RU2743978C1 - Composition of penetrating action for waterproofing of porous concrete surfaces - Google Patents

Abstract

FIELD: chemistry.SUBSTANCE: invention relates to waterproofing compositions of penetrating action. Proposed composition contains the following components, wt%: sodium carbonate 12.0-14.0, polycarboxylic acid 2.0-3.0, Portland cement M400 60.0-70.0, sodium hydroxide 0.5-2.0, mechanically activated aluminum hydroxide 0.5-1.0, construction sand, fraction up to 600 mcm - balance. Before use, the proposed composition is diluted with water at ratio of 5:2 pts.wt. and is applied in the form of a paste on the wetted surface of the concrete with a layer with thickness of up to 2-3 mm. pH of the alkaline aqueous solution penetrating into concrete is 13.7-14.1.EFFECT: high efficiency of waterproofing action of the composition during infiltration of water in the direction of the coating and longer duration of development of waterproofing properties (stability) of the composition in high humidity and microbiota activity.4 cl, 3 tbl

Description

The invention relates to the field of production of waterproofing materials of penetrating action, designed to increase moisture resistance, frost and corrosion resistance of concrete structures and are applied by plastering on a moistened concrete surface.

Currently, there is a wide range of technological methods for waterproofing concrete structures (Zarubina L.P. Waterproofing of structures, buildings and structures. - SPb: BHV-Petersburg, 2011. - 272 C). A common method is the introduction of hydrophobic additives directly into the cement-sand mixture, which, after hardening, acquires water-repellent properties. In turn, approaches to increasing the moisture resistance and chemical resistance of ready-made concrete structures are based on three basic principles. Traditionally, appropriate protective coatings are applied to their surface. These coatings can be created with pasting (sheet, roll, membrane) or coating (mastic) materials based on bitumen and / or polymers, and also applied by plastering using a cement-sand mixture with the addition of water glass and organic water repellents (bitumen and polymer dispersions , solutions of salts of fatty organic acids). Another approach is the sealing and hydrophobizing impregnation of the pores of the concrete surface to a certain depth by means of capillary suction of stabilized emulsions of water repellents, organosilicon fluids and active compounds, the interaction of which with each other and / or with cement stone leads to the formation of bulk sediments in the pore space (so-called clogging ), which ultimately causes blockage of these pores.

However, the application of these protective coatings, as a rule, is difficult and ineffective at high concrete humidity due to water infiltration, for example, at hydraulic facilities, tunnels, foundations, plinths and basements of buried-type structures with a high level of groundwater. In this case, the proper result can be achieved within the framework of the third approach - when applying penetrating plaster coatings containing a cement-sand mixture and various water-soluble additives.

Penetrating waterproofing is one of the most powerful and progressive methods of protecting reinforced concrete structures, which can be performed both by applying surface coatings, even from the side opposite to the action of water, and by injection. In addition to imparting waterproofing properties and resistance to water pressure, it increases the strength and durability of concrete structures, does not require repairs during their operation and is distinguished by manufacturability and ease of work. However, at the same time, it is also a relatively expensive method of waterproofing, as a result of which it is used to a limited extent.

There is a wide range of commercial penetrating compounds used for waterproofing various structures: Kalmatron, Antigidron, Lakhta, Aquablok Plus, Stromix, Gidroflex, Gidroteks-K, Aquatron-6, Kalmaflex, SK TRON, Nanotron, Gambit SuperPro, Betocrete, Penetron, Vandex, Thora, WASCON, Waterplag, X1PEX, Osmoseal, Thoroseal and others. Their components are usually kept secret by manufacturers.

There are at least three types of penetrating waterproofing compositions depending on the nature of the water-soluble additive, namely, compositions containing only inorganic active ingredients, compositions with organosilicon additives, and compositions with additives of polymers or conventional organic compounds, usually organic acids. and their derivatives. In this case, organic components are usually introduced together with inorganic ones. To ensure deep penetration into the pores of concrete by diffusion, the water-soluble compounds used must have high mobility in an aqueous medium, therefore, a sufficiently low molecular weight.

Known composition based on water-soluble active inorganic salts "Kalmatron", used to obtain a concrete mixture or surface treatment of concrete, containing, in wt. %:

Sodium carbonate, Na ₂ CO ₃ , 30.0-51.3 Sodium sulfate, Na _{2 SO 4} , 20.5-40.0 Sodium chloride, NaCl 0.4-0.5 Sodium nitrate, NaNO ₃ , 14.5-27.7 Calcium nitrate, Ca (NO ₃ ) ₂ , 0.4-15.0

The composition is introduced in the amount of 0.03-0.7 wt. % in the preparation of a concrete mixture, and for plastering on the concrete surface, mix in an amount of 3-10 wt. % with a cement-sand mortar containing quicklime. When tested for water resistance in accordance with GOST 12730.5-84, the samples coated with such a protective compound withstand a water pressure of 1 MPa (concrete grade W10), while the control ones - only 0.2 MPa (concrete grade W2). The tests carried out (the test method is not described) show that the depth of penetration of surface coatings into concrete for 7-28 days is up to 15 cm (Patent RU 2052413 C1, publ. 20.01.1996).

A known composition for protecting concrete surfaces, containing a cement-sand mixture, mineral additives and water with the following content of components, in wt. %:

Sodium carbonate, Na ₂ CO ₃ , 2.0-3.0 Sodium sulfate, Na _{2 SO 4} , 2.5-3.6 Sodium nitrate, NaNO ₂ , 0.9-1.8 Calcium hydroxide, Ca (OH) ₂ , 0.8-1.0 Calcium chloride, CaCl ₂ , 0.05-0.15 Calcium carbide, CaC ₂ , 0.75-1.15 Cement 36.0-40.0 Sand 39.0-49.0 Water rest

The protective layer obtained on the basis of this composition has the following indicators: degree of clogging 95-100%, compressive strength 50 MPa, tensile strength 7 MPa, water resistance after applying a protective layer - 16 tech. atm. (W16), and after removal - 14 tech. atm. (W14), frost resistance 300-350 cycles (Patent RU 2072335С1, publ. 27.01.1997).

Known waterproofing composition for impregnating the surface of concrete, containing the following components, in wt. %:

Sodium carbonate, Na ₂ CO ₃ , 1.7-2.5 Sodium sulfate, Na _{2 SO 4} , 1.7-3.0 Sodium chloride, NaCl 0.2-0.5 Sodium nitrate, NaNO ₃ , 1.7-3.0 Calcium nitrate, Ca (NO ₃ ) ₂ , 2.0-2.2 Microsilica 4.0-12.0 Sodium silicate lump, Na ₂ SiO ₃ , 7.0-10.0 Portland cement 55.0-70.0 Quartz sand (0.35-0.45 m ² / g) 10.0-15.0

The depth of penetration of the components of the composition into concrete at the age of 7-28 days is 4-5 cm.As a result, an effective protective waterproofing barrier is created, increasing the grade of concrete in terms of water resistance W2 to W8 and increasing frost resistance from 75 to 500 cycles (Patent RU 2350583 C1, publ. 03/27/2009).

Known waterproofing composition "Penetron"("Penetron", TU 5775-001-39504194-96) by ICS / Penetron International Ltd. (USA), containing Portland cement, quartz sand and a complex of active chemical additives. These additives are kept secret, but attempts have been made to uncover their chemical nature. So, according to information borrowed from patent RU 2576760, a qualitative analysis of the Penetron material showed that it includes cations of alkali and alkaline earth metals (Ca ²⁺ , Na ⁺ , Mg ²⁺ ), as well as hydroxide, chloride, carbonate, sulfate and aluminate anions.

Waterproofing based on the "Penetron" mixture allows to achieve an indicator of concrete water resistance up to 1.2 MPa, its frost resistance of at least 300 cycles, protects concrete from aggressive media, and reinforcement from corrosion.

The mechanism of compaction of the internal structure of concrete with Penetron material consists of several stages. The first stage is the migration of water-soluble chemically active components over wet concrete. The second stage is the first stage of reactions of chemically active components in the presence of water (not water vapor!) With ionic complexes of calcium and aluminum, oxides, metal salts (some of the constituents of cement stone). The third stage is the second stage of reactions, as a result of which chemically stable insoluble filamentary crystals are formed in the form of an openwork web filling microcracks and capillaries of concrete (http://penetronkazan.ru/analogi_penetron_kazan/).

Known cementing composition of capillary action "Aquablock plus", obtained on the basis of water-soluble organosilicon compounds, containing, in wt. h .:

Sodium methylsiliconate 0.2-1.0 White cement, Portland cement or their mixture 40-42 Quartz-feldspar sand 3-6,

Used cement and sand are additionally ground to a state of powders with a specific surface area of 2-3 m ² / g. As a result, thin (about 1 mm) durable (up to 65 MPa in compression) coatings are obtained, and the water resistance of reinforced concrete structures increases to W10 (Patent RU 2132309 C1, publ. 27.06.1999).

Known waterproofing composition of penetrating action with the addition of water-soluble polymers, which (in terms of dry state) contains the following components in wt. %:

Sodium carbonate, Na ₂ CO ₃ , 0.27 Sodium sulfate, Na _{2 SO 4} , 0.49 Sodium nitrate, NaNO ₃ , 0.48 Sodium chloride, NaCl, 0.07 Aluminum sulfate, Al ₂ (SO ₄ ) ₃ , 0.06 Calcium nitrate, Ca (NO ₃ ) ₂ , 0.55 Redispersible polymer powders 14.4 Expanding cement 27.6 Filler (sand) 54.0 Fiber 2.0

In another version of the composition, some of the sand is replaced by active forms of silicon oxide (tripoli, diatomite, silica or bentonite in an amount of 3.6 wt%). Using these mixtures, the water resistance of the W6 prototype sample increased to W12 and W14, respectively (Patent RU 2408553 C1, publ. 10.01.2011).

Known composition for preventing the carbonization of concrete, containing the following components in wt. %:

sodium carbonate 10-13 organic polyacid 1-3 Portland cement 45-55 filler rest.

Citric or tartaric acid is used as an organic polyacid, and sand, glass powders, sodium silicate, vermiculite, ash, etc. are used as a filler. After mixing with water (i.e. wetting to a pasty state), the composition is applied in a thin layer on the concrete surface, which gives it not only moisture resistance (while maintaining vapor permeability), but also complicates the penetration of carbon dioxide and oxygen into concrete: as a result, carbonization of concrete and corrosion of metal reinforcement are significantly slowed down. The function of the organic additive and the mechanism of the clogging action of such a material are not indicated by the authors of the patent (Patent EP 0084951 A2, publ. 1983).

The mechanism of concrete waterproofing using the compositions described above is carried out through the interaction of a cement stone with an alkaline solution of electrolytes, penetrating into these pores from the applied coating, with the subsequent formation of bulk crystalline deposits. In this regard, the main disadvantage of the known compositions is a decrease in the efficiency of their use in the presence of capillary flow (infiltration) of water through the concrete towards the applied waterproofing coating, since the counter movement of water reduces the rate of penetration of its soluble components into the pores. Therefore, the use of these compositions requires that the capillary flow of water is absent or small, which is not always possible. In addition, the disadvantage of the known compositions is the insufficient duration of the waterproofing action (stability) under conditions of 100% humidity and high microbiota activity. For different compositions, this is due to different reasons: hydrolysis of organosilicon compounds, insignificant depth of penetration of inorganic (silicates) and organic polymer compounds into concrete, degradation of organic compounds under the action of bacteria and oxygen, removal of poorly retained ions in the form of readily soluble chlorides, nitrates, alkali metal sulfates ...

Closest to the claimed composition - the prototype, is a composition for waterproofing porous concrete surfaces, which is a dry mixture of sodium carbonate (7-12 wt.%), Citric acid (3-6 wt.%), Portland cement (20-25 wt. %) and sand with a fraction of up to 600 microns (the rest), which is applied after mixing with water (in a ratio in wt. h. 5: 2) on a moistened concrete surface in 1-2 layers up to 2 mm thick each, followed by moistening the coating for 3 days (RU 2325370 C1, publ. 27.05.2008).

When the soluble components of this known composition interact with concrete, needle-like crystals of calcium citrate are formed in its pores, [Ca ₃ (C ₆ H ₅ O ₇ ) ₂ (H ₂ O) ₂ ] ⋅2H ₂ O, which provide a clogging effect, and the depth of penetration of these coating components in concrete is up to 20 cm in 28 days (method for determining the depth of penetration is not specified).

The known composition makes it possible to increase the moisture resistance class of a concrete sample from W2 to W22 (definition by "wet spot", GOST 12730.5-84), and frost resistance - from 75 cycles to 500 (GOST 10060-87).

The disadvantages of the known composition are:

- insufficient effectiveness of the waterproofing action of the composition, associated with too slow clogging of pores in concrete, since before the formation and growth of sediment particles in the pores, a long initial period is required, during which the diffusion of chemically active substances deep into the pore space and their interaction with concrete until reaching oversaturation of the solution with the resulting products of this interaction;

- insufficient stability of the waterproofing action of the composition under conditions of 100% humidity and high activity of the microbiota, due to the fact that calcium citrate, which is responsible for the clogging of pores and cracks in concrete, has a rather high solubility in water (0.95 g / l), low resistance acidic and readily biodegradable.

The objective of the invention is to develop a new waterproofing composition of penetrating action, which has increased efficiency when applied to the surface of concrete with strong water infiltration and long-term resistance to external factors (excess water and microbiota).

EFFECT: increasing the effectiveness of the waterproofing action of the composition during water infiltration in the direction of the coating and increasing the duration of the manifestation of the waterproofing properties (stability) of the composition in conditions of high humidity and microbiota activity.

The task is achieved by the proposed composition for waterproofing porous concrete surfaces, containing the following components, in wt%:

Sodium carbonate 12.0-14.0 Polycarboxylic acid 2.0-3.0 Portland cement М400 60.0-70.0 Sodium hydroxide 0.5-2.0 Mechanically activated aluminum hydroxide 0.5-1.0 Building sand, fraction up to 600 microns rest.

Before use, the proposed composition is diluted with water in a ratio of 5: 2 (in parts by weight) and applied in the form of a paste on a moistened concrete surface with a layer up to 2-3 mm thick. In this case, the pH of the penetrating into concrete from the composition of the aqueous solution (penetrating solution) is 13.7-14.1.

The claimed composition, after its application to concrete, launches a sequence of fast and slow physical and chemical processes in the pores of concrete, which makes it possible to suppress water infiltration through the pores of concrete at the initial stage, i.e. immediately after coating, and their subsequent clogging with deposits of bulk nanoporous metal-organic coordination polymers formed as a result of the interaction of concrete with soluble components of the composition. At the same time, it surpasses the prototype and is not inferior to the best commercial samples of penetrating waterproofing in terms of its ability to make concrete waterproof and resistant to external factors.

After applying the proposed waterproofing composition to the concrete surface after 28 days, the measured water resistance corresponds to the W14-W16 grade, while the control sample has the W4 water resistance.

The defining differences of the proposed composition, in comparison with the prototype, are:

- the addition of sodium hydroxide, as well as higher values of the ratio of the mass fractions of cement / soda and soda / polycarboxylic acid, which, when mixed with water, together provides a higher pH of the penetrating solution, due to which a completely different sequence is started when the composition is applied to the concrete surface physicochemical processes of interaction of the components of this solution (penetrating solution) with the components of concrete, leading to clogging of pores in concrete: not with poorly soluble calcium citrate as in the prototype, but with the resulting metal-organic coordination polymers (MOCP);

- the inclusion of aluminum hydroxides (gibbsite, pseudoboehmite) soluble in an alkaline medium - suppliers of Al ³⁺ ions for the formation of MOCPs subjected to mechanical activation in order to increase the rate of their dissolution in alkalis;

- the use of organic polycarboxylic acids, the molecules of which contain olefinic or aromatic fragments, as an organic linker to obtain MOCP, which gives MOCP hydrophobicity, resistance to aggressive media (high humidity, organic acids, microbiota) with a significantly lower solubility compared to calcium citrate ...

The combination of the selected components of the composition, together with the experimentally selected optimal concentrations of the components, can increase the efficiency (waterproofing properties) and durability of the composition due to the fact that the water-soluble components of the composition have high mobility in water and, due to this, the ability to penetrate into the smallest pores, and also have certain chemical activity in order to initiate, on the one hand, electrochemical (fast) processes on the surface of concrete pores, which result in a strong deceleration of the capillary flow of water, and, on the other hand, chemical (slow) processes that ultimately lead to clogging of cracks and pores in the volume of concrete formed by nanoporous metal-organic framework structures (organometallic coordination polymers, MOCP), which have water-repellent properties, but at the same time are permeable to gases and water vapor.

The physicochemical mechanism of action of the proposed waterproofing composition is as follows.

The network of pores and cracks in solid bodies of a corpuscular structure, which include concretes, is a free space between their loose-packed particles, which are relatively weakly connected to each other due to the small area of contacts between them. When applied to wet concrete of the proposed waterproofing composition of a penetrating action, a number of physicochemical processes occur in the following sequence:

(I) the formation of an electric double layer (DES) on the surface of pores and cracks upon contact with an electrolyte solution penetrating into the pores from the applied composition, as a result of which the rate of water infiltration through small cavities drops sharply, which is due to the high viscosity of the solution within the DES (Ankomah A.V. Filtration-rate technique for determining zero point of charge of iron oxide. // Clays Clay Miner. 1991. V. 39. No. 1. P. 100);

(II) an increase in the wedging pressure (RD) between loosely packed particles of mineral components of concrete due to the occurrence of DES on their surface (Deryagin, B.V. Theory of stability of colloids and thin films. - M .: Nauka, 1986. - 206 s), which contributes to the destruction of contacts between these particles: as a result, the separated particles fill the space of the pores, which causes a decrease in their hydraulic radius, and, as a consequence, the rate of water infiltration decreases;

(III) selective dissolution of particles of the mineral components of concrete and contacts between them under the action of chemically active additives of an alkaline nature, which leads, on the one hand, to the intensification of processes (II), and on the other, to the accumulation of colloidal particles of hardly soluble components, as well as dissolved compounds of multivalent cations (mainly silicon and aluminum) in a solution that has penetrated into the pore space;

(IV) the formation of sols during the hydrolysis of compounds extracted with water from the applied waterproofing composition and / or formed during process (III), which is caused by a drop in the pH of the solution in the pores as a result of chemical processes according to (III) and / or dilution of this solution during its penetration deep into the porous space filled with water;

(V) coagulation of the sol with the formation of a gel, and in the presence of organic linkers, such as polycarboxylic acids, in the solution, chemical crosslinking of the sol nanoparticles into a three-dimensional framework with the formation of nanoporous metal-organic coordination polymers (MOCPs) with water-repellent properties, which ultimately eventually leads to clogging of the pores;

(VI) aging of the chemical compounds precipitated according to (V), caused by a further drop in the pH of the solution in the pores due to the occurrence of processes (III) - (IV) and various hydrothermal processes: phase transformations, hydration, recrystallization of the formed sediments, etc.

The appearance of DES (stage (I)) is due to the ionization of acid-base functional groups on the surface of particles of concrete components when it comes into contact with the electrolyte. In this case, the jump in the electric potential in the DES is the higher, the greater the difference in the pH values of the isoelectric point of the surface (pH _et ) and the pH of the solution. The pH values of _et for various concretes, measured by us by the method of weighed portions (Noh, JS, Schwarz, JA Estimation of the point of zero charge of simple oxides by mass tiration. // J. Colloid. Interface Sci. 1989. V. 130. P. 157) are 11.51-11.85. Thus, in order for DES to appear on the surface of concrete in contact with the solution, it is necessary that the pH values of the solution be either less or greater than this pH value _et . It is preferable that the pH of the penetrating solution was greater than 12, since under these conditions the cement stone is chemically unstable, which will automatically ensure the progress of stage (III). From the consideration of the above scheme of the flow of clogging of concrete pores, it follows that the pH of the penetrating solution formed when the waterproofing composition is wetted is a key characteristic that determines the intensity of processes (I) - (IV) in the pore space of concrete.

The invention is illustrated by the following specific examples.

Example 1.

By dry mixing of powders, a waterproofing composition of penetrating action is prepared, containing the following components, in wt. %:

Sodium carbonate, 12.0 Lemon acid 2.5 Portland cement М400 60.0 Sodium hydroxide 2.0 Pseudoboehmite mechanically activated 0.5 Building sand, fraction up to 600 microns, 23.0

Example 2.

Dry mixing of powders prepare a waterproofing composition of penetrating action, containing the following components in wt. %:

Sodium carbonate 13.0 Terephthalic acid 3.0 Portland cement М400 70.0 Sodium hydroxide 0.5 Pseudoboehmitemechanoactivated 1.0 Building sand, fraction up to 600 microns, 12.5

Example 3.

Dry mixing of powders prepare a waterproofing composition of penetrating action, containing the following components in wt. %:

Sodium carbonate 12.0 Fumaric acid 2.0 Portland cement М400 60.0 Sodium hydroxide 1.0 Mechanically activated gibbsite, 1.0 Building sand, fraction up to 600 microns, 24.0

Example 4.

By dry mixing of powders, a waterproofing composition of penetrating action is prepared, containing the following components, in wt. %:

Sodium carbonate 14.0 Fumaric acid 2.0 Portland cement М400 60.0 Sodium hydroxide 1.0 Mechanically activated gibbsite 0.5 Building sand, fraction up to 600 microns, 22.5

Example 5.

By dry mixing of powders, a waterproofing composition of penetrating action is prepared, containing the following components, in wt. %:

Sodium carbonate 12.0 Fumaric acid 3.0 Portland cement М400 60.0 Sodium hydroxide 1.0 Mechanically activated gibbsite 1.0 Building sand, fraction up to 600 microns, 23.0

Example 6 (prototype composition).

According to the example of patent RU 2325370, a waterproofing composition of a penetrating action is prepared by dry mixing of powders, containing the following components in wt. %:

Sodium carbonate 8.0 Portland cement М400 20.0 Citric acid, monohydrate 5.0 Building sand, fraction up to 600 microns, 67.0.

Example 7.

Measurement of the rate of infiltration of water after exposure to alkaline penetrating solutions from waterproofing compositions prepared according to examples 1-6, on a layer of fine-grained concrete powder.

The experiment is carried out on an apparatus such as a suction filter at room temperature. It consists of two glass tubes with an inner diameter of 6 mm, which are flanged, and between the flanges a paper filter (white tape), a backing made of fine metal mesh (to prevent the filter from breaking during evacuation) and a rubber sealing ring are clamped. The top tube is graduated in volume units to record the rate of fluid flow through the tube.

A suspension consisting of 400 mg of fine-grained concrete powder with a fraction of less than 200 μm and 5 ml of distilled water is evacuated to remove trapped air in the pores of the powder particles, and then poured onto a filter. The movement of water through the layer of powder deposited on the filter is maintained by creating a pressure drop (730-740 mm Hg) by evacuation. In this case, the volumetric rate of its infiltration through the layer is recorded. As the water is consumed, a fresh portion of it is added, avoiding contact of the surface of the sediment layer with air. Upon reaching a constancy of the rate of fluid flow through the layer, its value is documented (V _o , cm ³ / min). Then, 1 ml of an aqueous solution from a waterproofing composition is filtered through a layer of powder (this solution is preliminarily obtained by centrifuging a suspension of 50 g of this material in 50 ml of water 20 minutes after mixing), after which water is passed again, determining the rate of its infiltration (V, cm ³ / min) as described above. At the end of the experiment, the layer of powder is washed off with water from the filter and then it is ensured that the rate of water flow directly through the filter under the same conditions significantly exceeds the values of V and V ₀ .

The degree of deceleration of the rate of water infiltration (η) after the action of an aqueous solution from the waterproofing composition on the concrete powder is calculated as η = V / V ₀ . The pH values of aqueous solutions from waterproofing compositions prepared according to examples 1-6, and the degree of deceleration (η) of the rate of water infiltration through a layer of concrete powder after the action of these solutions on it are presented in Table 1.

From the data in Table 1, it can be seen that the pH values of aqueous solutions from the proposed compositions are in the range of 13.7-14.1 and exceed the pH values for similar solutions for the prototype composition (pH 12.30) and the commercial waterproofing material "Penetron" (pH 13.28). As a result, the inhibitory effect of solutions from the compositions according to examples 1-6 on water infiltration through the pores between the particles of fine-grained concrete is more intense than for reference samples (almost 2 times compared to the prototype). It is pointed out that the low value of the parameter η for the prototype due to the small difference between the pH of a solution thereof (12,30) and the pH _iep concrete (11,85), whereby the DPP at the surface of the concrete powder particles are not sufficiently developed, and therefore the value of the disjoining pressure is also small.

High pH values of aqueous solutions from the proposed waterproofing compositions are achieved not only by introducing alkali (NaOH) into them, but also by a sufficiently large mass ratio of cement / soda and soda / polycarboxylic acid, which ensures the formation of free alkali in situ during the interaction of Na ₂ CO ₃ with hydroxides of alkaline earth metals found in cement, after mixing these mixtures with water.

Example 8.

Testing the waterproofing properties of the composition.

A cement stone sample was ground in a ball mill to a particle size of 0.2-10 microns (the resulting material was used to simulate dust-like concrete particles, which can be separated from the walls of its pores and cracks due to the occurrence of wedging pressure under the action of water-soluble components of the composition penetrating from the waterproofing coating into concrete). Weighed portions of this powder were placed in measuring tubes, sealed with water, aqueous solutions from the proposed compositions and reference samples in a solid / liquid ratio of 1:10, shaken for 10 minutes and then allowed to settle. At certain intervals, the volume of the resulting precipitate was recorded and its strength was evaluated (as resistance to agitation). At the end of the experiments (28 days), the precipitates were washed with water, dried at 110 ° C, and the characteristics of their porous structure were determined by the method of low-temperature nitrogen adsorption. The results are summarized in Table 2, which presents the values of the relative volume of the sediment of cement stone powder after a certain time after mixing with water (No. 1), aqueous solutions from the proposed composition (No. 3-7) and comparison samples (No. 2, 8) , as well as the strength and type of these sediments and the textural properties of the final material (after 28 days). At the same time, strength (1) was defined as resistance to shaking: "-" the precipitate collapses under weak impact, "+" is resistant to strong shaking, "±" collapses under moderate shaking; type of sample (2) - powder (p), flakes (x), gel (g).

The textural properties of the final material (3) were determined by nitrogen adsorption at 77 K on an ASAP 2400 setup (Micrometritics). The values of the specific surface area of the samples (S _BET ) were calculated by the BET method, and the values of the volume of mesopores (V _me ) and their specific surface area (S _Me ) were calculated from the adsorption branch of the hysteresis of capillary condensation of nitrogen in accordance with the BJH model (Barrett, E.R., Joyner , LG, Halenda, PP II J. Amer. Chem. Soc. 1951. V. 73. P. 373). Mesopore diameter (D) was calculated as D = 4V _me / S _mt .

As can be seen from the data in Table 2, the water-soluble compounds that are formed when the proposed waterproofing composition is mixed with water are capable of intensively interacting with the cement stone, turning it into bulk solid products with a developed surface and porosity (see No. 3-7). In this case, the volume of the material increases by 1.65-2.1 times. These products are amorphous gels containing mineral and organic components, which corresponds to the MOQF of an irregular structure. On the contrary, water-soluble compounds from the prototype lead to an insignificant increase in the volume of the obtained material - only 1.1 times (see No. 2). At the same time, its specific surface area and porosity remain relatively low, which means that the crystalline hydrates of calcium citrate formed under these conditions are rather dense new formations in comparison with those described above.

Thus, after processing the concrete surface with the proposed waterproofing composition, the efficiency of clogging of pores and cracks in concrete will be significantly higher than that of the prototype.

Example 9.

Testing the water resistance of concrete samples after applying the proposed waterproofing composition.

The test of the waterproofing composition of the penetrating action was carried out in accordance with GOST 12730.5-84 by the "wet spot" method using concrete specimens of water resistance class W4, having a cylindrical shape with a diameter of 150 mm and a height of 100 mm. Before application, the dry mixture of the composition was sealed with water in a solid / liquid ratio. = 5: 2 (pbw), thoroughly stirred and used no later than 30 min after preparation. A layer of waterproofing composition with a thickness of 2-3 mm was applied with a spatula to the end surface of a well-moistened concrete sample, through which water infiltration was ensured under a pressure of 0.6 MPa. For the next 3 days, the layer was periodically moistened with a spray gun, thereby ensuring the penetration of dissolved active components from the applied composition into the pores of the concrete. Evaluation of water resistance for coated samples was carried out at the age of 28 days. Then the coating was removed, and the waterproofing characteristics were determined immediately after removing the coating, as well as after soaking in river water for a year. The measurement results are shown in Table 3, which presents data on the water resistance of concrete before and after applying samples of the claimed waterproofing composition of a penetrating action, after removing these compositions and soaking the samples in river water for a year.

Table 3 shows that in terms of its waterproofing properties, the proposed composition exceeds the prototype by 1.3-1.5 times (2-3 steps in moisture resistance) and demonstrates increased resistance to aggressive external factors (excess water, aqueous microbiota), not inferior to the best commercial samples penetrating waterproofing.

Thus, as can be seen from the above examples and tables, the proposed waterproofing composition of the penetrating action demonstrates high efficiency and stability.

Penetrating composition for waterproofing porous concrete surfaces.

Claims (5)

1. Composition of penetrating action for waterproofing porous concrete surfaces, containing a dry mixture of sodium carbonate, Portland cement, polycarboxylic acid and sand, characterized in that it additionally contains sodium hydroxide and mechanically activated aluminum hydroxide in the following ratio of components, wt%: Sodium carbonate 12, -14.0 Polycarboxylic acid 2.0-3.0 Portland cement М400 60.0-70.0 Sodium hydroxide 0.5-2.0 Mechanically activated aluminum hydroxide 0.5-1.0 Building sand, fraction up to 600 microns, rest. 2. A composition according to claim 1, characterized in that it contains citric, or fumaric, or terephthalic acid as a polycarboxylic acid. 3. A composition according to claim 1, characterized in that it contains mechanically activated pseudoboehmite or gibbsite as mechanically activated aluminum hydroxide. 4. The composition according to claim 1, characterized in that after mixing with water in a composition: water ratio of 5: 2, it provides the pH of the alkaline aqueous solution penetrating into the concrete of 13.7-14.1.