LU84196A1 - AGENT FOR WATERPROOFING AND / OR CONSOLIDATION OF SOILS AND / OR CONSTRUCTION MATERIALS AND METHOD FOR ITS IMPLEMENTATION - Google Patents

Description

Patent application%, from ............................................ .......

-v ..............

Designation of the Inventor (1) The undersigned ............ Jean. .Waxweiler ................................................ ...............................................

21-25, Allée Scheffer, Luxembourg acting as eJdépsssûX— agent of the depositor - (2) ............ Sooiéfcê-Anonyme -Dite î -SoletanGhe ......... .................................................. ......................

6f rue de Watford, .............

F- 92005 NANTERRE CEDEX France (3) of the invention concerning: ................. Agen.t .... ld.î.é.tanahéif.lcatlan. ... and. / Qu. of ... .cQn, s.Ql.id.ati.on ... of .... sQ.is/ and / or construction materials and process for its ..... ............ m.ise .... en ... o.euyr.e, ..................... .................................................. .................................................. ...............

designates as inventor (s): 1. Name and first names. ..Mr. -Gouveno.t -Daniel ........................................ .........................................

Address ..... l., .... Allëe Gambetta ^ France 2. Name and first names ............................ .................................................. .................................................. ........................................

Address ................................................. .................................................. .................................................. ........................................

3. Surname and first names ............................................. .................................................. .................................................. .....................

Address ................................................. .................................................. .................................................. ........................................

He affirms the sincerity of the above-mentioned indications and declares to assume full responsibility for them.

......... Luxembourg ..........................., on ........ 7 .. ...July. .198.2 ............... 19 ............

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(signature) A 68026! __ (1) Last name, first names, company, address.

(2) Last name, first names and address of the depositor.

ΐ I -2,> * © SERIE 120; "SILACSOL"! ! i

DESCRIPTIVE MEMORY SUPPORTING A PATENT INVENTION APPLICATION TO BE FILED IN LUXEMBOURG

In the name of the Société Anonyme known as: SOLETANCHE

For: "Sealing and / or consolidation agent for soils and / or building materials and process for its implementation" BSB / BC / Cde 57421 -1-

The present invention relates to an agent for sealing and / or consolidating soils and building materials such as mortars, concretes, masonry and a method for its implementation.

More particularly the sealing and / or consolidating agent is intended for the treatment of alluvia or rocks having voids.

Soils, whether cracked rocks or alluvium, must sometimes be consolidated to ensure their stability. This is so when digging excavations or drilling, to avoid the collapse of the walls. 20 The implantation of bridge piers or buildings on these soils may also require consolidation in order to prevent their collapse.

Furthermore, sealing of these soils may prove necessary when they support structures such as dams.

25 Mortars, binders and concretes may have certain variations in volume which may result in more or less deep and wide cracks, which are detrimental to sealing, to the protection of reinforcement and possibly to the stability of structures. Furthermore, alterations can occur over time under the influence of certain external agents capable of causing a porosity more or less accentuated by dissolution of hydrated salts.

Subsequent treatment of these materials is therefore necessary in order to improve the seal and / or consolidate them.

The problem posed by sealing and / or consolidating soils and building materials is therefore essentially the same as knowing how to reach the voids of the cracks and those present in the alluvium using an agent capable of damaging them. easily penetrate and permanently fill them.

The sealing and / or consolidating agents used at present belong essentially to two categories, namely on the one hand solutions of synthetic resins and on the other hand solutions (or grout) of alkali silicates more particularly of sodium or potassium silicates.

Resins or products based on resins which lead to the formation of polymeric compounds may in certain cases prove to be useful, but they are relatively expensive products whose fluidity does not always allow microcracks or micropores. In addition, the injection of resins is a relatively recent technique, so that the durability of structures or soils treated with these products is not certain.

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The current technique therefore essentially consists in using alkaline suspensions of sodium silicate, products which are readily available but which have been found to have numerous drawbacks.

This is because the lime, present in building materials and certain soils, once in contact with sodium silicate causes the formation of a silica gel, due to the excess of silica relative to the sodium hydroxide in the solutions of treatment.

Sodium silicate is in fact a colloidal solution of silicic acid in soda and its neutralization leads to its transformation into a gel by electrical discharge of the silicic ions which condense to form polysilicon ions.

The untimely formation of a silica gel has the consequence of blocking the injection so that certain voids cannot be reached. In addition, the gelation is never complete since sodium hydroxide remains in the structure of the gel. On the other hand, the gels obtained are not stable over time, and tend to dissociate by releasing soda again, which constitutes a non-negligible source of pollution and instability.

The present invention makes it possible to remedy the drawbacks of known agents in that it provides a sealing and / or consolidation agent which is easily injectable even in microcracks of the order of approximately 10 μ and which exhibits very high reactivity. with respect to lime capable of leading to mineralization of soils and / or building materials by the formation of stable and insoluble hydrated lime silicates, more particularly of tobermorite (2 SiC ^ 3 CaO 3 ^ 0), thus ensuring the sustainability of the treatment applied to these soils and materials.

The tests carried out on test pieces have in fact made it possible to show that with the aid of the agent according to the invention there was no gelation by percolation through porous micro-mortars, no more than any appearance of a layer of gel at the exit of the test pieces. The formation of hydrated lime silicate crystals, more particularly tobermorite, using the agent according to the invention has been confirmed by the various X-ray diffractometry examinations.

The sealing and / or consolidation agent according to the invention therefore makes it possible to ensure: (a) an excellent injection into the voids and microvides present in the floors and / or building materials, (b) the formation of stable and insoluble hydrated lime silicates, (c) lasting stability over time of the products formed after injection, -3- and (d) an almost total absence of pollution.

The subject of the present invention is a sealing and / or consolidating agent for floors and / or construction materials, usable by injection, characterized in that it is in the form of a concentrated alkaline solution of silica, non-colloidal, obtained by dissolving at room temperature silica with an average particle diameter of less than 100 U in sodium hydroxide, the ratio being less than 2 and the silica content of the solution being greater than approximately 20% by weight .

The non-colloidal nature of the agent according to the invention could be qualitatively demonstrated by the Tyndall effect (measurement of the nephelometric index).

The silica used can be pure silica or preferably siliceous products containing at least 80 to 90% by weight of SiC 4 of non-vitreous structure.

Among the preferred compounds, mention may in particular be made of pyrogenic silicas also known as fumed silicas which come from industrial waste, kieselguhr, gaize or even silica aerogels.

The particle size of the silica or siliceous product which is of great importance in order to obtain rapid and complete dissolution in the sodium hydroxide, should therefore be if possible less than 100 y but preferably less than 50 y.

It goes without saying that according to the invention other siliceous products such as those mentioned above can be used insofar as they satisfy the necessary solubility criteria.

The soda used for dissolving the silica is preferably in the form of a solution between 35 and 37 ° B, that is to say having a density between about 1.32 to 1.35.

Upon dissolution, there is a certain exotherm which is unnecessary to control since no adverse impact on the reactivity of the sealing and / or consolidating agent has been noted.

The SiO 2 / Na 2 O ratio is also of great importance, which, as indicated above, must be less than 2 but preferably between 1.5 and 1.8. Indeed, in the case of a higher ratio, the silica 35 would tend to form a gel and therefore to prevent good injection deep into the microcracks or microvides.

The maximum silica content is not critical insofar as the ratio 81 () 2 / ^ 20 remains less than 2. However for practical reasons relating in particular to the viscosity of the agent according to the invention, this content 40

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Is generally not more than about 30% by weight and is preferably between 23 and 27%.

It has in fact been observed that in order to obtain a good injection, it was desirable that the viscosity of the sealing and / or consolidating agent according to the invention be between approximately 5 and 50 cP, preferably between 20 and 30 cP, an appropriate viscosity obtainable by dilution with water.

The agent according to the invention may also contain certain additives capable of improving penetration into cracks or voids.

According to a variant of the invention, the sealing and / or consolidating agent can contain lime or a calcium salt such as for example calcium chloride, formate, acetate or propionate.

The addition of lime or a calcium salt is more generally recommended for the treatment of certain soils and / or materials poor in lime.

In soils and materials rich in hydrated lime, the silica dissolved in the agent according to the invention makes it possible, after reaction, to lead to the formation of hydrated lime silicates (tobermorite). However, this is not the case for soils and / or materials that are particularly poor in hydrated lime, for which it is necessary to directly compensate for this absence by supplying industrial lime or indirectly using a calcium.

When the agent according to the invention contains lime, this is generally present in an amount such that the CaO / SiC 2 ratio is greater than 0.3, the maximum ratio being 1.50.

. According to the invention, a calcium salt is preferably used, more particularly calcium chloride insofar as after its neutralization by soda it leads, in addition to the lime formed, to a non-polluting salt (sodium chloride).

The dissolved silica then reacts with the lime formed to give insoluble and stable hydrated lime silicates.

The quantity of calcium salts must be sufficient for the total neutralization of the sodium hydroxide, an excess of sodium hydroxide being capable of subsequently causing pollution phenomena. Although an excess of calcium salt can be used, it is preferable according to the invention to use the stoichiometric quantity necessary for the neutralization of the sodium hydroxide contained in the agent.

If the enrichment in calcium salt of the sealing and / or consolidating agent according to the invention constitutes a preferred embodiment, this addition can nevertheless be achieved by injecting a solution of the calcium salt prior to the agent's injection. Such a process however requires two successive injections and therefore makes the treatment longer and more expensive.

The various studies carried out using the agent according to the invention have made it possible to show that the formation of the tobermorite crystals takes place approximately 10 hours after the injection and that their formation continues until approximately 7 days after the injection. 'injection.

X-ray diffraction or scanning electron microscopy examinations showed a large abundance of hydrated lime silicate crystals from 7 days.

The very good reactivity observed is explained by the activity of the dissolved silica and by the freshness of the solution.

The subject of the present invention is also a method of sealing and / or consolidation, this method consisting in injecting under pressure the agent according to the invention as defined above in voids or microvides of soil, or in cracks or microcracks in building materials, using conventional injection equipment.

The method according to the invention is very particularly intended for the treatment of soils to be sealed or to consolidate whether they are cracked rocks or alluviums.

For cracked rocks, drilling is first carried out and the agent according to the invention is then injected by the techniques known as forward injection or upward injection.

For alluvial deposits due to the risk of landslides, a now conventional process known as "cuff tube" is used (French patent no. 986,619).

The injection pressure is generally between 5 and 20 bars and the amount of the consolidating and / or sealing agent between 30 and 40% of the volume of the soil which it is intended to treat.

30 During the sealing work, the treatment can be checked by taking a sample which is subjected to permeability measures.

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An alluvial soil with a permeability of approximately 10 m / s will pass after injection and hardening to a permeability of approximately 10 ^ -10 ^ m / s.

In order to better understand the invention, an example of embodiment and implementation of the sealing and / or consolidation agent according to the invention will now be described by way of illustration and without any limiting nature. invention.

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EXAMPLE

In a soil rich in very permeable lime (permeability of 10 m / s) a 10 m deep borehole is carried out with a view to the sealing treatment of a soil volume of lm3. An injection tube is introduced into the borehole and an injection of a solution obtained by dissolving 170 kg of silica with an average particle size of approximately 50 μl in 300 liters of sodium hydroxide is then carried out under an initial pressure of 3 bars. 36 ° B and 70 liters of water (the characteristics of the solution after formation were as follows: Si02 / Na20 ratio = 1.8%; S1O2 = 26.6%; Na2Ü = 14.8%; I ^ O = 58 , 6%; 10 viscosity 40-50cP). When the rejection pressure has stabilized at around 10 bars, the injection is stopped, which has been found to correspond to an amount of the solution injected of the order of 320 liters.

After a week, a new measurement of the permeability revealed that it had increased to 10 ^ m / s, indicating perfect sealing of the treated soil.

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Claims (12)

1. Sealing and / or consolidating agent for soils and building materials, usable by injection, characterized in that it is in the form of a concentrated alkaline solution of silica, not colloidal, obtained by dissolution at ambient temperature of silica with an average particle diameter of less than about 100% in sodium hydroxide, the ratio S ^ / I ^ O being less than 2 and the silica content of the solution being greater than about 20% by weight. 2. Agent according to claim 1, characterized in that the silica used is a siliceous product containing at least 80 to 90% by weight of SiO 3 of non-vitreous structure. . 3. Agent according to any one of claims 1 and 2, characterized in that the silica is pyrogenic silica (fumed silica), kiselguhr, gaize or a silica aerogel. 4. Agent according to any one of the preceding claims, characterized in that the Si02 / Na20 ratio is preferably between 1.5 and 1.8. 5. Agent according to any one of the preceding claims, characterized in that the maximum silica content is not more than about 20% by weight and preferably between 23 and 27%. 6. Agent according to any one of the preceding claims, characterized in that its viscosity is between approximately 5 and 50cP, preferably between 20 and 30cP. 7. Agent according to any one of the preceding claims, characterized in that it contains lime in a CaO / SiO 2 ratio. greater than 0.3 with a maximum of 1.5, 8. Agent according to any one of claims 1 to 6, characterized in that it contains a calcium salt such as chloride, formate, acetate or calcium propionate. 9. Agent according to claim 8, characterized in that the calcium salt is present in an amount making it possible to completely neutralize the soda. 10. A method of sealing and / or consolidating soils and building materials, characterized in that it consists in injecting * 35 under pressure according to conventional techniques a sealing and / or consolidating agent according to one any of claims 1 to 9. 11. Method according to claim 10, characterized in that prior to the injection of the sealing agent and / or 40 -8- * * consolidation according to any one of claims 1 to 6 is injected with a solution of a calcium salt. 12. Method according to claim 11, characterized in that the calcium salt solution is a calcium chloride solution. Λ t