CS252318B1 - Expansion pad and grout with reduced filterability - Google Patents

Abstract

Expansion tamponage and injection mixture with reduced filterability based on cement with ground lime, containing polyvinyl alcohol as an anti-filtration additive. The purpose of the invention is to increase the anti-filtration effect of the mixture and eliminate the negative side effects of polyvinyl alcohol, in particular the extended setting time, reduced fluidity and foaming. The purpose is achieved by the composition of the mixture. It contains in parts by weight 50 to 70 Portland cement, 1 to 10 finely ground lime, 20 to 40 water, 0.3 to 6 anti-filtration and plasticizing additive, which consists, expressed in weight percentages, of 30 to 70% of dry matter of polyvinyl alcohol, 70 to 3d% of derivatives of salts of ligninsulfonic acids or formaldehyde either with naphthalenesulfonic acids, or with alkylsulfonated polyphenols, or with melamine. The solution can be used in the fields of deep drilling, mining and underground engineering, and in the field of foundation construction.

Description

The invention relates to an expansion tamponage and injection mixture with reduced filterability based on cement with ground lime containing polyvinyl alcohol as an anti-filtration additive.

The purpose of the invention is to increase the anti-filtration effect and eliminate the negative side effects of polyvinyl alcohol, especially the extended setting time, reduced fluidity and foaming of the mixture. The mixture is intended especially for tamponing deep wells and soil injection.

Expansion tamponage mixtures seal the borehole better than mixtures without hydration reactions, the resulting tamponage stone has a stronger bond to the borehole wall and to the casing column and is denser and less permeable. The advantages of expansion injection mixtures for soil consolidation and isolation can also be characterized. Expansion tamponage and injection mixtures based on ordinary cement with 1 to 15% by weight of finely ground lime are known /US 3 883 361, 3 884 710,

046 583, 4 002 483/, which are suitable for strengthening non-cohesive but impermeable rocks.

The disadvantage of known expansion tamponage mixtures is that in porous geological formations the liquid phase is filtered out of them into the surrounding rock, the mixture thickens and becomes unpumpable. Similarly, when injecting porous rocks, the liquid phase is filtered out of known expansion injection mixtures, capillaries and cracks are clogged with the drained mixture and parts of the rock remain uninjected.

Also known are expansion tamponage and injection mixtures based on cement, containing polyvinyl alcohol as an anti-filtration additive in an amount of 0.5 to 1.5% by weight, based on cement /Rakhlmbayev et al., Obrabotka cementnych rastvorov polyvinylovym spirtom, Nauchnotechnicheskij sbornik Burenle, Moscow 1967, Voloshln et al., O mechanizme ponizhenija vodootdači tamponažnogo rastvora polyvinylovym spirtom, Sbornik IV., Kiev 1977, pp. 137-8/.

The disadvantage of known expansion tamponage and injection mixtures with polyvinyl alcohol is that the anti-filtration effect of polyvinyl alcohol occurs only in connection with some types of cement. It has a low to negligible effect, for example, in connection with Portland, slag-Portland and fast-setting cements. In addition, its negative side effects are more pronounced, such as prolonging the setting of the mixture, reducing its fluidity and tendency to foam. The negative effects of polyvinyl alcohol could not be eliminated even by adding soda and a plasticizer, analogously to the tamponage mixture without a hydration reaction /CS 214 490/.

The above-mentioned shortcomings are eliminated by the expansion tamponage and injection mixture with reduced filterability according to the invention, the essence of which is that it consists of 50 to 70 parts by weight of Portland or slag Portland cement, 1 to 10 parts by weight of finely ground lime, 20 to 40 parts by weight of water and 0.3 to 6 parts by weight of an anti-filtration and plasticizing additive, containing 30 to 70% by weight of polyvinyl alcohol dry matter and 70 to 30% by weight of derivatives of salts of lignin sulfonic acids or condensates of formaldehyde with naphthalene sulfonic acids, or with alkyl sulfonated polyphenols, or with melanin.

The mixture according to the invention exhibits a high anti-filtration effect with unchanged expansion efficiency. The anti-filtration and plasticizing additive, polyvinyl alcohol with a plasticizer, does not reduce the expansion effect of lime and at the same time synergistically potentiates the anti-filtration effect.

High expansion values and low filtration values do not suppress the secondary favorable properties of the mixture. For example, a mixture with an optimal linear expansion of 4% exhibits low filterability values, 15 cm^ at 0.7 MPa, while being stable, having good fluidity, low internal friction and the resulting cement stone, characterized by increased impermeability, reliably adheres to most types of rocks. The mixture according to the invention guarantees full effectiveness even at elevated temperatures up to 70 °C.

It can be prepared from all types of cement, especially from conventional Portland, slag Portland and rapid-setting cements. The application of additional additives to adjust the mixture according to the requirements of local conditions, especially the application of surfactants, is possible.

Examples

Property 1 of the expansion tamponage and injection mixtures with reduced filterability according to the invention were verified during mine sealing works and tested in the laboratory. Six samples of the mixture prepared from Portland cement class 400 or slag Portland cement class 325, finely ground lime with a residue of 8% on a mesh of 0.02 mm and polyvinyl alcohol in the form of an aqueous 16% solution were tested. As a plasticizer, a formaldehyde condensate with naphthalenesulfonic acids was used, as a plasticizing retarder, an alkylsulfonated polyphenolic condensate with formaldehyde or salts of ligninsulfonic acids in the form of sulfite calcinations, and as a defoamer, 2-ethylhexanol was applied to the mixture. Sample mixtures according to the invention were prepared at 22 °C + 3 °C by mixing cement with finely ground lime and adding mixing water in which the remaining components were dissolved. The mixture was mixed for 30 seconds in a high-speed laboratory mixer at a mixer speed of 5,000 to 9,000 min ^-1 and for 20 minutes in a slow-speed laboratory mixer at a mixer speed of 140 min ^-1 . The laboratory test methodology was in accordance with industry standards and internationally applied procedures.

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The specific gravity of the mixture in kg. m was determined pycnometrically, the setting time on the Vicat apparatus and the filterability at a pressure of 0.7 MPa after 30 min. The compressive and bending strength of the cement stone was determined on test specimens measuring 20x20x80 mm. The linear expansion was monitored on a column of the mixture in a glass cylinder so that the change in the height of the column was transmitted by a piston to a height change indicator. The determined expansion was expressed in percent as the ratio of the change in the height of the column of the mixture after 24 hours from its mixing to the initial height. The volumetric change of the cement stone was determined by measuring the longitudinal deformations of test specimens measuring 40x40x160 mm in the longitudinal axis of the specimen during its hardening. The measured volumetric changes of the cement stone were expressed in percent as the ratio of the change in the length of the test specimen in specified time intervals to the original length of the specimen. The adhesion of the cement stone was determined as the contact strength between the cement annulus and the inner metal roller of the adhesiometer. The shear strength V was calculated from the relationship

=. —· /MPa/ where N is the force required to break the contact between the cement annulus and the inner roller of the adhesion meter and S is the contact area.

The results of laboratory testing of six different samples of the mixture according to the invention and the composition of the components from which the samples were prepared are shown in the following table.

Mixture composition and type of test Dimension 1 Trial 2 sample 3 4 5 6 Portland cement grade 400 62.00 64.83 65.52 62.52 62.67 Class 325 Slag Portland Cement - - - - - 62.67 Finely ground lime 4.67 4.14 3.45 3.99 4.00 4.00 Water % 32.09 29.97 29.97 32.48 32.42 32.09 Polyvinyl alcohol in dry matter mass 0.75 0.66 0.66 0.75 0.75 0.75 Condensate of formaldehyde with naphthalene sulfonic acids 0.46 0.37 0.37 - - 0.46 Formaldehyde condensate with alkylsulfonated polyphenols 0.13

Salts of lignosulfonic acids

/sulphate firings/ - - - 0.23 - - 2-ethylenehexanol 0.03 0.03 0.03 0.03 0.03 0.03 Specific gravity , -3 kg.m 1,900 1,890 1,920 1,820 1,780 1,830 Start of solidification h-min 8-30 7-10 7-10 7-50 7-30 14-30 Setting time 12-00 9-10 9-50 10-00 10-20 19-40 Compressive strength after 7 days MPa 7.2 16.0 18.3 10.9 6.4 4.0 Bending strength after 7 days 4.1 5.4 6.3 4.6 3.6 1.9 Volume change of cement stone 'after 2 days' % 1.4 1.3 0.8 2.0 2.5 1.5 after 7 days 1.6 1.5 1.0 2.0 2.6 1.7 after 14 days 1.7 1.5 1.0 2.0 2.6 1.7 Linear expansion % 2.3 1.7 0.9 2.3 2.5 2.4 Adhesion after 2 days MPa 1.3 2.5 3.4 2.0 1.5 0.7 Filtration cm^/30 5.5 74 92 163//15° 7 138//18 °/ 5.5

The table shows that the expansion and tamponage mixture according to the invention exhibits good physical and mechanical properties at low filterability. Samples containing Portland cement 1 to 5 have a significantly shorter setting time, greater strength and better adhesion to the environment than the sample containing slag Portland cement, sample no. 6. However, the latter has higher corrosion resistance. If the mixture is required to have very low filterability, even at the expense of strength, the dosage of components according to sample 1 is selected. On the contrary, if the mixture is required to have high strength at the expense of filterability, the dosage of components according to sample 3 is selected. The samples according to the table do not exhaust the entire variability of possible combinations of components, for the selection of which the purpose and ambient conditions are decisive. Due to these possibilities, the mixture according to the invention is applicable for tamponing deep wells, even in environments with temperatures up to 70 °C, for eliminating caverns in wells, for tamponing small-diameter wells, for grouting in rock, for sealing and grouting work on the surface and in mines.

The invention is applicable in the field of deep drilling, mining and underground engineering, and in the field of foundation construction.

Claims (1)

SUBJECT OF THE INVENTION An expandable tamponage and injection composition with reduced filterability, characterized in that it consists of 50 to 70 parts by weight of Portland or slag-portland cement, 1 to 10 parts by weight of finely ground lime, 20 to 40 parts by weight of water and 0.3 to 6 parts by weight of antifiltration and plasticizers containing 30 to 70% by weight of polyvinyl alcohol dry matter and 70 to 30% by weight of derivatives of salts of ligninsulphonic acids or formaldehyde condensates with either naphthalenesulphonic acids or alkylsulphonated polyphenols, or melamine.