Filtrate reducer additive for swelling clay grouts and cement-swelling clay grouts

An additive for swelling clay grouts and cement-swelling clay grouts, intended to reduce the filtrate, lower and stabilize viscosity, retard rigidification time, limit sweating and sedimentation of the solid constituents, is an alkaline ethylenic acid polymer and/or copolymer, with molecular weight between 500 and 20,000, but preferably between 1000 and 6000. This additive is especially advantageous in the fields of civil engineering, building, public works and drilling.

The present invention concerns a new additive for swelling clay grouts and 
cement-swelling clay grouts, commonly used in civil engineering, building, 
public works and drilling, intended to greatly reduce filtrates, decrease 
and stabilize their viscosity, limit sedimentation of the solid 
constituents and retard rigidification. 
As used herein, cement-swelling clay grouts relate to grouts, mortars and 
plastic concretes, composed or not of a mixture which contains, among its 
constituent materials, swelling clays such as bentonites consisting of at 
least 60% by weight montmorillonite, or betonitic clays consisting of, for 
example, between 10 and 60% by weight montmorillonite, or montmorillonite, 
attapulgite, sepiolite, illite base clays, or other argillaceous 
constituents. 
The technician has known for some time that in the fields of civil 
engineering, building, public works, drilling, etc., the application of 
cement-swelling clay grouts presents problems which result in loss of time 
and product for the applier and make on-site handling difficult. 
This is why, for example, that during the construction of water-tight walls 
or shields in aquiferous permeable ground, the construction of 
prefabricated reinforced walls or the strengthening or tightening of 
ground, the use of cement-swelling clay grouts, when applied, often 
results in significant, bothersome problems such as, for example, changes 
in consistency with the premature thickening of the grout, which may 
either be due to filtration through the permeable ground or to significant 
grout loss because of infiltration in the ground near the work area. 
The on-site user experiences the above-cited problems which he knows well 
and which he has had to tolerate, for these problems effect construction 
time and construction costs. To illustrate one of the particular, harmful 
problems, the professional knows by experience that very often he must use 
a large quantity of grout, sometimes up to three times as much as the dig, 
when he works on very permeable terrain, for example, alluvial terrain. 
For several years, the technician, in his research, has tested ways to 
obtain cement-swelling clay grouts which would display basic qualities 
such as reduced filtrates, viscosity remaining low and constant in time, 
limited sedimentation of the solid constituents and retarded 
rigidification. 
Although much research has been done to alleviate the above-mentioned 
problems, the literature in the field focuses mainly on slow setting 
compositions. This literature cites, as common practice, adding slow 
setting compositions to, for example, concretes, these compositions 
generally being put in solution in the preparation water of said concretes 
in order to modify the hydration speed of the cement compounds. 
With this in mind, French Pat. No. 1 437 173 describes one such composition 
consisting of a slow setting agent and a soluble sulfate, with the slow 
setting agent being a lignosulfonic, gluconic, adipic, tetrahydroxyadipic, 
salicylic acid or a salt of these acids. 
To the same end, French Pat. No. 2 115 751 describes a clinker and/or blast 
furnace slag base hydraulic binder slow setting composition, said 
composition composed of polyphenols from the extraction of catechuic type 
Tanins. 
When used correctly, all of these additives are effective in retarding the 
setting of a hydraulic binder, or in making it more fluid, without 
disturbing mechanical performance, in specific technical applications such 
as utilization of hydraulic binder by pumping or distribution from a 
preparation plant, concreting in hot weather, concrete repair work, long 
distance and low depth grouting, etc. 
However, none of these additives applied to cement-swelling clay grouts 
were able to optimize those basic qualities desired for so long by the 
technician; these being greatly reduced filtrates, viscosity that is low 
and constant in time, limited sedimentation of solid constituents and slow 
rigidification. 
Well aware of these observations, the applicants, having researched a long 
time in this field, have found and developed a new additive performing 
well with cement-swelling clay grouts and able to reduce considerably the 
above-mentioned problems. 
The additive in the invention designed for swelling clay grouts and 
cement-swelling clay grouts, is characterized in that it is an ethylenic 
acid alkaline polymer and/or copolymer soluble in aqueous medium, with an 
average molecular mass comprised between 500 and 20,000, but preferably 
between 1000 and 6000. 
These ethylenic polymers and/or copolymers are prepared according to known 
processes by radical polymerization in aqueous medium or ethylenic acid 
hydroalcoholic medium in the presence of polymerization regulators such 
as, for example, hydroxylamine base organic compounds, and in the presence 
of polymerization initiators such as peroxides and persalts, for example, 
hydrogen peroxide, persulfates, etc. 
The ethylenic acid polymers and/or copolymers are generally made from 
ethylenic monomers, alone or in mixture, of acrylic, methacrylic, 
itaconic, maleic, fumaric, methallyl sulfonic acids and the methylic, 
ethylic, propylic, isopropylic and butylic esters of these acids; this is 
because the applicants have observed that when these esters are present, 
even in small quantities, the qualities of the new additive are 
reinforced. 
When the ethylenic acid polymers and/or copolymers are prepared in a known 
manner by radical polymerization in a hydroalcoholic medium, the alcohol 
is selected from the group composed of methanol, ethanol, propanol, 
isopropanol, butanol. 
After radical polymerization in the presence of well known regulators and 
initiators, the aqueous solution of polymerizate obtained is neutralized 
by an appropriate agent such as sodium, potassium, ammonium, lithium 
hydroxide or by a primary secondary or tertiary, aliphatic or cyclic 
amine, such as for example the mono, di or tri-ethanolamines, mono, di or 
tri-ethylamine, cyclohexylamine, methylcyclohexylamine, etc. 
The aqueous solution of polymerizate neutralized as above can be used in 
this form as a filtrate reducer additive, but it can also be treated, by 
all known methods, to eliminate its aqueous phase and isolate the 
neutralized ethylenic polymer and/or copolymer in the form of a fine 
powder which can be used as such as a filtrate reducer additive for 
cement-swelling clay grouts. 
In practice, the above grouts are formed of 5-600 kg/m.sup.3 of swelling 
clays, and preferably from 25 kg-400 kg/m.sup.3, and of 40 kg-2000 
kg/m.sup.3 of cement, and preferably from 80-400 kg/m.sup.3 of cement 
combined or not with aggregates of diverse origins and various size. 
The cements entering into the composition of the above grouts are generally 
common cements, for example, slag cements which are resistant to 
aggressive waters, such as, for example, water containing sulfates, sea 
water, etc. 
The amount of additive introduced into the cement-swelling clay grout is 
comprised between 0.01% by weight and 10%, but is preferably comprised 
between 0.5% and 2% by weight of dry material with respect to the swelling 
clay mass present. 
There are many ways that the additive in the invention can be introduced 
into the swelling clay grouts and the cement-swelling clay grouts. 
First, it can be incorporated into the swelling clay beforehand at any 
stage of its manufacture, this clay then being used to prepare the grout 
itself. 
It can also be added to the grout preparation water or to the swelling clay 
gel previously prepared. In this case, the cement is added to bentonite 
gel. 
Or the additive can be introduced into the already prepared cement-swelling 
clay grout. 
The applicants were able to observe that the additive in the invention 
introduced into the cement-swelling clay grouts improved significantly the 
properties of handling, fluidity, stability, homogeneity as well as the 
clogging properties due to the reduction of filtrates. 
It is therefore remarkable that within the given low weight concentrations, 
the additive in the invention, for the set grout, causes almost no 
sweating, no segregation of cement particles, fluidity which is much 
improved, low and stable in time as well as a 60-90% reduction of 
filtrates tested according to standard API RP 13 B. 
Finally, the applicants were particularly interested in noting that the 
additive in the invention has the added advantage of increasing the 
mechanical characteristics of the grouts once they have hardened, and 
improving the tightness characteristics of all the construction works 
built with these grouts because of the additive's excellent homogeneity. 
The significance and advantages of the invention will be better appreciated 
with the following examples.

EXAMPLE 1 
The purpose of this example is to show the object of the invention when the 
additive is an alkaline polyacrylate and to demonstrate the effects of 
this additive by comparing the characteristics of cement-bentonite grouts 
containing increasing quantities of said additive going from 0-4% by 
weight of commercial product to 40% dry extract with respect to the 
bentonite. 
The filtrate reducer additive was obtained by radical polymerization of 
acrylic acid in a hydroalcoholic medium constituted by a mixture of water 
and isopropanol, according to processes well known to the technician. 
The aqueous solution of acrylic polymer, free of isopropanol and 
neutralized by sodium hydroxide, had a dry material concentration of 40% 
and a density of 1.3. 
The average molecular weight of said polymer measured by gel chromatography 
was 3000. 
Then a cement-swelling clay grout was prepared by introducing, at 
15.degree. C. into a 5 liter beaker, 2000 g of water and 60 g of Bentonite 
(Bentonil C.V. 15 prepared with bentonite from the Island of Kimolos), 
subjecting the suspension thusly constituted to stirring for 5 minutes by 
means of a Rayneri stirrer, with a rotation speed of 2200 RPM, this 
stirrer equipped with a centripetal turbine 500 millimeters in diameter. 
After the bentonite gel has set for one hour, the additive in the invention 
is added, in the form of a 40% dry material aqueous solution, and the 
mixture is stirred for two minutes. 
Finally, 400 g of CLK 45 cement, composed of 20% clinker and 80% slag, is 
introduced into the additive-added bentonite gel and subjected to the same 
stirring for 7 minutes. 
The cement (C) water (W) ratio, written C/W, of the cement-bentonite grout 
is equal to 0.2. 
The additive in the invention was introduced into the bentonite gels in 
concentrations increasing from 0-4% by weight of product to 40% with 
respect to the bentonite. test 1 is the reference test for the 
cement-bentonite grout without said additive and tests 2-5 demonstrate the 
object of the invention. 
The various bentonite gels before and after the additive was added, then 
after the cement was introduced, underwent several checks, such as 
apparent MARSH viscosity, API filtrate and cake, sweating and 
rigidification time corresponding to MARSH viscosity of 1 minute 30 
seconds, with the grout being stirred slowly between 400 and 600 RPM. 
MARSH viscosity is measured in an apparatus with the same name, formed of a 
cone with a 1500 cm3 capacity, equipped at its bottom with a nozzle 
calibrated at 4.74 millimeters (3/16 inch USA) and a cm3 graduated cup; to 
take this measurement, close the nozzle, fill the cone with the suspension 
that has been previously filtered on a 10 Mesh screen, then determine the 
time required for a 946 cm3 (1/4 gallon USA) flow of the aforementioned 
suspension. This time expressed in seconds is commonly referred to as 
MARSH viscosity. 
The filtrate and cake were measured according to US standard API No. RP 13 
B. 
Sweating is measured with a 1-liter graduated test tube into which a 
cement-bentonite grout is placed. After setting for 4 hours, the change in 
separation between the suspension and the aqueous phase is observed and 
measured; sweating is expressed as a percentage of the volume of aqueous 
phase compared with the initial volume of grout. 
All results for the various bentonite gels before and after the cement is 
introduced obtained by the above-mentioned check methods are shown in 
Table 1 below. 
TABLE 1 
______________________________________ 
Test 1 
Test 2 Test 3 Test 4 
Test 5 
______________________________________ 
Additives as in 
0% 1% 2% 3% 4% 
invention 
for bentonite gel only 
Marsh Viscosity 
33.5 31 30 29 28.5 
in seconds 
A.P.I. filtrate 
14 13.5 13 12 11.5 
in cm3 
for grout after addition of 200 g/l 
of CLK 45 cement 
Marsh Viscosity 
43 41 38 37 36 
in seconds 
A.P.I. filtrate 
195 135 95 65 45 
in cm3 
Cake thickness 
9 6.5 4.5 2.5 2.1 
in mm 
Sweating in % 
1 0 0 0 0 
Rigidification time 
4-5 6-7 8-9 10-12 more than 
in hrs. 20 
______________________________________ 
The introduction of the additive in the invention causes a very significant 
reduction of filtrate, as indicated by the API measurement when the 
additive in the invention is introduced in increasing quantities. 
It can also be seen that when said additive is introduced into the 
cement-swelling clay grout, there is almost no sweating. 
Marsh viscosity is reduced to a value which greatly facilitates work 
conditions after the additive in the invention is added. Finally, the 
rigidification time is actually quite increased enabling easier on-site 
handling. 
EXAMPLE 2 
This example shows the general behavior of the additive no matter which 
swelling clay is used in the grout. 
In this case, the swelling clay was prepared with a treated Bavarian 
bentonite (Bentonil C for drilling). 
The additive used was the same as in example 1, as were the operating 
conditions, checks, etc., for this additive and grouts. 
As in example 1, the additive in the invention was introduced in 
concentrations increasing from 0-4% by weight of commercial product to 40% 
dry extract with respect to the swelling clay. 
Test 6 is the reference test for the grout without additive and tests 7-10 
demonstrate the object of the invention. 
All results obtained with these checks are found in Table 2 below. 
TABLE 2 
______________________________________ 
Test 6 Test 7 Test 8 Test 9 
Test 10 
______________________________________ 
Additives as in 
0% 1% 2% 3% 4% 
invention 
for Bentonite gel only (approx. 24 hrs. set) 
Marsh Viscosity 
42 34 33 32 32 
in seconds 
API filtrate 
27 19 18 18 17 
in cm3 
for grout after addition of 200 g/l 
of CLK 45 cement 
Marsh Viscosity 
35 35 34 33 33 
in seconds 
API filtrate in 
155 82 78 72 70 
cm3 after 30 min 
Cake thickness 
7.5 4 3 2.8 2.5 
in mm 
Sweating in % 
2.5 1.5 1.0 0.8 0.5 
Rigidification time 
4-5 7-8 9-10 15 25 
in hours 
______________________________________ 
As in example 1, there is a considerable reduction of filtrate and sweating 
and an increase in rigidification time. All of these improved 
characteristics attest to the very beneficial effects of the additive in 
the invention. 
EXAMPLE 3 
This example illustrates, comparatively, the behavior of the additive in 
the invention when it is chosen from acrylic polymers as well as from 
acrylic copolymers. 
For this example, the applicants performed three reference tests: 11 
(reference test without additive, 12 (a sodium polyacrylate additive) and 
13 (an acrylic copolymer additive in the form of sodium salt). 
The swelling clay used for these tests as well as the preparation 
conditions, implementation and checks of grouts were the same as in 
example 1. 
The additive in the invention introduced at the rate of 3% by weight of 
commercial product to 40% dry extract with respect to the swelling clay, 
was: 
test 12: the same polymer as in example 1, 
test 13: an acrylic, methacrylic and methallyl sulfonate acid copolymer in 
the form of sodium salt with an average molecular weight equal to 3000, 
obtained according to processes known to the technician, by radical 
copolymerization in a hydroalcoholic medium constituted by a mixture of 
water and isopropanol. 
All the results obtained for the various bentonite gels before and after 
the addition of 200 g/l of CLK 45 cement are given in Table 3 below. 
TABLE 3 
______________________________________ 
Test 13 
Test 12 acrylic 
acrylic polymer 
copolymer 
Test 11 
40% dry ext. 40% dry ext. 
______________________________________ 
Additives as in 
0% 3% 3% 
invention 
for Bentonite gel only 
Marsh viscosity 
33.5 29 30 
in seconds 
API filtrate 
14 12 13 
in cm3 
For grout after addition of 200 g/l 
of CLK 45 cement 
Marsh viscosity 
43 39 39 
in seconds 
API filtrate in 
195 65 80 
cm3 after 30 min 
Cake thickness 
10 2.5 4.5 
in mm 
Sweating in % 
1.5 0 0 
Rigidification 
4-5 10-12 8-10 
time in hours 
______________________________________ 
As can be seen, the introduction of an acrylic copolymer as an additive in 
the invention produces almost the same results as those already observed 
when the additive is an acrylic polymer, i.e., greatly reduced filtrate, 
almost no sweating and reduced Marsh viscosity. 
EXAMPLE 4 
In this example, the applicants have shown, in tests 14-21, that the 
qualities provided to the cement-swelling clay grouts with the additive in 
the invention (test 15), these qualities being low and stable viscosities, 
filtrate reduction and reduced cake thickness, are much better than those 
qualities given to the same grouts into which additives from prior art 
were introduced, additives such as: calcium lignosulfite (tests 16 and 
17), ferrochrome lignosulfonate (tests 18-19) and sulfonic 
polynaphtylmethane (tests 20 and 21). 
In all these tests, the swelling clay was the same as in example 1. 
The grout preparation conditions and the checks were also the same as in 
example 1. 
Also, the additive in the invention introduced in test no. 15 was the same 
as in example 1. 
All the results obtained for the Bentonite gel and for the grouts after the 
addition of 200 g/l of CLK 45 cement are given in table 4 below. 
TABLE 4 
__________________________________________________________________________ 
Reference 
test 14 
Test 15 
Test 16 
Test 17 
Test 18 
Test 19 
Test 20 
Test 21 
__________________________________________________________________________ 
Additive 
no Sodium 
Calcium ligno- 
Ferrochrome 
Sulfonic poly- 
type additive 
poly- 
sulfite - 
lignosulfonate 
naphtyl methane - 
acrylate - 
25% dry ext. 
powder - 
40% dry ext. 
40% 95% dry ext. 
dry ext. 
Concentration 
0 3 10 20 3.5 7 10 20 
in % of com- 
mercial product 
for bentonite gel only 
Marsh vis- 
33.5 29 31.5 
31 31 31 31.5 31.5 
cosity in sec. 
for grout after addition of 200 g/l of CLK 45 cement 
Marsh viscos- 
43 37 43 52 42 40 44 38 
ity in sec. 
API filtrate 
195 65 130 95 130 110 105 78 
in cm3 after 
30 minutes 
Cake thick- 
10 2.5 7.5 4.5 7.5 5 6 3.5 
ness in mm 
Sweating in % 
1.5 0 0 0 0 0 0 0 
Rigid. time 
4-5 10-12 
16 30 15 8 6 8 
in hours 
__________________________________________________________________________ 
All of these results demonstrate the remarkable performance of grouts into 
which the applicants have introduced the additive in the invention, 
especially concerning filtrate reduction.