KR870001414B1 - Sealing and consolidation agent for ground and construction materials - Google Patents

Abstract

Additive soils and construction materials, used by injection are obtd. in the form of a conc. alk. soln. of non-colloidal silica obtd. by dissolution at ambient temp. of silica particles of diameter below 100 microns in soln., the SiO2/Na2O ratio being below 2 and the silica content of the soln. above 20 wt. %. The compsn. is used for treating alluvial clays and rocks having voids. Max. silicacontent is 23-27 wt. %.

Description

Sealing and Consolidating Agent for Soil and Building Materials

The present invention relates to sealing and consolidation agents for building materials such as ground and mortar, concrete, masonry.

In particular, hermetic and consolidation agents are used to treat rock or alluvial layers with cavities.

Whether the ground is cracked or alluvial, the ground must be consolidated from time to time to ensure stability. This is to prevent the fall of the wall when excavating or drilling a wall.

To install pillars of buildings or bridges on these grounds, it is necessary to consolidate the ground to prevent sedimentation.

In addition, sealing these soils is necessary for work such as dams. Mortars, binders and concrete cause volume changes, resulting in rather deep and wide cracks that damage watertightness, reinforcement and construction stability. In addition, the porosity may be somewhat higher because the quality is degraded due to the influence of certain external materials and the hydrated salt is dissolved.

Therefore, subsequent processing of these materials is necessary in view of enhancing water tightness and / or compaction.

Thus, the problems inherent by the sealing and consolidation of ground and building materials are essentially the same. In other words, materials that can be easily penetrated and filled into building materials are used to reach cavities and gaps in the alluvial layer.

Currently used hermetic and consolidation agents fall into two classes: synthetic resin solutions and alkali silicate (particularly sodium or potassium silicate) solutions (or fillers).

Resin- or resin-based materials that form polymeric compounds are useful in some cases, but the cost of the materials is relatively high and their fluidity prevents them from always penetrating deep into microcracks or micropores.

Moreover, injecting resins is a relatively recent technique, but the ground treated by these materials or the durability of this building is poor.

Thus, although alkaline suspensions of sodium silicate are currently used, this material, although readily available, also has various disadvantages.

Once the lime present in the building material and the ground is in contact with sodium silicate, silica gel is formed because of the excess of silica relative to sodium in the treatment solution.

Sodium silicate is actually a colloidal solution of silicic acid and soda, which is neutralized and converted into a gel by electrical discharge of silicate ions, and the silicate ions condense to form polysilicate ions.

If the silica gel is formed prematurely, the injection is blocked and the cavity cannot be reached. Moreover, complete gelation is not achieved because soda remains in the structure of the gel. On the other hand, the obtained gel is not stable for a long time and tends to interfere with soda re-release, causing contamination and instability, which is a problem that cannot be neglected.

The present invention provides a very large and about 10 μm reactive and lime capable of mineralizing the ground and / or building materials by the formation of stable and insoluble hydrated lime silicates, particularly tobermorite (2SiO ₂ · 3CaO · 3H ₂ O). The disadvantages of the conventional method can be solved by providing a sealant and a consolidation agent which can be easily injected into a fine gap of a degree so that the treated ground and the quality of these materials can be maintained as they are.

As a result of experimenting with Test-Pieces, it was confirmed that when using the sealing and consolidation agent according to the present invention, no gelation occurred through the pores of the porous micromortar, and no layer of gel appeared at the exit of the test piece. .

It was confirmed by various experiments by X-ray diffraction that crystals of hydrated lime silicate (particularly tobermorite) were formed by the sealing and consolidation agent according to the present invention.

Therefore, the sealing and consolidation agent according to the present invention,

(a) has good injection into the cavity microcavities present in the ground and / or building materials;

(b) a stable, insoluble hydrated lime silicate is formed,

(c) the stability of the product formed after injection is permanent,

(d) It is hardly contaminated.

The present invention provides an alkali concentrate of non-colloidal silica, obtained by dissolving silica in soda with an average particle diameter of less than 100 μm at ambient temperature, wherein the ratio of SiO ₂ / Na ₂ O is less than 2, and the silica in solution The content relates to sealing and consolidating agents for ground and / or building materials which can be used for injection, characterized in that the content is at least about 20% by weight.

The non-colloidal properties of the sealant and consolidation agent according to the invention can be demonstrated qualitatively by the tindall effect (turbidity index measurement).

The silica used may be a siliconaceous material that contains at least 80 to 90 weight percent SiO ₂ in the pure state, or preferably in the non-glassy structure.

Among the preferred compounds, mention may be made of pyrogenic silica, such as so-called fumed silica obtained from industrial waste, diatomaceous earth, gaize or silica airgel.

Since the particle size of the silica or silicon material is very important in obtaining rapid and complete dissolution in soda, it should be less than 100 μ, preferably less than 50 μ, if possible.

It is not said that according to the present invention other silicon materials as mentioned above can be used as long as they meet the required solubility criteria.

Soda used to dissolve silica is preferably in the form of a solution having a density of 35 to 37 ° B., i.e., about 1.32 to 1.35. An exothermic reaction occurs during dissolution which does not require heat control unless it has an undesirable effect on the seal and reaction with the compaction agent.

The ratio of SiO ₂ / Na ₂ O is very important and should be less than 2 as indicated above, preferably 1.5 to 1.8. At higher ratios, the silica tends to form a gel, thus preventing satisfactory injection deep into the microcracks or microcavities.

The maximum content of silica is not a problem as long as the SiO ₂ / Na ₂ O ratio is 2 or less. However, based on practical reasons relating to the viscosity of the sealant and consolidation agent according to the invention, the content of such silica is generally less than about 30% by weight, with 23 to 27% being preferred.

In order to achieve a satisfactory injection, it has been found that the viscosity of the sealant and consolidation agent according to the invention is preferably about 5 to 50 cP, preferably 20 to 30 cP, and suitable viscosities can be obtained by dilution with water.

The sealing and consolidation agents according to the invention may further contain additives which can enhance penetration into the gaps or cavities.

According to a variant of the invention, the sealant and consolidation agent may contain lime or calcium salts (eg calcium chloride, formate, acedate or propionate).

The addition of lime or calcium salts is generally desirable for treating ground and / or building materials that lack lime.

In the case of building materials and ground rich in hydrated lime, the silica dissolved in the sealant and consolidation agent according to the present invention may form hydrated lime silicate (tober morlite) after the reaction. However, for materials and / or grounds that are particularly lacking in hydrated lime, it is necessary to add industrial lime directly or indirectly to compensate for the lack of lime using calcium salts.

When the sealing and consolidating agent according to the invention contains lime, lime is generally present in an amount such that the CaO / SiO ₂ ratio is at least 0.3 and the maximum ratio is 1.50.

According to the invention, calcium salts, in particular calcium chloride, are preferably used as long as calcium salts are neutralized with soda and then produce not only lime but also uncontaminated salts (sodium chloride).

Thus, the dissolved silica reacts with the produced lime to provide a stable and insoluble hydrated lime silicate. Since excessive soda is likely to cause contamination, the amount of calcium salt should be sufficient to completely neutralize the soda. Excess calcium salts may be used, but it is preferred in the present invention to use stoichiometric amounts necessary to neutralize the soda contained in the hermetic and consolidation agents.

Strengthening the sealant and compaction agent according to the invention with calcium salts is a preferred form of embodiment, but it is advantageous here to inject a solution of calcium salt prior to injecting the sealant and compaction agent. However, this method requires two consecutive injections, resulting in longer processing times and higher costs.

As a result of various tests conducted with the sealant and the consolidation agent according to the present invention, crystals of toberlite were formed about 10 hours after the injection, and the formation continued for about 7 days after the injection.

X-ray diffraction or scanning electron microscopy experiments showed that after 7 days, crystals of hydrated lime silicate were very richly formed.

The functional and clear solution of the dissolved silica reacted very well.

The present invention also relates to a sealing and consolidation method, which method uses a conventional injection device, which is a special or microcavity in building materials, or a microcavity or cavity in ground, according to the present invention. Consolidating agent is injected under pressure.

The method according to the invention is intended to treat the ground of siled rock or alluvial layer by hermetic and consolidation. In the case of cracked rock, the drill hole is first drilled and then the sealant and consolidation agent of the present invention are injected by known methods such as excavation injection or ascension injection.

In the case of alluvial layers, a conventional method known as "tubes with cuffs" (see French Patent No. 986, 619) is used because of the risk of falling.

The infusion pressure is generally 5 to 20 bar, and the amount of consolidation and sealant uses 30 to 40% of the volume of the ground to be treated.

During the closure process, samples may be taken for penetration testing to investigate treatment performance.

Penetration ground with alluvium of about 10 ^-3 m / s after injection and curing is chimtudo a change of about 10 ^-6 to 10 ^-7 m / s.

In order to make the present invention easier to understand, the examples using the sealing and compacting agents according to the present invention are described below, but this is not a limitation of the present invention.

EXAMPLE

In order to seal 1m3 of ground, drill holes 10m deep are made in the ground rich in very permeable lime (penetration 10 ^-2 m / s). An injection solution obtained by inserting an injection tube into a drill-hole and then dissolving 170 kg of silica with an average particle size of about 50μ in about 300 L of 36 ° B and 70 L of water. ₂ / NaO ₂ = 1.8%; SiO ₂ = 26.6%: NaO ₂ = 14.8%; H ₂ O = 58.6%; Viscosity: 40 to 50 cP) is injected under 3 bar of initial pressure. When the rejection pressure was stabilized at about 10 bar, the injection was stopped, demonstrating that the amount of solution injected was equivalent to 320 liters.

One week later, new permeability measurements showed a change of 10 ^-6 m / s, indicating that the treated soil was completely enclosed.

Claims (11)

Silica having an average particle diameter of less than 100 μ was in the form of an alkaline concentrate of non-colloidal silica obtained by dissolving in soda at room temperature, adding lime or calcium salt, if necessary, and having a ratio of SiO ₂ / NaO ₂ . A sealing and consolidating agent for ground and building materials which can be used for injection, characterized in that less than 2 and the silica content in the solution is about 20% by weight or more. The sealant and consolidator of claim 1, wherein the silica used is a silicon material containing at least 80 to 90 weight percent of the non-glass structured SiO ₂ . The sealant and consolidation agent according to claim 1, wherein the silica is pyrogenic silica (fumed silica), diatomaceous earth, gayes or silica airgel. The sealing and consolidating agent according to claim 1, wherein the ratio of SiO ₂ / NaO ₂ is 1.5 to 1.8. The sealant and consolidator of claim 1, wherein the maximum silica content is 23-27 weight percent. The sealant and consolidator of claim 1, wherein the viscosity is about 5 to 50 cP. The sealing and consolidation agent according to claim 1, wherein lime is contained at a ratio of CaO / SiO ₂ of 0.3 or more and a maximum of 1.5. The sealant and consolidator of claim 1, which contains calcium chloride, formate, acetate or propionate calcium salt. 9. The hermetic and consolidation agent of claim 8, wherein the calcium salt is present in an amount capable of completely neutralizing the soda. 7. The sealant and consolidator of claim 6, wherein the viscosity is between about 20 and 30 cP. A method of sealing and consolidating ground and building materials, characterized by injecting a solution of calcium salt under pressure before injecting the sealing and consolidating agent according to claim 1.