Preparation and application of an emulsified compacting shrinkage feeding agent for concrete

Abstract

The present invention discloses the preparation and application of an emulsified, compacting, and feeding agent for concrete, belonging to the technical field of concrete admixtures. The emulsified, compacting, and feeding agent for concrete comprises modified latex powder, polyethylene glycol, and water. The modified latex powder is prepared by coating calcium sulfate and aluminum sulfate powder with a gel coat solution composed of aluminum hydroxide and a polymer emulsion, followed by drying. The modified latex powder, polyethylene glycol, and water are mixed and stirred to produce the emulsified, compacting, and feeding agent for concrete. The emulsified, compacting, and feeding agent for concrete of the present invention controls and adjusts the expansion efficiency of concrete, avoiding early ineffective expansion. The polymer emulsion also increases the toughness and waterproof properties of concrete, significantly improving the crack resistance and waterproof properties of concrete.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete admixtures, in particular to the preparation and application of an emulsified, compacting and shrinkage-feeding agent for concrete. Background Art

[0002] Concrete expansion agent belongs to the calcium sulfoaluminate type concrete expansion agent, does not contain sodium salt, is not easy to cause concrete alkali aggregate reaction, and has good durability, stable expansion performance, and continuously increasing strength. Ordinary concrete often leaks due to shrinkage cracking, which reduces its usability and durability. By adding expansion agent to cement, it can be mixed into shrinkage compensating concrete. Shrinkage compensating concrete has the functions of compensating concrete shrinkage and compacting concrete, and improving concrete impermeability. In civil engineering, it is mainly used for waterproofing and crack resistance. It is used more frequently in the preparation of high-grade waterproof concrete and the appropriate extension of the spacing between expansion joints or post-casting strips. The application of shrinkage compensating concrete greatly improves the crack resistance and waterproofing ability of concrete structures, and prevents the occurrence of temperature difference cracks in large-volume concrete and high-strength concrete. However, traditional powder expansion agents have problems such as being inconvenient to use and add, being easily affected by moisture and failing, and not being easy to disperse evenly. Therefore, it is particularly important to invent an emulsified compacting shrinkage compensation agent for concrete that is easy to use, not easily affected by moisture, and easy to disperse evenly. Summary of the Invention

[0003] In response to the above shortcomings of the existing technology, the present invention provides an emulsified compacting shrinkage feeding agent for concrete, which is not only easy to use and not easily affected by moisture, but also can control and adjust the expansion efficiency, thereby improving the crack resistance and waterproofing ability of the concrete structure. This is specifically achieved through the following technologies.

[0004] The invention provides a modified latex powder. The powder particles of the modified latex powder have a structure in which a mixture of calcium sulfate and aluminum sulfate is used as a core and a gel coat is wrapped around the core. The gel coat comprises aluminum hydroxide and a polymer emulsion.

[0005] The modified latex powder of the present invention has the characteristic of intelligent regulation. When the emulsified dense shrinkage feeding agent is added to concrete, the cementitious material in the concrete undergoes a hydration reaction. When the alkalinity reaches a certain value, the gel coat composed of aluminum hydroxide and polymer emulsion opens pores due to the slow dissolution of the aluminum hydroxide, exposing the calcium sulfate and aluminum sulfate in the gel coat, which then triggers a hydration reaction of the calcium sulfate and aluminum sulfate to generate expanded ettringite crystals. This process consumes a large amount of water. As the damaged area of ​​the gel coat gradually increases, the hydration reaction probability of the calcium sulfate and aluminum sulfate increases. Therefore, by adjusting the ratio between the raw materials of the modified latex powder, the thickness of the gel coat and the amount of aluminum hydroxide can be controlled, thereby achieving adjustable expansion rate, adjustable expansion ratio, and crack-resistant and waterproof performance with excellent waterproof effect.

[0006] Preferably, the polymer emulsion is at least one of vinyl acetate copolymer emulsion, acrylate polymer emulsion, silicone emulsion and the like.

[0007] Preferably, the solid content of the polymer emulsion is 50-60%.

[0008] Preferably, the aluminum hydroxide is aluminum hydroxide powder of 120 mesh and above.

[0009] Preferably, the calcium sulfate is calcium sulfate powder of 120 mesh and above.

[0010] Preferably, the aluminum sulfate is aluminum sulfate powder of 120 mesh and above.

[0011] Preferably, the mass ratio of calcium sulfate to aluminum sulfate is (3-5):(4-6).

[0012] Preferably, the mass ratio of aluminum hydroxide to polymer emulsion is (6-8):(30-40).

[0013] Preferably, the mass ratio of the core to the gel coat is (7-11):(36-48).

[0014] The preparation method of the modified latex powder comprises the following steps: adding aluminum hydroxide and polymer emulsion into water, stirring and mixing to obtain a gel coating solution, adding calcium sulfate and aluminum sulfate, stirring and mixing, spray drying, and drying to obtain the modified latex powder.

[0015] Preferably, the spray drying conditions are: vacuum degree of -0.05 to -0.09 MPa, temperature of 100 to 110° C., speed of 4 to 8 m / s, and nozzle diameter of 0.1 to 0.3 mm.

[0016] An emulsified compacting shrinkage feeding agent for concrete comprises the modified latex powder and polyethylene glycol.

[0017] Preferably, the mass ratio of the modified latex powder to the polyethylene glycol is (30-40):(1-5).

[0018] The application of the emulsified compacting shrinkage feeding agent for concrete is to mix the raw materials of the emulsified compacting shrinkage feeding agent for concrete, modified latex powder, polyethylene glycol and water, to obtain a mixture, and then add it into concrete.

[0019] Preferably, in the above mixture, the mass fraction of the modified latex powder is 30-40%.

[0020] Preferably, the amount of the emulsified compacting shrinkage feeding agent for concrete in the concrete is 1 to 3% based on the total mass of the cementitious material.

[0021] Compared with the prior art, the present invention is beneficial in that:

[0022] (1) The emulsified compacting shrinkage-feeding agent for concrete provided by the present invention is a liquid concrete additive with micro-expansion. The liquid emulsified compacting shrinkage-feeding agent for concrete controls and adjusts the expansion efficiency of concrete, avoiding early ineffective expansion. At the same time, the emulsified compacting shrinkage-feeding agent for concrete of the present invention contains a polymer emulsion, which increases the toughness and waterproof performance of concrete. The use of modified latex powder in combination with polyethylene glycol is more conducive to the reaction of calcium sulfate and aluminum sulfate in the modified latex powder, so that the crack resistance and waterproof performance of concrete are significantly improved. The 48h water absorption ratio of the concrete added with the present invention can be controlled below 48%, the penetration height ratio can be controlled below 24%, and the crack resistance ratio can reach 64%;

[0023] (2) The present invention selects aluminum hydroxide powder with a mesh size of 120 or larger, calcium sulfate powder with a mesh size of 120 or larger, and aluminum sulfate powder with a mesh size of 120 or larger, and adjusts the ratio of each raw material of the modified latex powder to control the thickness of the gel coat and the amount of aluminum hydroxide, and to control the hydration reaction of calcium sulfate and aluminum sulfate, thereby achieving adjustable expansion rate and adjustable expansion ratio, and ultimately improving the crack resistance and waterproof performance of the concrete;

[0024] (3) Compared with traditional powder expansion agents, the concrete emulsified compacting shrinkage feeding agent of the present invention has the advantages of being easy to use and add, not easily ineffective due to moisture, and easy to disperse evenly. DETAILED DESCRIPTION

[0025] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0026] The following specific embodiment provides a method for preparing a modified latex powder, comprising the following steps: adding 6 to 8 parts of aluminum hydroxide powder and 30 to 40 parts of a polymer emulsion to water and stirring to mix; adding 3 to 5 parts of calcium sulfate powder and 4 to 6 parts of aluminum sulfate powder and stirring to mix; then spray drying, and further drying the obtained powder to obtain the modified latex powder.

[0027] Optionally, the particle size of the aluminum hydroxide powder, the calcium sulfate powder and the aluminum sulfate powder is above 120 mesh.

[0028] Optionally, after adding aluminum hydroxide powder and polymer emulsion, stirring is carried out at 1800-2200 r / min for 15-25 minutes.

[0029] Optionally, after adding calcium sulfate powder and aluminum sulfate powder, stirring is continued for 25 to 35 minutes at the same stirring speed as above.

[0030] Optionally, the spray drying conditions may be selected as follows: vacuum degree -0.05 to -0.09 MPa, temperature 100 to 110° C., flow rate 4 to 8 m / s, and nozzle diameter 0.1 to 0.3 mm.

[0031] Optionally, after spray drying, the drying condition is: drying at 100-110° C. for 1-3 hours.

[0032] A method for preparing an emulsified, dense shrinkage-feeding agent for concrete comprises the following steps: adding 30 to 40 parts of the modified latex powder and 1 to 5 parts of polyethylene glycol to 55 to 69 parts of water to obtain the emulsified, dense shrinkage-feeding agent for concrete, wherein the mass fraction of the modified latex powder is 30 to 40%.

[0033] Optionally, after adding the modified latex powder and polyethylene glycol to water, the stirring method is to stir at 1800-2200 r / min for 25-35 minutes.

[0034] Optionally, the polymer emulsion may be one or more of vinyl acetate copolymer emulsion, acrylate polymer emulsion or silicone emulsion; the solid content of the polymer emulsion is 50-60%.

[0035] Optionally, the polyethylene glycol can be selected from one or more of polyethylene glycol-200, 400, 600, 800, and 1200.

[0036] The technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] This embodiment provides a method for preparing a modified latex powder, comprising the following steps: adding 7 parts of 600-mesh aluminum hydroxide powder and 35 parts of a vinyl acetate copolymer emulsion with a solid content of 55% to water, stirring at a high speed of 2000 r / min for 20 minutes, slowly adding 5 parts of 800-mesh calcium sulfate powder and 6 parts of 1000-mesh aluminum sulfate powder, continuing to stir at a high speed of 2000 r / min for 30 minutes after the addition, and then vacuum spray drying at 105° C., with a vacuum degree reaching -0.09 MPa, a nozzle diameter of 0.1 mm, and an initial speed controlled at 6 m / s. The resulting powder is dried at normal pressure at 105° C. for 2 hours to obtain the modified latex powder.

[0039] This embodiment provides a method for preparing an emulsified, dense, and feeding agent for concrete, comprising the following steps: dissolving 30 parts of the modified latex powder and 3 parts of polyethylene glycol-400 in 67 parts of deionized water, and stirring at a high speed of 2000 rpm for 30 minutes to obtain an emulsified, dense, and feeding agent for concrete.

[0040] Example 2

[0041] This embodiment provides a method for preparing a modified latex powder, comprising the following steps: adding 6 parts of 120-mesh aluminum hydroxide powder and 30 parts of a vinyl acetate copolymer emulsion with a solid content of 50% to water, stirring at a high speed of 1800 r / min for 15 minutes, slowly adding 3 parts of 120-mesh calcium sulfate powder and 4 parts of 120-mesh aluminum sulfate powder, continuing to stir at a high speed of 1800 r / min for 25 minutes after the addition, and then vacuum spray drying at 100°C, with a vacuum degree reaching -0.05 MPa, a nozzle diameter of 0.2 mm, and an initial speed controlled at 4 m / s. The resulting powder is dried at normal pressure at 100°C for 1 hour to obtain the modified latex powder.

[0042] This embodiment provides an emulsified, dense shrinkage-feeding agent for concrete. The preparation method is as follows: 35 parts of the modified latex powder and 1 part of polyethylene glycol-400 are dissolved in 64 parts of deionized water, and the mixture is stirred at a high speed of 2000 r / min for 25 minutes to obtain the emulsified, dense shrinkage-feeding agent for concrete.

[0043] Example 3

[0044] This embodiment provides a method for preparing a modified latex powder, comprising the following steps: adding 8 parts of 800-mesh aluminum hydroxide powder and 40 parts of a vinyl acetate copolymer emulsion with a solid content of 60% to water, stirring at a high speed of 2200 r / min for 25 minutes, slowly adding 5 parts of 800-mesh calcium sulfate powder and 6 parts of 1000-mesh aluminum sulfate powder, continuing to stir at a high speed of 2200 r / min for 35 minutes after the addition, and then vacuum spray drying at 110° C., with a vacuum degree reaching 0.1 MPa, a nozzle diameter of 0.3 mm, and an initial speed controlled at 8 m / s. The resulting powder is dried at normal pressure at 110° C. for 3 hours to obtain the modified latex powder.

[0045] This embodiment provides an emulsified, dense shrinkage-feeding agent for concrete. The preparation method is as follows: 40 parts of the modified latex powder and 5 parts of polyethylene glycol-400 are dissolved in 55 parts of deionized water, and the mixture is stirred at a high speed of 2200 r / min for 35 minutes to obtain the emulsified, dense shrinkage-feeding agent for concrete.

[0046] Comparative Example 1

[0047] This comparative example provides an emulsified, dense shrinkage feeding agent for concrete. The preparation method comprises the following steps: adding 7 parts of 600-mesh aluminum hydroxide powder and 35 parts of a vinyl acetate copolymer emulsion having a solid content of 55% to water; stirring the mixture at a high speed of 2000 r / min for 20 minutes; slowly adding 5 parts of 800-mesh calcium sulfate powder and 6 parts of 1000-mesh aluminum sulfate powder; continuing to stir the mixture at a high speed of 2000 r / min for 30 minutes; then adding 3 parts of polyethylene glycol-400 and 67 parts of deionized water; and continuing to stir the mixture at a high speed of 2000 r / min for 30 minutes to obtain the emulsified, dense shrinkage feeding agent for concrete.

[0048] That is, this comparative example is basically the same as Example 1, except that the aluminum hydroxide, vinyl acetate copolymer emulsion, calcium sulfate and aluminum sulfate are not pre-prepared into modified latex powder.

[0049] Comparative Example 2

[0050] This comparative example is basically the same as Example 1, except that no polyethylene glycol is added during the preparation of the emulsified compacting shrinkage feeding agent for concrete, that is, the emulsified compacting shrinkage feeding agent for concrete in this comparative example contains only 30 parts of modified latex powder and 70 parts of deionized water.

[0051] Comparative Example 3

[0052] This comparative example is basically the same as Example 1, except that the amounts of aluminum hydroxide and polymer emulsion used in the preparation method of the modified latex powder are different, that is, the preparation method of the modified latex powder includes 5 parts of aluminum hydroxide and 29 parts of vinyl acetate copolymer emulsion.

[0053] Comparative Example 4

[0054] This comparative example is basically the same as Example 1, except that the amount of core and gel coat used in the preparation method of the modified latex powder is different, that is, the preparation method of the modified latex powder includes 12 parts of core and 35 parts of gel coat.

[0055] Comparative Example 5

[0056] This comparative example is basically the same as Example 1, except that 100-mesh aluminum hydroxide powder is used in the preparation of the modified latex powder.

[0057] Comparative Example 6

[0058] This comparative example is basically the same as Example 1, except that 100-mesh calcium sulfate powder is used in the preparation of the modified latex powder.

[0059] Comparative Example 7

[0060] This comparative example is basically the same as Example 1, except that 100-mesh aluminum sulfate powder is used in the preparation of the modified latex powder.

[0061] Application example: Performance test:

[0062] The concrete of Examples 1 to 3 and Comparative Examples 1 to 7 was prepared into standard test pieces with emulsified densifying shrinkage feeding agent, cement, standard sand and water, and the restricted expansion rate, 48h water absorption ratio, penetration height ratio and anti-cracking performance ratio were tested.

[0063] (1) Limit expansion rate test

[0064] Experimental materials: Cement uses the benchmark cement specified in GB 8076-2008 "Concrete Admixtures"; standard sand meets the requirements of GB / T 17671-2021 "Test Method for Cement Mortar Strength"; water meets the requirements of JGJ 63-2006 "Standard for Water for Concrete".

[0065] The standard specimens of Examples 1 to 3 and Comparative Examples 1 to 7 were prepared according to the test method for limiting expansion rate in GB 23439-2009 "Concrete Expansion Agents", and the lengths of the specimens were measured. The length measurement data were calculated to obtain the limiting expansion rate of the concrete to which the emulsified densifying shrinkage feeding agents for concrete of Examples 1 to 3 and Comparative Examples 1 to 7 were applied. The standard for limiting expansion rate and the test results are shown in Table 1.

[0066] (2) 48h water absorption ratio and penetration height ratio test

[0067] Experimental Materials:

[0068] The cement is the cement that complies with the provisions of Appendix A of GB 8076-1997 “Concrete Admixtures”; the sand is the standard sand that complies with the provisions of GB 178-1997 “Standard Sand for Cement Strength Test”; the mass ratio of cement to standard sand is 1:3.

[0069] The concrete emulsified densifying shrinkage feeding agent of Examples 1 to 3 and Comparative Examples 1 to 7 was mixed with cement, standard sand and water according to the test method in JC 474-2008 "Mortar and Concrete Waterproofing Agent" to prepare benchmark and test specimens, and the test specimens were tested for water absorption ratio (48h) and penetration height ratio. The standards and test results of the 48h water absorption ratio and penetration height ratio are shown in Table 1.

[0070] (3) Anti-cracking performance comparison test

[0071] Experimental materials: Cement meets the benchmark cement specified in Section 5.1.1 of GB 8076-1977 "Concrete Admixtures"; sand meets the requirements of JGJ 52-2006 "Standard for Quality and Test Methods of Sand and Stone for Ordinary Concrete"; mixing water meets the requirements of JGJ 63-2006 "Standard for Water for Concrete".

[0072] The concrete emulsified densifying shrinkage-feeding agent of Examples 1 to 3 and Comparative Examples 1 to 7 was mixed with cement, sand and water to prepare reference mortar and test mortar according to the experimental method in JC / T951-2005 "Test Method for Anti-cracking Performance of Cement Mortar", and the anti-cracking performance ratio of the tested mortar was tested. The standard and test results of the anti-cracking performance ratio are shown in Table 1.

[0073] Table 1 Performance test standards and results of Examples 1 to 3 and Comparative Examples 1 to 7

[0074]

[0075] It can be seen from Table 1 that the emulsified densifying shrinkage-feeding agents for concrete prepared in Examples 1 to 3 can improve the anti-cracking performance ratio and expansion restriction ratio of concrete, while reducing the penetration height ratio and water absorption ratio.

[0076] Compared with Example 1, the anti-cracking performance ratio and the limited expansion rate of Comparative Example 1 are significantly reduced, and the water absorption ratio (48h) and the penetration height ratio are significantly increased. This is because the modified latex powder is not prepared in advance in Comparative Example 1, so the calcium sulfate and aluminum sulfate are not wrapped in advance, and the expansion rate cannot be adjusted by controlling the gel coat thickness and the amount of aluminum hydroxide, resulting in poor anti-cracking and waterproof performance of the final prepared concrete.

[0077] Compared with Example 1, the anti-cracking performance ratio and the limited expansion rate of Comparative Example 2 are reduced, and the water absorption ratio (48h) and the penetration height ratio are increased. The reason may be that in the process of preparing the shrinkage feeding agent for concrete in Comparative Example 2, polyethylene glycol is not added. Polyethylene glycol has the effects of reducing shrinkage, moisturizing and retaining water during the reaction process, and can serve as the basis for the reaction of calcium sulfate and aluminum sulfate. When polyethylene glycol is not added during the preparation of the shrinkage feeding agent, calcium sulfate and aluminum sulfate lack a good reaction basis, resulting in low anti-cracking performance ratio and limited expansion rate of the prepared concrete, and high water absorption ratio (48h) and penetration height ratio.

[0078] Compared with Comparative Example 1, the anti-cracking performance ratio and the limited expansion rate of Comparative Examples 3 to 4 are improved to a certain extent, and the water absorption ratio (48h) and the penetration height ratio are reduced to a certain extent; however, compared with Example 1, the anti-cracking performance ratio and the limited expansion rate of Comparative Examples 3 to 4 are still significantly reduced, and the water absorption ratio (48h) and the penetration height ratio are still significantly increased; this is because the amount of aluminum hydroxide and vinyl acetate copolymer emulsion is reduced in Comparative Example 3. When the core amount is the same, the prepared gel coat is too thin and the core cannot be well wrapped, so the reaction of calcium sulfate and aluminum sulfate cannot be controlled, which ultimately leads to poor anti-cracking and waterproof performance of the prepared concrete; in Comparative Example 4, the core amount is increased and the gel coat amount is reduced, which results in the gel coat being unable to well wrap the core, which ultimately leads to poor anti-cracking and waterproof performance of the prepared concrete.

[0079] Compared with Example 1, the crack resistance ratio and limited expansion ratio of Comparative Examples 5 to 7 are significantly reduced, while the water absorption ratio (48h) and penetration height ratio are significantly increased. This is because Comparative Examples 5 to 7 respectively use 400-mesh aluminum hydroxide powder, 500-mesh calcium sulfate powder, and 700-mesh aluminum sulfate powder. Therefore, the gel coat composed of the aluminum hydroxide and vinyl acetate copolymer emulsion cannot effectively wrap the calcium sulfate and aluminum sulfate, thereby causing the calcium sulfate and aluminum sulfate to undergo hydration reaction prematurely, absorbing and consuming a large amount of water, resulting in a rapid increase in the water absorption ratio and penetration height ratio, and a rapid decrease in the limited expansion ratio and crack resistance ratio, that is, the purpose of effectively controlling expansion cannot be achieved.

[0080] The above specific embodiments describe the implementation of the present invention in detail, but the present invention is not limited to the specific details of the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

Claims

1. An emulsified compacting shrinkage feeding agent for concrete, characterized in that: It comprises modified latex powder and polyethylene glycol; the powder particles of the modified latex powder are structured such that a mixture of calcium sulfate and aluminum sulfate is used as a core and a gel coat is wrapped around the outside, the gel coat comprises aluminum hydroxide and a polymer emulsion, the mass ratio of the core to the gel coat is (7-11):(36-48); the mass ratio of the aluminum hydroxide to the polymer emulsion is (6-8):(30-40); the aluminum hydroxide is aluminum hydroxide powder with a mesh size of 120 or larger, the calcium sulfate is calcium sulfate powder with a mesh size of 120 or larger, and the aluminum sulfate is aluminum sulfate powder with a mesh size of 120 or larger.

2. The emulsified compacting shrinkage feeding agent for concrete according to claim 1, characterized in that: The mass ratio of the calcium sulfate to the aluminum sulfate is (3-5): (4-6).

3. The emulsified compacting shrinkage feeding agent for concrete according to claim 1, characterized in that: The mass ratio of the modified latex powder to the polyethylene glycol is (30-40): (1-5).

4. The use of the emulsified compacting shrinkage feeding agent for concrete according to any one of claims 1 to 3, characterized in that: The raw material modified latex powder of the concrete emulsified compacting shrinkage feeding agent, polyethylene glycol and water are mixed evenly to obtain a mixture, which is then added into the concrete.

5. The use of the emulsified compacting shrinkage feeding agent for concrete according to claim 4, characterized in that: In the mixture, the mass fraction of the modified latex powder is 30-40%.

6. The use of the emulsified compacting shrinkage feeding agent for concrete according to claim 4, characterized in that: The amount of the concrete emulsified compacting shrinkage feeding agent in the concrete is 1-3% based on the total mass of the cementitious material.

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