Continuous mixing and injection of lime-fly ash slurry

Method of treating subsurface layers of the earth for controlling movement of subsurface water and building strength of the subsurface layers characterized by injecting at a plurality of predetermined depths and at a plurality of predetermined spaced-apart locations a lime-fly ash slurry consisting essentially of water, particulate hydrated lime and particulate fly ash; the particulate lime and fly ash being present as particulate solids and a proportion of from twenty-five percent by weight of the water to as much as two hundred percent by weight of the water when employed along. The particulate solids comprise lime and fly ash in proportions ranging from three parts lime to one part fly ash to one part lime to ten parts fly ash. The injection is carried out by pumping the slurry of one of the particulate solids and water through a jet slurry mixing apparatus for aspirating in the other dry particulate solid. Preferably the fly ash will be aspirated into a slurry of the lime in water. Injection occurs within less than ten minutes from admixture so as to obtain additional strength compared to conventional prior art processes. Minor amounts of additives may be employed to obtain desired properties. In particular embodiments there are disclosed the use of additional materials such as cement, attapulgite, sandy loam and bentonite. These additional materials may be employed in concentrations of twenty-five to two hundred percent by weight of the water and are in addition to the lime and fly ash in the slurry.

FIELD OF THE INVENTION 
This invention relates to treating subsurface layers adjacent the surface 
of the earth to either control movement of subsurface water or build 
strength of the subsurface layers or both. More particularly, this 
invention relates to improving the subgrade, as for reuse of environmental 
waste sites, stabilizing subgrades for buildings, roadbeds, slopes, and 
the like. 
DESCRIPTION OF THE PRIOR ART 
The prior art is replete with a wide variety of materials that have been 
employed to stabilize soil or improve subgrades in the subsurface layers 
adjacent the surface of the earth for a variety of purposes. The 
applications have been varied as improving subgrades for streets, runways, 
railroads, dewatering projects and more recently improving the slopes to 
prevent failure of slopes adjacent a highway, adjacent a view railroad or 
the like. Of course, pretreating building sites for reducing swell, and 
improving the strength and waterflow characteristics of soils has long 
been a problem plaguing the civil engineer and the architectural engineer. 
The problems have been varied and the techniques have been varied to try 
to overcome them. Lime slurries have been worked into the top layer, for 
example, the top several to as much as fourteen or more inches in depth to 
improve and stabilize soils, or subgrades. Other more exotic and expensive 
treatments such as injection of furfural alcohol that have been found to 
work in subterranean formations have been tried. Such exotic treatments 
have proven too expensive and not altogether successful because of the 
lack of metamorphosed rock in the subsurface layers adjacent the surface 
of the earth. Expressed otherwise, these exotic treatments were infeasible 
and engineeringly inoperable because of the numerous small cracks and 
crevices and the like that traverse through the soil and the soils were 
composed largely of sedimentary or amorphous materials, humous matter, 
non-crystallographic materials and other matter that could not be 
considered metamorphosed as with the subterranean formations. 
Earlier I was a co-inventor with Gene Cain and Joe Doyle Teaque in the U.S. 
Pat. No. 4,084,381 entitled "STABILIZATION OF EARTH SUBSURFACE LAYERS", 
issued Apr. 18, 1978 and assigned to Woodbine Corporation. 
In the prosecution of that application, several patents were cited against 
the patent application as follows: 
One of the patents cited, namely, Goldie, 707,840 is over seventy years 
old, yet its invention has not been commercially successful. The Goldie 
reference describes forming a cementitous mass with a ballast. This 
prevents water from draining from ballast and has the disadvantage of 
breaking and cracking under rolling trains. There is no teaching in this 
patent of deep injection to cure ballast pockets or sinks. It is clear 
that the use of a hopper to seal a localized area ballast to surface, as 
described in the Goldie reference is economically infeasible for repairing 
long mileage of tracks along a railroad. 
U.S. Pat. No. 2,815,294, Havelin et al, describes a method of stabilizing 
soil compositions employing lime and fly ash in aggregate form. This 
patent does not describe the injection and, as pointed out at column 4, 
the mixing is carried out by breaking up the soil and mixing the soil with 
a lime fly ash and aggregate in predetermined portions, using soil 
breaking and mixing equipment such as conventionally employed for form and 
construction purposes. Thus, this is clearly a different process from this 
invention described and claimed hereinafter. 
U.S. Pat. No. 2,942,993, Handy, merely shows the accelerating of a setting 
of a mixture of lime, soil and fly ash with a carbonate and does not teach 
injection. 
U.S. Pat. No. 3,076,717, Minnick and 3,852,084, Webster et al, describe, 
similarly as did Havelin, admixing particular combinations of soil, 
aggregate and lime fly ash and reapplying aggregate to form a 
substantially homogeneous layer on top of existing soil for forming high 
strength foundations for highways, buildings or the like. These patents 
require removal of a layer of soil, if native soil is employed and not 
admixed on the surface, admixing with other ingredients into the 
homogeneous mass replacement and compaction. It is clear that these 
patents describe a different process from the following process. Also, 
they are more expensive processes. 
U.S. Pat. No. 3,756,507, describes a new type of railroad track bed in 
which a road bed supports a multiplicity of longitudinally interconnected 
concrete slabs and define a space between the lateral supports and the 
slabs that are filled with cellular resin or elastomer. This is really a 
different design of road bed, not a reinforcement of existing foundation. 
The concrete, as Henry Ford found out with his railroad is not, per se, 
satisfactory. Consequently, the foam synthetic resin bodies are employed. 
This construction will be disadvantageous because of the tendency to trap 
water and be vulnerable to the vagaries of freezing and thawing 
contractions and expansion. Moreover, the patent describes a very 
expensive installation that is engineeringly feasible for replacing 
thousands of miles of track that exist in this country. 
Also cited in the prosecution of the earlier application was Japanese 
721,6840, Asahi. This patent describes grinding lime in the presence of 
two to ten percent water and up to 0.5 percent non-ionic surfactant to 
help with the grinding. A preferred non-ionic surfactant is also listed. 
The Canadian Havelin patent, 585,628, is substantially the same as the U.S. 
case. 
Subsequent to issuing, U.S. Pat. No. 4,084,381 was involved in litigation 
and a request for reexamination was filed by the defendant in the 
litigation. That request for reexamination was voluminous but can be 
supplied if the examiner deems this necessary. The respective references 
cited in that request for reexamination are as follows: 
U.S. Pat. No. 3,243,962, Ratliff was one of the patents cited in that case 
along with Havelin 2,815,294. The Ratliff patent, 3,243,962, describes a 
method and apparatus for treating soil in which a slurry comprising forty 
percent by weight of lime and sixty percent by weight of water is injected 
into the soil. The patent also describes the use of a wetting agent. 
Cited in the request for reexamination were several literature articles 
including: 
"PFA in Grouting" showing the formation of typical grouts; specific 
surfaces and particle sizes of materials for the grouts; and the blending 
of cement in PFA slurries. Interestingly, the inventor of the invention in 
this application was invited to speak by the publisher of the articles 
entitled "PFA in Grouting" at a subsequent seminar on a new use of fly 
ash. Consequently, it appears that the publisher felt also that that 
invention was different from the invention described and claimed 
hereinafter as well as in U.S. Pat. No. 4,084,381. 
Also cited in the reexamination request of U.S. Pat. No. 4,084,381 was the 
following: 
"Grouting in Engineering Practice," Bowen, John Wiley & Sons, describes the 
aspects of grouting, history of grouting, current practice using material 
such as cement, cement and sand, clay-cement, slag-cement, resin 
gypsom-cement, clays, asphalt, pulverized fuel ash and a large number of 
colotal and low viscosity chemicals. That article also discusses openings 
in the soils and rocks and the use of their respective delineated 
ingredients specifically, as well as accelerators or other additive and 
inert material such as sand. There is also a discussion of the pozzolans 
such as the natural pozzolans comprising volcanic glass, opal, pumicite, 
clay minerals, zeolites and hydrated oxides of aluminum. That article also 
points out at page 21 that one of the most useful of the grouting 
additives is pulverized fuel ash (PFA) which is often employed in 
conjunction with cement. That article notes that it can be used alone and 
that its primary advantage is its low cost. This booklet has some one 
hundred and fifty-two pages so it is virtually impossible to quote all of 
its material. It is sufficient to note that it does not make obvious the 
invention described and claimed hereinafter. 
SOIL MECHANICS AND FOUNDATIONS, third edition, the Macmillan Company, 
Collier-Macmillian Limited, London 1970, has a discussion of grouting and 
injection stabilization. There are formulas relating the parameters in 
grouting, as well as a discussion of injection method showing injecting 
into a hole with a suitable gauge to measure the pressure of the 
injection, also illustrating schematically grouting into open rock joints 
with angle holes intersecting the widest possible spread of rock joints. 
There is a discussion of grouting cavities and pavements. 
"Soil Stabilization Principles and Practice," Ingles and Metcalf, Wiley and 
Sons, New York and Toronto, 1973 discloses soil stabilization by reacting 
lime with clay minerals of the soil or pozzolanic components such as 
hydrous silica to form a tough water-in-soluble gel of calcium silicate. 
Schematic illustrations are enclosed as are other criteria. 
"CHEMISTRY AND TECHNOLOGY OF LIME AND LIMESTONE," Boynton, Interscience 
Publishers, a Division of John Wiley and Sons, New York, N.Y., 1966 
discloses many of the reactions of limestone to produce hydrated lime. The 
book also has other reactions of hydrated and unslaked lime. The book also 
shows the ingredients of unslaked lime and of limestone. 
"Soil Mechanics and Foundations Division," proceedings of the American 
Society of Civil Engineers, "Cement Grouting," 1962 contains in the 
introduction there a statement "Pressure grouting has been described as a 
process of injecting suitable cementitious slurries or similar materials 
into inaccessible places, such as underlying foundations of structures, 
for the purpose of sealing seams, cracks and fissures or for filling 
voids." There are also additional statements of projected and conceptual 
ideas as well as relating the necessity for field investigation of some of 
the ideas; for example, at page 55, there appears the quote "Pore-like 
openings are typical of sands and gravels, the grouting of which is not 
examined in detail in this report. However, the same general types of 
openings are found in many sandstones and volcanic rocks,..." There is a 
discussion of methods of treatment including the drilling and grouting by 
injection into the drillholes and the like. There are some seventy-one 
pages in this article, so it is not feasible to quote all of the material 
therein. 
"Journal of the Soil Mechanics and Foundations Division," proceedings of 
the American Society of Civil Engineers, "Cement and clay grouting 
foundations" The Use of Admixtures in Cement Grouts. This article contains 
a discussion of a variety of cement and clay grouting admixtures, noting 
that admixtures of pozzolans, slags and natural cement can be included 
also there is contained a note about the addition of other pozzolans 
including fly ash, along with cement. There are fifteen pages in this 
article. 
"Journal of the Soil Mechanics and Foundations Division," proceedings of 
the American Society of Civil Engineers, "Cement and Clay Grouting of 
Foundations: Suggested Specification of Pressure Grouting," shows a 
variety of cement and clay grouting formulations with synopsis of earlier 
works. There is listed equipment, grouting materials and definitions of 
the procedures for locating grout holes to be drilled for injection of the 
grout. 
"Journal of the Soil and Mechanics Foundations Division," proceeding of the 
American Society of Civil Engineers, "Soil Mechanics and Foundations 
Division," presents symposium on grouting of granular materials, at Fort 
Campbell, on preventing vibration and on research. This article contains 
discussions showing drilling of large diameter holes and injecting a fill 
for supporting a load onto a glacial fill underneath the load. There is 
also a discussion of the Doshi Dam as well as schematic drawings showing 
the principle of grouting (32 pages in all). Included is only a copy of 
their foreword of the article: "Grouting, of Ft. Campbell Theater 
Building." 
AIME PETROLEUM TRANSACTIONS, "A New Material for Deepwell Cementing," 
Smith, Halliburton, shows thickening times and the like for 
pozzolan-lime-cement admixtures with no retarders and the like and 
discussions. 
"Grouts and Drilling Muds in Engineering Practice," Symposium of the 
British National Society of International Society of Soil Mechanics and 
Foundations Engineering at the Institute of Civil Engineers held in May 
1963 shows grout injections with high pressure in deep mines with slurries 
including water-cement, water-bentonite, water-cement grouts with other 
additives and the like. 
"Transportation Engineering Journal of ASCE," proceedings of the American 
Society of Civil Engineers, Volume 101, TE4, November, 1975, contains a 
variety of articles including the approach regions for railway tunnels, 
signaling for track guided systems, multi-mobile transportation, inter 
alia; and includes: "New and Conventional Uses of Fly Ash," Joshi, et al, 
which describes fly ash production and use in soil stabilization, 
manufacture of cement block, as a component of concrete mixes, lightweight 
aggregate, bricks and states that literature references describe 
stabilization of sandy and silty soils used in mixtures of fly ash and 
lime or cement, including a Table of the Composition of Fly Ashes and 
compositions of Cement Stabilized Fly Ash. 
"Highway Research Record" No. 442, Soil Stabilization, Highway Research 
Board, 1973, describes a variety of additives such as cements for 
controlling soil-cement interrelationships and includes eleven reports 
like Determinations of Realistic Cutoff Dates for Late-Season Construction 
with Lime-Fly Ash and Lime-Cement-Fly Ash Admixtures. There appears in 
this report a discussion on the use of these materials including the 
typical degree day calculation for strength versus degree day. This 
article cites that earlier British study on LFA mixtures. The data are 
apparently related to admixing of soil with these slurries and then 
replacing the soil and do not make obvious the invention described and 
claimed hereinafter, although its sounds otherwise to the uninitiated and 
less expert soil stabilizer. 
"Soil and Soil-Aggregate Stabilization," a symposium, 1955, Washington, 
D.C. describes state of the art soil stabilizing information and includes 
an article entitled "Soil Stabilization With Lime-Fly Ash Mixtures: 
Preliminary Studies With Silty and Clayey Soils," by Chu, Davidson, 
Goecker and Moh, which is again conventional stabilization. 
"Highway Research Correlation Service," Highway Research Board of the 
National Academy of Sciences-National Research Counsel, Washington, D.C., 
1962, included an article on lime and fly ash proportions in soil, lime 
and fly ash admixtures and some aspects of soil lime stabilization by 
Mateous and Davidson. The soils with which the lime and fly ash slurries 
were mixed were dune sand, triable loess, alluvial clay and gumbotil four 
limes and eight fly ashes were tried and respective seven day and 
twenty-eight day curing strengths were measured. 
And finally that request for reexamination includes articles by the 
inventor of this invention, including "Stabilization By Lime-Slurry 
Injection, Railway Track and Structures," October, 1975, in which the 
inventor delineated the advantages of injection of lime slurry along a 
railroad track and "Southern Injects Lime Slurry to Stabilize Soft Track," 
containing substantially similar information by the inventor. 
Moreover, other patents have been issued directed to soil stabilization 
including the following: 
U.S. Pat. No. 3,971,222 "Soil Stabilization," Griffith, shows soil 
stabilization by introducing materials such as lime beneath the earths 
surface. 
U.S. Pat. No. 3,375,872, "Method of Plugging or Sealing Formations with 
Acidic Salicylic Acid Solution," McLaughlin et al, describes the use of 
more exotic materials such as salicylic acid for plugging or sealing 
formations. 
U.S. Pat. No. 2,680,602, Nelson, et al, "Agitator Device For Digester 
Tanks," describes an agitator for digester tanks. 
As can be seen, none of the prior art actually make obvious the invention 
described and claimed hereinafter. 
Experience with injection of lime-fly ash slurries has indicated several 
problems and several features that would be desirable that have not been 
heretofore provided by the prior art. In U.S. Pat. No. 4,084,381 we listed 
ten features that are desirable and, of course, it is desirable that the 
method of the invention provide those features. In addition it is 
desirable that the invention provide the following features not heretofore 
provided. 
(1) The injected material should set to as high a strength as possible. 
Some of the prior art injections did not have as high a set strength as 
desired. 
(2) There should be as low a loss of volume, or shrinkage, with the setting 
of the material such as the injected slurry of lime-fly ash. 
(3) There should be as low a leachate as possible. In the prior art, some 
of the slurries that here employed had relatively low percentage solids so 
that there was a relatively high volume of leachate, or leached 
supernatant liquid. 
(4) The method should allow pumping the slurry for injection without fly 
ash setting, or achieving high viscosity, during the pumping operation. 
(5) The method should approach continuous bleeding and injection as near as 
possible, yet: 
(a) allow air to escape before injection so as to be pumpable without 
"vapor locking" the pump and obtain as great a density of the set material 
as possible; 
(b) allow testing of the slurry before injection in order to maintain the 
parameters within preset limits. 
(c) allow maintaining parameters during injection 
(d) facilitate rapid restoration of optimum control parameters if 
deviations shown by the testing. 
(6) The method should allow use of other additives such as retarders or 
inert fillers without adversely effecting the other features. 
(7) The method should allow pumping higher ratios of solids to water; for 
example, greater amounts of lime and fly ash to the water, (referred to as 
percent solid) than the prior art batch approach used in U.S. Pat. No. 
4,084,381. The method of this invention advantageously will allow up to 
twelve pounds per gallon or more to achieve higher strengths, less bleed 
off water and faster sets. 
(8) The method of this invention should allow better introduction of 
additives such as accelerators by adding to the lime slurry and injecting 
within ten minutes to achieve a better final product and result. 
(9) The method should allow a much higher production rate to the customer. 
For example, the old method would allow fifty to sixty tons per day 
whereas the method of this new invention would allow up to one hundred 
tons per day or more. 
It can be seen that the prior art has been deficient in providing an 
economical process that has one or more of the foregoing features. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of this invention to provide a method that is 
economical and provides one or more of the foregoing features not 
heretofore provided by the prior art. 
It is a specific object of this invention to provide a method that is 
economical and provides a plurality of the features delineated 
hereinbefore and not heretofore provided. 
It is a specific object of this invention to provide a method that has all 
of the features delineated hereinbefore as desirable and not heretofore 
provided. 
In accordance with this invention there is provided a method of treating 
subsurface layers of the earth for controlling movement of subsurface 
water and building strength of subsurface layers characterized by 
injecting a plurality of predetermined depths and at a plurality of 
predetermined spaced-apart locations a lime-fly ash slurry consisting 
essentially of water, particulate hydrated lime and particulate fly ash; 
the particulate lime and fly ash being present as particulated solids and 
a proportion of twenty-five percent (25%) by weight of the water by as 
much as two hundred percent (200%) by weight of the water when employed 
alone. The particulate solids comprising lime and fly ash are present in 
proportions in the range of from 3:1 to 1:10 and the injection is carried 
out by pumping a slurry of one of the particulate solids and water through 
a jet slurry mixing apparatus means and thereby aspirating in the other 
particulate solid when the slurry of the one particulate solid is pumped 
therethrough. The other dry particulate solid is fed thereinto such that 
admixture occurs substantially immediately. 
Actual experience and laboratory testing has shown that the set strength 
and set time of the injected slurry is improved if it is not subjected to 
severe agitation, or admixing for a time interval greater than ten minutes 
and, preferably, less than six; and if it is injected within ten minutes 
of having passed through the high pressure pump and sent to the injectors. 
One advantage of this invention is that additional ingredients such as 
cement, attapulgite, sandy loam or bentonite can be added in an additional 
percentage by weight of from twenty-five percent (25%) to two hundred 
percent (200%) by weight of the water to get exactly the properties needed 
for the injected mass once it has set up in place. 
By this invention, the subsurface layers are treated in situ without 
requiring removal, admixture into a homogeneous mass, replacement and 
compaction.

DESCRIPTION OF PREFERRED EMBODIMENTS 
As indicated hereinbefore and as will become clearer later hereinafter, 
this invention can be employed in a wide variety of circumstances for 
improving the subsurface layers by either controlling movement of 
subsurface water or building the strength of subsurface layers, or both. 
The descriptive matter of U.S. Pat. No. 4,084,381 is incorporated herein 
by reference. A portion of the descriptive matter of U.S. Pat. No. 
4,084,381 is repeated for convenience of the reader. 
The water that is employed in the slurry that is injected into the 
subsurface layers may be any of the water from economical and normally 
employed sources. If the water is to be displaced into a potable source of 
water, it should be potable itself, since the lime and fly ash do not 
ordinarily render it non-potable; particularly, after the water has been 
passed through the soil. Usually, the job will be close enough to a 
conventional water supply that the conventional sources of water can be 
employed. A conventional source may comprise city water mains, railroad 
storage facilities, highway department storage facilities, lakes, streams 
and the like. Preferably, the water will not have a high concentration of 
materials that would react with the lime that will be added in the slurry 
and would not have significant concentration of either materials referred 
to as retarders or accelerators in order that the water will not influence 
the setting of the materials in the slurry. 
The lime that is employed in the slurry may be any of the conventionally 
available limes, such as a dolomitic lime or a high calcium lime, more 
accurately referred to as calcium hydroxide. The lime that is preferably 
employed may have minor amounts of other impurities therein, but will 
ordinarily analyze better than seventy percent (70%) by weight calcium 
oxide and better than twenty percent (20%) by weight combined moisture. 
The lime is particulate lime, preferably small particles. By small 
particles it is meant particles that will all pass through a fifty mesh 
standard screen and more than ninety-five (95%) of which will pass through 
a hundred mess screen, U.S. standard sieve size. As will be discussed in 
more detail hereinafter, with this concentration of calcium hydroxide, the 
lime will react in time with the fly ash in the slurry and with the 
constituents of the soil when injected to form a relatively high strength 
material in the soil. 
The fly ash that is employed in the slurry is a pozzolanic by-product of 
coal-burning power plants. Preferably, the fly ash is of the "self 
hardening type". Expressed otherwise, the fly ash has enough lime in it to 
harden if compacted after being moistened and form a water impervious 
mass. To accomplish this, the fly ash should have an analysis that shows 
an excess of five percent (5%) by weight of unslaked lime, or calcium 
hydroxide (CaO); preferably, more than about ten percent (log) by weight 
thereof. A type C fly ash is preferred and in most cases lime-fly ash 
slurries prepared with a Type C fly ash and within the guidelines set 
forth herein will be satisfactory. Tests can be conducted to verify 
durability and suitability. Some Type F fly ashes can be employed in this 
process if other additives are also added to produce a mix that 
demonstrates durability without significant loss of strength when soaked 
in water. It is preferable that the fly ash have less than two percent 
(2%) by weight of organic carbon and should have no greater loss on 
ignition than two percent (2%) by weight. Table I hereinafter gives a 
typical chemical composition of fly ash. In Table I, the concentration is 
given percent by weight (% by Wt.). 
TABLE I 
______________________________________ 
Fly Ash 
Typical Analysis 
Concentration 
Component (% by wt.) 
______________________________________ 
SiO.sub.2 51.0% 
Al.sub.2 O.sub.3 18.0 
Fe.sub.2 O.sub.3 5.0 
CaO 20.0 
MgO 3.5 
SO.sub.3 1.0 
Na.sub.2 O .05 
K.sub.2 O .05 
Loss on ignition .05 
Specific Gravity 2.50 
Retained on #325 sieve 
24% 
Surface are (cm.sup.2 /cm.sup.3) 
6300 
______________________________________ 
The fly ash is particulate, preferably small particles size. In fly ash 
only one percent (1%) is retained on a fifty mesh screen, ninty-six 
percent (96%) passing through one hundred mesh screen. 
One of the chemical reactions that occurs when hydrated lime and fly ash 
are injected into subsurface layers or soils, is the cementing action, 
commonly referred to as pozzolanic reaction The abundance of silicas and 
aluminas in fly ash increases the cementing action with the hydrated lime. 
The resulting reaction product is water insoluble and renders the fissures 
that formerly served as flow paths impervious to the subsurface flow of 
water, or moisture. In addition, the materials that are formed stabilize 
the soils to prevent slope failures, stabilize the soils for building 
foundations and performs other features delineated hereinbefore. In 
addition, we have found that we are able to form a cementitious type 
product with the reaction of the lime and fly ash alone when injected in 
accordance with this invention; namely, on a continuous basis or within 
less than ten minutes from the admixture of the lime and fly ash into the 
slurry. 
It is frequently helpful in the preferred embodiment of this invention to 
employ a surfactant. In the early patent U.S. Pat. No. 4,084,381, the 
inventor spoke of employing a surfactant as a necessary ingredient of the 
preferred embodiment. 
The surfactant that is normally employed in the slurry, if a surfactant is 
used, is preferably a nonionic type surfactant, although a cationic and 
anionic type surfactant can be employed. The nonionic surfactants are 
usually the polyethylene oxide surfactants. By polyethylene oxide 
surfactants is meant a surfactant molecule in which the polyethylene oxide 
groups are combined in an average with a moiety that is selected from a 
class consisting of alkyl or alkyl aryl type moiety. Illustrative of the 
alkyl type moieties are the hydrocarbon moieties having six to eighteen 
carbon atoms. Illustrative of the alkyl aryl moieties are the alkyl groups 
having six to twelve carbon atoms combined onto a phenyl ring. A typical 
nonionic surfactant is nonyl phenol with an average of from eight to one 
hundred mols of ethylene oxide associated with each mol of nonyl phenol 
Typically, an average of about thirty mols of ethylene oxide will be 
associated with each mol of nonyl phenol. If desired, of course, the 
octa-, heptyl-, or hexyl-moieties may be associated with the phenol and 
employ from eight to one hundred mols of ethylene oxide in association 
therewith, depending upon the hydrophillic versus hydrophobic 
characteristics desired. 
Any suitable surfactant can be employed if surfactant is used. Early, a 
nonionic surfactant that was employed in the prior trials with this 
invention was the Wet-It Surfactant, Chemical Research, Inc., Dallas, Tex. 
As indicated, an anionic surfactant such as sodium lauryl sulfate or a 
cationic surfactant such as cetyl pyridinium chloride can be employed if 
desired. 
The surfactant may be employed in a concentrated form or may be diluted and 
applied in an aqueous solution, the latter facilitating forming the 
slurry. 
In the slurry of this invention, the particulate lime and the particulate 
fly ash are present as particulate solids in a proportion within the range 
of 25-200 percent by weight of the water and in a proportion of lime to 
fly ash within the range of from 3 to 1 (3:1) to 1 to 10 (1:10). 
Preferably, the lime is employed in a proportion of about one-fourth of 
the particulate solids and the fly ash comprises the remaining 
three-fourths of the particulate solids, although this proportion can vary 
depending upon the composition of the fly ash. Different types of jobs 
require different proportions; for example, application of lime-fly ash 
slurry for land fills may require 8-10 pounds of solids per gallon of 
water to prevent phase separation and reduce "bleed water". Also such 
injections may require a lime-rich mixture where the proportion of lime is 
in the range of 3:1 to 1:4. 
The surfactant, when it is employed, is employed in a concentration of at 
least 0.001 percent by volume; preferably, at least 0.01 percent by volume 
The best concentration of surfactant that has been achieved is in the 
range of 0.01-1 percent by volume of the slurry, preferably about 0.03 by 
volume. Expressed otherwise, the liquid surfactant is employed in a 
proportion of one part to about thirty-five hundred parts slurry when the 
surfactant is undiluted surfactant. 
The remainder of the slurry is frequently water, although other ingredients 
can include other dry ingredients, such as cement, attapulgite and 
bentonite or the like. When the latter additional ingredients are 
employed, they may be employed in a range of from 25 to 200 percent 
(25-200%) by weight of the water. 
It is noteworthy in this invention that one object is to get the optimum 
water to minimize supernatant water or shrinkage when the lime and fly ash 
in slurry sets up in situ. For example, if 20 percent of the water is 
obtained as free water, it is not acceptable in certain applications, so 
the proportions need to be adjusted to obtain a range that is more nearly 
acceptable; for example, less than 10 to 15 percent (10-15%) and, 
preferably, about not more than five to eight percent (5-8%) free water. 
Somewhat larger free water proportions can be tolerated in certain dry 
clays or the like. 
Additional materials, such as retarders or accelerators, may be employed to 
accelerate or retard the set and improve durability of the lime fly ash 
injected with the slurry. For example, a chemical additive may be added in 
an amount to effect concentration in the range of one-half to five percent 
(1/2-5%) by weight of slurry if desired. 
As indicated, presenting as low a loss of volume as possible when the lime 
and fly ash sets up is desired and is one of the objects sought to be 
achieved by this invention. Moreover, the mixing is carried out to achieve 
the maximum strength possible with a given proportion of lime fly ash 
slurry. 
With this in operation, the injection in accordance with this invention is 
carried out similarly as described in U.S. Pat. No. 4,084,381, but 
different as can be seen by considering the following descriptive matter 
in conjunction with the appended Figs. 
Injection rigs have been developed to inject the lime-fly ash slurry into 
the ground but without requiring predrilled holes, although the drilling 
of holes and injection by way of the holes can still be performed if 
desired. Ordinarily, the lime-fly ash slurry will be injected at a 
predetermined array of holes at predetermined spacing in the neighborhood 
of from one to ten feet apart. For example, it has been found that an 
injection on about five foot centers in both lateral and longitudinal 
directions affords a good interlacing injection pattern that accomplishes 
the objectives. 
Tests such as described in Bulletin 331, LIME SLURRY PRESSURE INJECTION 
BULLETIN, National Lime Association, Arlington, Virginia, published in 
1986, can be employed for evaluating candidate sites. Often times, a site 
will be injected more than one time to achieve a progressive filling of 
the voids. A minimum curing time of 48 hours is usually allowed between 
each injection pass. 
Referring to FIG. 1, there is described a specific embodiment that has been 
successfully employed in accordance with this invention. Other embodiments 
are possible, of course. 
Referring to FIG. 1, the apparatus 11 for treating subsurface layers of the 
earth includes a first mixing means for admixing small particulate solids 
of a first one of two dry ingredients consisting essentially of fly ash or 
lime with water to form a first slurry; and a first storage means for 
storing the first slurry and simultaneously maintaining the first slurry 
in a substantially uniform admixture so that it can be tested to ascertain 
that certain properties are within certain predetermined ranges. The 
apparatus 11 also includes a first pumping means in the form of a pump 15 
for pumping the first slurry. The pump 15 is connected by way of conduit 
17, with the first storage means so as to be able to pump the first slurry 
therefrom. The apparatus 11 also includes a second storage means 19, which 
may be the shipping truck itself, for storing small particles of the 
second of the two dry ingredients, consisting essentially of lime or fly 
ash in transportable form; and a means 21 for transferring, or 
transporting, the transferable small particles of the second dry 
ingredient. The apparatus 11 also includes a second admixing means 23 for 
admixing the second dry ingredient with the first slurry to form a second 
slurry referred to as a lime-fly ash slurry. The apparatus 11 also 
includes a deaeration/averaging tank 25. Where one of the particulate 
solids is fed by air to the second admixing means 23 for admixing into the 
slurry, it is imperative that a deaeration tank be provided to allow the 
air to escape from the slurry before the pump takes its suction The 
pumping means 27 is also thought of as a high pressure pump, since it must 
generate the pressure sufficient to inject the slurry through the injector 
means 29. The second admixing means 23 is serially connected with the 
deaeration/averaging tank 25 such that the slurry can be tested in the 
averaging tank if desired. If there is any variable that needs correction 
to keep it from going out of control parameters, the correction can be 
made appropriately, as described herein. 
The first mixing means is provided for admixing at least one of the two dry 
ingredients of either lime or fly ash with water to form a first slurry. 
Preferably, lime is the first admixed with water to form the first slurry. 
The first storage means is provided for storing the first slurry and 
simultaneously maintaining the first slurry substantially uniformly 
admixed, as indicated. In the illustrated embodiment the first mixing 
means and the first storage means are shown in the form of a lime-water 
tank 13 having mixing paddles therewithin, as known in the art for 
admixing the slurry. Expressed otherwise, the first mixing means is a part 
of the first storage means and may include a plurality of paddles disposed 
along a longitudinally extending axis such that when the dry ingredient, 
such as the lime, is blown into the tank, the paddles admix it with the 
water and maintain it in substantially uniformly mixed condition. The tank 
can comprise any of the usual large tanks such as implied in U.S. Pat. No. 
4,084,381 or illustrated and described in U.S. Pat. No. 4,233,015. 
Preferably, the tank is large enough that an entire load of lime can be 
incorporated into the tank, whether the lime is in the form of slaked lime 
or quicklime that is to be slaked in situ in the tank in accordance with 
U.S. Pat. No. 4,233,015. 
The first pumping means is in the form of a pump. A pump designed to pump 
slurry is ordinarily employed. For example, a centrifugal pump may be 
employed although any suitable pump such as a positive displacement pump 
can be employed, as desired. 
A conduit 17 connects serially the illustrated tank 13 and the first 
pumping means in the form of pump 15 and may comprise any of the usual 
conduit It is preferable that the conduit be readily assembled and 
disassembled, so it may incorporate quick-connect and quick-disconnect 
fittings for connecting sections of conduit or connecting sections of 
hoses into the conduit 17. 
In the illustrated embodiment of FIG. 1, a fresh water conduit 31 with the 
appropriate valving is employed such that the fresh water can be added to 
the fluid stream as it flows, flowed back into the tank 13, or flowed 
through the pumping means 15, as for flushing or the like. 
Ordinarily, a truck carrying the first dry ingredient is employed as a 
storage means such that the dry ingredient can be blown directly from the 
truck into the tank 13 where it is admixed with the water. Such a truck is 
only shown schematically in FIG. 1, similarly as is the conduit and air 
compressor line for blowing the dry ingredient into the tank 13. 
Similarly, a second storage means 19 in the form of a truck for the other 
dry ingredient is illustrated in FIG. 1. These trucks may be appropriate 
to the nature of the dry ingredient. For example, suitable bins may be 
provided to facilitate flowing of a powder or small particles into a line 
such that the small particles can be conveyed as a fluidized stream to the 
receiving mixing means. As illustrated in FIG. 1, the truck 19 serving as 
a second storage means will hold fly ash where lime is already added into 
the water to form the first slurry in the tank 13. Air from a high 
pressure source such as an air compressor 33 may be employed to both 
pressurize the tank 19 and to flow air through the line 35 so as to convey 
the second dry ingredient, such as the fly ash, to the second mixing means 
23. As will be understood, the bins on the truck 19 and their respective 
valves may be opened as desired to allow the small particles to flow into, 
or be entrained within, the air in the stream for pneumatically being 
conveyed as a fluidized stream to the second mixing means 23. This type of 
conveying is well known and need not be described in great detail herein. 
Thus, it can be seen that the air from the air compressor 33 flowing 
through the conduit and entraining the small particles serves as the means 
for transferring the small particles of the second dry ingredient. In the 
illustrated embodiment, where lime is employed from the truck to be 
admixed into tank 13 with the water, the fly ash will be send through the 
conduit 35 to the second mixing means 23. 
On the other hand, when fly ash is employed and admixed into the tank 13, 
lime will be in the second storage means 19. Ordinarily, it is preferable 
to admix the lime into the slurry and then flow the fly ash as the dry 
ingredient into the second admixing means 23. 
The second admixing means 23 is provided for mixing the second dry 
ingredient consisting essentially of small particles of the second 
ingredient of either fly ash or lime with the first slurry to form a 
second slurry referred to as a lime-fly ash slurry. The second mixing 
means is connected with the first pumping means, as by conduit 37. The 
conduits 35 and 37 are ordinarily fairly large sizes; for example, 3-4 
inches in nominal diameter, or larger so as to be able to convey the 
respective first slurry or the fluidized dry constituent to the second 
admixing means 23. The second admixing means 23 is ordinarily referred to 
as a jet mixer. For example, a Halliburton direct feed jet mixer can be 
employed. Such a Halliburton jet mixer is illustrated in FIG. 2. In the 
illustrated Halliburton jet mixture, the first slurry at pressures up to 
sixty pounds per square inch (60 p.s.i.) is introduced into the inlet line 
39. The dry ingredient is passed through the conduit 35. In the FIG. 1 a 
pressure gage 41 is employed. In this type arrangement, the dry 
ingredient, such as the fly ash, is aspirated into the wet ingredient, 
such as the first slurry, to form the lime-fly ash slurry. As will be 
recognized, the Halliburton direct feed jet mixer has a rotary orifice 
internally thereof, although this is not necessary in this invention. Such 
a rotary orifice allows mixing different sizes of particles and different 
flow rates of the respective streams such as the slurry or the fluidized 
small particle streams. Other jet mixes can be employed as the second 
admixing means 23. 
The deaeration/averaging tank 25 is connected with the second admixing 
means 23, as by way of conduit 43 for conveying the lime-fly ash slurry to 
the deaeration/averaging tank 25. 
The deaeration/averaging tank 25 has a volume that is much smaller than 
that of the large tank 13. For example, it is small enough that the 
lime-fly ash slurry is maintained substantially uniformly admixed 
therewithin just by flow of the injection rate through the tank. If 
desired, an additional mixer could be installed in the tank, although it 
has not been necessary in the embodiments that have been used to date. 
Specifically, a flow director, or flow baffle, can be employed to ensure 
that the slurry is admixed within the deaeration/averaging tank 25. 
Moreover, the volume of the deaeration/averaging tank 25 is less than that 
required for ten minutes of pumping, For example, the pumping rate may be 
in excess of one hundred gallons per minute (gpm); whereas the volumetric 
storage capability of this tank will be only about three foot liquid in 
about a four foot diameter tank, or about two hundred and seventy gallons 
in the embodiments that we have employed. The deaeration/averaging tank 
allows entering gases such as air to be vented and serves as a surge means 
to allow testing for variables and ensures that the second or subsequent 
pumping means will always have adequate positive suction. The 
deaeration/averaging tank 25 is sometimes referred to as a holding tank. 
The second pumping means in the form of pump 27 may comprise a duplex or 
triplex mud pump, a progressing cavity pump or the like in order to 
achieve the injection pressures while pumping a difficultly pumpable 
slurry such as the lime-fly ash slurry. 
In the illustrated embodiment, a rock trap 45, FIG. 1 can be installed 
upstream of the pump 27 to prevent taking into the pump larger size 
pellets that would cause difficulty with pumping. Similarly, such rock 
traps, or filters, can be employed upstream of the first pumping means 15 
if desired. 
In the illustrated embodiment, the fresh water conduit 47 is provided for 
any purpose desired. For example, should the lime-fly ash slurry become 
too viscous, fresh water can be added to decrease the viscosity of the 
lime-fly ash slurry. On the other hand, the water can be flowed backward 
through the valve 51 into the holding tanks as a method of backflushing, 
or can be flowed through the pumping means 27, similarly as was the fresh 
water from fresh water conduit 39 float flowed through the first pumping 
means 15. 
The second pumping means has its discharge side connected with injector 
means 29. As can be seen in FIG. 3, the discharge side of the second 
pumping means is preferably connected into a manifold 53, carried by an 
injection rig or the like. The manifold is then connected to injector 
rods, or tubes 55, by way of conduit incorporating a valve 57 on each 
injector The valves 57 enable controlling flow from the manifold to the 
respective injector tubes. Respective relief valves 59 will relieve to a 
vent line 61 in the event that pressure becomes too high, as by plugging 
of the injector tubes. 
In operation, the method is carried out as a method of treating subsurface 
layers of the earth for controlling movement of subsurface waters, 
building strength of subsurface layers comprising injecting at a plurality 
of predetermined depths and a plurality of predetermined spaced apart 
locations the lime and fly ash slurry consisting essentially of water, 
particulate hydrated lime and particulate fly ash in the fly ash slurry. 
The injection is carried out rapidly after all of the ingredients are 
admixed into the lime-fly ash slurry, as at the second mixing means 23. 
Specifically, the apparatus is connected as described hereinbefore and as 
illustrated in FIG. 1. The lime-fly ash slurry in conduit 43 exiting the 
second mixing means 23 is sent through the deaeration/averaging tank 25, 
the second pumping means 27, through the injector rods and into the earth 
layers. The injection is carried out in less than ten minutes, preferably 
less that five minutes after the slurry has passed through the pump 27 
serving as a second pumping means 27. It has been found that this 
surprising building of strength can be achieved with this technique 
contrasted with the prior art approaches. 
The following examples illustrate this. 
Two lime-fly ash slurries were formed by two distinct methods. The first 
method serving as a type of the prior art injection was the admixing of 
lime and fly ash in proportion of one pound lime and three pounds fly ash 
per gallon of water in a large mixing tank with appropriate stirring. This 
lime-fly ash was then injected and had with the soil a low set strength in 
compression; for example, up to two pounds per square inch (psi). 
EXAMPLE 1 
In contrast, a lime slurry was made to the same predetermined 
specification, for example, one pound lime per gallon of water and the 
slurry fed through second mixing means 23 in the form of a Halliburton jet 
mixer. Fly ash was aspirated into the lime slurry and the resulting 
lime-fly ash slurry was quickly injected into the earth layers. Subsequent 
testing showed that the resulting set material in the earth layers had 
strengths in compression as high as 200 psi. 
In some embodiments of this invention we have used up to one to three 
percent (1-3%) by weight of an additive such as sodium bicarbonate to 
ensure that the lime-fly ash slurry and soil aggregate sets up well and 
gives good results. 
In employing the lime-fly ash slurry in land fills, additional dry solids 
such as the montmorillinite, cement, or the like have been added and have 
been injected in less than five minutes so as t give a set product that 
has reduced "leachate," or bleedwater. 
EXAMPLE 2 
In a landfill, we have employed the lime-fly ash slurry in accordance with 
this invention and apparently effected a cementation with the components 
of the landfill so as to negate escape of methane and other gases, 
apparently because of the tortuous paths and void filling. In addition, 
the pH being greater than about eight appears to kill microorganisms that 
produce methane gas in the anaerobic process. Also it appeared that the 
set material formed a structural honeycomb to add strength and reduce any 
later settling. 
In other embodiments, additives such as cement and bentonite have been 
employed in the slurry and still obtain satisfactory results. The results 
have been so good, in fact, that we believe we can employ inert filler 
such as sandy loam and still obtain satisfactory results, including 
strength and durability. 
Referring to FIG. 4, there is illustrated another embodiment of this 
invention which demonstrates the flexibility of this invention. In FIG. 4, 
the apparatus 11 is included on a working pad 63 serviced by a road 65 
having a cattle guard 67 or the like at the entrance thereto. 
Suitable tanks 69 are employed as necessary to carry out this invention. 
The second pumping means 27 in this instance is simply a series of 
centrifugal pumps through which the slurry rapidly passes without severe 
agitation. Merely flowing through a line is not severe agitation, whereas 
passage through a centrifugal pump is. It is noteworthy that the 
cumulative time of passage of slurry through the respective plurality of 
centrifugal pumps 27, as well as the other series connected pumps 71 along 
the line, is less than ten minutes from the time the slurry is in the 
deaeration/averaging tank 25 until it passes through the high pressure 
pump 73, and in most instances less than six minutes. In the illustrated 
embodiment, the track along a river or levy or the like may be up to five 
miles or so, such that the conduit 77 may be stretched with a plurality of 
pumps 71 for a distance that is appreciable. In the illustrated 
embodiment, injection into a levy 79 along a river 81 was carried out at 
distances up to five miles. While the working pads 63 can be near the 
center of such a long lineal distance, it still may require appreciable 
length of conduit 77 and a plurality of pumps 71. 
It is imperative, however, that the slurry be injected through the injector 
means 29 and into the ground, such as the slope of the levy 79, within ten 
minutes after it passes through the high pressure pump 73. Preferably, the 
injection is within six minutes from the time it passes through the high 
pressure pump 73 in order to obtain best results. 
As indicated hereinbefore, no more than ten minutes of cumulative agitation 
must be experienced by the slurry from the time the second dry ingredient 
is added in the jet mixing valve 23 and, in addition, the injection be 
carried out within ten minutes from the time it passes through the high 
pressure pump 73. 
The reasons for the increased efficacy and the surprisingly improved 
performance in accordance with this invention when these precautions 
observed is not completely understood. However, we theorize that continued 
agitation breaks down an initial set of lime-fly ash slurry. This is based 
on laboratory and field observations using this compared with a prior 
method. The invention works whether or not the theory is correct. In fact, 
it is proven that this invention can be employed to achieve surprisingly 
improved performance when compared with the prior art, as illustrated in 
Example 1. 
It is sufficient to note that in the embodiment of FIG. 4, an actual case 
history has been performed with the corps of Engineers and samples taken 
to illustrate satisfactory set of the injected slurry when performed in 
accordance with this invention, this set having the surprisingly improved 
results when compared with the prior art approaches. 
The method of this invention provides the advantageous features delineated 
hereinbefore as being desirable and not heretofore provided 
(1) Specifically, this invention provides an injected material that will 
set to a much higher strength than heretofore possible. 
(2) This invention provides an injection that has a loss of volume, or 
shrinkage, that is much lower than the prior art approaches. 
(3) This invention provides a lower leachate than the prior art approaches. 
(4) This method provides a method of pumping without the fly ash setting, 
or the result from slurry reaching high viscosity, during pumping. This 
method provides an approach that is as close as possible to continuous 
blending and injection yet allows air to escape, allows testing the 
slurry, allows maintaining parameters during injection and facilitates 
rapid restoration of optimum control parameters if deviation is shown by 
the testing. 
(6) This method allows use of other additives such as retarders or 
accelerators or inert fillers without adversely effecting the other 
features of this invention. 
(7) This invention allows pumping high ratios of lime-fly ash to water; 
that is, higher percentage solids, than the prior art methods. 
(8) This invention allows better introduction of additives such as 
accelerators or retarders by adding them to the slurry and injecting them 
within ten minutes. 
(9) This invention allows much higher production rates than possible 
heretofore. 
From the foregoing it can be seen that this invention accomplishes the 
objects delineated hereinbefore and provides improved process in this area 
of technology. 
Although this invention has been described with a certain degree of 
particularity, it is understood that the present disclosure is made only 
by way of example and that numerous changes in the details of construction 
and the combination and arrangement of parts may be resorted, to without 
departing from the spirit and the scope of the invention, reference being 
had for the latter purpose to the appended claims.