CS254340B2 - Method of soil imperviousness and engineering structures consolidation - Google Patents

Abstract

Method for improving the strength and impermeability of soils and engineering structures by forming a hydrogel composed of silicic acid and a cross-linked swellable organic polymer in or on the soil or structure treated. According to the invention an aqueous solution of a silicic acid gel precursor is contacted with a water-soluble gel-forming vinyl monomer in the presence of a redox polymerization catalyst system; a cross-linking agent for the polymer obtained; an organic polycarboxylic acid; optionally an additive which modifies the structure of the gel formed and optionally a filling agent. By the method of the invention a homogeneous, stable, strong and elastic gel is obtained.

Description

The invention relates to a method for strengthening and improving the impermeability of soils and civil engineering structures, particularly ducts and pipelines. The terms "soil" and "civil engineering" are used in the broadest sense: these terms therefore also include different storage tanks, tunnels, natural and artificial cavities, rocks and similar formations, and the surrounding lands.

It is well known that most civil engineering structures, such as underground ducts, pipelines and storage tanks, do not have the required impermeability characteristics, either due to the poor quality of construction materials, partly due to insufficient impermeability of pipe joints, or damage to civil engineering due to aging or traffic; with similar effects, it is also well known that repairs to civil engineering works, especially underground canals and pipelines, require excessive investment and are laborious, and in many cases results are inadequate.

Hungarian Patent No. 153,975 describes a simple and fast method for strengthening and improving the impermeability of soils and civil engineering works. In this method, water glass or water glass containing medium is applied to the treated articles or the water glass or water glass containing medium is introduced into the treated articles and then the water glass is exposed to hydrogen fluoride, silica terafltioride and / or hydrogen silicofluoride. The water glass gels quickly when in contact with fluoride gas and completely clogs leaks, gaps, cracks and cracks. When using this method to impart water impermeability to underground civil engineering structures (such as canals or storage tanks), there is a further advantage that water glass that enters the soil through cracks solidifies well, thereby improving the laying of civil engineering structures and solidifying adjacent soil. Gaseous fluorides have the further advantage of improving the corrosion resistance of concrete and reinforced concrete parts. .

Despite its numerous advantages, however, this method has only a narrow application in practice. The widespread use of this process is greatly limited by the fact that hydrogen fluoride and silica tetrafluoride are highly toxic and are banned in many countries for environmental reasons. A further disadvantage is the fact that the resulting silica gel is not elastic, so that it cannot follow the movement of civil engineering or treated soil. Since the swelling of the silica gels is insufficient, it cannot block new cracks formed in the gel due to movements.

Hungarian Patent Nos. 177,343, 181,056, 181,775 and 181,573 disclose the use of various polymerizable organic monomers, in particular acrylic acid and acrylamide monomers, as starting materials for gelling reactions. Gels formed from such compounds are bravely elastic and have good swelling in water, but are relatively soft and cannot withstand damage caused by greater stress. Another drawback is that most of the monomers used as gel-forming agents are very expensive and the gel-forming technology itself requires special training and equipment.

The above drawbacks are overcome in Hungarian patents Nos. 186,586 and 189,250, according to which water glass is applied together with various gel-forming, water-soluble organic polymers and crosslinkers for these polymers. In these cases, the silica gel co-precipitates with the cross-linking of the polymer to form gels composed of mineral and organic blocks in which the beneficial properties of perfectly organic and perfectly mineral gels are combined. However, using large-scale applications, it has been found that the methods of these patent applications are very difficult to carry out. Due to the high average molecular weight, the gelling polymers, even when used in small quantities, increase the viscosity of the starting water glass solutions to such an extent that the resulting mixtures are very difficult to handle and operate, so that their application and removal of their excess involves numerous technical problems. Sometimes it is not possible to introduce the required amount of polymer into water glass solutions, since a very dense, honey-like mixture is formed which cannot be applied to the structures by the available injection devices. Gel formulations having a suitably low viscosity generally contain a small amount of polymer, and the elasticity and swelling of the resulting gels using such mixtures is still insufficient.

It has now been found that it is possible to avoid all of the above-mentioned difficulties and drawbacks when adding monomers of gel-forming polymers instead of preformed polymers to the waterglass and polymerizing and crosslinking the polymer are carried out simultaneously with the silica gel formation.

The invention therefore relates to a process for strengthening and impermeability of soils and civil engineering structures by forming a hydrogel consisting of a silicic acid precursor which is an aqueous solution of an alkali metal waterglass having an alkali metal silicate content of 5 to 20% by weight, a gel-forming vinyl water-soluble monomer a C = C double bond containing a C 3 -C 5 aliphatic carboxylic acid, its water-soluble salt, amide or mixture of said compounds in an amount of 3 to 15% by weight, in the presence of a polymerization catalyst redox system, crosslinking agent of the obtained polymer, organic polycarboxylic acid which is optionally substituted with one or more hydroxyl groups, a saturated or unsaturated aliphatic dicarboxylic acid having 3 to 10 carbon atoms in an amount of 2 to 10 percent by weight, optionally a structure-modifying additive formed gel and optional filler.

When contacting the components (silicic acid precursor and water-soluble gel-forming vinyl monomer), the following chemical processes occur at the same time:

The monomers polymerize as a result of the action of the catalyst redox system, the resulting linear polymer reacts with the crosslinking agent to form the crosslinked polymer, and - the precursor forms a gel of silicic acid due to the action of the polycarboxylic acid.

Since these chemical processes are simultaneous and all the intermediates formed in the process interact with each other, a gel is formed in which the organic and mineral moieties are combined. Visually, the gel formed clearly differs from the gels obtained according to the above-mentioned Hungarian patents Nos. 186,586 and 189,250. The gels of these Hungarian patents are opaque and organic and inorganic blocks are readily distinguishable in their structure, i.e. according to these Hungarian applications they obtain gels with inhomogeneous microstructure. In contrast, the gels prepared according to the process of the present invention are transparent, indicating their homogeneous structure. Therefore, it can be assumed that an organic-mineral copolymer is formed as opposed to a mixture of organic and mineral polymer blocks.

Any compound that forms a silica acid gel upon contact with the acid can be used as the precursor of the silica gel. The most preferred silicic acid gel precursors are various water glasses (sodium silicate, potassium silicate and the like), but water-soluble silicones and polysilicates commonly used in the preparation of molds may also be used.

Among the gel-forming, water-soluble vinyl monomers are, for example, acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid and the water-soluble components and esters of these acids, acrylamide, methacryanediol. These monomers may be used alone or in the form of a mixture of two or more monomers.

Aldehydes (e.g. glyoxal, glutaraldehyde) or divinyl or trivinyl compounds (e.g. methylene-bis-acrylamide, ethylene-bis-acrylamide, triacryltriazine) can be used as organic polymer crosslinking agents.

The boiling agent should be sufficiently soluble in water; their solubility in water should be at least 1%.

The redox catalyst system used in the process according to the invention consists of an oxidizing component and a reducing component. Any of the known redox type free radical initiators used conventionally for the production of vinyl polymers can be used. The oxidizing component may be, for example, hydrogen peroxide, alkaline persulfate or a water-soluble organic peracid, and the reducing component may be, for example, a water-soluble organic amine, a water-soluble metal salt of varying valence, thiosulfate or bisulfite.

Polycarboxylic acids (i.e., organic acids with at least two carboxylic groups) which can be used in the process according to the invention are, for example, tartaric acid, citric acid, succinic acid, malic acid and ascorbic acid.

The weight ratio of silica precursor gel to vinyl monomer based on dry weight can vary within wide limits, for example 10: 1 to 1: 10; Preferred weight ratios are 5: 1 to 1: 1 and especially 4: 1 to 2: 1. For economic reasons, it is preferable to use vinyl monomers in small amounts. It has been found that the elasticity and swelling of the gel remains substantially the same as that of a perfectly organic gel even at a high mineral content, the higher the silicic acid content, the higher the strength and stress resistance.

The weight ratio of silica gel precursor to polycarboxylic acid, based on dry weight, may be 1: 0.3 to 1: 0.06; A preferred weight ratio is 1: 0.2 to 1: 0.08, and especially about 1: 0.1.

The amount of crosslinking agent, based on the dry weight of the vinyl monomer contained, may be 1: 0.01 to 1: 0.3, based on the vinyl monomer; a preferred ratio is 1: 0.05 to 1: 0.2.

The amount of redoxcatalyst system, calculated on the weight of vinyl monomer contained, may be 1: 0.01 to 1: 0.5; a preferred ratio is 1: 0.05 to 1: 0.3. The catalyst system comprises oxidizing and reducing components, preferably in approximately equimolar amounts.

The gel-forming composition may optionally also contain at least one additive which affects the properties of the gel formed. These additives may be commonly known additives for crosslinked vinyl polymers, such as plasticizers, stabilizers, decomposition inhibitors and the like, of which melamine, urea, monomethylurea and thiourea are particularly mentioned. The amount of such optional additives may be as high as the amount of vinyl monomer present.

The gel-forming composition may optionally contain at least one filler commonly used in such compositions as, for example, asbestos, sand, fly ash, bentonite. The amount of filler is not critical and is essentially limited by technological factors (e.g., spreadability, ease of application).

Using the method of the invention for the treatment of soil or civil engineering, it is possible to mix the individual components of the gel-forming mixture with each other in a suitable sequence of given compatibility at the place where the treatment is carried out (for example, any engineering structure to be repaired). However, it is preferable to use two pre-prepared solutions and mix them at the point of use. The composition of the two aqueous solutions should be chosen with a view to ensuring that both solutions remain stable and can be stored for a longer period of time, and to avoid premature gel formation. The following compatibility factors should be taken into account when choosing the appropriate composition of the solutions:

- the silicic acid gel precursor must not be mixed with the polycarbonic acid, - the two components of the redox catalyst system must not be in the common solution, and - the aqueous vinyl monomer solution must not contain the oxidation component of the redox catalyst system in free state. for example in the form of a complex).

In view of the above compatibility factors, the two aqueous solutions to be mixed at the place of use may have the following composition:

Solution 'A':

silica gel precursor (e.g., water glass), redox catalyst system oxidant, water.

Solution 'B':

water soluble vinyl monomer, organic polymer crosslinker, polycarboxylic acid, redox catalyst system reducing component, water.

Or, solution "A": · silica gel precursor, redox catalyst system reducing component, water, solution ,, B ^U :

water-soluble vinyl monomer, organic polymer crosslinking agent, polycarboxylic acid, oxidizing component of the redox catalyst system in a masked form (e.g. complexed with urea), water.

Optional additives and fillers may be added to any of the "A" and "B" solutions, provided the compatibility requirements are met. Thus, for example, the acidic filler (e.g., acid fly ash) may not be added to the solution containing the silica gel precursor.

As mentioned above, the method of the invention can be used in the construction industry to improve the strength and impermeability of soils and civil engineering works. For this purpose, the individual components of the gel-forming composition - preferably in the form of two pre-prepared aqueous solutions - are mixed together at the place of use, for example in the treated soil or in the treated civil engineering or on the treated soil or civil engineering. When the process according to the invention strengthens the soil, it is preferable to fill both aqueous solutions into the tanks of a two-tank injector equipped with a mixing head and inject a mixture of both solutions into the treated soil. If the method according to the invention is to repair the duct, it is advantageous to use so-called "filling techniques", the two solutions being introduced one after the other into the duct to be repaired.

The process according to the invention has all the main advantages of the processes known from the prior art cited by the aforementioned patents. Like the known methods, it is a fast, safe and economical way of consolidating soils or civil engineering works and impermeability to civil engineering works. Compared to the known methods, the process according to the invention has the following advantages:

- no chemicals harmful to the environment and environment are used, - a solid gel is formed sufficiently flexible and swellable to compensate for damage after repair, for example due to soil movement, road wear, - the gel-forming mixture is easy to handle; The lifetime of the formed gels greatly exceeds the lifetime of the gels formed by known methods, which is attributed to the homogeneous structure of the formed organic-mineral copolymer gel.

The invention is illustrated by the following non-limiting examples.

Example 1

Prepare two aqueous solutions of the following composition:

Solution 'A':

water ml potassium persulfate1,8 g thiourea 14,0 g concentrated water glass solution (dry matter 37% w / w) 50,0ml

A solution 'B ^L'

water 80.0ml methacrylic acid 16.0ml tartaric acid 10.0g methylene-bis-acrylamide 0.5g ferrous sulfate 0.5g

The two solutions are mixed together with vigorous stirring. A homogeneous transparent gel is formed within 7.5 minutes.

Comparative test

Prepare two aqueous solutions of the following composition:

Solution 'A':

water 90.0 ml potassium persulfate 1.8 g thiourea 14.0 g

Solution "B":

water 80.0 ml acrylic acid 16.0 ml tartaric acid 10.0g methylene-bis-acrylamide 0.5g ferrous sulfate 0.5g

None of these solutions contains water ^: glass. The two solutions are mixed together with vigorous stirring. Within 12 minutes a homogeneous, transparent, perfectly organic gel is obtained.

Comparative test В

Prepare two aqueous solutions having the following composition:

Solution 'A':

water 40.0 ml thiourea 14.0 g concentrated water glass solution (dry matter 37% w / w) 50.0 ml

Solution 'B':

water 80.0 ml acrylic acid to 16.0 g tartaric acid 10.0 g methylene-bis-acrylamide 0.5 g was mixed with vigorous stirring. Within a minute an opaque mineral gel is formed. The gel shows strong syneresis.

Example 2

Prepare two aqueous solutions of the following composition:

The _solution? A ^c; :

water 40.0 ml potassium persulfate 1.8 g thtomočovma 14,0 g concentrated aqueous solution water glass (dry matter 37% weight / weight) 50.0 ml Solution "B": water, 80.0 ml acrylic acid 16,0 g succinic acid 10,0 g methylene-bis-acrylamide 2,0 g ferrous sulfate ' 1.0 g

The two solutions are mixed with intensive stirring. A transparent gel is formed within one minute.

Example. 3

Prepare two aqueous solutions of the following composition:

Solution 'A': water 70.0 ml potassium persulfate 0,9 g melamine 7,0 g concentrated aqueous solution of water glass (dry matter 37% weight / weight) 25.0 ml Solution "B": science 80.0 ml methacrylic acid 16,0 g tartaric acid 10,0 g methylene-bis-acrylamide 0.5 g ferrous sulfate 0.5 g

The two solutions are mixed together under intense agitation. A homogeneous, transparent gel is formed over 120 minutes.

Example 4

Prepare two aqueous solutions of the following composition:

Solution 'A':

water 16.0 ml potassium persulfate 0.8 g melamine 6.0 g

Since no redox catalyst system is included, no vinyl polymer can be formed. Concentrated aqueous waterglass solution (dry matter 37% w / w) 20.0 ml

Solution 'B':

water 50.0 ml itaconic acid 4.0g ferrous sulfate 0.5g methylene-bis-acrylamide 0.5g citric acid 2.0g

Mix both solutions with vigorous stirring. A homogeneous, transparent gel is formed over 15 minutes.

Example 5

Prepare two aqueous solutions of the following composition:

Solution 'A':

water 19.0 ml concentrated aqueous glass solution (dry matter 37 ° / w / w) 80.0 ml triethanolamine

1.0 ml

Solution 'B':

water 85.0 ml acrylic acid 15.0 ml citric acid 10,0 ml hydrogen peroxide in the form complex with urea 4.0 g methylene-bis-acrylamide 0.5 g

The two solutions are mixed together with vigorous stirring. A homogeneous, transparent gel is formed over 18 minutes.

Compressive strength and deformation resistance of gels prepared according to the above examples and comparative examples are measured by standard methods. The results are summarized in Table I. From the values shown in the Table, it is apparent that the gels prepared by the method of the invention are of better quality than the gels prepared by known methods.

TABLE I

Example number Comparative test A Comparative test В

Compressive strength Pa

210

23'0

150

190

170 ·

130

Deformation%

Example 6

Aqueous solutions of the following composition are prepared:

Solution 'A':

water 40 ml potassium persulfate2 g urea10 g concentrated aqueous potassium water glass solution with a dry matter content of 40% by weight. 40ml

Solution 'B':

methacrylic acid 10 ml water 80 ml sodium acrylate 10 g • ascorbic acid 15 g methylene-bis (acrylamide) 1 g ferrous sulphate 0.1 g homogeneous gel whose compressive strength is 20 kg / m ² , deformation 50 · ° /O.

Example 7

Aqueous solutions of the following composition are prepared:

Solution 'A':

water40 ml potassium persulfate2 ml urea10 g concentrated aqueous solution of water glass Na ⁺ and K ⁺ (1: 1), dry matter content 38,5% 40 ml

Solution 'B':

water 80 ml acrylamide 10 g ammonium acrylate 20 g malic acid 5 g methylene-bis-acrylamide 1 g ferrous sulphate 1 g

Mix both solutions with vigorous stirring. Within 30 minutes a vista of 254340 is formed

The two solutions were mixed with vigorous stirring, and within 60 minutes a homogeneous, transparent gel was formed having a compressive strength of 15 kg / m ² , a deformation of 52 ° / o.

Example -8

Aqueous solutions of the following composition are prepared:

Solution 'A':

water 40 ml potassium sulphate2 g urea10 g concentrated aqueous solution

Na-water glass (dry matter content 37%) 60ml

Solution "B":

water 80ml acrylic acid 10ml methacrylamide 5ml tartaric acid 1'0g methylene-bis-acrylamide 1g ferrous sulfate 1g

The two solutions are mixed with vigorous stirring. A homogenous transparent gel, a compressive strength of 22 kg / m ² , a deformation of 48% is formed from the mixture within 20 minutes.

ExampleQ

Solutions "A" and "B" of the composition of Example 1 are used to repair the channel as follows:

The channel section to be treated is shown in Fig. 1. The channel section, defined by balls 2 and 3, is cleaned accordingly and then closed at the pipe stoppers 1. Then the closed section is filled with solution "A" of balls 2. Solution ,, The pressure required to inject the solution into leaks, cracks and cavities is reached by the filled ball to the appropriate height. Depending on the channel defects through which solution A penetrates, a height of 1 to 2 m is maintained in the ball 2. If necessary, the solution in the ball 2 is replenished. After a reasonable time, usually after 10 to 20 minutes, the remainder of the liquid is pumped back from the channel section into the 4 ball tank 2.

Thereafter, as indicated in FIG. 2, the solution "B" is introduced from the tank 6 into the channel section of the balls 2. Here again, the pressure required to inject the solution into leaks, cracks and cavities is achieved by filling the ball 2 to a reasonable height. Make up the solution as necessary. After a reasonable period of time, preferably when the leakage ceases, the remainder of the liquid is pumped back into the tank 2 through the balls 2 and the pipe plugs are removed. This completes the operation.

If the result is to be verified by a water or air-tightness test, this can be done before the piping caps are removed. This control can be avoided by allowing the solution to act in the ball 2 for a reasonable period of time. If the level in Ball 2 does not decrease after 15 minutes (or if the level falls within the tolerable limits), this means that the channel is reasonably waterproof.

Solutions "A" and "B", penetrated by defects, inadequate joints or cracks in the duct, form a stable gel 5 inside and around the treated duct. This allows not only perfect sealing of the canal leaks, but also solidification of the surrounding soil surrounding the canal and making it waterproof. As a result, channel laying conditions are also significantly improved, which is a decisive factor in the stability and durability of the channel network.

Claims (3)

SUBJECT A method of consolidating and improving the impermeability of soils and civil engineering structures by forming a hydrogel of silicic acid and crosslinked swellable organic polymer in a treated soil or civil engineering or in a treated soil or civil engineering, characterized by contacting an aqueous alkaline water glass solution. metals with an anhydrous alkali metal silicate content of 5 to 20 wt. With a gel-forming vinyl water-soluble monomer comprising at least one C = C double bond containing an aliphatic carboxylic acid having 3 to 5 carbon atoms, its water-soluble salt, amide or a mixture of said compounds in an amount of 3 to 15% % in the presence of a polymerization catalyst redox system, a crosslinking agent of the obtained polymer; OF THE INVENTION is an organic polycarboxylic acid which is optionally substituted by one or more hydroxyl groups, a saturated or unsaturated aliphatic dicarboxylic acid having 3 to 10 carbon atoms in an amount of 2 to 10% by weight, optionally an additive modifying the structure of the gel formed and the optional filler. 2. A process according to claim 1, wherein the components of the gel-forming composition are contacted by mixing two previously prepared aqueous solutions. 3. A process according to claim 2, wherein one aqueous solution comprises an aqueous alkali metal water glass solution of the oxidation component of the catalyst redox system in a masked form and optionally an additive and / or filler.