SK280334B6 - Injection grout for sealing and/or consolidating soils or materials exhibiting a very low permeability and process of making it - Google Patents

Abstract

An injection grout for sealing and/or consolidating soils or materials exhibiting a very low permeability, of the type consisting of the mixture of a powder based on slag in suspension in water and of a silica liquor. The silica liquor has an SiO2/Na2O molar ratio lower than 0.8 and a silica content of between approximately 0.01 and 5 % by weight. A process for preparing said injection grout can be characterised in that a powder based on a blast slag, which is suspended in water with a dispersion agent added thereto, is mixed with an aqueous solution of sodium silicate obtained by dissolving a silicon dioxide powder or siliceous product, whereas the particles have a diameter less than 100 um, in an aqueous solution of NaOH having the thickness preferably in the range between 1.32 - 1.34 g.ml-1.

Description

Technical field

The invention relates to an injection mortar for sealing and / or reinforcing soil or materials having a very low permeability and to a process for the production of this injection mortar.

BACKGROUND OF THE INVENTION

EP 0 336 825 and DE 2 228 791 disclose injection mortars obtained by mixing blast furnace slag dust suspended in water and aqueous sodium silicate solution having a silica to sodium oxide ratio of less than 2 and a silica content of more than 10% by weight. These grouts generally provide satisfactory results, but in some cases where the soil or the material to which the grout is applied has a very low permeability, for example a 10 ' ⁴ ms- ¹ permeability, said grout has insufficient penetration capability.

It is therefore an object of the invention to provide an injection mortar of the type described in said patent documents, which would have sufficient penetration capability even in materials or soils with very low permeability.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION The present invention provides an injection mortar for sealing and / or reinforcing soil or materials having very low permeability, consisting of a mixture of blast furnace slag dust suspended in water and an aqueous sodium silicate solution, characterized in that the aqueous sodium silicate solution has a molar oxide ratio % silica to sodium less than 0.8 and a silica content of 0.01 to 5% by weight.

Preferably, the aqueous sodium silicate solution has a silica content of 0.5% by weight. Preferably, the grout according to the invention comprises a filler, more preferably an inert filler. Preferably, the filler is a filler selected from the group consisting of magnesium carbonate, magnesium calcium carbonate and calcium carbonate. Preferably, the grout according to the invention comprises fine cement. Preferably, all solids of the injection mortar have a size of less than 100 µm, more preferably less than 50 µm. The blast furnace slag dust preferably has a particle size of less than 10 µm.

The invention also relates to a process for the preparation of said grout, which comprises mixing blast furnace slag dust suspended in water to which a dispersant has been added with an aqueous solution of sodium silicate obtained by dissolving a silica powder or silica product, having a particle size below 100 pm, in aqueous sodium hydroxide solution, preferably having a density of 1.3185 to 1.3424 g.mľ ^first Preferably, a filler or fine cement suspension is also added to the mixture.

The advantage of the grout according to the invention is its ease of manufacture and its ability to penetrate into low permeability soils and materials in order to seal and / or solidify them.

It is generally known that suspensions prepared from slag are not very stable because their suspended solids tend to have a significant tendency to sedimentation due to gravity. In order to achieve the desired stability of the suspension, it is necessary to use a liquid carrier phase in which the solid particles are suspended and of sufficient density. The sodium silicate solutions used in the prior art and having a silica content of more than 10% by weight, while having a sufficient density to achieve the desired stability of the injection mortar suspension, on the other hand, is detrimental to achieving the desired penetration of the injection mortar. even very fine pores of soils or materials to which grout is applied.

It has now been found in the present invention that when a sodium silicate solution having a silica to sodium oxide molar ratio of less than 0.8 and a silica content in the solution of less than 5% by weight is used to prepare the injection mortar, sufficient density to keep the mortar stable after injection without significantly reducing the ability of the mortar to penetrate into the micropores or micro-cracks of the soil or materials to which the mortar is applied.

According to a preferred embodiment of the invention, the injection mortar is produced by mixing three components specified below. The first component is blast furnace slag dust suspended in water to which a dispersant has been added. The dust based on blast furnace slag or other slag-containing product preferably has a particle size of less than 15 µm, for example 10 µm. Such a suspension may be obtained, in particular, by the method described in French patent document 85 08886 or 90 12703. The second component of the injection mortar according to the invention is an aqueous sodium silicate solution obtained by dissolving silica in aqueous sodium hydroxide solution, preferably having a density of 1,3185 to 1,3424 g.ml ^-1 , wherein a silica powder or similar silica product having a particle size of less than 100 µm, more preferably less than 50 µm, is dissolved. The third component is a filler suspension, which is any powder product selected depending on the desired modification of the properties of the grout. As the filler, calcium carbonate, magnesium carbonate, magnesium calcium carbonate or other similar inert filler may be advantageously used. The density, resulting mechanical strength, stability and pH of the injection mortar can be modified by suitable filler selection.

In a preferred embodiment of the invention, powdered dolomite is used as a filler, which favorably affects the final strength and stability of the solidified grout and reduces its pH. The filler can also be replaced by fine cement. The grout according to the invention may also contain a fourth component, which is a dispersing agent, preferably selected from the group consisting of naphthalenesulfonates, melamine and derivatives thereof.

When the slag fraction is increased in said mixture of three components, an increase in the stability and strength of the grout after solidification and a decrease in penetration capacity is achieved.

The slag product may be, for example, blast furnace slag dust containing, for example, 85% by weight of slag and 15% by weight of a clinker.

Increasing the proportion of aqueous sodium silicate solution results in an increase in stability and strength after solidification of the injection mortar, without substantially altering its penetration capability. By increasing the molar ratio of silica to sodium oxide, an increase in the stability of the injection mortar is achieved without affecting the post-setting strength and penetration capability of the injection mortar. By increasing the filler content, the stability of the injection mortar is increased without substantially altering its strength after solidification, but the penetration ability of the injection mortar is impaired.

Within the scope of the invention, it has been found that an injection mortar having an initial pH of 13 to 13.5, after solidification, has a pH in the range of 12 to 12.5, which is comparable to an injection mortar manufactured using Portland cements. Such a decrease in the pH of the injection mortar is particularly pronounced when a magnesium-containing filler such as dolomite is used in the invention, and these fillers have been shown to be more effective at lowering the pH after grouting of the injection mortar than other carbonates.

In a further embodiment of the invention, the injection mortar does not contain a filler suspension, although it decreases its stability but increases its penetration capability.

Within the scope of the invention, it is desirable to introduce as small particles as possible into the injection mortar, i. j. particles of less than 100 µm, preferably less than 50 µm.

DETAILED DESCRIPTION OF THE INVENTION

In order to further elucidate the invention, the following examples are provided to illustrate the invention, and are not intended to limit the scope of the invention as defined by the claims.

Example 1

In order to obtain the grout for application in soft soils having a permeability of 10 ^"4 M. S ^'1 is first prepared a suspension of the slag powder having a maximum particle size of 10 pm in water. This suspension can be obtained by centrifugation or decantation. The proportion of dust slag in this suspension is 250 kg per 1 m ^{3 of} water. Furthermore, an aqueous sodium silicate solution by introducing 0.5% by weight of fine silica in an aqueous solution of sodium hydroxide having a density of 1.3185 g.mľ ^first The sodium silicate solution obtained has a molar ratio of silica to sodium oxide of 0.02. Finally, a dolomite suspension having a particle size of up to 10 µm is prepared, the proportion of dolomite in this suspension being 350 kg per m ³ . The injection mortar is then prepared immediately prior to application by simultaneous mixing of the following components in the indicated amounts:

said slag suspension 4001, said dolomite suspension 5801, said sodium silicate solution 291, dispersant (melamine resin) 61.

The grout thus prepared contains 100 kg of slag and 200 kg of dolomite, which is a total of 300 kg of dry matter per m ^{3 of} grout.

This grout has a setting time of about one hour and its sweating value does not exceed 5%. This grout can be injected into sand having a permeability of 10 ' ⁴ ms ¹ . During the preparation, the injection mortar has a pH of 13.2, which drops to 12.2 after solidification. The strength of the solidified grout after 7 days is 15 kg.cm &^lt; ^{2 &gt};.

Example 2

For the purpose of preparing grout for application to the same soil as specified in Example 1, the following ingredients are mixed together in the amounts indicated:

the slag suspension described in Example 1,200 L, the dolomite suspension described in Example 1,430 L, a sodium silicate solution analogous to the sodium silicate solution of Example 1, but in which the molar ratio of silica to sodium oxide is 0.3 29 L, water 3401 .

The grout thus prepared contains 50 kg of slag and 150 kg of dolomite, i.e. a total of 200 kg of dry matter per m ^{3 of} grout. This grout has a setting time of one hour and 30 minutes and has a sweating value of less than 5%. The grout is suitable for injection into said soil and sand having a permeability of 10 ^-4 meters per second ^"first

Example 3

In order to prepare for the application of grout to a sand having a permeability of approximately equal to 10 ^'4 M. S' ¹ is first prepared a suspension of powder slag particles having a particle size not exceeding 10 pm. This suspension contains 250 kg of dust slag per 1 m ^{3 of} water. Said suspension may be obtained by centrifugation or sedimentation processes. Next, a calcite suspension is prepared with a particle granulometry not exceeding 10 µm. This suspension contains 350 kg of calcite per m ^{3 of} water. The grout is then prepared by mixing the following ingredients together in the indicated amounts: said slag suspension 200 L, the described calcite suspension 430 L, a sodium silicate solution analogous to the sodium silicate solution of Example 1, but wherein the molar ratio of silica to sodium oxide is 0; 8 291, water 3001, deflocculating agent (naphthalenesulfonate).

The grout thus obtained contains 50 kg of slag and 150 kg of calcite, i.e. a total of 200 kg of dry matter per m ^{3 of} grout. Its setting time is one hour and 30 minutes and its sweating value is about 30%. The injection mortar initially has a pH of 13.5, which does not drop after solidification. The strength of the solidified grout after 7 days is 5-7 kg.cm &^lt; ^{2 &gt};.

Example 4

For the purposes of reinforcement of soil deposited having a permeability of 10 ^"4 to 10" ³ m s' ^1, the grout prepared in the following manner. First, a slag suspension is prepared with a particle size granulometry not exceeding 10 µm using 250 kg of slag per 1 m ^{3 of} water. Next, a sodium silicate solution containing 3% by weight of silica was prepared by dissolving the silica in an aqueous sodium hydroxide solution as described in the previous examples. This solution has a molar ratio of silica to sodium oxide of 0.5. The grout is then prepared by mixing the following ingredients together in the indicated amounts:

said slag suspension 7501, sodium silicate solution prepared according to the method291, water 2111, dispersant (melamine resin) 71.

The grout thus obtained contains 200 kg of slag per 1 m ^{3 of} grout. The grout is not very stable and there is no change in pH after solidification. The strength of the solidified grout after 7 days is 25 to 50 kg.cm &^lt; ² >.

PATENT CLAIMS

Claims (11)

An injection mortar for sealing and / or solidifying soil or materials having very low permeability, consisting of a mixture of blast furnace slag suspended in water and an aqueous sodium silicate solution, characterized in that the aqueous sodium silicate solution has a molar ratio of silica to oxide % sodium below 0.8 and a silica content of 0.01 to 5 wt. An injection mortar according to claim 1, characterized in that the aqueous sodium silicate solution has a silica content of 0.5% by weight. An injection mortar according to claim 1 or 2, characterized in that the blast furnace slag dust has a particle size of less than 10 µm. An injection mortar according to any one of claims 1 to 4 3, characterized in that it contains solid particles the largest size of which is less than 100 µm, preferably less than 50 µm. An injection mortar according to any one of claims 1 to 5 4, characterized in that it comprises a filler. Injection mortar according to claim 3, characterized in that it contains an inert filler as filler. An injection mortar according to claim 5, characterized in that it contains a filler selected from the group consisting of magnesium carbonate, magnesium calcium carbonate and calcium carbonate as filler. Injection mortar according to claim 5, characterized in that it contains calcium carbonate as filler. An injection mortar according to claims 1 to 4, characterized in that it contains fine cement. A method for producing an injection mortar according to any one of claims 1 to 4, characterized in that the blast furnace slag powder suspended in water to which the dispersant has been added is mixed with an aqueous solution of sodium silicate obtained by dissolving the silica powder. or silica product having a particle size below 100 pm, in aqueous sodium hydroxide solution, preferably having a density of 1.32 to 1.34 g.mľ ^first Method according to claim 10, characterized in that a filler or fine cement suspension is also added to the mixture.