Additive for retaining water, curing and inhibiting water evaporation in plastic stage of concrete as well as preparation method and application of additive

Abstract

The invention relates to an additive capable of retaining water, curing and inhibiting water evaporation in a concrete plasticity stage, a preparation method and application. The additive comprises a modified styrene-acrylic emulsion, a potassium silicate / lithium silicate mixture, lithium polysilicate, a silane or siloxane emulsion, a water reducing agent, a coalescing agent and deionized water. In the potassium silicate / lithium silicate mixture, the modulus of potassium silicate and the modulus of lithium silicate are both greater than 3.0, and the weight ratio of potassium silicate to lithium silicate is 1: (0.1-2); the ratio of SiO2 to Li2O in the lithium polysilicate is greater than or equal to 40; the silane or siloxane emulsion is in a uniform and stable white emulsion state, and the active matter content is 50%; the density is 0.95 g / cm < 3 >, the approximate pH value is 8, and the product is weakly alkaline. The wear resistance and compressive strength of the additive are particularly high, and the additive can reduce evaporation of water on the surface of concrete, prevent the surface of concrete from cracking and the like; in addition, the constructability of the concrete can be improved, and the concrete has the characteristics of bleeding prevention, difficulty in layering and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete additives, and specifically relates to an additive that can retain water, maintain solidity and inhibit water evaporation in the plastic stage of concrete, a preparation method and application thereof. Background Art

[0002] During the actual concrete paving process, due to the influence of strong winds and high temperatures, the evaporation rate of concrete moisture is greater than the water seepage rate, resulting in a large negative pressure in the concrete, which is unable to resist the resulting shrinkage, causing surface cracking, stickiness, crusting and other problems, seriously affecting the construction progress and quality. Summary of the invention

[0003] The purpose of the present invention is to solve the problems of water retention and water evaporation in the concrete construction process and the problems arising therefrom, and to provide an additive, preparation method and application thereof for retaining water, maintaining solidification and inhibiting water evaporation in the plastic stage of concrete. The additive for retaining water, maintaining solidification and inhibiting water evaporation in the plastic stage of concrete of the present invention is directly sprayed on the plasticity that has not yet been initially set, has excellent water retention and water evaporation inhibition functions, and has excellent physical properties, can improve the wear resistance ratio and compression resistance of concrete, prevent concrete surface cracking and other properties; at the same time, it can improve the workability of concrete, prevent water seepage, and is not easy to delaminate and other characteristics.

[0004] To solve the above problems, the present invention is implemented through the following technical solutions:

[0005] The first object of the present invention is:

[0006] Provided is an additive for retaining water, maintaining solidity and inhibiting water evaporation in the plastic stage of concrete, comprising the following components in parts by weight:

[0007] 5-50 parts of modified styrene-acrylic emulsion, 5-40 parts of potassium silicate / lithium silicate mixture, 5-50 parts of lithium polysilicate, 0.1-5 parts of silane or siloxane emulsion, 0.1-5 parts of water reducing agent, 0.01-3 parts of film-forming aid, and 20-65 parts of deionized water;

[0008] In the potassium silicate / lithium silicate mixture, the modulus of potassium silicate and lithium silicate are both greater than 3.0, and the weight ratio of potassium silicate to lithium silicate is 1:0.1-2;

[0009] The ratio of SiO2:Li2O in the lithium polysilicate is ≥40;

[0010] The silane or siloxane emulsion is in a uniform and stable white emulsion state, with an active matter content of 50% and a density of 0.95 g / cm 3 , the pH value is approximately 8, which is weakly alkaline;

[0011] The modified styrene-acrylic emulsion is prepared by adopting a core-shell emulsion polymerization process, using methyl methacrylate as a core monomer and styrene as a shell monomer to form sandwich-shaped or half-moon-shaped latex particles. The prepared emulsion has the advantages of fast drying speed, good film-forming property, excellent early water resistance and good adhesion.

[0012] The additives for retaining water, maintaining solidity and inhibiting water evaporation in the concrete plastic stage of the present invention are further optimized as follows:

[0013] The modified styrene acrylic emulsion has the appearance of milky white slightly blue phase liquid, solid content ≥43%, viscosity 2000-7000cps, pH value 7-9, glass transition temperature 28-32°C, and minimum film forming temperature 20-24°C.

[0014] The additives for retaining water, maintaining solidity and inhibiting water evaporation in the concrete plastic stage of the present invention are further optimized as follows:

[0015] The modified styrene-acrylic emulsion is preferably one or a combination of Acronal 7035, Acronal 338AP of BASF, BLJ 8586, BLJ 818 of Baolijia.

[0016] After the modified styrene-acrylic emulsion is evenly coated on the concrete surface, the water in the emulsion begins to penetrate into the capillaries of the concrete or evaporate. As the water evaporates, the emulsion particles gradually approach and contact, forming a dense accumulation state. As the surface of the emulsion particles softens, they fuse with each other through the van der Waals force between molecules to form a continuous polymer film. The water in the emulsion enters the capillaries of the concrete, and at the same time, some small molecular monomers and polymer segments also penetrate into the capillaries to form a mechanical intercalation effect, which helps to improve the adhesion of the coating. The modified styrene-acrylic emulsion contains functional monomers (such as carboxyl, hydroxyl, etc.), which can react with alkaline components (such as Ca(OH)2) in concrete to further enhance adhesion and durability. After film formation, the coating forms a continuous closed layer on the concrete surface and in the pores, blocking the penetration of water and other corrosive media. In the modified styrene-acrylic emulsion, by adding a suitable proportion of styrene, the hydrophobicity and impermeability of the film layer are improved. Cross-linking components such as methyl methacrylate (MMA) improve the compactness and chemical resistance of the film layer. At the same time, the modified styrene acrylic emulsion has a high proportion of hydrophobic components, which helps the coating film prevent water penetration. The modified styrene acrylic emulsion selected by the present invention forms a continuous protective layer on the surface of the substrate through film formation, which has the following effects:

[0017] 1. Seal the pores on the concrete surface;

[0018] 2. Provide flexibility and resist the expansion of micro cracks in the substrate;

[0019] 3. Good adhesion ensures long-term stability of the film.

[0020] The effects of the silane or siloxane emulsion are as follows:

[0021] Silane or siloxane emulsion contains hydrophobic groups (such as methyl, alkyl, etc.), and the hydrophobic layer formed after the reaction can significantly reduce the water absorption of the substrate surface and prevent water from intruding. After construction, the silane or siloxane emulsion can quickly play a water-retaining role, so that a hydrophobic layer is formed on the surface of the building material to reduce the volatilization of water; at the same time, the silane or siloxane emulsion can penetrate deeply into the interior of the building material, fundamentally improve the density of the building material, and reduce the overflow of water from the pores, rather than just forming a waterproof film on the surface. The silane or siloxane emulsion uses water as a dispersion medium, does not contain organic solvents, is environmentally friendly, and meets the requirements of modern buildings for environmentally friendly materials. During the construction process, no harmful gases and pollutants will be generated, which is harmless to the health of construction workers.

[0022] The synergistic effect of silane or siloxane emulsion and modified styrene acrylic emulsion is manifested in the following aspects:

[0023] (1) Penetration and reaction of silane or siloxane: Silane or siloxane molecules are small and highly permeable, and can penetrate deep into the pores of concrete and react with the substrate to form a hydrophobic layer. This hydrophobic layer provides a base for the subsequent styrene acrylic emulsion to adhere to, while reducing the risk of moisture rising.

[0024] (2) Surface sealing of modified styrene acrylic emulsion: The modified styrene acrylic emulsion forms a film on the surface of the silane-modified substrate, further sealing the pores and microcracks to form a continuous protective film.

[0025] (3) Improve durability: The hydrophobic properties of silane or siloxane are combined with the mechanical properties of modified styrene acrylic emulsion, so that the waterproof layer has both high hydrophobicity and resistance to external stress and substrate deformation.

[0026] The role of the lithium polysilicate is: small particle size, excellent permeability; while quickly penetrating, it can generate calcium silicate and lithium silicate gel, with a dense structure, which can effectively fill the concrete voids and prevent water from overflowing. The specific chemical reaction equation is as follows:

[0027] Li + +SiO2+Ca(OH)2→CaSiO3↓+2LiOH

[0028] Li + +SiO2+OH - →LSH(Gel)

[0029] The reaction equation of the potassium silicate / lithium silicate mixture with calcium hydroxide, a by-product of cement hydration, is as follows:

[0030] Li2SiO3+Ca(OH)2→CaSiO3↓+2LiOH

[0031] K2SiO3+Ca(OH)2→CaSiO3↓+2KOH

[0032] The generated alkali-insoluble strong alkali weak acid salt (alkaline) precipitate fills the voids in the concrete in a gel state, which can significantly improve the wear resistance and Mohs hardness of the concrete floor or wear-resistant aggregate floor, and can effectively seal the floor. The principle is:

[0033] The strength of concrete mainly comes from the calcium silicate compound (CSH) generated by the silicon and calcium in the cement under the action of water. CSH is the main strength-promoting substance in concrete. After the initial setting, the concrete continues to undergo a slow CSH hydration reaction. This reaction cannot be fully carried out under natural conditions, and there is always a large amount of free calcium ions (Ca 2 + ) does not participate in the formation of CSH. The active silicate ions contained in this additive effectively penetrate and react with the unreacted free calcium (Ca 2+ ) reaction to form calcium silicate hydrate (CSH) gel, which is a permanent gel that can form a three-dimensional network structure. Correspondingly, the added lithium polysilicate can further promote the reaction and make the reaction more complete. This can compact the concrete, effectively seal the ground, and improve the compressive strength and wear resistance of the concrete.

[0034] The additives for retaining water, maintaining solidity and inhibiting water evaporation in the concrete plastic stage of the present invention are further optimized as follows:

[0035] The water reducer is one or a combination of high-efficiency naphthalene-based water reducer, lignin-based water reducer and polycarboxylic acid-based water reducer.

[0036] The additives for retaining water, maintaining solidity and inhibiting water evaporation in the concrete plastic stage of the present invention are further optimized as follows:

[0037] The film-forming aid is one or a combination of alcohols, alcohol esters, alcohol ethers, and alcohol ether ester film-forming aids.

[0038] The second object of the present invention is:

[0039] Provided is a method for preparing the aforementioned additive that retains water, maintains solidity and inhibits water evaporation in the concrete plastic stage, which comprises the following preparation steps:

[0040] The modified styrene acrylic emulsion, a mixture of potassium silicate / lithium silicate, lithium polysilicate, silane or siloxane emulsion, a water reducer, a film-forming aid and deionized water are added into a suitable stirring tank in proportion, stirred at a speed of 600 rpm, and dispersed for 10 minutes to obtain the additive.

[0041] The third invention object of the present invention is:

[0042] A coating method for the additive described above that plays a role in retaining water, maintaining solidity and inhibiting water evaporation in the plastic stage of concrete is provided, which comprises the following preparation steps:

[0043] s1. The additives for retaining water and inhibiting water evaporation in the concrete plastic stage are sprayed directly on the surface of the non-initial setting plastic concrete to reduce the evaporation of water from the concrete surface;

[0044] s2. After one week of natural drying, proceed with subsequent processing.

[0045] The fourth invention objective of the present invention is:

[0046] Provided is a coating, which is prepared by the coating method described above and coated on a substrate, wherein the substrate includes but is not limited to concrete and wear-resistant aggregate floor.

[0047] Spraying the additive of the present invention, which plays a role in retaining water, maintaining solidity and inhibiting water evaporation in the plastic stage of concrete, on the surface of plastic concrete that has not yet set can reduce the rapid evaporation of water on the concrete surface and improve the strength, wear resistance and durability of the concrete. In addition, it can also effectively reduce or eliminate the cracking and peeling of the concrete surface caused by plastic shrinkage and environmental factors (such as strong winds and high temperatures). This product provides a new solution for ensuring engineering quality.

[0048] Additives that retain water, maintain solidity and inhibit water evaporation in the plastic stage of concrete can form a dense mixed film on the surface of plastic concrete, which has the characteristics of high temperature resistance and wind resistance, thereby significantly inhibiting the evaporation of water in the plastic state of concrete and reducing the plastic cracking of concrete. At the same time, this material will not have side effects on the cement hydration process or the concrete itself, and has high application value and many advantages.

[0049] Compared with the prior art, the additive of the present invention, which plays a role in retaining water, maintaining solidity and inhibiting water evaporation in the plastic stage of concrete, has the following main advantages:

[0050] (1) The wear resistance and compressive strength of the additive of the present invention are particularly high;

[0051] (2) The additive of the present invention has good storage stability, a long open time, a long workable time, almost no change in viscosity during the workable time, and stable performance that is not easily lost;

[0052] (3) The additive of the present invention can reduce the evaporation of water on the concrete surface and prevent the concrete surface from cracking;

[0053] (4) The additive of the present invention can improve the workability of concrete and has the characteristics of preventing water seepage and being difficult to delaminate. DETAILED DESCRIPTION

[0054] In order to make the application, technical scheme and advantages of the present invention more clear, the present invention is described in detail in conjunction with specific embodiments. It should be understood that the embodiments are only used to illustrate the present invention, but not to limit the protection scope of the present invention. All simple improvements to the preparation method of the present invention under the premise of the concept of the present invention belong to the protection scope of the present invention.

[0055] Example 1 and the raw materials that can be used in the present invention are shown in Table 1.

[0056] Table 1

[0057]

[0058]

[0059] Example 1

[0060] An additive for retaining water, maintaining solidity and inhibiting water evaporation in the plastic stage of concrete, comprising the following components in parts by weight:

[0061] 5-50 parts of modified styrene-acrylic emulsion, 5-40 parts of potassium silicate / lithium silicate mixture, 5-50 parts of lithium polysilicate, 0.1-5 parts of silane or siloxane emulsion, 0.1-5 parts of water reducing agent, 0.01-3 parts of film-forming aid, 20-65 parts of deionized water; (See Table 1 for specific amounts)

[0062] In the potassium silicate / lithium silicate mixture, the modulus of potassium silicate and lithium silicate are both greater than 3.0, and the weight ratio of potassium silicate to lithium silicate is 1:0.1-2;

[0063] The ratio of SiO2:Li2O in the lithium polysilicate is ≥40;

[0064] The silane or siloxane emulsion is in a uniform and stable white emulsion state, with an active matter content of 50% and a density of 0.95 g / cm 3 , the pH value is approximately 8, which is weakly alkaline;

[0065] The emulsion is a modified styrene-acrylic emulsion, which is prepared by adopting a core-shell emulsion polymerization process, using methyl methacrylate as a core monomer and styrene as a shell monomer to form sandwich-shaped or half-moon-shaped latex particles.

[0066] The additive for retaining water, maintaining solidity and inhibiting water evaporation in the concrete plastic stage comprises the following preparation steps:

[0067] The modified styrene acrylic emulsion, a mixture of potassium silicate / lithium silicate, lithium polysilicate, silane or siloxane emulsion, a water reducer, a film-forming aid and deionized water are added into a suitable stirring tank in proportion, stirred at a speed of 600 rpm, and dispersed for 10 minutes to obtain the additive.

[0068] Table 1

[0069] raw material Dosage Range Example 1 Example 2 Example 3 Lotion BLJ-8586 5～50 30 30 30 Potassium silicate / lithium silicate mixture 5～40 20 25 30 Lithium Polysilicate 5～50 5 6 7 Silane or silicone emulsion 0.1～5 2 3 4 PCA-I water reducing agent 0.1～5 0.5 0.5 0.5 Film-forming agent CZ12 0.01～3 2 2 2 Deionized water 20～65 40.5 33.5 26.5 Total 100 100 100 100

[0070] The preparation methods of Examples 2 and 3 are the same as those of Example 1, the main difference being that the amounts of some raw materials are different, as shown in Table 1 for details.

[0071] Results test:

[0072] According to JC901-2002 Cement Concrete Curing Agent Specification, the solid content, drying time, water solubility after film formation, and heat resistance of film formation were tested; according to JC / T 477-2015 Specification for Moisture Evaporation Inhibitor in Plastic Stage of Concrete, the volatile organic compound content (VOC) / (g / l), moisture evaporation inhibition rate, concrete surface appearance, total cracking area reduction rate, wear reduction rate, and compressive strength ratio were tested; according to JC / T906-2002 Cement-based Wear-resistant Material Type I Specification for Concrete Floor, the wear resistance ratio was tested. The results are shown in Table 2 below.

[0073] Table 2

[0074]

[0075] Commercially available products 1 and 2 are commercially available concrete plastic stage moisture evaporation inhibitors.

[0076] As can be seen from Table 2, Example 1 of the present invention has significantly improved the performance of inhibiting water evaporation, and meets the standard requirements in many aspects such as solid content, drying time, water solubility after film formation, film heat resistance, concrete surface appearance, total crack area reduction rate, wear reduction rate, compressive strength ratio, and wear resistance ratio.

[0077] Example 2 of the present invention has a significant improvement in the performance of inhibiting water evaporation. It meets the standard requirements in many aspects such as solid content, drying time, water solubility after film formation, film heat resistance, concrete surface appearance, total crack area reduction rate, wear reduction rate, compressive strength ratio, and wear resistance ratio. In addition, since the film-forming aid in Example 2 contains VOC, the amount of film-forming aid used can be significantly reduced, and VOC can be reduced (the VOC content is calculated to be <50g / L), making the product more environmentally friendly and safe.

[0078] The results of Example 3 of the present invention are shown in Table 2, and all meet the requirements.

[0079] The commercially available product 1 has a solid content equivalent to that of the present invention, but due to its poor film-forming material, it cannot form a film. Therefore, the commercially available product 1 is unqualified in terms of water evaporation inhibition rate and total crack area reduction rate.

[0080] Compared with the commercially available product 2, the embodiment of the present invention has obvious advantages in terms of water evaporation inhibition rate, film-forming property, and VOC content, and is also comparable to and superior to the commercially available product 2 in other properties.

[0081] To sum up, the above are only preferred embodiments of the present invention and are not intended to limit the present invention in any form. Any equivalent changes, modifications and evolutions made by technicians familiar with the profession without departing from the scope of the technical solution of the present invention using the disclosed technical content are regarded as equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the technical solution of the present invention.

[0082] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0083] The experimental methods without specific conditions in the present invention are usually carried out under conventional conditions or conditions recommended by the manufacturer.

[0084] Unless otherwise stated, the various optimization technical solutions in the present invention can be combined with each other.

[0085] Unless otherwise indicated, percentages and parts are by weight.

[0086] Experimental methods without specific conditions specified in the instructions and examples are usually carried out under conventional conditions or conditions recommended by the manufacturers.

[0087] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any method and material similar or equivalent to the described content can be applied to the method of the present invention.

Claims

1. An additive that retains water, maintains solidity and inhibits water evaporation during the plastic stage of concrete, characterized in that: It includes the following components in parts by weight: 5-50 parts of modified styrene-acrylic emulsion, 5-40 parts of potassium silicate / lithium silicate mixture, 5-50 parts of lithium polysilicate, 0.1-5 parts of silane or siloxane emulsion, 0.1-5 parts of water reducing agent, 0.01-3 parts of film-forming aid, and 20-65 parts of deionized water; In the potassium silicate / lithium silicate mixture, the modulus of potassium silicate and lithium silicate are both greater than 3.0, and the weight ratio of potassium silicate to lithium silicate is 1:0.1-2; The ratio of SiO2:Li2O in the lithium polysilicate is ≥40; The silane or siloxane emulsion is in a uniform and stable white emulsion state, with an active matter content of 50% and a density of 0.95 g / cm 3 , the pH value is approximately 8, which is weakly alkaline; The modified styrene-acrylic emulsion is prepared by adopting a core-shell emulsion polymerization process, using methyl methacrylate as a core monomer and styrene as a shell monomer to form sandwich-shaped or half-moon-shaped latex particles.

2. The additive for retaining water, maintaining solidity and inhibiting water evaporation in the plastic stage of concrete according to claim 1, characterized in that: The water reducer is one or a combination of high-efficiency naphthalene-based water reducer, lignin-based water reducer and polycarboxylic acid-based water reducer.

3. The additive for retaining water, maintaining solidity and inhibiting water evaporation in the plastic stage of concrete according to claim 1, characterized in that: The film-forming aid is one or a combination of alcohols, alcohol esters, alcohol ethers, and alcohol ether ester film-forming aids.

4. The additive for retaining water, maintaining solidity and inhibiting water evaporation in the plastic stage of concrete according to claim 1, characterized in that: The modified styrene acrylic emulsion has the appearance of milky white slightly blue phase liquid, solid content ≥43%, viscosity 2000-7000cps, pH value 7-9, glass transition temperature 28-32°C, and minimum film forming temperature 20-24°C.

5. The additive for retaining water, maintaining solidity and inhibiting water evaporation in the plastic stage of concrete according to claim 4, characterized in that: The modified styrene-acrylic emulsion is one or a combination of Acronal 7035, Acronal 338AP of BASF, BLJ 8586 and BLJ 818 of Baolijia.

6. A method for preparing the additive for retaining water, maintaining solidity and inhibiting water evaporation in the plastic stage of concrete according to claim 1, characterized in that: It comprises the following preparation steps: The modified styrene acrylic emulsion, a mixture of potassium silicate / lithium silicate, lithium polysilicate, silane or siloxane emulsion, a water reducer, a film-forming aid and deionized water are added into a suitable stirring tank in proportion, stirred at a speed of 600 rpm, and dispersed for 10 minutes to obtain the additive.

7. A coating method of the additive for retaining water, maintaining solidity and inhibiting water evaporation in the plastic stage of concrete according to claim 1, characterized in that: It comprises the following preparation steps: s1. The additive for retaining water and inhibiting water evaporation in the plastic stage of concrete is sprayed directly on the surface of the plastic concrete before initial setting; s2. After one week of natural drying, proceed with subsequent processing.

8. A coating, characterized in that: The coating is prepared by the coating method according to claim 7 and coated on a substrate.

Images