Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Field of the invention
The invention relates to a new injectable grout with improved properties.
Prior art
Injectable grouts based on hydraulic binder are widely employed for the
5 consolidation and/or sealing treatment of soils or of structures. These grouts may
be based on Portland cement with or without secondary constituents, on cement
produced from blast furnace slag, on alumina cement and the like.
These grouts can be injected to fill the intergranular cavities in soils,
fissures in a terrain or a structure, or spaces intended to provide seals, for example
10 of anchor rods or of nails or of reinforced micropiles.
The most important properties of an injectable grout are the stability, the
drainage resistance, the viscosity of the grout at the time of its use and the
compressive strength of the set grout.
Although a wide range of grouts is available, there is always need for
15 products with higher performance.
Summary of the invention
The invention is therefore aimed at providing an injectable grout based on
hydraulic binder with improved properties, in particular with high stability.
More precisely, the invention relates to an injectable grout including a
20 hydraulic binder in suspension in water, which additionally includes, relative to the
weight of the hydraulic binder, (A) from 2 to 50% by weight of particles of at least
one mineral substance whose median diameter is smaller than half the median
diameter of the particles of the hydraulic binder, and (B) from 0.05 to 5% by
weight of hydroxyethyl cellulose.
The invention also relates to a process for consolidation and/or sealing of
granular media and/or of fissured media by injection into such a medium of a
curable grout based on a hydraulic binder, wherein the said grout is as defined
above.
The particulate mineral substance (A) may be a substance which is inert
30 towards the hydraulic binder or reactive with the latter, provided that this reactivity
does not appreciably degrade the essential properties of the grout. Nonlimiting
examples of powders of mineral substances that can be employed are powdered
*
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mica, talc, kaolin, calcite, felspar, dolomite, silica, titanium dioxide, alumina and
the like. Where silica is concerned, fume silica and ground or precipitated silica
can be employed equally well.
The mineral substance (A) must have a finer particle size than that of the
S hydraulic binder employed, because its function is to provide a better particle size
distribution of the particles in suspension.
Tests have shown that better results are obtained when the median particle
diameter d50 of the mineral substance is smaller than half the median particle
diameter of hydraulic binder. The d50 of the powdered mineral substance will
10 usualIy be between 0.01 and 10,um, preferably between 0.01 and 5 ,um.
The proportion of mineral substance is not very critical and depends on
the fineness of the powder employed. Broadly speaking, it can represent from 0.2to 50% of the weight of the hydraulic binder. Below 0.2%, of the effect of the
addition of mineral substance is insignificant, whereas above 50% the addition of
15 the mineral substance can degrade the properties of the grout or of the product
obtained after the grout has set. It is usually preferred to incorporate from 1 to
10% of particulate mineral substance (A), in particular 2 to 5%.
Hydroxyethyl celluloses are products which are well known and
commerically available, which it seems pointless to describe further here. They are
20 employed in the invention as water-retainers.
The Applicant Company has found that, among the various types of
cellulose ethers, only hydroxyethyl celluloses and methyl hydroxyethyl celluloses
are usable, since carboxymethyl celluloses and carboxymethyl hydroxyethyl
celluloses cause flocculation of the grouts. Furthermore, the Applicant Company
25 has found that hydroxyethyl celluloses give grouts exhibiting properties that are
much superior to those of the grouts including methyl hydroxyethyl celluloses,
especially in respect of viscosity, drainage resistance and mechanical strength in the
short term.
The hydroxyethyl cellulose (HEC) may be employed in a proportion of
30 0.05 to 5% of the weight of the hydraulic binder. Below 0.05% the improving
effect produced is not significant and above 5% the viscosity of the grout tends to
become too high. The best results are obtained with a proportion of HEC
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representing 0.1 to 1% of the weight of the hydraulic binder. An HEC grade
exhibiting a low degree of viscosity will preferably be employed if it is desired to
obtain the lowest possible viscosity of the grout.
The hydraulic binder employed may be any known hydraulic binder, for
5 example Portland cement, slag cements, alumina cements, pozzolanas, fly ash and
the like.
It is also possible to incorporate into the grout any of the adjuvants
commonly employed in compositions based on hydraulic binder, especially
plasticizers, or in grouts, for example calcareous or siliceous fillers of coarser
10 particle size than that of the mineral substance of the invention.
The proportion of hydraulic binder in the water is that of the conventional
grouts. To give an indication, the hydraulic binder/water weight ratio may vary
from 0.2: 1 to 3: 1, preferably from approximately 0.5: 1 to 1.5: 1, depending
on the type of hydraulic binder. In particular, in the case of ultrafine cement the
C/W ratio will be lower than 1: 1, preferably from 0.3: 1 to 0.8: 1.
The invention will now be illustrated further by the following nonlimiting
examples.
In the examples the properties of the grouts were determined by the
following methods.
The drainage resistance is measured by a filtration test. The apparatus
employed is a Baroid'R~ filter press of the kind commonly employed for charac-
terizing drilling muds. A volume of approximately 600 cm3 of grout is introducedinto a cell whose lower part consists of a filter surface. A pressure of 0.7 MPa is
applied to the grout. The quantity of water passing through the filter surface is then
25 measured as a function of the period of application of the pressure and compared
with the result obtained with a control grout free from the additives (A) and (B) of
the invention.
The stability of the grout is determined by a settling test. One liter of
grout is introduced into a graduated glass test tube. The grout is kept at rest for
30 2 hours and the quantity of supernatant water is then measured. This water,
expressed as percentage of the initial volume, characterizes the settlement of the
grout.
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The viscosity, expressed in seconds, is the time taken by one liter of grout
to flow through a Marsh cone in which the diameter of the nozzle is equal to
4.75 mm.
The compressive strength Sc is measured on the set grout by the simple
5 compressive crushing method for cylindrical test pieces with a slenderness ratio of
2 (diameter = 40 mm, height = 80 mm) with the aid of a crushing press after 1,
2, 3 or 4 days' setting, depending on the case, and is expressed in MPa.
Examples 1 to 9, control examples 1 to 5 and comparative examples 1 and 2.
Grouts which had the compositions summarized in the table below were
10 prepared by the following general operating method:
The slaking water is introduced into a mixer, the mixer is started up, the
cellulose ether is dissolved in the slaking water and the hydraulic binder is then
added and, finally, the fine powder.
The properties of the resulting grouts were determined by the
15 abovementioned methods and the results have been collected in the table below.
In control examples 1 and 2, examples 1 and 2 and comparative examples
1 and 2 the binder employed was a CLK 45 type blast furnace slag cement from theSociété des Ciments Français, which had a d50 of approximately 11 ,um.
In the case of the control examples 3 and 4 and examples 3, 4, 5 and 6,
20 the binder employed was a CPA 55 type Portland cement also from the Société des
Ciments Français, which had a d50 of approximately 18,um.
In examples 7-9 and control example 5 the binder employed was an
ultrafine cement sold under the trade name SpinorA by the Société Ciments
d'Origny, which had a d50 of 2.5,um.
The source and the applicable d50 of the other materials employed were
as follows:
Supplier Trade name d5Q in ,um
SiO2 Elkem Microsilica 0.5
Al2O3 Degussa Aluminum Oxide C 0.02
TiO2 Degussa Titanium Dioxide P250.03
H EC 20 Hoechst Tylose H20
HEC 300 Hoechst Tylose H300 P
MHEC 300 Hoechst Tylose MH 300 P
TABLE
Cellulose ether Mineral powder Filtrate Mar_h Settle- Sc, MPa
Ex. C/W decrea_e/ vio-co- ment at
Nature ~/C O~ vi9- Nature %/C d50 control, oity, 2 hours, ld 2d 3d 4d
cosity
Control 1 1 - 0 - 0 21 ?
Ex. 1 1 HEC 0.5 300 sio, 5 0.50 98 46 4 2.2
Comp. ex. 1 1 MHEC 0.5 300 SiO, 5 0.50 87 60 3 1.5
Control 2 1.5 - 0 - 0 11 ?
Ex. 2 1.5 HEC 0.3 20 SiO, 5 0.50 97 42 0 10.2
Comp. ex. 2 1.5 MHEC 0.3 20 SiO, 5 0.50 71 58 0 8.0
Control 3 1 - O - O 18 ? ? ~n
Ex. 3 1 HEC 0.3 20 SiO, 2.5 0.50 79 36 2 1.8 5.3
Ex. 4 1 HEC 0.3 20 TiO, 5 0.03 73 37 3 1.8 4.7
Control 4 1.5 - 0 - 0 13 ? ?
Ex. 5 1.5 HEC 0.4 20 SiO, 5 0.50 97 49 0 6.5 16.5
Ex. 6 1.5 HEC 0.4 20 TiO, 2 0.03 88 60 1 4.4 10.7 t~
Control 5 0.5 - O - O 13 ? ? ~~
Ex. 7 0.5 HEC 0.4 20 SiO~ 5 0.50 51 36 0 0.98 1.75
Ex. 8 0.5 HEC 0.4 20 Tio, 2 0.03 34 38 0 1.15 2.27 C~
Ex. 9 0.5 HEC 0.4 20 Al,03 2 0.02 47 37 0 0.88 2.10
Note_ : C/W : Cement/water weight ratlo.
%/C : Weight percentage of the con_tituent in relation to cement.
HEC : H~IL~Arothyl celluloee.
NHEC : Nethyl h~d.~Arothyl cellulo~e.
? : Not nea_ured becau_e _ettlement very high (~ o not o-ignilicant).
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From this table it can be seen that the grouts of the invention have
properties which are markedly superior to those of the controls or to those of grouts
incorporating methyl hydroxyethyl cellulose, despite the close relationship of the
latter to hydroxyethyl cellulose.
