A composite additive for anti-cracking concrete and a preparation method thereof

Abstract

The application discloses a kind of concrete composite additive for anti-cracking and preparation method thereof, wherein the concrete composite additive specifically includes the following weight fraction components: deionized water: 100 parts;Polymer monomer: 50-80 parts;Modified polycarboxylic acid water reducing agent: 5-25 parts;Air entraining agent: 10-20 parts;Nano silicon dioxide: 5-15 parts;Ultrafine fly ash: 10-15 parts;Emulsifier: 5-8 parts;Tackifier: 3-6 parts;Urea: 2-4 parts;Hydraulic lime: 2-4 parts.By applying the concrete composite additive of the application to concrete, the working performance of anti-cracking concrete can be improved by reducing the water-cement ratio and introducing stable and uniform air bubbles, and the strength of anti-cracking concrete can be improved while reducing the amount of cement by using high pozzolanic activity components, which plays the role of air entraining and stabilizing bubbles, reducing glue and enhancing.

Description

Technical Field

[0001] The invention belongs to the field of concrete admixture technology, specifically relating to a concrete composite additive for crack resistance and its preparation method. Background Technology

[0002] Concrete admixtures are chemical substances added during concrete production to modify certain properties or achieve specific functions. Based on their function, admixtures can be classified into various types, such as reinforcing agents, water-reducing agents, retarders, accelerators, air-expanding agents, densifying agents, waterproofing agents, and antifreeze agents. For concrete construction in complex environments, composite admixtures are generally used to improve concrete performance.

[0003] Currently, common composite admixtures, such as air-entraining water-reducing agents, while improving the workability of concrete, are not suitable for concrete projects in complex environments. The performance improvement effect of general composite admixtures on concrete is very limited under complex and variable environmental conditions such as low temperatures and high winds. Furthermore, the formulation and preparation process of composite admixtures specifically developed for crack-resistant concrete projects in cold regions are still unclear. Therefore, it is urgent to find a formulation and preparation process for crack-resistant concrete admixtures that can entrain air, stabilize foam, and "reduce binder while strengthening". Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a concrete composite additive for crack resistance.

[0005] Another objective of this invention is to provide a method for preparing the above-mentioned concrete composite additive for crack resistance.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: a concrete composite additive for crack resistance, the concrete composite additive specifically comprising the following components in parts by weight: deionized water: 100 parts;

[0007] Polymer monomer: 50-80 parts;

[0008] Modified polycarboxylate superplasticizer: 5-25 parts;

[0009] Air-entraining agent: 10-20 parts;

[0010] Nano silica: 5-15 parts;

[0011] Ultrafine fly ash: 10-15 parts;

[0012] Emulsifier: 5-8 parts;

[0013] Tackifier: 3-6 parts;

[0014] Urea: 2-4 parts;

[0015] Hydraulic lime: 2-4 parts;

[0016] Preferably, the polymer monomer is at least one of butyl methacrylate and hydroxyethyl methacrylate.

[0017] Preferably, the air-entraining agent is sodium dodecylbenzenesulfonate.

[0018] Preferably, the thickener is polyacrylamide.

[0019] Another technical solution of the present invention is achieved as follows: a method for preparing a crack-resistant concrete composite additive, the method specifically comprising:

[0020] Emulsifier is added to deionized water and heated to 30-40℃. Then, polymer monomers and thickeners are added and stirred evenly. The mixture is then heated to 55-65℃, and water-reducing agent, air-entraining agent, nano-silica, ultrafine fly ash, and hydrated lime are added and stirred evenly. The mixture is then cooled to room temperature to obtain a composite additive for crack-resistant concrete. The polymer monomers are added in two stages, with the initial addition being 20-40%.

[0021] Preferably, the stirring time after adding the polymer monomer and thickener is 1-2 hours.

[0022] Preferably, the stirring time after adding water-reducing agent, air-entraining agent, nano-silica, ultrafine fly ash and hydrated lime is 2.5-3.5h.

[0023] Compared with existing technologies, by applying the concrete composite additive of the present invention to concrete, the workability of crack-resistant concrete can be improved by reducing the water-cement ratio and introducing stable and uniform air bubbles. Furthermore, the high pozzolanic active components can increase the strength of crack-resistant concrete while reducing cement usage, playing a role in air entrainment and foam stabilization, and "reducing adhesive content and strengthening concrete." In addition, the synergistic effect of the water-reducing agent and the air-entraining agent can introduce stable and uniform air bubbles, playing a role in air entrainment and foam stabilization. Meanwhile, the ultrafine fly ash has a stronger "ball bearing effect." Therefore, under the multiple effects of the various components and by using the preparation method of the present invention to prepare the concrete composite additive, the concrete composite additive can significantly improve the workability of concrete. Moreover, the effects of nano-silica, ultrafine fly ash, and hydraulic lime can improve the strength performance of concrete while reducing cement usage, thus reducing raw material costs. Attached Figure Description

[0024] The above and other objects, features, and advantages of this application will become more apparent from the more detailed description of the embodiments of this application in conjunction with the accompanying drawings. The drawings are provided to further illustrate the embodiments of this application and form part of the specification. They are used together with the embodiments of this application to explain this application and do not constitute a limitation thereof. In the drawings, the same reference numerals generally represent the same components or steps. Figure 1 This is a flowchart illustrating the preparation process of crack-resistant and seepage-resistant composite additives. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0026] The raw materials or additives used in the embodiments of this invention can all be obtained by purchasing or self-manufacturing.

[0027] This invention provides a concrete composite additive for crack resistance, which specifically comprises the following components in parts by weight:

[0028] Deionized water: 100 parts;

[0029] Polymer monomer: 50-80 parts;

[0030] Modified polycarboxylate superplasticizer: 5-25 parts;

[0031] Air-entraining agent: 10-20 parts;

[0032] Nano silica: 5-15 parts;

[0033] Ultrafine fly ash: 10-15 parts;

[0034] Emulsifier: 5-8 parts;

[0035] Tackifier: 3-6 parts;

[0036] Urea: 2-4 parts;

[0037] Hydraulic lime: 2-4 parts;

[0038] The polymer monomer is at least one of butyl methacrylate and hydroxyethyl methacrylate; the air-entraining agent is sodium dodecylbenzene sulfonate, which has the characteristic of uniformly introducing air bubbles; the nano-silica has high pozzolanic activity, which can significantly replace cement in the hydration reaction, reduce cement usage, and improve concrete strength, playing a role in "reducing adhesive content and strengthening concrete"; the ultrafine fly ash has a ball-bead effect to improve the fluidity of concrete, improve its workability, and has high pozzolanic activity, which can improve the strength performance of concrete, playing a role in "reducing adhesive content and strengthening concrete"; the hydraulic lime provides calcium ions to the admixtures, nano-silica, and ultrafine fly ash, promoting the generation of hydration products, which is beneficial to the formation and development of concrete strength; the thickener is polyacrylamide, which can increase viscosity and stabilize air bubbles, while also improving the workability of concrete; the urea is used to lower the freezing temperature of concrete, facilitating construction in cold regions.

[0039] This invention also provides a method for preparing the above-mentioned concrete composite additive, the method specifically comprising:

[0040] Emulsifier is added to deionized water and heated to 30-40°C. Then, polymer monomers and thickeners are added and stirred evenly. The mixture is then heated to 55-65°C, and water-reducing agent, air-entraining agent, nano-silica, ultrafine fly ash, and hydrated lime are added and stirred evenly. The mixture is then cooled to room temperature to obtain a concrete composite additive for crack resistance. 6. The method for preparing the concrete composite additive according to claim 5, characterized in that the polymer monomer is added in two stages, with the initial addition amount being 20-40%.

[0041] The stirring time after adding the polymer monomer and thickener is 1-2 hours; the stirring time after adding the water-reducing agent, air-entraining agent, nano-silica, ultrafine fly ash and hydrated lime is 2.5-3.5 hours.

[0042] The following are specific examples.

[0043] Example 1

[0044] The concrete composite additive for crack resistance provided in Example 1 of this invention specifically includes the following components in parts by weight: 100 parts deionized water, 50 parts polymer monomer, 5 parts modified polycarboxylate superplasticizer, 5 parts air-entraining agent, 5 parts nano silica, 5 parts ultrafine fly ash, 5 parts emulsifier, 3 parts thickener, 2 parts urea, and 2 parts hydraulic lime.

[0045] Furthermore, the preparation method of the above-mentioned crack-resistant concrete composite additive provided in Embodiment 1 of the present invention specifically comprises:

[0046] After adding the emulsifier to deionized water and heating it to 30-40℃, add the macromolecular polymer and thickener and stir for 1-2 hours. Then heat it to 55-65℃ and add the water-reducing agent, air-entraining agent, nano silica and ultrafine fly ash and stir for 2.5-3.5 hours. After cooling to room temperature, add urea and hydraulic lime and stir for 2 hours to obtain the composite admixture.

[0047] In addition, the concrete composite additive obtained in Example 1 of the present invention is added to the concrete. The concrete components by weight are: cement: 190 parts, grade I fly ash: 90 parts, silica fume: 105 parts, coarse aggregate: 1080 parts, fine aggregate: 790 parts, composite admixture: 6.8 parts, 15wt% polyethylene glycol aqueous solution: 120 parts, recycled fiber: 11.5 parts, and water: 180 parts.

[0048] Example 2

[0049] The concrete composite additive for crack resistance provided in Embodiment 2 of the present invention specifically includes the following components in parts by weight: 100 parts deionized water, 60 parts polymer monomer, 10 parts modified polycarboxylate superplasticizer, 15 parts air-entraining agent, 8 parts nano silica, 10 parts ultrafine fly ash, 6 parts emulsifier, 4 parts thickener, 3 parts urea, and 3 parts hydraulic lime.

[0050] Furthermore, the preparation method of the concrete composite additive for crack resistance provided in Example 2 of the present invention is the same as that in Example 1, and will not be repeated here.

[0051] In addition, the crack-resistant concrete composite additive obtained in Example 2 of the present invention is added to the concrete. The concrete components by weight are: cement: 190 parts, grade I fly ash: 90 parts, silica fume: 105 parts, coarse aggregate: 1080 parts, fine aggregate: 790 parts, composite admixture: 6.6 parts, 15wt% polyethylene glycol aqueous solution: 120 parts, recycled fiber: 11.5 parts, and water: 180 parts.

[0052] Example 3

[0053] The concrete composite additive for crack resistance provided in Embodiment 3 of the present invention specifically includes the following components in parts by weight: 100 parts deionized water, 70 parts polymer monomer, 18 parts modified polycarboxylate superplasticizer, 18 parts air-entraining agent, 10 parts nano silica, 13 parts ultrafine fly ash, 8 parts emulsifier, 5 parts thickener, 3 parts urea, and 4 parts hydraulic lime.

[0054] Furthermore, the preparation method of the concrete composite additive for crack resistance provided in Example 3 of the present invention is the same as that in Example 1, and will not be repeated here.

[0055] In addition, the crack-resistant concrete composite additive obtained in Example 3 of the present invention is added to the concrete. The concrete components by weight are: cement: 190 parts, grade I fly ash: 90 parts, silica fume: 105 parts, coarse aggregate: 1080 parts, fine aggregate: 790 parts, composite admixture: 6.3 parts, 15wt% polyethylene glycol aqueous solution: 120 parts, recycled fiber: 11.5 parts, and water: 180 parts.

[0056] Example 4

[0057] The concrete composite additive for crack resistance provided in Example 4 of this invention specifically includes the following components in parts by weight: 100 parts deionized water, 80 parts polymer monomer, 25 parts modified polycarboxylate superplasticizer, 20 parts air-entraining agent, 15 parts nano silica, 15 parts ultrafine fly ash, 5 parts emulsifier, 6 parts thickener, 4 parts urea, and 4 parts hydraulic lime.

[0058] Furthermore, the preparation method of the above-mentioned crack-resistant concrete composite additive provided in Example 4 of the present invention is the same as that in Example 1, and will not be repeated here.

[0059] In addition, the crack-resistant concrete composite additive obtained in Example 3 of the present invention is added to the concrete. The concrete components by weight are: cement: 190 parts, grade I fly ash: 90 parts, silica fume: 105 parts, coarse aggregate: 1080 parts, fine aggregate: 790 parts, composite admixture: 6.1 parts, 15wt% polyethylene glycol aqueous solution: 120 parts, recycled fiber: 11.5 parts, and water: 180 parts.

[0060] Figure 1 The flowchart illustrates the preparation process of a crack-resistant and impermeable composite additive. The main steps include adding an emulsifier to deionized water and heating to 30-40°C; adding a thickener and then adding the polymer emulsion in two batches, stirring constantly until homogeneous; and stirring for 1-2 hours after adding the polymer monomer and thickener. The mixture is then heated to 55-65°C, and water-reducing agent, air-entraining agent, nano-silica, ultrafine fly ash, and hydrated lime are added and stirred for 2.5-3.5 hours before cooling to room temperature to obtain the composite additive for crack-resistant concrete.

[0061] Performance testing

[0062] Slump test: The slump of concrete was tested in accordance with the "Test Procedures for Cement and Cement Concrete in Highway Engineering" (JTG E30-2005).

[0063] Mechanical performance testing: The strength of concrete was tested in accordance with the "Test Procedures for Cement and Cement Concrete in Highway Engineering" (JTG E30-2005). Concrete specimens of 100mm×100mm×100mm and 100mm×100mm×400mm were formed according to the procedure. After curing for 2 days, the specimens were demolded and placed in a standard curing room for curing for 28 days before the strength test was conducted.

[0064] Crack resistance testing: The crack resistance performance was tested using the circular ring constraint method. The inner diameter of the circular ring constraint device was 30.4 cm, the outer diameter was 45.6 cm, and the height was 16 cm. Four crack inducers were added to the inner steel ring. The inclusion of crack inducers can accelerate the cracking process of concrete and significantly reduce the test cycle.

[0065] To verify the crack resistance of the composite additive obtained in this invention, workability and mechanical property tests were conducted on the crack-resistant concrete containing the composite additive in Examples 1-4. The crack resistance was also tested using a circular ring restraint device. Specific test results are shown in the table below.

[0066] Table 1. Crack resistance test results of concrete composite additives obtained in Examples 1-4

[0067]

[0068] Analysis of the comparative examples and Table 1 shows that adding composite additives can effectively improve the slump, strength, and crack resistance of crack-resistant concrete. The improved workability is mainly attributed to the significant increase in the content of air-entraining agent and ultrafine fly ash, which introduces a large number of uniformly distributed, closed, and stable air bubbles into the concrete. In addition, the "ball effect" in the system is further enhanced, thus significantly improving the workability of the concrete.

[0069] Analysis of Examples 1 and 4, along with Table 1, reveals that the improvement in mechanical properties is primarily attributed to the increased content of ultrafine fly ash and nano-silica. The highly reactive nano-silica participates in the hydration reaction while simultaneously promoting the decomposition of the fly ash particle shell, releasing the internal active SiO2 and Al2O3 components. This further promotes the formation and development of concrete strength, resulting in higher mechanical properties.

[0070] Analysis of Examples 1, 3, and 4, along with Table 1, reveals that the improvement in crack resistance is primarily attributed to the significant increase in the density of the concrete structure. The highly reactive mineral admixtures, through the hydraulic lime, provide sufficient calcium hydroxide to fully participate in the hydration reaction within the concrete, thereby generating a sufficient amount of cementitious material (CSH gel) for the concrete system. This significantly increases the system's density and improves its crack resistance.

[0071] In summary, by applying the concrete composite additive of this invention to concrete, the workability of crack-resistant concrete can be improved by reducing the water-cement ratio and introducing stable and uniform air bubbles. Furthermore, the high pozzolanic active component can increase the strength of crack-resistant concrete while reducing cement usage, playing a role in air entrainment and foam stabilization, and "reducing adhesive content and strengthening concrete." In addition, the synergistic effect of the water-reducing agent and the air-entraining agent can introduce stable and uniform air bubbles, playing a role in air entrainment and foam stabilization. Meanwhile, the ultrafine fly ash has a stronger "ball bearing effect." Therefore, under the multiple effects of the various components and by using the preparation method of this invention to prepare the concrete composite additive, the concrete composite additive can significantly improve the workability of concrete. Moreover, the effects of nano-silica, ultrafine fly ash, and hydraulic lime can improve the strength performance of concrete while reducing cement usage, thus reducing raw material costs.

[0072] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A composite additive for crack-resistant concrete, characterized in that, The concrete composite additive specifically includes the following components in parts by weight: deionized water: 100 parts; Polymer monomer: 50-80 parts; the polymer monomer is at least one of butyl methacrylate and hydroxyethyl methacrylate; Modified polycarboxylate superplasticizer: 5-25 parts; Air-entraining agent: 10-20 parts; Nano silica: 5-15 parts; Ultrafine fly ash: 10-15 parts; Emulsifier: 5-8 parts; Tackifier: 3-6 parts; Urea: 2-4 parts; Hydraulic lime: 2-4 parts.

2. The concrete composite additive according to claim 1, characterized in that, The air-entraining agent is sodium dodecylbenzenesulfonate.

3. The concrete composite additive according to claim 1, characterized in that, The thickener is polyacrylamide.

4. The method for preparing the concrete composite additive according to any one of claims 1-3, characterized in that, The method is as follows: Emulsifier is added to deionized water and heated to 30-40℃. Then, polymer monomers and thickeners are added and stirred evenly. After heating to 55-65℃, modified polycarboxylate superplasticizer, air-entraining agent, nano silica, ultrafine fly ash, urea and hydraulic lime are added and stirred evenly. After cooling to room temperature, a concrete composite additive for crack resistance is obtained.

5. The method for preparing the concrete composite additive according to claim 4, characterized in that, The polymer monomer is added in two stages, with the initial addition amount being 20-40%.

6. The method for preparing the concrete composite additive according to claim 4, characterized in that, The stirring time after adding the polymer monomer and thickener is 1-2 hours.

7. The method for preparing the concrete composite additive according to claim 4, characterized in that, The stirring time after adding modified polycarboxylate superplasticizer, air-entraining agent, nano silica, ultrafine fly ash and hydraulic lime is 2.5-3.5h.

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