Composite additive for self-repairing concrete as well as preparation method and application of composite additive

Abstract

The invention discloses a composite additive for self-repairing concrete as well as a preparation method and application thereof, and belongs to the technical field of civil engineering materials. In order to realize long-term efficient self-repairing of concrete, the composite additive for the self-repairing concrete is prepared by mixing the following components in parts by weight: 10-62 parts of an additive, 1-4 parts of a complexing agent, 20-30 parts of silica fume and 5-10 parts of a super absorbent polymer, the additive is one or a mixture of more of magnesium oxide, sodium silicate and calcium formate, and the complexing agent is one or a mixture of more of sodium hexametaphosphate and ethylenediamine tetraacetic acid tetrasodium salt. The super absorbent polymer is a mixture of one or more of polyacrylate, polyacrylamide and an acrylate-acrylamide copolymer. The method is simple in process, high in operability, low in raw material cost and capable of achieving industrial mass production.

Description

Technical Field

[0001] The invention belongs to the technical field of civil engineering materials, and specifically relates to a composite additive for self-repairing concrete and a preparation method and application thereof. Background Art

[0002] During the use of concrete, cracks are easily generated due to factors such as the external environment, load, and changes in temperature and humidity. These cracks not only affect the safety of the concrete structure, but may also cause the corrosive media in the environment to enter the concrete matrix, causing steel corrosion problems, thereby shortening the service life of the concrete structure. In order to alleviate the harm caused by cracks to concrete, concrete repair technology has been widely studied and developed in recent years. Traditional repair technologies generally use materials such as filling or coating epoxy resins and polyurethanes. Although these methods can temporarily repair cracks, they have problems such as low repair efficiency, long cycle, and high cost. Therefore, concrete self-repair technology has gradually become a research hotspot. This technology mainly adds some specific repair agents during the concrete mixing process, including microcapsules or micro glass tubes containing healing materials, microorganisms that can induce carbonate precipitation, mineral admixtures that can promote the formation of repair products, and crystallization admixtures. When the concrete cracks, water and carbon dioxide in the environment enter the cracks and react with the repair agents on the crack surface to generate various repair products, thereby achieving self-repair of the cracks.

[0003] The invention patent with the authorization announcement number CN 114230273 B discloses a repair agent with amino acids, calcium chloride and urea as the main components, wherein calcium chloride can provide calcium ions to increase the concentration of calcium ions in concrete cracks, amino acids can increase the migration efficiency of calcium ions through chelation, and urea can provide carbon dioxide through hydrolysis reaction to increase the concentration of carbonate ions in cracks. The above reactions can accelerate the formation of calcium carbonate at the cracks. The invention patent with the authorization announcement number CN 116803943 B discloses a self-repairing admixture, including urea, plant urease and magnesium oxide. Plant urease can promote the decomposition of urea, thereby inducing calcium ions inside the concrete to produce calcium carbonate crystals with gelling properties. At the same time, magnesium oxide can reduce the generation of early cracks and further improve the self-repairing ability of concrete. However, the repair effect of existing repair agents is poor and the repair speed is slow, which is difficult to meet the repair needs in actual projects. Summary of the invention

[0004] The problem to be solved by the present invention is to achieve long-term and efficient self-repair of concrete, and a composite additive for self-repairing concrete and a preparation method and application thereof are proposed.

[0005] To achieve the above object, the present invention is implemented through the following technical solutions:

[0006] A composite additive for self-repairing concrete, prepared by mixing an admixture, a complexing agent, silica fume and a highly absorbent polymer, wherein the components are 10 to 62 parts of the admixture, 1 to 4 parts of the complexing agent, 20 to 30 parts of silica fume and 5 to 10 parts of the highly absorbent polymer in parts by weight;

[0007] The additive is a mixture of one or more of magnesium oxide, sodium silicate and calcium formate.

[0008] The complexing agent is a mixture of one or more of sodium hexametaphosphate and tetrasodium ethylenediaminetetraacetate.

[0009] The highly water-absorbent polymer is a mixture of one or more of polyacrylic acid salt, polyacrylamide and acrylate-acrylamide copolymer.

[0010] Furthermore, the particle size of the super absorbent polymer is 80 to 120 meshes.

[0011] Furthermore, the polyacrylate includes sodium polyacrylate.

[0012] Furthermore, the acrylate-acrylamide copolymer includes sodium acrylate-acrylamide copolymer.

[0013] Furthermore, the components of the composite additive for self-repairing concrete are calculated by weight as follows: 10 parts of magnesium oxide, 10 parts of sodium silicate, 42 parts of calcium formate, 1 part of sodium hexametaphosphate, 3 parts of tetrasodium ethylenediaminetetraacetate, 26 parts of silica fume, and 7 parts of sodium polyacrylate.

[0014] Furthermore, the components in the composite additive for self-repairing concrete are calculated by weight as follows: 42 parts of calcium formate, 2 parts of sodium hexametaphosphate, 2 parts of tetrasodium ethylenediaminetetraacetate, 26 parts of silica fume, and 7 parts of sodium acrylate-acrylamide copolymer.

[0015] A method for preparing a composite additive for self-repairing concrete comprises the following steps:

[0016] Step 1. Weigh 10 to 62 parts of admixture, 1 to 4 parts of complexing agent, 20 to 30 parts of silica fume, and 5 to 10 parts of highly absorbent polymer by weight for standby use;

[0017] Step 2. Put the admixture, complexing agent, silica fume and super absorbent polymer weighed in step 1 into a concrete mixer and mix them evenly to obtain the composite additive for self-repairing concrete.

[0018] Furthermore, in step 2, the speed of the concrete mixer is 20 to 80 r / min, and the mixing time is 5 to 15 min.

[0019] An application of a composite additive for self-repairing concrete is used for preparing self-repairing concrete.

[0020] Furthermore, cement, fly ash, the composite additive for self-repairing concrete, river sand, crushed stone, water and water reducing agent are uniformly mixed to obtain self-repairing concrete, and the amount of the composite additive for self-repairing concrete added to the self-repairing concrete is 2-6% of the total mass of cement and fly ash.

[0021] Beneficial effects of the present invention:

[0022] The composite additive for self-repairing concrete described in the present invention comprises an admixture, a chelating agent, silica fume and a highly absorbent polymer. The admixture and silica fume can provide active magnesium source, silicon source and calcium source, promote the continuous hydration of unhydrated cement particles, and improve the generation of hydration products; the chelating agent can chelate calcium ions in the concrete matrix and migrate to the cracks, reacting with carbonate ions and silicate ions to generate calcium carbonate and calcium silicate; the highly absorbent polymer has the ability to absorb, retain and release water, can absorb moisture in a humid environment and store it in an internal three-dimensional network, and when the environment is dry, the highly absorbent polymer can release moisture to promote the continuous hydration reaction and repair reaction at the cracks.

[0023] The preparation method of the composite additive for self-repairing concrete described in the present invention has simple process, strong operability, low raw material cost, and can realize industrial mass production.

[0024] The application of the composite additive for self-repairing concrete described in the present invention can enable the components of the repair agent to exert a synergistic effect when the concrete cracks, thereby achieving long-term and efficient self-repair of the concrete. The repair agent has strong compatibility with the concrete and does not change the production process and workability of the concrete, thus having extremely high engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a diagram showing the effect of a composite additive for self-repairing concrete on the compressive strength of concrete according to Example 4 of the present invention;

[0026] Figure 2 This is a diagram showing the effect of a composite additive for self-repairing concrete on the electric flux of cracked concrete according to Example 5 of the present invention;

[0027] Figure 3 This is a diagram showing the effect of a composite additive for self-repairing concrete on the ultrasonic velocity of cracked concrete according to Example 5 of the present invention;

[0028] Figure 4 This is a diagram showing the effect of a composite additive for self-repairing concrete described in Example 5 of the present invention on the repair efficiency of cracked concrete. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the specific embodiments described are only part of the embodiments of the present invention, rather than all of the specific embodiments. The components of the specific embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations, and the present invention can also have other embodiments.

[0030] Therefore, the following detailed description of the specific embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents the selected specific embodiments of the present invention. Based on the specific embodiments of the present invention, all other specific embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0031] In order to further understand the content, features and effects of the present invention, the following specific implementation modes are given as examples and described in detail with reference to the accompanying drawings:

[0032] Example 1

[0033] A composite additive for self-repairing concrete is prepared by mixing an admixture, a chelating agent, silica fume and a highly absorbent polymer, wherein the admixture comprises one or more of magnesium oxide, sodium silicate and calcium formate, the chelating agent comprises one or more of sodium hexametaphosphate and tetrasodium ethylenediaminetetraacetate, and the highly absorbent polymer comprises one or more of polyacrylate, polyacrylamide and acrylate-acrylamide copolymer, and the components are calculated by weight as follows: 10 parts of magnesium oxide, 1 part of sodium hexametaphosphate, 20 parts of silica fume and 5 parts of sodium polyacrylate.

[0034] Furthermore, the particle size of the super absorbent polymer is 80 to 120 meshes.

[0035] A method for preparing a composite additive for self-repairing concrete comprises the following steps:

[0036] Step 1. Weigh 10 parts of magnesium oxide, 1 part of sodium hexametaphosphate, 20 parts of silica fume, and 5 parts of sodium polyacrylate respectively by weight and set aside;

[0037] Step 2. Put the magnesium oxide, sodium hexametaphosphate, silica fume and sodium polyacrylate weighed in step 1 into a concrete mixer and mix them evenly to obtain the composite additive for self-repairing concrete.

[0038] Furthermore, in step 2, the rotation speed of the concrete mixer is 20 r / min, and the mixing time is 15 min.

[0039] An application of a composite additive for self-repairing concrete, wherein cement, fly ash, the composite additive for self-repairing concrete, river sand, crushed stone, water and a water reducing agent are mixed to prepare self-repairing concrete with long-term and efficient self-repairing ability.

[0040] Furthermore, the composite additive for self-repairing concrete is added as an external additive, and the amount of the additive is 2% of the total mass of cement and fly ash.

[0041] Example 2

[0042] A composite additive for self-repairing concrete is prepared by mixing an admixture, a chelating agent, silica fume and a highly absorbent polymer, wherein the admixture comprises one or more of magnesium oxide, sodium silicate and calcium formate, the chelating agent comprises one or more of sodium hexametaphosphate and tetrasodium ethylenediaminetetraacetate, and the highly absorbent polymer comprises one or more of polyacrylate, polyacrylamide and acrylate-acrylamide copolymer, and the components are calculated by weight as follows: 10 parts of sodium silicate, 3 parts of tetrasodium ethylenediaminetetraacetate, 30 parts of silica fume and 10 parts of sodium polyacrylate.

[0043] Furthermore, the particle size of the super absorbent polymer is 80 to 120 meshes.

[0044] A method for preparing a composite additive for self-repairing concrete comprises the following steps:

[0045] Step 1. Weigh 10 parts of sodium silicate, 3 parts of tetrasodium ethylenediaminetetraacetate, 30 parts of silica fume, and 10 parts of sodium polyacrylate respectively by weight and set aside;

[0046] Step 2. Put the sodium silicate, tetrasodium ethylenediaminetetraacetate, silica fume and sodium polyacrylate weighed in step 1 into a concrete mixer and mix them evenly to obtain the composite additive for self-repairing concrete.

[0047] Furthermore, in step 2, the rotation speed of the concrete mixer is 80 r / min, and the mixing time is 5 min.

[0048] An application of a composite additive for self-repairing concrete, characterized in that cement, fly ash, the composite additive for self-repairing concrete, river sand, crushed stone, water and a water reducing agent are mixed to prepare self-repairing concrete with long-term and efficient self-repairing ability.

[0049] Furthermore, the composite additive for self-repairing concrete is added externally, and the amount of the additive is 6% of the total mass of cement and fly ash.

[0050] Example 3

[0051] A composite additive for self-repairing concrete is prepared by mixing an admixture, a chelating agent, silica fume and a highly absorbent polymer, wherein the admixture comprises one or more of magnesium oxide, sodium silicate and calcium formate, the chelating agent comprises one or more of sodium hexametaphosphate and tetrasodium ethylenediaminetetraacetate, and the highly absorbent polymer comprises one or more of polyacrylate, polyacrylamide and acrylate-acrylamide copolymer, and the components are calculated by weight as follows: 42 parts of calcium formate, 2 parts of sodium hexametaphosphate, 2 parts of tetrasodium ethylenediaminetetraacetate, 26 parts of silica fume and 7 parts of sodium acrylate-acrylamide copolymer.

[0052] Furthermore, the particle size of the super absorbent polymer is 80 to 120 meshes.

[0053] A method for preparing a composite additive for self-repairing concrete comprises the following steps:

[0054] Step 1. Weigh 42 parts of calcium formate, 2 parts of sodium hexametaphosphate, 2 parts of tetrasodium ethylenediaminetetraacetate, 26 parts of silica fume, and 7 parts of sodium acrylate-acrylamide copolymer respectively by weight and set aside;

[0055] Step 2. Put the calcium formate, sodium hexametaphosphate, tetrasodium ethylenediaminetetraacetate, silica fume and sodium acrylate-acrylamide copolymer weighed in step 1 into a concrete mixer and mix them evenly to obtain the composite additive for self-repairing concrete.

[0056] Furthermore, in step 2, the rotation speed of the concrete mixer is 55 r / min, and the mixing time is 10 min.

[0057] An application of a composite additive for self-repairing concrete, characterized in that cement, fly ash, the composite additive for self-repairing concrete, river sand, crushed stone, water and a water reducing agent are mixed to prepare self-repairing concrete with long-term and efficient self-repairing ability.

[0058] Furthermore, the composite additive for self-repairing concrete is added externally, and the amount of the additive is 3% of the total mass of cement and fly ash.

[0059] Example 4

[0060] A composite additive for self-repairing concrete is prepared by mixing an admixture, a chelating agent, silica fume and a highly absorbent polymer, wherein the admixture comprises one or more of magnesium oxide, sodium silicate and calcium formate, the chelating agent comprises one or more of sodium hexametaphosphate and tetrasodium ethylenediaminetetraacetate, and the highly absorbent polymer comprises one or more of polyacrylate, polyacrylamide and acrylate-acrylamide copolymer, and the components are calculated by weight as follows: 10 parts of magnesium oxide, 10 parts of sodium silicate, 42 parts of calcium formate, 1 part of sodium hexametaphosphate, 3 parts of tetrasodium ethylenediaminetetraacetate, 26 parts of silica fume and 7 parts of sodium polyacrylate.

[0061] Furthermore, the particle size of the super absorbent polymer is 80 to 120 meshes.

[0062] A method for preparing a composite additive for self-repairing concrete comprises the following steps:

[0063] Step 1. Weigh 10 parts of magnesium oxide, 10 parts of sodium silicate, 42 parts of calcium formate, 1 part of sodium hexametaphosphate, 3 parts of tetrasodium ethylenediaminetetraacetate, 26 parts of silica fume, and 7 parts of sodium polyacrylate by weight respectively, and set aside;

[0064] Step 2. Put the magnesium oxide, sodium silicate, calcium formate, sodium hexametaphosphate, tetrasodium ethylenediaminetetraacetate, silica fume and sodium polyacrylate weighed in step 1 into a concrete mixer and mix them evenly to obtain the composite additive for self-repairing concrete.

[0065] Furthermore, in step 2, the rotation speed of the concrete mixer is 55 r / min, and the mixing time is 10 min.

[0066] An application of a composite additive for self-repairing concrete, characterized in that cement, fly ash, the composite additive for self-repairing concrete, river sand, crushed stone, water and a water reducing agent are mixed to prepare self-repairing concrete with long-term and efficient self-repairing ability.

[0067] Furthermore, the composite additive for self-repairing concrete is added externally, and the amount of the additive is 3% of the total mass of cement and fly ash.

[0068] Furthermore, the prepared self-repairing concrete was placed in a standard curing room at a temperature of 20±2°C and a relative humidity of more than 95% for curing for 7, 14, and 28 days.

[0069] Comparative Example 1

[0070] Ordinary concrete is prepared by mixing cement, fly ash, river sand, crushed stone, water and water reducing agent.

[0071] Furthermore, the prepared ordinary concrete was placed in a standard curing room at a temperature of 20±2°C and a relative humidity of more than 95% for curing for 7, 14, and 28 days.

[0072] Example 5

[0073] The difference between this embodiment and embodiment 4 is that the self-repairing concrete prepared in embodiment 4 and cured in a standard curing room for 28 days is placed on a pressure testing machine, and the loading speed is set to 0.5 kN / s. When the load reaches 30±5 kN, a crack with a width of less than 500 μm appears in the middle of the concrete.

[0074] Furthermore, the pre-cracked self-repairing concrete was immersed in water for 28 days of curing.

[0075] Comparative Example 2

[0076] The difference between this comparative example and comparative example 1 is that the ordinary concrete prepared in comparative example 1 and cured in a standard curing room for 28 days is placed on a pressure testing machine, and the loading speed is set to 0.5 kN / s. When the load reaches 30±5 kN, a crack with a width of less than 500 μm appears in the middle of the concrete.

[0077] Furthermore, the pre-cracked ordinary concrete was soaked in water for 28 days.

[0078] The compressive strength of the concrete of Example 4 and Comparative Example 1 was tested. Figure 1 The results show that the composite additive for self-repairing concrete can improve the compressive strength of concrete. Figure 2 The ultrasonic velocity of the cracked concrete of Example 5 and Comparative Example 2 was tested. Figure 3 The electric flux reduction rate and ultrasonic wave velocity recovery rate are calculated as evaluation indicators of repair efficiency, as shown in Figure 4 As shown, the results show that the composite additives used in self-repairing concrete can significantly improve the repair efficiency of cracked concrete.

[0079] It should be noted that relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0080] Although the present application has been described above with reference to specific embodiments, various modifications may be made thereto and parts thereof may be replaced with equivalents without departing from the scope of the present application. In particular, as long as there is no structural conflict, the various features in the specific embodiments disclosed in the present application may be used in combination with each other in any manner, and the fact that these combinations are not exhaustively described in this specification is only for the sake of omitting space and saving resources. Therefore, the present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A composite additive for self-repairing concrete, characterized in that: The invention is prepared by mixing an admixture, a complexing agent, silica fume and a highly absorbent polymer, wherein the components are 10 to 62 parts of the admixture, 1 to 4 parts of the complexing agent, 20 to 30 parts of silica fume and 5 to 10 parts of the highly absorbent polymer in terms of weight. The additive is a mixture of one or more of magnesium oxide, sodium silicate and calcium formate. The complexing agent is a mixture of one or more of sodium hexametaphosphate and tetrasodium ethylenediaminetetraacetate. The highly water-absorbent polymer is a mixture of one or more of polyacrylic acid salt, polyacrylamide and acrylate-acrylamide copolymer.

2. A composite additive for self-repairing concrete according to claim 1, characterized in that: The particle size of the highly water-absorbent polymer is 80 to 120 meshes.

3. A composite additive for self-repairing concrete according to claim 1 or 2, characterized in that: The polyacrylate includes sodium polyacrylate.

4. A composite additive for self-repairing concrete according to claim 1 or 2, characterized in that: The acrylate-acrylamide copolymer includes sodium acrylate-acrylamide copolymer.

5. The composite additive for self-repairing concrete according to claim 4, characterized in that: The components of the composite additive for self-repairing concrete are calculated by weight as follows: 10 parts of magnesium oxide, 10 parts of sodium silicate, 42 parts of calcium formate, 1 part of sodium hexametaphosphate, 3 parts of tetrasodium ethylenediaminetetraacetate, 26 parts of silica fume, and 7 parts of sodium polyacrylate.

6. The composite additive for self-repairing concrete according to claim 4, characterized in that: The components of the composite additive for self-repairing concrete are calculated by weight as follows: 42 parts of calcium formate, 2 parts of sodium hexametaphosphate, 2 parts of tetrasodium ethylenediaminetetraacetate, 26 parts of silica fume, and 7 parts of sodium acrylate-acrylamide copolymer.

7. A method for preparing a composite additive for self-repairing concrete according to any one of claims 1 to 6, characterized in that: The steps include: Step 1. Weigh 10 to 62 parts of admixture, 1 to 4 parts of complexing agent, 20 to 30 parts of silica fume, and 5 to 10 parts of highly absorbent polymer by weight for standby use; Step 2. Put the admixture, complexing agent, silica fume and super absorbent polymer weighed in step 1 into a concrete mixer and mix them evenly to obtain the composite additive for self-repairing concrete.

8. The method for preparing a composite additive for self-repairing concrete according to claim 7, characterized in that: In step 2, the speed of the concrete mixer is 20 to 80 r / min, and the mixing time is 5 to 15 min.

9. An application of a composite additive for self-repairing concrete according to any one of claims 1 to 6, characterized in that: Used to prepare self-healing concrete.

10. The use of a composite additive for self-repairing concrete according to claim 9, characterized in that: The self-repairing concrete is obtained by uniformly mixing cement, fly ash, the composite additive for self-repairing concrete, river sand, crushed stone, water and water reducing agent. The amount of the composite additive for self-repairing concrete added to the self-repairing concrete is 2-6% of the total mass of cement and fly ash.

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