Composition of matter useful for earthen formation treatment

A gel-forming composition of matter comprising an aqueous solution of a mixture of certain percentages of monomeric acrylamide and monomeric N,N' methylenebisacrylamide and a polymerization catalyst and containing certain percentages of an unfired natural diatomaceous earth having a certain particle size is used in treating earthen formations around the joints of sewer pipes, whereby fluid loss from the composition into the earthen formation is substantially reduced.

BACKGROUND OF THE INVENTION 
Mixtures of acrylamide and N,N'methylenebisacrylamide dispersed in an 
aqueous medium have been catalyzed and injected into earthen formations 
for a plurality of years wherein the aqueous solution is catalyzed with a 
sufficient amount of the polymerization catalyst so as to cause the 
mixture of monomeric acrylamide and the monomeric bisacrylamide to form a 
substantial gelled material in the earthen formation and thereby block the 
permeation of water in the area of the gel. The aqueous solutions of this 
mixture of monomers have been used with various additives in order to 
achieve various diverse effects in the earthen formations. These uses vary 
from stabilization of the soil, waterproofing of concrete or masonry 
surfaces, hydraulic cement compositions, for the prevention of gas loss 
during gas drilling and other drilling operations such as oil wells and 
the like. 
1. Field of the Invention 
The present invention is in the field of a treatment of earthen formations, 
and more particularly, earthen formations around sanitary sewer joints 
that are filled with said gel to control ground water infiltration. The 
invention also covers said gel in a dried soil application where there is 
no water in the storm sewer joint and the soil around the sewer is dry. 
2. Description of the Prior Art 
The idea of using mixtures of acrylamide and N,N'methylenebisacrylamide in 
aqueous solutions for the stabilization of soil was developed in the early 
1950's. Reference is made to the U.S. Pat. Nos. 2,801,983; 2,801,984; 
2,801,985; 2,868,753; 2,940,729; 3,056,757; 3,136,360; and 3,223,163, all 
of which patents are incorporated herein by reference. 
SUMMARY OF THE INVENTION 
This invention relates to a composition of matter comprising an aqueous 
solution containing from about 5% to about 20%, by weight, based on the 
total weight of the solution of a mixture of (A) from about 80% to 99.5%, 
by weight, of monomeric acrylamide and correspondingly (B) from about 20% 
to 0.5% by weight of monomeric N,N'methylenebisacrylamide wherein the 
percentages by weight of said monomers total 100%, and (C) from about 4% 
and 20%, by weight, of an unfired natural diatomaceous earth, 80 percent 
of which, having a particle size between about 2 .mu. and 10 .mu. and the 
percentage by weight of said diatomaceous earth is based on the total 
weight of the solution. This invention also relates to the use of this 
composition in a catalyzed state in the treatment of earth formations. 
This invention also relates to compositions of matter containing the 
mixtures of the monomers in an aqueous solution containing the said 
unfired natural diatomaceous earth in conjunction with an inorganic, 
hydrated water-soluble metal salt wherein said metal is selected from the 
group consisting of alkaline earth metals, aluminum and chromium in 
certain percentages. 
The monomeric acrylamide is used in combination with the monomeric 
N,N'methylenebisacrylamide in a weight ratio of between about 80% to 99.5% 
: 20% to 0.5% respectively wherein these percentages are by weight and 
total 100%. It is preferred to use the acrylamide in a weight ratio 
varying between 85% and 96% and the N,N'methylenebisacrylamide 
correspondingly between about 15% and 4%. For optimum results, the 
acrylamide is used in a weight ratio of 95% and the 
N,N'methylenebisacrylamide is used correspondingly in a weight ratio of 5% 
wherein the percentages are always based on the total weight of the two 
monomeric matials. The amount of the mixture of these monomers in the 
aqueous solution may be varied between about 5% and 20%, by weight, based 
on the total weight of the solution of the monomer mixture in the water. 
It is preferred to use between about 8% an 15%, by weight, of the monomers 
based on the total weight of the monomer mixture in solution. The mixture 
of the monomeric acrylamide and the monomeric N,N'methylenebisacrylamide 
is a commercially available material and is designated as AM-9 for the 
sake of brevity. Cyanamid AM-9 is a trademark used by American Cyanamid 
Company to identify its chemical grout. 
The diatomaceous earth used in the composition of the present invention is 
an unfired natural diatomaceous earth, 80 percent of which, having a 
particle size between about 2 .mu. and 10 .mu. and used in an amount 
varying between about 4% and 20%, by weight, based on the total weight of 
the solution of the AM-9. When a diatomaceous earth material is first 
recovered from nature, it is washed and sold with its natural properties 
or it is fired to change its properties. When the diatomaceous earth 
material is to be fired, it is introduced into a kiln and the kiln is 
heated at a temperature varying between about 1700.degree. and 
1900.degree. F. for a period of time varying between about 10 minutes and 
about 60 minutes. During this firing step, the organic materials contained 
within the natural diatomaceous earth are burned off and the particle size 
of the diatomaceous earth is changed. The particle size is increased as a 
result of the firing step. The surface properties of the diatomaceous 
earth are also changed during the firing step which causes the fired 
material to settle out of a dispersion in water very quickly. The unfired 
diatomaceous earth settles very slowly in water as compared to the fired 
diatomaceous earth. This change in the surface properties of the 
diatomaceous earth causes it to settle out very quickly in grouting 
equipment which is used in the field. For the purposes of the present 
invention, there is needed a non-settling diatomaceous earth system in 
order to give a practical system for applying this chemical grout to 
grouting sewer joints in the field. It is theorized that during the kiln 
firing step that the surface properties of the diatomaceous earth are 
changed, the particles agglomerate and their surface area is reduced. 
These larger diatomaceous earth particles filter out undissolved solids 
from the AM-9 solution and allow the remaining solution to penetrate 
further into the stabilized mass; thereby increasing fluid loss. 
In the U.S. Pat. No. 3,136,360, issued in the name of Ramos and McLaughlin, 
the diatomaceous materials, which they disclosed, are the fired 
diatomaceous earth materials and they use these materials because they are 
interested in substantially increasing the fluid loss of their composition 
in the earthen formation that is being treated. When the larger size 
particles of fired diatomaceous earth are used, the tendency to "blind" is 
minimized and, therefore, the fluids can penetrate through the particle 
size agglomerates and this results in the increased fluid loss. The 
expression "blind" is used to identify that situation when one fills up 
the holes with small particles and thereby prevents the fluid from being 
lost. The use of such large particle size fired diatomaceous earth 
markedly improves the penetration of the AM-9 solution into the earthen 
formation whereas when the unfired diatomaceous earth material of much 
smaller particle size is used, the total composition blinds the holes by 
filling them up and reduces the penetration. The total composition, when 
blinded, stays where it is injected in the earthen formation and becomes 
gelled therein due to the presence of the catalytic material and the 
resulting gel protects the sewer pipes. Ramos et al. state that they use 
the finely-divided water-inert filter aid material in sufficient quantity 
to substantially increase the fluid loss of said composition into the 
formation to be treated. Ramos et al. make use of relatively small 
percentages of their fired diatomaceous earth material. The largest amount 
that Ramos et al. utilize is 10 grams which is calculated to be about 1% 
based on a 1,000 g. total solution. The smallest amount that Ramos et al. 
utilize is 0.75 grams which is about 0.075%. These quantities are shown in 
Table 1 of the above-cited Ramos et al. patent. Ramos et al., therefore, 
utilize smaller percentages of larger particle size of a fired 
diatomaceous earth material whereas in the present invention much larger 
quantities of smaller particle size unfired diatomaceous earth is utilized 
for a completely different purpose, namely, to reduce the penetration and 
to keep the composition where it is required until it has gelled and, 
thereby, protecting the sewer pipes which it surrounds to prevent ground 
water infiltration. The amount of the unfired natural diatomaceous earth 
that is used in the composition of the present invention will vary between 
about 4% and 20%, by weight, based on the total weight of the AM-9 
solution. It is preferred to use between about 8% and 15% of the unfired 
diatomaceous earth material, by weight, based on the total weight of the 
AM-9 aqueous solution. 
Reference is made hereinabove to the U.S. Pat. No. 3,056,757 which 
discloses and claims the use of certain inorganic, hydrated, water-soluble 
metal salts in an AM-9 solution wherein said metal is selected from the 
group consisting of alkaline earth metals, aluminum and chromium and said 
salt is present in a weight ratio of said monomer mix to said salt in the 
range between about 1:1.5 to about 1:12 respectively. This means that when 
there is 5% of the AM-9 in the aqueous solution, one may use as little as 
7.5% of the salt in the solution. The upper amount of the metal salt which 
may be used in the composition of the present invention may be as high as 
about 240% by weight based on the total amount of the monomer mixture 
present in the solution. The above-cited patent, which is incorporated 
herein by reference, shows the use of percentages varying between about 0% 
to about 40%, by weight, of calcium chloride based on the total weight of 
the gel of the AM-9. 
The inorganic, solid, hydrated, water-soluble metal salt, such as calcium 
chloride that is used in combination with the said diatomaceous earth is 
preferably used in an amount varying between 5% and 10%, by weight, based 
on the total weight of the aqueous solution of the mixture of the 
monomers. 
The catalyst used in the composition of the present invention just prior to 
its use and injection into an earthen formation can be any one of a 
plurality of well-known catalysts and catalyst combinations that have been 
used with AM-9 compositions over a period of years. One of the most 
frequently used catalyst systems is a redox system comprising a mixture of 
ammonium persulphate and sodium thiosulphate or a mixture of ammonium 
persulphate and sodium bisulfite. The amount of the catalyst used can be 
varied considerably depending on the type of gel one wishes to produce and 
the speed of the gellation. These gels may be in the form of a slurry, a 
thick solid, a rubbery solid or a stiff solid. Ordinarily, one would use 
between about 0.01% to about 10.0%, by weight, based on the total weight 
of the polymerizable monomer mix. It is preferred to use about 1% to about 
2%, by weight, same basis. If desired, one may make use of any of the 
conventionally available peroxide catalysts as the catalytic material for 
the polymerization of the monomer mix, such as benzoyl peroxide, tertiary 
butyl hydroxide, tertiary butylhydroperoxide, and the like. The U.S. Pat. 
No. 2,940,729 illustrates a plurality of additional catalytic materials 
which can be used in the composition of the present invention immediately 
prior to use. Said patent is incorporated herein by reference. 
The type of earthen material that can be treated with the composition of 
the present invention may be sand, kaolnite, Ventura clay, Connecticut top 
soil and the like. When the compositions of the present invention are 
being used near sewer pipes, and more particularly, storm sewer pipes, 
such pipes are frequently embedded in crushed stone. It is in such an 
application that the calcium chloride proves to be most effective since 
the use of calcium chloride in combination with the unfired natural 
diatomaceous earth enables one to control the shrinkage in the dry soil 
application where there is no water and in the storm sewer joint where the 
soil or crushed stone around the sewer joint is dry. The unfired natural 
diatomaceous earth used in the composition of the present invention gives 
increased strength to the gel ultimately produced in situ, especially when 
it is used in earthen formations composed principally of crushed stone, 
namely, open sewer joints that are embedded in said crushed stone. 
In order that the concept of the present invention may be more completely 
understood, the following examples are set forth in which all parts are 
parts by weight unless otherwise indicated. These examples are set forth 
primarily for the purpose of illustration and any specific enumeration of 
detail contained therein should not be interpreted as a limitation on the 
case except as is indicated in the appended claims.

EXAMPLE I 
Into a suitable mixing vessel, there is introduced 342 parts of water, 95 
parts of monomeric acrylamide, 5 parts of N,N'methylenebisacrylamide, 8 
parts of dimethylaminopropionitrile and 50 parts of a commercially 
available unfired natural diatomaceous earth material having a particle 
size of about 80% between 2.mu.-10.mu.. The four materials are blended 
together to make a substantially homogeneous blend. In a separate mixing 
vessel there is introduced 440 parts of water, 50 parts of the same type 
of unfired diatomaceous earth introduced into the first mixing tank and 10 
parts of ammonium persulfate. The ingredients in the second mixing tank 
are thoroughly blended together to produce a substantially homogeneous 
stable suspension. The two mixtures are withdrawn separately from their 
mixing tanks and are blended together just before the time when they are 
injected into a soil formation around a sewer joint in order to direct the 
infiltration of the ground water into the joint. The soil temperature is 
about 60.degree. F. and the gel time at that temperature is about 30 
seconds. There results around the sewer joints that are embedded in 
crushed stone, the required grout with increased viscosity, which had the 
required strength and blinding action so as to cause the grout to gel 
close to the sewer joint. 
EXAMPLE II 
Into a suitable mixing vessel there is introduced 266 parts of water, 95 
parts of monomeric acrylamide, five parts of N,N'methylenebisacrylamide, 
four parts of dimethylaminopropionitrile, 100 parts of calcium chloride 
and 30 parts of unfired natural diatomaceous earth having a particle size, 
of about 80%, between 2.mu. and 10.mu.. The components are thoroughly 
blended together to make a stable suspension. Into a separate mixing 
vessel, there is introduced 352 parts of water, 8 parts of ammonium 
persulfate, 100 parts of calcium chloride and 40 parts of the same 
commercially available unfired natural diatomaceous earth material used in 
the first tank having a particle size average, about 80%, between 2.mu. 
and 10.mu.. The contents of the second mixing vessel are thoroughly 
blended to produce a stable suspension. The contents of the two mixing 
vessels are then blended together, at the moment of use, and are 
introduced into an earthen formation having a temperature of about 
60.degree. F. and the composition gels in about 20 seconds. The resulting 
grout had increased strength viscosity and blinding action so as to cause 
the grout to gel close to a sewer joint. 
To the compositions of the present invention one may add other inert or 
active solids, including polymers, copolymers, crosslinking agents, 
inhibitors, root inhibitors, shelf life stabilizers for the liquid AM-9 
and the like. This is done to increase the utility of the AM-9 based 
grouting system in order to control infiltration in sewer joints, to 
control underground water flow, to stabilize solids and to increase the 
strength of stabilized soils.