (LL), the plastic limit
(PL), and the plasticity index  (PI) are listed in Table 7.  The fixation pro-
cess increased the LL and the PI of the sludge in some cases and decreased the
values in other cases.  The data are plotted on a standard plasticity chart in
Figure 15.  For all sludges the points plotted below the A-line, the arbitrary
boundary between silts and inorganic clays.  However, fixed sludges tended to
appear further below the A-line than did the raw sludges, indicating a general
decrease in plasticity due to the fixation process.

Classification

     Because raw sludges and sludges fixed by process B are soil-like in tex-
ture, these sludges were classified according to the USCS; but the classifica-
tion of these sludges does not indicate that they are soils.  The sludges were
classified as ML, MH or SM, all silty soils (see Table 7), and exhibited prop-
erties similar to these soil types.  General statements concerning the proper-
ties of these soil types and of their behavior under a variety of field condi-
tions have been formulated on the basis of extensive experience and are sum-
marized in Tables 5 and 6.

Specific Gravity

     The specific gravities of raw and fixed sludges are presented in Table 8.
A total of 42 tests were conducted on samples of raw and fixed sludges.  Values
of specific gravity (Gg) were within the range of common minerals and soils as
shown in Figure 16.

     Values of Gg for the raw sludges varied from 2.41 to 3.96, a range extend-
ing somewhat higher than that of soils.  In general, the various fixation pro-
cesses caused only slight changes in Gs.  Process A resulted in either lower or
unchanged Gs values for all sludges.  Processes B, E, F, and G caused slight
changes, resulting in values both higher and lower than the Gs values of the
corresponding raw sludges.  Process C reduced the Gs of raw sludges 200 and 700
significantly.  Values were 34 or 51 percent lower respectively than those of
the corresponding raw sludges.  From these comparisons it seems that changes
in Gs do not seem to be dependent on the type of sludge processed, although
sludges 500 and 1000 experienced decreases in Gs for all fixation processes
tested.

     The Gs of fixed sludge D-200 reported in Table 8 is the bulk specific
gravity (Gfc), determined by dividing the total weight of the plastic cylinder
containing the sludge by the weight of an equal volume of water.  Since the
volume of the sludge mass includes void spaces, G^ is not  comparable to Gs.
In addition, the value for G^, of the test specimen of fixed sludge D-200 is
indicative of sludge D-200 only when the process involves  the same relative
proportions of sludge and plastic as the test specimen.  A variation of either

                                      35

-------
                TABLE 7.   PHYSICAL PROPERTIES OF RAW SLUDGES
                          AND SLUDGES FIXED BY PROCESS B

Sludge
R-100
R-200
R-300
R-400
R-500
R-600
R-700
R-800
R-900
R-1000
B-100
B-200
B-300
B-400
B-500
B-600
B-800
B-900
B-1000
D50
mm
0.016
0.015
0.044
0.029
0.016
0.009
0.016
0.022
0.020
0.0076
0.014
0.015
0.125
0.012
0.0074
0.011
0.022
0.023
0.016
LL
%
42
107
50
51
95
NP
201
37
NP
44
NP
98
NP
100
80
108
38
51
64
PL
%
36
58
37
38
67
NP
109
30
NP
37
NP
76
NP
85
70
100
33
47
57
PI
%
6
49
13
13
28
NP
92
7
NP
7
NP
22
NP
15
10
8
5
4
7
uses*
classification
ML
MH
MH
MH
MH
ML
MH
ML
ML
ML
ML
MH
SM
MH
MH
MH
ML
MH
MH

D,-n = median grain size

 LL = liquid limit

 PL = plastic limit

 PI = plasticity index

 NP = non-plastic

  * = Use of the USCS indicates only that sludges have properties similar to
      those of soils and does not mean that sludges are silts, sandy silts,
      etc.   See Tables 4-6 for description of soils in each classification.
                                     36

-------
CO
      300
      200 -
                100     2OO    300    400
                       LIQUID  LIMIT, LL
                 10       20      30      40
             D   RAW
             O   PROCESS B
                                                  50       60      70      80
                                                 LIQUID LJMIT, LL, %
120
          Figure 15.  Plasticity chart  for  raw sludges and sludges fixed by process B (see Table 4).

-------
                                     o
                                     o
                                      I
                                          BIOTITE
                                                      AUGITE
                     BAUXITE
                                                             TOPAZ


UJ
K ==
t a-m
_l -
i tao
1 1 II


g
a:
|

g
31INnOV»
9 a tw-a
1 1


QUARTZ
|
UJ
i
o
<
t_
g
a:
|
c
>
ON C
a: a
I


?g §g
3in r-i r-
i i i
:ce a: a:
1 III

UJ
Q
Ujg
Em
o-z.
U-I
1 1


o
•z.
o
o
1


AZURITE
1


SIDERITE
1


g
1

                                  SPECIFIC GRAVITY OF SOLIDS

1 TALC

I BIOTITE J

I BAUXITE |
UJ
t —
i_ n:^ o g oo o
— D- Cn S ooo o
<. a: > ' ' ' ' J.
, i ii i I i h I
UJ
5 y ¥
ggli ^g go
1 « ^ ^ i ( ^
^

• T If
OUJj^
i t
o ' =
§OC3^ O -
000 0-
*?r«< i*T « ^

"n 'n T
^
? ^J
5 t
— ^^
? o
1
<
o

g
rH
I
O
1

13
m
i
Ul
1
UJ
h-

E
O
_J
Q
a
_l 	 1
                                    SPECIFIC GRAVITY OF SOLIDS
Figure  16.
Specific gravities of  common minerals compared to those of raw

and  fixed sludges.


                              38

-------
                TABLE 8.  COMPARISON OF SPECIFIC GRAVITIES OF
                          RAW AND FIXED SLUDGESt
Specific Gravity
Fixation Process
Sludge
100
200
300
400
500
600
700
800
900
1000
Raw
2.41
2.70
3.96
2.51
2.85
2.53
3.09
2.82
2.76
2.99
A
2.41
2.49
2.71
2.47
2.57
2.52

2.67
2.58
2.45
B C
2.58
2.73 1.77
3.68
2.35
2.74
2.57
1.74
2.84
2.73
2.84
D E F G
2.54 2.70
1.18*

2.55 2.49
2.72 2.50
2.57 2.46 2.41



2.61 2.44

Note:  Blank spaces indicate processors did not fix that sludge.   See
       Table 2.

* Bulk specific gravity of entire cylinder of fixed sludge, including plastic
  coating and voids within sludge structure.

T This Table presents corrections to data presented in Tables 13  and 14 of
  Reference 1.
                                     39

-------
the specimen volume or the thickness of the plastic coating will result in
different values of G, , due to the dissimilarity of the sludge and the plas-
tic.                 b

Moisture-Volume-Weight Relationships

Water Content—

     The water contents (w) of samples of fixed sludge were determined and
are listed in Table 9.  These data indicate that the relative amount of
available interstitial water after fixation is greatly process-dependent.
Sludges fixed by process B exhibited values of w comparable to those of
natural soils.  Processes A, C, E, F, and G produced fixed sludges with a
wide range of properties.  These fixed sludges were plastic or rubber-like
masses or hard materials resembling concrete.  The conventional w determina-
tion has little meaning for such materials.  The w of the sludge portion of
sample D-200 is unknown because the plastic coating on the sample prevents
the escape of any water from within the sludge mass.

Void Ratio and Porosity—

     Values for the void ratio (e) and the porosity (n) of the fixed sludges
are presented in Table 9.  The results are also presented in a comparison
graph in Figure 17.  The data indicate that the e and n of the fixed sludges
are process-dependent.  Processes A, C, E, and F resulted in fixed sludges
whose e values vary between 0.601 and 1.418, corresponding to n values be-
tween 37.5 percent and 58.7 percent.  These values are comparable to those of
fine sa'nds, silts, and silty clays.  Processes B and G resulted in fixed
sludges whose e values range between 1.617 and 3.857, corresponding to n
values between 61.8 percent and 79.4 percent.  These values are in the range
of values typical of soils with significant amounts of small clay particles.
The e and n of fixed sludge D-200 were not determined because the value of G
was not known.  Values of e and n for the sludge mass inside the plastic
coating would be meaningless because they would not be representative of the
fixed sludge as a whole, which includes the plastic coating.

Bulk and Dry Unit Weight—

     The bulk and oven-dry unit weights (y  and y ,, respectively) of the fixed
sludges were determined and are presented in Table 9-  Processes A and B
yielded materials whose y,  values are in the range typical of soils and whose
Yb and yd values differ, as would those of soils.  The remaining processes
resulted in materials having smaller differences between y, and y , in some
cases showing very little difference.  This is again indicative of process-
dependence.   The laboratory values of y,  and y, for sludge fixed by process
D were of course identical because the plastic coating prevented water from
escaping from within the sludge mass.

ENGINEERING PROPERTIES

Compaction
                                     40

-------
               TABLE 9.  PHYSICAL PROPERTIES OF FIXED SLUDGES*
Sludge
A-100
A-200
A-300
A-400
A-500
A-600
A-800
A-900
A-1000
B-100
B-200
B-300
B-400
B-500
B-600
B-800
B-900
B-1000
C-200
C-700
Specific**
gravity
2.41
2.49
2.71
2.47
2.57
2.52
2.67
2.58
2.45
2.58
2.73
3.68
2.35
2.74
2.57
2.84
2.73
2.84
1.77
1.74
Water
content
%
23.8
29.7
20.6
24.2
41.4
15.6
15.8
20.9
23.7
77.5
83.6
97.2
69.5
67.3
88.9
30.3
63.3
70.9
43.2
45.6
Void
ratio
0.860
1.008
0.963
0.768
1.377
0.663
0.881
1.418
0.958
2.711
2.595
3.857
1.794
2.150
2.811
1.181
2.225
2.717
1.097
1.409
Porosity
%
46.2
50.2
49.0
43.4
57.9
39.9
46.8
58.7
48.9
73.1
72.2
79.4
64.2
68.3
73.8
54.1
69.0
73.1
52.3
58.5
Bulkf
unit
weight
lb/ft3
100.1
100.4
103.9
108.3
95.5
109.3
102.6
85.9
96.6
77.0
87.1
93.2
89.0
90.8
79.6
105.9
86.2
81.5
75.4
65.7
Dry
unit
weight
lb/ft3
80.9
77.4
86.2
87.2
67.5
94.6
88.6
66.6
78.1
43.4
47.4
47.3
52.5
54.3
42.1
81.3
52.8
47.7
52.7
45.1
D-200

E-100
E-400
E-500
E-600
E-1000

F-600
1.18

2.54
2.55
2.72
2.57
2.61

2.46
                tt
                              73.6
 6.4
 8.7
 6.5
10.7
 0.7
 3.7
0.671
1.072
0.822
0.601
0.987

0.996
40.2
52.2
45.1
37.5
49.7
101.
 82.
 99.
49.1
110.9
 82.7
 81.0
                                 73.6
 94.9
 76.
 93.
100.
 82.0
 78.1
G-100
G-400
G-500
G-600
G-1000
2.70
2.49
2.50
2.41
2.44

10.7
7.6
13.3
17.0

1.737
2.198
1.991
1.617

63.5
68.7
66.6
61.8

62.7
52.5
56.9
68.1

56.8
48.8
50.3
58.2
*   Tests conducted using 60 C oven for drying; this Table presents
    corrections to data presented in Tables 13 and 14 of Reference 1.
**  Value determined using one sample, all others are average for three
    samples.
t   Sample air-dried prior to determination of unit weight.
tt  Bulk specific gravity of entire cylinder of fixed sludge including plastic
    coating and voids within sludge structure.
NOTE:  The water content, void ratio and porosity of sample D-200 could not
       be determined because the sample was sealed in plastic.
                                     41

-------
                                                    POROSITY, %
M
3

33


50 60 67
l i i

OTTAWA SAND



| UNIFORM SILT

>

1


1 II II








SANDY OR SILTY CLAY |


WELL GRADED
GRAVEL, SAND,
SILT, CLAY MIXES















CLAY (30-50% CLAY SIZES)


m
i
1







COLLOIDAL CLAY •
m
t
0.5
£
rr
c
m
.0
\
]j
5
o
o
\
1 O
ij ,
> ' m
>
1
*
u
c
c
>
)
•) <
1 \
•> c
11





71 75 78 80

^

> i
> .
3 C
3 C
1 C
1 \
~) C
5C
c
3 C
?
n
3
3
Cl
I
CD
I
	 ,.., ! !
1.0 1.5 2.0
VOID RATIO
^"
c
c
c
<


1
TO 12 ^
a t
3 <
3 (
3
D 0
1 \
1
J
i
3D
jt
D
D
1 1 1 1
2.5 3.0 35 4.0
           Figure 17.  Void ratio  and  porosity of common soils compared to those of fixed sludges,

-------
     The 15-blow compaction.test was  conducted on nine sludge samples fixed
by process B to determine the moisture-density relationships of the fixed
sludges and test results are presented  in Figure 18.  Values of the optimum
water content  (OMC) at which maximum  Y
-------
 80
                   B-800
  70
                                     B-300
H
X
UJ
a:
o
 -60
                                                B-900
  50
                                                         B-1000
                            B-200
  40
                I
                                                                  B-100
                                                                     B-600
    20
               35
95
                    50         65          80
                      WATER  CONTENT,  %
Figure 18.   Compaction curves for sludges fixed by process B.
                             44
110

-------
Ol
                   .1000
                                                                      F.500
                      1.0     1.5
                      AXIAL STRAIN, %
1.0      1,5
 AXIAL STRAIN,
                            Figure 19.   Composite  stress-strain  curves  for fixed sludges.

-------
  50 i-
  40
UJ
K
  30
8
UJ
tt
0.
  20
  10
           B-400-,
             1         2

                 AXIAL STRAIN, '
                                                     50
                                                     40
                                                     30
                                                   111
                                                   C
                                                   H
                                                   g 20

                                                   a
                                                     10
                                                                         B-500
                                                                                    e-900
                                                                                   a-300
                                                                                     I
                                                                           2       "  3


                                                                        AXIAL STRAIN, %
                            2000
                            1500
                          HI
                          o:
                          >  1000
                          UJ
                          a:
                          c.
                          5
                          o
                          o
                             500
                                                               D-200
                                              AXIAL STRAIN, %
           Figure  20.   Composite stress-strain curves  for  fixed sludges.
                                               46

-------

                                     A 1000
Figure 21.  Photographs of specimens after unconfined  compression test,  FGD
            sludge fixed by process A.

                                     47

-------

Figure 22.  Photographs of specimens after unconfined compression test, indus-
            trial sludge fixed by process A.


-------


Figure 23.   Photographs of specimens after unconfined compression test, FGD
            sludge fixed by process B.
                                     -

-------
                                     B 300

                                     B 800
                                     B 900
Figure 24.  Photographs of specimens  after  unconfined compression test, indus-
            trial sludge  fixed  by  process B.

-------
Figure 25.  Photograph of specimen during unconfined compression test, indus-
            trial sludge  (200) fixed by process D.
                                    E-600
Figure 26.  Photograph of specimens after unconfined compression test, FGD
            sludge fixed by process E.
                                       i

-------




Figure 27.  Photographs of specimens after unconfined compression test,  FGD
            sludge fixed by process G.
                                     5 2

-------
   6.0
    1.0
 V)
 
-------
           TABLE 10.  CHANGES IN DRY UNIT WEIGHT AFTER COMPACTION
                      OF SLUDGES FIXED BY PROCESS B^


Sludge
B-100
B-200
B-300
B-400
B-500
B-600
B-800
B-900
B-1000

Without
compaction
Ib/ft3
43.4
47.4
47.3
52.5
54.3
42.1
81.3
52.8
47.7
Dry unit weight*
Maximum
after
compaction**
lb/ft3
42.9
50.2
76.0
56.9
51.5
41.9
74.1
60.0
50.5

Change
due to
compaction
lb/ft3
-0.5
+2.8
+28.7
+4.4
-2.8
-0.2
-7.2
+7.2
+2.8
Optimum
water
content
%
82.5
73.0
46.0
47.0
65.0
89.5
37.0
50.5
73.5

*   Drying performed in 60 C oven.

**  15-blow compaction test, 7400 ft-lb/cu ft compactive effort.

t   This Table presents corrections to data presented in Tables 13 and 14
    of Reference 1.
                                     54

-------
            TABLE 11.  SUMMARY OF UNCONFINED COMPRESSION TEST DATA
Sludge
A-100
A-200
A-300
A-500
A-600
A-800
A- 900
A-1000
B-100
B-200
B-300
B-400
B-500
B-600

B-800
B-900
B-1000
C-200
C-700
D-200f
E-100
E-400
E-500
E-600
E-1000
F-600
G-400
G-500
G-600
G-1000
Initial
dry unit
weight
Ib/cu ft
80.9
77.4
86.2
67.6
94.6
88.6
71.1
78.1
41.7
60.5
74.6
65.4
58.3
44.2

83.9
62.2
53.5
52.7
45.1
69.1
95.0
82.7
93.3
100.3
82.7
69.6
56.8
48.8
50.3
58.2
Undralned
shear
strength*
Ib/sq in








11.85
16.23
3.98
22.28
21.37
17.66

10.82
12.34
11.62













Unconfined
compressive
strength
Ib/sq in
100.28
77.39
169-14
188.32
403.08
133.73
26.28
337.40
23.71
32.47
7.96
44.59
42.74
35.32

21.64
24.68
23.23
747.33
308.66
1542
2574
719-33
2200.67
4486.70
1374
395.66
242.56
86.36
126.07
144.25
Modulus
of
elasticity
Ib/sq in
1.10 x 104
1.45 x IQ,
2.55 x 10,
3.03 x 107
7.50 x 107
2.30 x 10,
2.34 x 10^
1.10 x 10
3.57 x loi?
3.03 x 10^
3.61 x 10,
3.64 x 10^
1.00 x 10,
3.39 x 10,
X
1.23 x 10,
1.16 x 10,
1.10 x 10
7.69 x lot
3.46 x 10
1.92 x 105
4.50 x 10^
1.26 x io;j
3.10 x KT
1.67 x 10,?
2.45 x 10
5.00 x 104
9.10 x 104
1.59 x 10,
1.64 x 107
5.28 x 10
*  Taken as one-half unconfined compressive strength.  Significant for soil-
   like sludges only.  Blank spaces indicate non-soil-like sludges.

t  Results meaningful only for material of same construction as test specimen.
   Larger or smaller samples require individual testing.
                                      55

-------
process B ranged from medium to hard in consistency.  In general, all fixed
sludges should perform satisfactorily as embankment construction material,
and bearing capacities should prove adequate for most general landfill ap-
plications (see Section 6).

           TABLE 12,  CONSISTENCY OF CLAY IN TERMS OF UNCONFINED
	COMPRESSIVE STRENGTH (FROM REFERENCE 6)	

                                            Unconfined compressive strength
Consistency                                            Ib/sq in

Very soft                                              < 3.5
Soft                                                     3.5-7
Medium                                                   7-14
Stiff                                                   14-28
Hard                                                    28-56
Very hard                                                > 56
Permeability

     Using the test procedures cited in Section 4, the coefficients of per-
meability  (k) of raw and fixed sludges were determined.  Table 13 presents
the data from the permeability testing of raw sludges and shows that k ranged
from 1.257 x 10~6 to 1.033 x 10~^ cm/sec.  Table 14 lists the physical prop-
erties and values of k of the samples of fixed sludges.  Values ranged from
4.540 x 10~H to 7.935 x 10~^ cm/sec, a great variation.  Raw sludges can be
described as having low permeability, while most fixed sludges have low to
very low permeability.  A few fixed sludges were practically impermeable
(k <_ 10"' cm/sec) and one (D-200), because of the plastic coating, was abso-
lutely impermeable to water; and no permeability tests of this fixed sludge
were run.  In the following paragraphs the influence of e and y^ on the per-
meability of raw and fixed sludges are discussed, as is the dependence of
permeability on the fixation process.  Also, the values of k of fixed sludges
are compared with those of soil and concrete.

     The discussion of permeability presented below is predicated on the
assumption that the sludge test specimens are representative of anticipated
field conditions.  The most significant considerations are of the effects of
discontinuities and incomplete saturation.  If the sludge is placed as a mass
of chunks or becomes cracked, the permeability will be greatly affected.  The
other consideration is the degree of saturation of the material.  The fixed
sludge samples could not be completely saturated during the test procedure,
which included 10 Ib/sq in differential pressure.  Complete saturation of
fixed sludge requires an extremely large hydraulic head and/or an exceedingly
long period of time, and might never be accomplished in the field.  Complete
saturation would be expected to result in a slight increase in permeability.

Influence of.Dry Unit Weight and Void Ratio—

     The permeability of porous media is known to be influenced by the size
of the pore spaces through which liquid can flow. >b»°  Two parameters, Yd


                                     56

-------
         TABLE 13.   SUMMARY OF PERMEABILITY TEST DATA FOR RAW SLUDGES

Percent
solids
Sludge %
R-100 54.8
63.1
R-200 33.8
39.5
R-300 43.1
46.1
R-400 51.1

59.8
R-500 59.2
45.0
R-600 69.9
77.5
R-700 36.9
45.5
R-800 60.2
62.5
R-900 43.9
50.3
R-1000 40.5
42.4
* All drying done

Water
content*i
%
82.5
58.6
194.9
153.0
132.3
116.8
95.7

67.0
145.6
121.6
43.0
29.4
171.4
119.2
119.2
60.3
128.2
98.7
146.5
136.1
in 60 C oven.
Samples were tested, densified
t Dry weight basis
•
Dry
unit
weight*
Ib/cu ft
58.8
64.4
28.1
36.1
43.9
54.9
57.9

70.1
30.3
36.0
86.9
103.6
27.7
33.5
64.0
73.2
46.8
53.1
43.2
48.9
Note two
, retested



Void
ratio
1.559
1.336
4.998
4.334
4.631
3.503
1.706

1.235
4.872
3.942
0.818
0.525
5.964
4.758
1.751
1.405
2.682
2.245
3.321
2.817
sets of data

Coefficient of
permeability #
cm/ sec
3.610 x 10"*
1.070 x 10~3
3.152 x 10':?
1.257 x 10
5.761 x 10"!?
1.318 x 10
9.498 x 10"*
M.n
7.784 x 10
4.373 x 10"*
2.505 x 1Q"3
2.013 x 10"*
1,439 x 10
6.557 x 10"!?
3.391 x 10"°
1,033 x 10"
8.165 x 10"3
3.524 x 10"*
2.834 x 10
8.461 x 10"*
6.536 x 10"3
for each sludge.
See Section 4.


# Corrected for water at 20 C.
**  Value questionable because flow restriction caused by sample support
    system may have influenced flow through sample.
                                      57

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        TABLE 14.  SUMMARY OF PERMEABILITY TEST DATA FOR FIXED SLUDGES

Sludge
A-100
A-200
A-300
A-500
A-600
A-800
A-900
A-1000

B-100
B-200
B-300
B-400
B-500
B-600

B-800
B-900
B-1000

C-200

C-700
D-200

E-100
E-400
E-500
E-600
E-1000
F-600
G-400
G-500

G-600
G-1000
Percent
solids
78.1
71.4
82.0
67.6
86.2
77.0
83.3
78.1

82.0
64.6
69.5
82.6
65.4
59.2

71.4
66.7
58.1

65.7

60.6
100.0

77.0
91.0
75.2
80.0
90.1
97.0
93.5
98.4

91.7
63.7
Water
content*t
28.3
40.6
22.4
47.8
16.1
30.2
19.5
27.8

21.9
55.6
43.7
21.2
52.7
68.8

39.9
49.8
71.9

52.1

64.7
0.0

30.9
11.3
33.4
24.7
10.4
3.7
7.7
2.9

9.1
56.8
Dry
unit
weight*
Ib/cu ft
76.9
73.2
84.3
62.3
92.5
82.4
68.0
73.7

60.0
52.9
73.7
63.7
54.2
44.4

71.4
61.5
45.1

38.4

36.5
73.6

81.0
72.5
77.9
88.3
77.3
78.1
53.1
50.6

53.0
54.0
Void
ratio
0.956
1.124
1.007
1.575
0.701
1.023
1.369
1.075

1.684
2.215
2.117
1.303
2.156
2.613

1.483
1.771
2.931

1.877

1.926


0.958
1.196
1.180
0.881
1.108
0.966
1.927
2.084

1.837
1.821
Coefficient of
permeability #
cm/ sec
2.057 x 10~,
4.039 x 10~'
_h
1.913 x 10 °
1.124 x 10~'
4.308 x 10~1
8.525 x 10~'
3.847 x 10 7
8.953 x 10
-A**
1.590 x 10
1.117 x 10~?^*
1.893 x 10~
1.082 x 10 ^
4.563 x 10 ;?
3.968 x 10 ;?
— S
3.617 x 10 ,
8.735 x IQ ,
6.625 x 10 5
-A**
1.148 x 10 ...
— ft 5RT7C
1.602 x 10
Impervious
_A**
7.935 x 10 ,
2.518 x 10 *
4.540 x 10 3
3.571 x 10
7.328 x 10
5.007 x 10~6
5.241 x 10~*
1.388 x 10 ~7 ..
—A X7C
1.224 x 10
4.047 x 10"°

*   All drying done in 60 C oven.

t   Dry weight basis.

#  Corrected for water at 20 C.

tt  Sample D-200 encapsulated in impervious plastic.

**  Value questionable because flow restriction caused by sample support
    may have influenced flow through sample.
                                     58

-------
and e, are used  to  describe  the pore  size  of  the  sludges.   Increasing values
of y  are indicative  of pore volume reduction,  and  therefore  of decreasing k,
while increasing values of e show increasing  pore volume and  increasing k.

     Raw sludges—Figures 29a  and 29b show the  relations between e and k, and
between Yd and k, respectively, for samples of  raw  sludge.  These plots show
that decreasing  pore  volume, as indicated  by  increasing y   and decreasing e,
was indicative of decreasing k.   Figure  29b also  shows that the values of k
of the raw sludges  are comparable to  those of loess and silty sand, although
the values of YJ of these soils are higher than those of most raw sludges.
The figure also  suggests that  compaction of the raw sludges to 100 Ib/cu ft
could reduce k to values near  those of the sandy  silt, although insufficient
data  exist to make a confident prediction.

     Fixed sludges—Figures  30a and 30b  show  the  relations  of e and y, with
k for sludges fixed by process A  or B.   The figures show that the samples of
sludge fixed by  process A were generally more dense and less  permeable than
were the sludges fixed by processes.   The  values  of k for sludges fixed by
process A ranged,from 1.124  x  10,  to 3.847 x 10~5  cm/sec, while k ranged
from 8.735 x 10   to  1.893 x 10    cm/sec for  sludges fixed by process B.
Collectively, the sludges fixed by process A  or B generally are less per-
meable with smaller pore size.  Separately, however, neither  process
exhibited such a trend.

     Figures 31a and  31b show  the relations of  e  and YJ with  k for sludges
fixed by process C, E, F, or G.   Since only a few samples of  sludge fixed by
each of these processes were tested,  no  process-dependence  is well-defined.
The .values of k  for the two  samples of sludge fixed by process C were 1.148 x
10   and 1.602.x 10  cm/sec.  The range of k for sludges fixed by process E
was 4.54 x 10    to 7.935 x  10 ,  and for  sludges fixed by process G, k
ranged from 4.047 x 10~  to  1.388 x 10  cm/sec.  Single samples of sludge
were fixed by process D or F.  Fixed  sludge sample,D-200 was  impermeable
(k = 0), and the k  of sludge F-600 was 5.007  x  10  .

     Taken collectively the  fixed sludges  exhibit some evidence of the in-g
fluence of pore  size  on permeability  at  values  of k greater than about 10
cm/sec.  As was  the case with  the total  group of  sludges fixed by process A
or B, decreasing pore sizes  generally correlated  with lower values of k.
There are insufficient data  to assess the  influence of pore size on k for
each fixing process,  but sludges  fixed by  process E are noteworthy.

     Sludges fixed  by process  E exhibited  a wide  range of k,  with no notice-
ableinfluence by either j,  or e.  The permeability of sludge E-500 (k = 4.54
x 10    cm/sec)  is  comparable  to  that of concrete,  whose k  is typically on
the order of 10     cm/sec.   Sludge 500 was the  least permeable of the sludges
fixed by process A, as well; but  since the permeabilities of  R-500 and B-500
were not the lowest in their respective  categories,  the occurrence of sludge
500 as the least permeable of  the  fixed  sludges is  process-dependent and is
of little practical significance.

DURABILITY
                                      59

-------
     o


     a-
     §  3
       120
     .JOO
     «•-


     •ie
     i 80
     o
       60
       40
       20
                                    i  i 11111	i   i
                                                                                   I   i  i i  i i I
                          10-7
    10-6               IO"5

COEFFICIENT  OF PERMEABILITY, cm/sec
              NOTE: Data for three types of

                   soil are from Cedergren,8
                     • RAW SLUDGE



                     O SOIL TYPE
                                                                                   „*..».*;
                          10-7               10-6              ICT3

                                     COEFFICIENT OF PERMEABILITY, cm/«ec
Figure 29.   Influence  of  pore size  on  the  permeability  of  raw sludges,



                                               60

-------
    IE
    O
    >
     120
     100
    *-

    1

    K*80
     60
     40
     20
            O—O  PROCESS A
               Q  PROCESS B
                                                        D
        10"
                                       |0~6             10-*
                                 COEFFICIENT OF PERMEABILITY, cm/ICC
                                                        10
                                                                        ,-4
            O—O PROCESS  A
               Q PROCESS  B
            III
        10-7
                            '   II I  I I II
                                            I   I  I  I I I III
                                       10-6              10-5
                                 COEFFICIENT OF PERMEABILITY, cm/sec
                                                                       10-4
Figure  30.
Influence of pore size on  the  permeability  of sludges fixed by
process  A or B.
                                            61

-------
N3
  0


 120



 100



I 80


f-"
5 60
UJ


I 40

i

 20
                                  & PROCESS  C
                                  • PROCESS  E
                                  • PROCESS  F
                                  A PROCESS  6
                                             to-'
& PROCESS C
• PROCESS E
• PROCESS F
A PROCESS 6
                                lO-io
                                             ID"9
                         10-'           IO'7           KT6
                              COEFFICIENT  OF PERMEABILITY, cm/sec
                                                                                                 10-'
                                                                                                               A
                                                 10-'           »-•
                                         COEFFICIENT OF PERMEABILITY, cm/iec
                        Figure  31.   Influence of pore  size  on  the  permeability of sludges  fixed by
                                       process  C, E, F,  or G.

-------
     To  determine the relative durability of the fixed  sludges, samples were
subjected  to  the  wet-dry tests and freeze-thaw tests  described in Section 4.
In  the following  paragraphs,  the test results and the influence of k and
strength on durability are discussed.  The term durability  refers to the
ability  of a  material to resist natural weathering stresses simulated by re-
peated cycles of  either wetting and drying or freezing  and  thawing.

     The time span simulated  by the test procedures is  not well defined.  The
12  test  cycles of freeze-thaw could simulate 12 years'  exposure to the ele-
ments, but the freezing and thawing of a thin lift of sludge could conceivably
occur on each of  12 consecutive days.  The same sort  of argument could be
made regarding the wet-dry test.   Both tests are useful for determining the
effect of  different fixation  processes on the durability of sludges, but
neither  test  is suitable for  estimating the performance of a fixed sludge mass
in  the field.

     Prediction of the long-term stability of fixed sludge subjected to the
environment is also hampered  by the lack of field experience.  Correlations
between  durability test data  and field performance for  stabilized soils are
scarce,  and such  correlations for fixed sludge are non-existent.  Careful
monitoring of fixed sludge landfills is required to develop relations between
laboratory testing and field  performance.   Due to these limitations the dura-
bility of  fixed sludge is discussed only in terms of  factors affecting test
response and  in comparing fixation processes.   The fixed sludges that with-
stand the  effects of durability testing with the least  amount of ill effect
are expected  to be the most durable in the field, but no estimate of actual
performance on the basis of laboratory testing is appropriate without field
verification.

Wet-Dry  Test  Results

     The results  of the wet-dry tests are presented in  Table 15 and Figure
32a as either percent of specimen weight lost after 12  test cycles or as the
number of  cycles  required to  disintegrate the specimen.  Photographs of some
of  the test specimens after 4 and 12 test cycles are  shown in Figures 33 and
34, respectively.   Most specimens disintegrated after fewer than 12 cycles,
with 9 specimens  failing during the first cycle.   Seven of the 30 specimens
tested remained intact after  12 cycles and the percent  of specimen weight
loss ranged from  0.00% to 41.70%.   The 4 specimens of sludges fixed by pro-
cess E all survived the test, as did the only specimen  of sludge fixed by
process  D.  The 12 test cycles did not result in the  removal of a measurable
amount of  material from the specimen of sludge fixed  by process D, which in-
dicates  only  that the plastic coating was not damaged during the test.  One
sludge fixed  by process A survived,  but that specimen experienced the loss of
41.70% of  its original weight.

Freeze-Thaw Test  Results

     Table  15 and  Figure 32b  present the results of the freeze-thaw tests.
Nineteen of the 22  specimens  failed during the test,  14 of these within the
first 2 cycles.   The  percent  weight  loss of the 3 specimens remaining intact
ranged from 0.00%  to  28.65%.   As  with the wet-dry test, sludge 200 fixed by

                                       63

-------
           TABLE 15.  SUMMARY OF DURABILITY TESTING OF FIXED SLUDGES

Percent wt. loss
after 12 test
cycles*
Sludge Wet-dry Freeze thaw
A-100
A-200
A-300
A-400
A-500
A-600
A-800
A-900
A-1000 4l.70t
B-100
B-200
B-300
B-400
B-500
B-600
B-800
B-900
B-1000
C-200
C-700
D-200 0.00 0.00
E-100 I5.80t
E-400 IS.OOt
E-500 10.85t 26.65t
E-600 21.05t
E-1000 6.60t 18.30t
F-600
G-400
G-500
G-600
G-1000
Number of
wet-dry
test cycles
to fail*
3
5
9
1
6
10
7
1

1
2
1
1
2
3
2
1
1
1
1






6
5
5
7
7
Number of
freeze-thaw
test cycles
to fail*
2



6


1

1
1
1
1
1
2
1
2
1
12
12

10
7



4
2


2

*  One test specimen unless otherwise noted.

t  Average value for two specimens.

Note:  Data reported as number of test cycles to fail or weight loss after 12
       test cycles (e.g. E-100, 15.80% weight loss after 12 wet-dry cycles and
       disintegration after 10 freeze-dry cycles).

                                      64

-------




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                                   PROCESS
    *  SAMPLE  DID NOT FAIL
       AFTER  12 TEST  CYCLES
FREEZE - THAW




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                                                                   BEG
     Figure  32.   Summary  of durability  testing  of fixed sludges,

                                    65

-------

Mk-
          SLUDGE TESTING
             E- 100
          SPECIMENS  1-3
                     '
SLUDGE TESTING
    E-300
SPECIMENS 1-3
         SLUDGE TESTING
             E- 4OO
         SPECIMENS  1-3

SLUDGE TESTING
   E-1000
SPECIMENS  1-3
SLUDGE TESTING
    C-200
SPECIMENS  1-3
SLUDGE TESTING
    C- 700
SPECIMENS  1-3
                                                                                                        v.>> -%

                      Figure 33.   Photographs  of  test specimens after 4 wet-dry test
                                   cycles, sludges fixed by process C or E  (from Reference  1).

-------
   .'
SPECIMEN
    (
SPECIMEN
   2

 E-100
SPECIMEN
   3
SPECIMEN
   1
SPECIMEN
   2
SPECIMEN
   3
SPECIMEN
   1
SPECIMEN
   2

 E-500
SPECIMEN
   3
SPECIMEN
1

SPECIMEN
2
C-200
SPECIMEN
3

SPECIMEN
t

SPECIMEN
2
C-700
SPECIMEN
3

SPECIMEN
1

SPECIMEN
2
E-1000
SPECIMEN
3


              Figure  34.   Photographs of  test  specimens after 12 wet-dry test cycles,
                           sludges fixed by  process C or E  (from Reference 1).

-------
process D exhibited no measurable weight loss from testing, again indicative
of the durability of the plastic coating.  Process E was the only other pro-
cess that produced fixed sludge capable of withstanding 12 freeze-thaw cycles
without disintegration.

Comparison of Test Severity

     The freeze-thaw test was expected to be more severe on the test speci-
mens because cycles of freezing and thawing are known to be more severe on
soil than are wet-dry cycles.   In general freezing and thawing had a more
harmful effect on the fixed sludges than did wetting and drying; fewer test
cycles were usually required to disintegrate the specimen by freezing and
thawing than by wetting and drying.  Sludges surviving both tests lost more
weight during the freeze-thaw test than during the wet-dry test.  A notable
exception to this trend, however, was sludge 200 fixed by process C.  Two
specimens survived until the 12th freeze-thaw cycle, but did not survive the
first cycle of wetting and drying.  This performance is process-dependent; no
other sample exhibited such a significant trend reversal.

Influence of Permeability and Compressive
Strength on Durability

     Since water is allowed to enter and exit the test specimen during each
of the two types of durability test, the permeability of the test specimen
should influence the test results.  In addition, since each test is designed
to evaluate the ability of the material tested to resist stress, sludges with
high strength were expected to be more durable than those with low strength.
In the following paragraphs, the influences of permeability and unconfined
compressive strength on durability are discussed.

     An investigation of the influence of permeability or compressive
strength on durability requires that durability tests be conducted using sam-
ples of fixed sludge that differ only in permeability or compressive strength,
respectively.  Since multiple test specimens of fixed sludges (e.g., the sam-
ples of A-100), were not identical, only specific statements consistent with
the test data are appropriate; and these statements must not be extrapolated
for application to all fixed sludges.  The influence of permeability and com-
pressive strength are discussed below on the basis of the data generated by
the testing of samples not grossly different* and must be viewed with caution.

Influence of Permeability—

     Wet-dry—Figure 35 shows the influence of permeability on the percent
weight loss during 12 wet-dry test cycles on samples of sludge fixed by pro-
cess E.  Process E was the only process that resulted in more than one fixed
sludge capable of surviving 12 wet-dry cycles without disintegration; and,
as Figure 35 shows, the durability of sludges fixed by process E was not a
function of permeability.  In Figure 36 the influence of permeability on the
number of wet-dry test cycles the fixed sludges were able to withstand is


*Specimens whose dry unit weight differed by more than 10 Ib/cu ft were con-
 sidered grossly different.

                                      68

-------
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i 1 1 1 1 1 1 1
)-" KT10 »-* KT" K)'7 ID"' IO"5 I0~* KT
                                                  COEFFICIENT OF PERMEABILITY, cm/Me
              Figure  35.   Influence of permeability on the  durability of  sludges fixed  by process E.

-------
   PROCESS  A
   PROCESS  B
   PROCESS  E
   PROCESS  G
      WET-DRY
	FREEZE-THAW
                                                             I   i I  I I I I
                                           I  I  I  I I I
I   I   I I  I I II
                        COEFFICIENT  OF  PERMEABILITY, cm/sec
      Figure 36.   Influence of permeability on the durability  of fixed sludges.

-------
shown.  Although there is considerable scatter in the data, the durability of
sludges fixed by process A generally increased with decreasing permeability.
Permeability apparently did not influence the durability of sludges fixed by
process B or G.

     One sample of sludge fixed by process D was subjected to the wet-dry
test, and this sample experienced no weight loss during the test.  This ex-
ceptional durability is attributed to the nature of the fixed sludge, which
was coated with plastic.  Since the fixed sludge is absolutely impermeable,
or waterproof, wetting and drying have no effect on sample integrity.

     Freeze-thaw—Figure 36 shows the influence of permeability on the dura-
bility of sludges fixed by processes A, B, and E.  Decreasing permeability
generally indicated increasing durability for sludges fixed by process A,
showed decreasing durability  for sludges fixed by process E, and had no in-
fluence on sludges fixed by process B.  The influence of permeability on the
resistance of fixed sludges to freeze-thaw cycles seems to be process-depen-
dent, but more data are required to substantiate this.

     As in the case of the wet-dry test, fixed sludge D-200 showed no meas-
urable loss in weight during  the freeze-thaw test.  The resistance of this
sludge to freeze-thaw cycles  is attributed to the durability of the plastic
coating.  In addition, since  the process includes drying the sludge prior to
encapsulation, little water exists within the sludge mass to expand and break
the plastic coating.

Influence of Compressive Strength—

     Wet-dry—The influence of compressive strength on the resistance to
wet-dry cycles is shown in Figure 37a for sludges fixed by Process E.  Pro-
cess E was the only process resulting in more than one fixed sludge capable
of surviving the wet-dry test without disintegration, and the effect of com-
pressive strength on percent weight loss is not well-defined, although a
trend toward decreasing durability with increasing compressive strength is
suggested.

     For the samples that did not survive the wet-dry test, those sludges
fixed by processes A, B, or G (Figure 37b), the erratic data suggest that
durability increased with compressive strength, opposite of the trend of
sludges fixed by process E.

     Freeze-thaw—Two samples of sludge fixed by process E survived the
freeze-thaw test without disintegration, and the effect of compressive
strength on their durability  is shown in Figure 37a.  As with the wet-dry
test, stronger (higher compressive strength) sludges fixed by process E were
less durable than weaker sludges fixed by this process.

     For the fixed sludges that disintegrated during the freeze-thaw test,
the effect of compressive strength on durability is shown in Figure 37c.
Sludges fixed by processes A or E were generally more durable with increasing
compressive strength, while the durability of sludges fixed by process B
or G was not influenced by compressive strength.

                                      71

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                 5>
                 5 8
                 O 6
                 O

                 3
                 >- 4
                 u.
                 O
                 E
                 Ul
                          O PROCESS A
                          Q PROCESS B
                          & PROCESS C
                          A PROCESS Q
                          	 WET-DRY
                                     10               100              1000
                                    UNCONFINED COMPRESSIVE STRENGTH,  Ib/iq in
                                                                                     10000
1
                 fe
                 tr
                  60
                 iso
                 U40
                 t
                 <3
                 3
                 3
                  20
                  10
                                                             ^	&
                          O PROCESS A
                          Q PROCESS B
                          & PROCESS C
                          • PROCESS E
                          A PROCESS 6
                          	FREEZE-THAW
                                                 .
                                   Q	—-£30T3 G3
                                    10               100              1000
                                     UNCONFINEO COMPRESSIVE STRENGTH, Ib/sq in
                          • PROCESS E
                          	— WET-DRY
                          	FREEZE-THAW
                                    10                100              1000
                                     UNCONFINED COMPRESSIVE STRENGTH, lb/«q in
                                                                                     10000
                                                                                     10000
Figure  37.    Influence  of  compressive strength  on the  durability of fixed
                 sludges.
                                                  72

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                                  SECTION 6

                          DISPOSAL OF FIXED SLUDGE

      In this section experience with the behavior of soil and other materi-
als with laboratory properties similar  to those of fixed sludge is used as
the basis for a discussion of the disposal of fixed sludge.  The discussion
in this section is concerned with the disposal of fixed sludge only.  The
discussion is brief and somewhat speculative because of the lack of informa-
tion on the performance of fixed sludge in the field.

      The discussion is limited to the  use of fixed sludge for landfilling
and embankment construction.  Using  fixed sludge for land reclamation (land-
fill) could increase the economic value of marginal land by increasing its
suitability for productive use, and  the substitution of fixed sludge for soil
in embankment construction would reduce the requirements for soil with which
the embankment would otherwise have  been constructed.  The use of fixed
sludge for landfilling and embankment construction requires that factors in-
cluding compaction, bearing capacity, consolidation, and slope stability be
considered; and these factors are discussed below.

COMPACTION

      Fixed sludge will generally not require compaction, and all but sludges
fixed by process B or F are too hard to be compacted by conventional methods.
Compaction may be required, however, to reduce the void spaces.  Fixed sludges
often have cracked (process B) or honeycombed structures (processes A, C, E,
F, and G) , and compaction may be an  effective method for making a sludge mass
more continuous.

Compaction of Soil-Like Fixed Sludge

      Sludges fixed by process B or  F are similar in consistency to very stiff
or cemented soils, and can be broken into small particles with moderate effort.
The compaction of these materials can be evaluated by comparing their com-
paction characteristics with those of similar soils.

      The compaction tests performed on samples of sludge fixed by process B
showed that the compactive effort of the 15-blow test (7400 ft-lb/cf) did not
substantially increase the unit weight  of the material over that resulting
from the fixation process (Table 10).   This suggests that moderate compaction,
by use of available equipment, will  be  useful only for producing a more homo-
geneous mass of sludge and that increased density will result only from the
application of a much larger compactive effort, requiring several passes of
heavy compaction equipment.
                                      73

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      Should a high degree of compaction be required, the sludge should be
spread in thin (12-18 in) lifts, cured, and pulverized by passes with a
steel-wheel or sheepsfoot roller.  Table 6 shows that steel-wheel and rubber-
tire rollers are effective for compacting gravelly soil and that sheepsfoot
and rubber-tire rollers are suitable for fine-grain soils.  Preliminary
selection of compaction equipment can be made from this table based on the
effectiveness of pulverization (i.e., the degree to which the sludge chunks
were ground-up); but, if compaction is critical to the performance of the
landfill, test sections should be prepared to evaluate different combinations
of equipment and determine the most economical procedure that will accomplish
the required compaction.

Compaction of Non-Soil-Like Fixed Sludges

      Sludges fixed by process A, C, E, or G are hard affer curing and there-
fore not suitable for compaction by rolling; but the use of vibrators of the
type used during concrete construction will probably increase the density and
integrity of lifts of fixed sludge.  As the sludge is placed for curing, the
vibrator could be used to consolidate the mass and could be especially effec-
tive for preventing honeycombing, characteristic of many fixed sludge samples
(see Figures 1-10).

BEARING CAPACITY

      Insufficient information is available to discuss bearing capacity in
detail, but the wide range of measured unconfined compressive strength indi-
cates that fixed sludges should exhibit a wide range of bearing capacity;
samples with high unconfined compressive strength are expected to have larger
bearing capacities than those of materials with lower values.  Sludges fixed
by processes that result in concrete-like materials would probably have such
a high bearing capacity that performance would be limited by the strength of
the foundation soil.  Thus, these fixed materials should not be restricted in
use to any great degree by their bearing capacity and should be suitable for
on-site uses such as the construction of service roads to and around the dis-
posal area and off-site uses such as landfill and roadway subgrade construc-
tion.

CONSOLIDATION

      The rate and amount of consolidation of a deposit of soil under load
are estimated from the results of consolidation tests, but no sludge con-
solidation tests were conducted during this study.  Some general indications
of fixed sludge consolidation characteristics are suggested by the results of
the unconfined compression test; but these are useful only for a qualitative
comparison between sludges, because the lack of lateral sample restraint af-
fects the deformation of the sample under load.

      The consolidation of fixed sludge will probably be inversely propor-
tional to the compressive strength; strong fixed materials are expected  to be
deformed less than are weaker materials under the same loading conditions.
Among the sludges with comparable strength, those with high moduli of elasti-
city will undergo smaller deformation than will those with low moduli of

                                     74

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elasticity under the same load.

      Regardless of the type of sludge or of the fixing process, any analysis
of settlement of a sludge landfill or embankment must include an analysis of
the soils underlying the deposit.  Sludges fixed by all processes except pro-
cess B are considerably stronger than most soils, and the settlement of struc-
tures constructed on such deposits will be due to the consolidation of layers
of compressible foundation soils.  Settlement due to deformation of the sludge
layer will be very minor in comparison to that of the foundation soils as
long as the integrity of the sludge is maintained.

EMBANKMENTS OF SOIL-LIKE FIXED SLUDGE

      Embankments of soil-like fixed sludges are expected to perform well if
designed conservatively and constructed carefully.  Since the fixed sludges
exhibit considerable strength, slopes can be expected to be stable, provided
that the embankment is compacted to a continuous mass, similar to the test
specimens.  Weathering may be of considerable concern to slope stability,
however, because wet-dry cycles and freeze-thaw cycles were shown to be capa-
ble of disintegrating sludges fixed by process B or F (Section 5).   Proper
drainage to reduce or prohibit the exposure of the embankment to freezing and
thawing and to wetting and drying may be useful to protect the integrity of
the embankment, but may be prohibitively expensive.  The use of a soil cover
will protect the sludge from erosion, can provide insulation against weather-
ing, and improves aesthetics by supporting vegetation.

      Slopes may also be subject to failure due to liquefaction or thixotrophy.
The compaction of the fixed materials includes pulverization of chunks of fixed
sludge into smaller particles.  Careful control of pulverization to result in
gravel-size particles and careful compaction will reduce the susceptibility of
the sludge to liquefaction and thixotrophy, unless water in the deposit can
cause the agglomerated sludge particles to "melt" into silt and fine-sand
size particles in which case considerable settlement can be expected.  Careful
control of moisture during and after construction will also reduce the risk of
failure by liquefaction or thixotrophy.

EMBANKMENTS OF NON-SOIL-LIKE FIXED SLUDGE

      The construction of embankments of sludges fixed by process A, C, E, or
G is expected to be similar to the construction of rock fills, because exca-
vation of fixed material, by using rippers or blasting to loosen the material
and a power shovel to excavate and load it, will result in large chunks of
material that will not be easily crushed for compaction.  Embankments of large
chunks of fixed sludge will be free-draining and not susceptible to frost, and
for these reasons they are expected to be very stable.
                                       75

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                                 REFERENCES
1.  Mahloch, J. L.,  et al, Pollutant Potential of Raw and Chemically Fixed
    Hazardous Industrial Wastes and Flue Gas Desulfurization Sludges, Interim
    Report.  U. S. Environmental Protection Agency, Cincinnati, OH, July 1976.

2.  U. S. Army, Office, Chief of Engineers, Laboratory Soils Testing, Engineer
    Manual 1110-2-1906, 30 November 1972.

3.  American Society for Testing and Materials (ASTM), Annual Book of ASTM
    Standards, Part  11, Philadelphia, PA, 1973.

4.  The Unified Soil Classification System, Technical Memorandum No. 3-357,
    U. S. Army Engineer Waterways Experiment Station, Vicksburg, MS, April
    1960.

5.  Means, R. E. and J. V. Parcher, Physical Properties of Soils, Charles E.
    Merrill Books, Inc., Columbus, OH, 1963,

6.  Terzaghi, K, and Ralph B. Peck, Soil Mechanics in Engineering Practice,
    John Wiley and Sons, Inc.", New York, NY, January 1967.

7.  Hough, B. K., Basic Soils Engineering, The Ronald Press Company, New York,
    NY, 1957.

8.  Cedergren, H. R., Seepage, Drainage, and Flow Nets, John Wiley and Sons,
    Inc., New York,  NY.

9.  Wang, S. Y., A Laboratory Study of the Durability Characteristics of
    Lime-Soil Mixtures, MS Thesis, Purdue University, West Lafayette, IN,
    1950.
                                      76

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                                   TECHNICAL REPORT DATA
                            (Please read Instructions on the reverse before completing)
  REPORT NO.
  EPA-600/2-77-139
2.
                              3. RECIPIENT'S ACCESSION-NO.
 . TITLE AND SUBTITLE
 PHYSICAL AND ENGINEERING PROPERTIES OF HAZARDOUS
 INDUSTRIAL WASTES AND SLUDGES
                              5. REPORT DATE
                               August 1977 (Issuing Datel
                                                           6. PERFORMING ORGANIZATION CODE
 . AUTHOR(S)
 M. J. Bartos,  Jr. and M. R. Palermo
                                                           8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
 Environmental Effects Laboratory
 U. S. Army Engineer Waterways  Experiment Station
 P. 0. Box  631
 Vicksburg,  Mississippi    39180
                              10. PROGRAM ELEMENT NO.
                              11. CONTRACT/GRANT NO.
                                IAG-D4-0569
 12. SPONSORING AGENCY NAME AND ADDRESS
 Municipal  Environmental Research Laboratory—Cin.,  OH
 Office  of  Research and Development
 U.S.  Environmental Protection Agency
 Cincinnati,  Ohio  45268
                              13. TYPE OF REPORT AND PERIOD COVERED
                                Jan,  1975-Aug, 1976	
                              14. SPONSORING AGENCY CODE
                                EPA/600/14
 15. SUPPLEMENTARY NOTES
 Robert E.  Landreth, Project  Officer    (513)684-7871
 16. ABSTRACT
      This  report presents  the results of a laboratory  testing program to investigate
  the properties of raw and  chemically fixed hazardous industrial wastes and flue gas
  desulfurization (FGD) sludges.

      Specimens of raw and  fixed sludges were subjected to a variety of tests commonly
  used in  soils engineering.   The grain-size distributions, Atterberg limits, specific
  gravities,  volume-weight-moisture relationships and permeabilities of raw and fixed
  sludges  were determined.   Selected fixed sludges were  subjected to appropriate
  engineering properties  (compaction and unconfined  compression) tests and durability
  (wet-dry and freeze-thaw)  tests.

      Test  results show  that  fixing can cause significant changes in the properties of
  sludge,  that fixed sludges are similar to soil, soil-cement, or low-strength concrete,
  and that properties are process-dependent.  On the basis of test specimen behavior,
  fixed  sludges can be expected to exhibit substantial engineering strength and suit-
  ability  for landfill and embankment construction,  although the durability tests show
  that weathering can be  a problem unless the fixed  sludges are protected by an earth
  cover.
                                KEY WORDS AND DOCUMENT ANALYSIS
                  DESCRIPTORS
                                              b.lDENTIFIERS/OPEN ENDED TERMS
                                              COS AT I Field/Group
 Wastes
 Stabilization
 Sulfates
 Sludge
 Soils
 Management
                  Flue Gas Cleaning
                  Chemical Fixation Waste
  13B
 8. DISTRIBUTION STATEMENT
 RELEASE TO  PUBLIC
                 19. SECURITY CLASS (ThisReport)
                   UNCLASSIFIED
21. NO. OF PAGES
    89
                 20. SECURITY CLASS (Thispage)

                   TTNCTASSTFTTO	
                                                                          22. PRICE
EPA Form 2220-1 (9-73)
                                             77
                                        
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