A crack-resistant precast concrete component and its preparation method

Abstract

This application relates to the field of precast concrete technology, specifically disclosing a crack-resistant precast concrete component and its preparation method. The crack-resistant precast concrete component is mainly made from the following raw materials in parts by weight: 150-160 parts water, 240-270 parts cement, 95-115 parts fly ash, 60-70 parts slag powder, 730-780 parts sand, 980-1100 parts crushed stone, 3-5 parts phase change material, 5-10 parts modified pre-oxidized fiber, and 6-7 parts water-reducing agent; the modified pre-oxidized fiber is obtained by treating the pre-oxidized fiber with γ-aminopropyltriethoxysilane, trimethylolpropane triacrylate, tetraethylenediamine, and sodium hydroxide. This crack-resistant precast concrete component significantly reduces the total crack area, reduces damage during transportation and hoisting, and also has the advantages of high compressive strength and high flexural strength, exhibiting excellent comprehensive performance.

Description

Technical Field

[0001] This application relates to the field of precast concrete technology, and more specifically, to a crack-resistant precast concrete component and its preparation method. Background Technology

[0002] With the development of information technology and the continuous maturation of construction technology, prefabricated buildings have gained recognition and acceptance. In prefabricated building construction, precast concrete components, such as wall panels, floor slabs, and stairs, are manufactured in a factory beforehand and then assembled during transportation and hoisting. This method offers advantages such as high production efficiency, short construction period, and low construction costs. However, after the precast concrete components are cast, cracks often appear on their surfaces. When the total crack area is too large, damage is likely to occur during subsequent transportation and hoisting. Summary of the Invention

[0003] In order to improve the crack resistance of precast concrete components and reduce the total crack area, this application provides a crack-resistant precast concrete component and its preparation method.

[0004] In a first aspect, this application provides a crack-resistant precast concrete component, which adopts the following technical solution:

[0005] A crack-resistant precast concrete component is mainly made of the following raw materials in parts by weight: 150-160 parts water, 240-270 parts cement, 95-115 parts fly ash, 60-70 parts slag powder, 730-780 parts sand, 980-1100 parts crushed stone, 3-5 parts phase change material, 5-10 parts modified pre-oxidized fiber, and 6-7 parts water-reducing agent; wherein the modified pre-oxidized fiber is obtained by treating the pre-oxidized fiber with γ-aminopropyltriethoxysilane, trimethylolpropane triacrylate, tetraethylenediamine trioxide, and sodium hydroxide.

[0006] The crack-resistant precast concrete component of this application incorporates a phase change material in the raw materials. This material undergoes a phase change upon temperature variation, significantly reducing the impact of internal and external temperature differences during cement hydration, thus improving crack resistance. Furthermore, it increases the fluidity and density of the raw materials, enhancing the mechanical properties of the crack-resistant precast concrete component. Modified pre-oxidized fiber is added to the raw materials, and through the synergistic effect of γ-aminopropyltriethoxysilane, trimethylolpropane triacrylate, tetraethylenediamine, and sodium hydroxide, a large number of secondary amine and carboxyl groups are introduced onto the surface. These groups chelate calcium ions generated during cement hydration and release them as calcium ions are consumed, reducing the effects of drying shrinkage and internal / external temperature differences, improving crack resistance, reducing shrinkage cracks and temperature cracks, and also increasing the bonding strength and integrity of the crack-resistant precast concrete component, thereby enhancing its mechanical properties.

[0007] The crack-resistant precast concrete component of this application achieves a total crack area of ​​<200mm through the synergistic effect of phase change materials and modified pre-oxidized fibers. 2 / m 2 This significantly reduces the total cracked area and minimizes damage to crack-resistant precast concrete components during transportation and hoisting. Furthermore, its 28-day compressive strength > 60 MPa and 28-day flexural strength > 8.5 MPa demonstrate high compressive and flexural strength, exhibiting excellent comprehensive performance and meeting market demands.

[0008] Optionally, the phase change material is a phase change microcapsule, and the phase change temperature of the phase change microcapsule is 40-70℃. Preferably, the phase change temperature of the phase change microcapsule is 45-65℃. More preferably, the phase change temperature of the phase change microcapsule is 48-64℃.

[0009] By adopting the above technical solution, the phase change microcapsule has a microcapsule structure with a core material and a shell material. The core material is biomass phase change wax, which can undergo a phase change due to temperature changes. The shell material is a polymer material, such as melamine-urea-formaldehyde resin, which can encapsulate the biomass phase change wax. This not only achieves the encapsulation of the biomass phase change wax and reduces its loss, but also has excellent high-temperature resistance. Furthermore, the phase change temperature of the phase change microcapsule is optimized to enhance its effectiveness and ensure the quality of crack-resistant precast concrete components.

[0010] Optionally, the modified pre-oxidized fiber is prepared using the following method:

[0011] T1. Add pre-oxidized fiber to water and mix, then add γ-aminopropyltriethoxysilane, stir for 3-5 hours, filter, and obtain grafted pre-oxidized fiber a.

[0012] T2. Add grafted pre-oxidized fiber a to an organic solvent and mix. Then add the first part of trimethylolpropane triacrylate and stir for 24-26 hours. Then add tetraethylenediamine triacrylate and stir for 24-26 hours. Then add the second part of trimethylolpropane triacrylate and stir for 24-26 hours. Filter to obtain grafted pre-oxidized fiber b.

[0013] T3. At a temperature of 70-80℃, add grafted pre-oxidized fiber b to water and mix. Then add sodium hydroxide, stir for 1-3 hours, adjust the pH to 5-6, filter, wash, and dry to obtain modified pre-oxidized fiber.

[0014] Optionally, the weight ratio of the pre-oxidized filament fiber, γ-aminopropyltriethoxysilane, the first part of trimethylolpropane triacrylate, tetraethylenediamine triacrylate, the second part of trimethylolpropane triacrylate, and sodium hydroxide is (9-11):(3-5):(3-4):(6.5-7.5):(17-25):(7-10).

[0015] By employing the above technical solution, γ-aminopropyltriethoxysilane is first grafted onto the surface of pre-oxidized fiber, introducing primary amine groups. Then, grafting is achieved through an addition reaction between the carbon-carbon double bond and the primary amine group in the first portion of trimethylolpropane triacrylate, increasing the branching amount and introducing ester groups. Subsequently, grafting is achieved through an amidation reaction between a primary amine group and an ester group in tetraethylenediamine, introducing both primary and secondary amine groups. Then, grafting is achieved through an addition reaction between the carbon-carbon double bond and the primary amine group in the second portion of trimethylolpropane triacrylate, further increasing the branching amount and introducing ester groups. Finally, the ester groups are hydrolyzed using sodium hydroxide, and by adjusting the pH value, carboxyl groups are formed, significantly increasing the amount of carboxyl and secondary amine groups on the surface of the pre-oxidized fiber. This enhances the bonding strength of crack-resistant concrete materials, reduces the effects of drying shrinkage and internal / external temperature differences, reduces the total crack area, and improves compressive and flexural strength, thus improving the overall performance of the modified pre-oxidized fiber.

[0016] Optionally, in step T1, the weight ratio of the pre-oxidized fiber to water is (9-11):(50-150); in step T2, the weight ratio of the first part of trimethylolpropane triacrylate to organic solvent is (3-4):(100-200); in step T3, the weight ratio of sodium hydroxide to water is (7-10):(50-150).

[0017] By adopting the above technical solution, the amount of water added in step T1, organic solvent in step T2, and water added in step T3 is optimized to increase the uniformity of raw material mixing and ensure the stability of modified pre-oxidized fiber preparation.

[0018] Optionally, the organic solvent is one or more of methanol, ethanol, propanol, n-butanol, n-pentanol, and isoamyl alcohol.

[0019] By adopting the above technical solution, the organic solvent is optimized, making the selection of organic solvents easier.

[0020] Optionally, the pre-oxidized fiber has an average fineness of 0.5-3D and an average length of 1-100mm. Preferably, the pre-oxidized fiber has an average fineness of 1-2.5D and an average length of 1-50mm.

[0021] By adopting the above technical solution, the average fineness and average length of the pre-oxidized fiber are optimized, facilitating the selection of the pre-oxidized fiber. In several embodiments, the average fineness of the pre-oxidized fiber is 1.5D and the average length is 10mm. Alternatively, the average fineness of the pre-oxidized fiber can be set to 0.5D, 0.8D, 1D, 1.2D, 2.2D, 2.5D, 3D, etc., as needed. Similarly, the average length of the pre-oxidized fiber can be set to 1mm, 5mm, 8mm, 15mm, 20mm, 30mm, 40mm, 50mm, 60mm, 70mm, 80mm, 90mm, 100mm, etc., as needed.

[0022] Optionally, the cement is silicate cement; the fly ash is Class II fly ash; the slag powder is S95 grade slag powder; and the water-reducing agent is a polycarboxylate water-reducing agent.

[0023] By adopting the above technical solutions, cement, fly ash, slag powder, and water-reducing agents are optimized, facilitating their selection. In several implementation schemes, the silicate cement is P.O42.5R, but it can also be set to P.O32.5R, P.O52.5R, etc., as needed. In several implementation schemes, the polycarboxylate water-reducing agent is AN4000, but it can also be set to PC-1009, 540P, etc., as needed.

[0024] Optionally, the fineness modulus of the sand is 2.3-3.0 and the mud content is ≤2%; the particle size of the crushed stone is 5-25mm continuous gradation.

[0025] By adopting the above technical solutions, the fineness modulus of sand and the particle size of crushed stone are optimized to maintain excellent bulk density and bulk weight, enhance the interaction of raw materials, and ensure the mechanical properties and quality of crack-resistant precast concrete components.

[0026] Secondly, this application provides a method for preparing the aforementioned crack-resistant precast concrete component, employing the following technical solution:

[0027] A method for preparing the crack-resistant precast concrete component includes the following steps:

[0028] S1. Mix water, cement, fly ash, slag powder, sand, crushed stone, phase change material, modified pre-oxygenated fiber, and water-reducing agent to obtain crack-resistant concrete.

[0029] S2. At a temperature of 20-30℃ and a relative humidity of ≥95%, the crack-resistant concrete is poured into the mold and cured for 2-3 hours. Then, the temperature is raised to 50-60℃ and cured for 5-6 hours. After cooling, the concrete is demolded to obtain the crack-resistant concrete precast component.

[0030] By adopting the above technical solutions, it is not only easier to prepare crack-resistant precast concrete components, but also to shorten the demolding cycle and improve the mold turnover rate.

[0031] In summary, this application has at least the following beneficial effects:

[0032] 1. The crack-resistant precast concrete component of this application incorporates phase change materials and modified pre-oxygenated fibers in the raw materials, and through the synergistic effect between them, achieves a total crack area of ​​<200mm. 2 / m 2 This significantly reduces the total cracked area and minimizes damage to crack-resistant precast concrete components during transportation and hoisting. Furthermore, its 28-day compressive strength > 60 MPa and 28-day flexural strength > 8.5 MPa demonstrate high compressive and flexural strength, exhibiting excellent overall performance.

[0033] 2. In the preparation method of the modified pre-oxidized fiber of this application, γ-aminopropyltriethoxysilane, trimethylolpropane triacrylate, and tetraethylenediamine are grafted onto the surface of the pre-oxidized fiber in steps, which greatly increases the number of branches, secondary amine groups, and ester groups. Sodium hydroxide is used to hydrolyze the ester groups, and by adjusting the pH value, carboxyl groups are formed. This introduces a large number of carboxyl and secondary amine groups onto the surface of the pre-oxidized fiber, enhancing the bonding strength and overall integrity, reducing the effects of drying shrinkage and internal / external temperature differences, reducing the total crack area, and improving compressive and flexural strength, thus enhancing the performance of the modified pre-oxidized fiber. Detailed Implementation

[0034] To make this application easier to understand, the following detailed description will be provided with reference to embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of application of this application. Unless otherwise specified, the raw materials or components used in this application can be obtained commercially or by conventional methods.

[0035] Preparation Example

[0036] Preparation Example 1

[0037] A modified pre-oxidized fiber is prepared by the following method:

[0038] T1. At a rotation speed of 500 r / min, add 10 g of pre-oxidized fiber to 100 g of water and stir for 5 min. Then add 4 g of γ-aminopropyltriethoxysilane and stir for 4 h. After filtration, obtain grafted pre-oxidized fiber a.

[0039] The pre-oxidized fiber has an average fineness of 1.5D and an average length of 10mm, and is selected from Guangdong Kaidun New Materials Co., Ltd.

[0040] T2. At a rotation speed of 500 r / min, the grafted pre-oxidized fiber a obtained in step T1 was added to 150 g of ethanol and stirred for 5 min. Then, 3.6 g of the first part of trimethylolpropane triacrylate was added and stirred for 25 h. Next, 6.8 g of tetraethylenediamine was added and stirred for 25 h. Then, 21.4 g of the second part of trimethylolpropane triacrylate was added and stirred for 25 h. The mixture was then filtered to obtain grafted pre-oxidized fiber b.

[0041] T3. At a temperature of 75℃ and a rotation speed of 500 r / min, the grafted pre-oxidized fiber b obtained in step T2 was added to 100 g of water and stirred for 5 min. Then, 8.7 g of sodium hydroxide was added and stirred for 2 h. Afterward, the pH value was adjusted to 5.5 with a 10% hydrochloric acid solution. Then, the mixture was filtered, washed twice with 100 g of water, and then dried to obtain the modified pre-oxidized fiber.

[0042] Preparation Example 2

[0043] A modified pre-oxidized fiber is prepared by the following method:

[0044] T1. At a rotation speed of 500 r / min, add 9 g of pre-oxidized fiber to 50 g of water and stir for 3 min. Then add 3 g of γ-aminopropyltriethoxysilane and stir for 3 h. After filtration, obtain grafted pre-oxidized fiber a.

[0045] The pre-oxidized fiber has an average fineness of 1.5D and an average length of 10mm, and is selected from Guangdong Kaidun New Materials Co., Ltd.

[0046] T2. At a rotation speed of 500 r / min, the grafted pre-oxidized fiber a obtained in step T1 was added to 100 g of ethanol and stirred for 3 min. Then, 3 g of the first part of trimethylolpropane triacrylate was added and stirred for 24 h. Next, 7.5 g of tetraethylenediamine was added and stirred for 26 h. Then, 25 g of the second part of trimethylolpropane triacrylate was added and stirred for 26 h. The mixture was then filtered to obtain grafted pre-oxidized fiber b.

[0047] T3. At a temperature of 80℃ and a rotation speed of 500 r / min, the grafted pre-oxidized fiber b obtained in step T2 was added to 150 g of water and stirred for 3 min. Then, 10 g of sodium hydroxide was added and stirred for 3 h. Afterward, the pH value was adjusted to 5.5 using a 10% hydrochloric acid solution. The mixture was then filtered, washed twice with 100 g of water, and then dried to obtain the modified pre-oxidized fiber.

[0048] Preparation Example 3

[0049] A modified pre-oxidized fiber is prepared by the following method:

[0050] T1. At a rotation speed of 500 r / min, 11 g of pre-oxidized fiber was added to 150 g of water and stirred for 10 min. Then, 5 g of γ-aminopropyltriethoxysilane was added and stirred for 5 h. After filtration, grafted pre-oxidized fiber a was obtained.

[0051] The pre-oxidized fiber has an average fineness of 1.5D and an average length of 10mm, and is selected from Guangdong Kaidun New Materials Co., Ltd.

[0052] T2. At a rotation speed of 500 r / min, the grafted pre-oxidized fiber a obtained in step T1 was added to 200 g of ethanol and stirred for 10 min. Then, 4 g of the first part of trimethylolpropane triacrylate was added and stirred for 26 h. Next, 6.5 g of tetraethylenediamine was added and stirred for 24 h. Then, 17 g of the second part of trimethylolpropane triacrylate was added and stirred for 24 h. The mixture was then filtered to obtain grafted pre-oxidized fiber b.

[0053] T3. At a temperature of 70℃ and a rotation speed of 500 r / min, the grafted pre-oxidized fiber b obtained in step T2 was added to 50 g of water and stirred for 10 min. Then, 7 g of sodium hydroxide was added and stirred for 1 h. Afterward, the pH was adjusted to 6 using a 10% hydrochloric acid solution. The mixture was then filtered, washed twice with 100 g of water, and then dried to obtain the modified pre-oxidized fiber.

[0054] Preparation Example 4

[0055] A modified pre-oxidized fiber differs from Preparation Example 1 in that the modified pre-oxidized fiber preparation method does not include steps T2 and T3, while the amount of γ-aminopropyltriethoxysilane added in step T1 is 35.8g.

[0056] The specific method for preparing modified pre-oxidized fiber is as follows: At a rotation speed of 500 r / min, add 10 g of pre-oxidized fiber to 100 g of water and stir for 5 min. Then add 35.8 g of γ-aminopropyltriethoxysilane and stir for 4 h. After filtration, wash twice with 100 g of water, and then dry to obtain modified pre-oxidized fiber.

[0057] Preparation Example 5

[0058] A modified pre-oxidized fiber, which differs from Preparation Example 1 in that, in step T2 of the modified pre-oxidized fiber preparation method, an equal amount of trimethylolpropane triacrylate is used instead of tetraethylenediamine.

[0059] Step T2 specifically involves adding the grafted pre-oxidized fiber a obtained in step T1 to 150g of ethanol at a rotation speed of 500r / min and stirring for 5min. Then, 31.8g of trimethylolpropane triacrylate is added and stirred for 25h. Afterward, the mixture is filtered to obtain grafted pre-oxidized fiber b.

[0060] Preparation Example 6

[0061] A modified pre-oxidized fiber, which differs from the preparation example 1 in that the modified pre-oxidized fiber preparation method does not include step T3.

[0062] Example

[0063] Table 1. Amounts of each raw material used in concrete (unit: g)

[0064] Example Example 1 Example 2 Example 3 water 155 150 160 cement 252 240 270 fly ash 104 115 95 Slag powder 63 70 60 sand 756 730 780 gravel 1044 1100 980 Phase change materials 4 3 5 Modified pre-oxidized fiber 8 10 5 Water reducing agent 6.3 7 6

[0065] Example 1

[0066] A type of crack-resistant precast concrete component, the raw materials and their proportions are shown in Table 1.

[0067] The cement used was silicate cement, specifically P.O42.5R; the fly ash was Grade II fly ash; the slag powder was iron slag powder, specifically S95 grade slag powder; the sand had a fineness modulus of 2.6 and a mud content of 0.5%; the crushed stone had a continuous gradation of 5-25mm; the water-reducing agent was a polycarboxylate superplasticizer, specifically AN4000; and the phase change material was a phase change microcapsule with a phase change temperature of 52℃, selected from Hefei Xineng Phase Change New Material Technology Co., Ltd. The modified pre-oxidized fiber was prepared using the method described in Preparation Example 1.

[0068] A method for preparing crack-resistant precast concrete components includes the following steps:

[0069] S1. Add sand to the crushed stone and mix for 5 minutes. Then add cement, fly ash, and slag powder, and mix for 5 minutes. Next, add phase change material and modified pre-oxidized fiber, and mix for 5 minutes. Then add water and water-reducing agent, and mix for 15 minutes to obtain crack-resistant concrete.

[0070] S2. At a temperature of 25℃ and a relative humidity of 98%, the crack-resistant concrete is poured into a mold and cured for 3 hours. Then, the temperature is raised to 52℃ and cured for 6 hours. Afterward, the temperature is lowered to 25℃, the concrete is demolded, and allowed to cure naturally to obtain the crack-resistant concrete precast component.

[0071] Example 2

[0072] A crack-resistant precast concrete component differs from Example 1 in that the raw material ratio of the crack-resistant precast concrete component is different, and the raw material ratio is shown in Table 1.

[0073] Example 3

[0074] A crack-resistant precast concrete component differs from Example 1 in that the raw material ratio of the crack-resistant precast concrete component is different, and the raw material ratio is shown in Table 1.

[0075] Example 4

[0076] A crack-resistant precast concrete component differs from Example 1 in that the modified pre-oxidized fiber in the raw materials of the crack-resistant precast concrete component comes from a different source, and the modified pre-oxidized fiber is prepared using the method of Preparation Example 2.

[0077] Example 5

[0078] A crack-resistant precast concrete component differs from Example 1 in that the modified pre-oxidized fiber in the raw materials of the crack-resistant precast concrete component comes from a different source, and the modified pre-oxidized fiber is prepared using the method of Preparation Example 3.

[0079] Example 6

[0080] A crack-resistant precast concrete component differs from Example 1 in that the source of the phase change material in the raw materials of the crack-resistant precast concrete component is different, and the phase change material is a phase change microcapsule with a phase change temperature of 48°C, and is selected from Hefei Xineng Phase Change New Material Technology Co., Ltd.

[0081] Example 7

[0082] A crack-resistant precast concrete component differs from Example 1 in that the source of the phase change material in the raw materials of the crack-resistant precast concrete component is different, and the phase change material is a phase change microcapsule with a phase change temperature of 64°C, and is selected from Hefei Xineng Phase Change New Material Technology Co., Ltd.

[0083] Comparative Example

[0084] Comparative Example 1

[0085] A crack-resistant precast concrete component differs from Example 1 in that the raw materials of the crack-resistant precast concrete component do not contain phase change materials or modified pre-oxygenated fibers.

[0086] Comparative Example 2

[0087] A crack-resistant precast concrete component differs from Example 1 in that, in the raw materials of the crack-resistant precast concrete component, an equal amount of phase change material replaces the modified pre-oxygenated fiber.

[0088] Comparative Example 3

[0089] A crack-resistant precast concrete component differs from Example 1 in that, in the raw materials of the crack-resistant precast concrete component, an equal amount of modified pre-oxygenated fiber replaces the phase change material.

[0090] Comparative Example 4

[0091] A crack-resistant precast concrete component differs from Example 1 in that the modified pre-oxidized fiber in the raw materials of the crack-resistant precast concrete component comes from a different source, and the modified pre-oxidized fiber is prepared using the method of Preparation Example 4.

[0092] Comparative Example 5

[0093] A crack-resistant precast concrete component differs from Example 1 in that the modified pre-oxidized fiber in the raw materials of the crack-resistant precast concrete component comes from a different source, and the modified pre-oxidized fiber is prepared using the method of Preparation Example 5.

[0094] Comparative Example 6

[0095] A crack-resistant precast concrete component differs from Example 1 in that the modified pre-oxidized fiber in the raw materials of the crack-resistant precast concrete component comes from a different source, and the modified pre-oxidized fiber is prepared using the method of Preparation Example 6.

[0096] Performance testing

[0097] Crack-resistant precast concrete components obtained in Examples 1-7 and Comparative Examples 1-6 were taken as samples, and the following performance tests were performed on the samples. The test results are shown in Table 2.

[0098] In accordance with GB / T50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete", the total crack area of ​​crack-resistant precast concrete components is tested, and the smaller the total crack area, the better the crack resistance of the crack-resistant precast concrete components.

[0099] According to GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete", the 28-day compressive strength and 28-day flexural strength of crack-resistant precast concrete components were tested.

[0100] Table 2 Detection Results

[0101]

[0102]

[0103] As can be seen from Table 2, the crack-resistant precast concrete components of this application have a low total crack area, ranging from 115.3 to 197.6 mm. 2 / m 2This reduces the likelihood of damage to crack-resistant precast concrete components during transportation and hoisting. It also possesses high compressive and flexural strength, with a 28-day compressive strength of 60.1-63.3 MPa and a 28-day flexural strength of 8.57-8.97 MPa, demonstrating superior mechanical properties and meeting market demands.

[0104] Comparing Example 1 with Comparative Examples 1-3, Comparative Example 1 did not add phase change materials or modified pre-oxidized fibers to the raw materials of the crack-resistant precast concrete; Comparative Example 2, compared to Comparative Example 1, added phase change materials to the raw materials of the crack-resistant precast concrete; Comparative Example 3, compared to Comparative Example 1, added modified pre-oxidized fibers to the raw materials of the crack-resistant precast concrete; and Example 1, compared to Comparative Example 1, added both phase change materials and modified pre-oxidized fibers to the raw materials of the crack-resistant precast concrete. This demonstrates that simultaneously adding phase change materials and modified pre-oxidized fibers to the raw materials of crack-resistant precast concrete, and through their synergistic effect, can significantly reduce the total crack area of ​​the crack-resistant precast concrete and improve its compressive and flexural strength.

[0105] Comparing Example 1 with Comparative Examples 4-6, the modified pre-oxidized fiber in the raw material of the crack-resistant precast concrete in Comparative Example 4 was obtained by treating the pre-oxidized fiber with γ-aminopropyltriethoxysilane; the modified pre-oxidized fiber in the raw material of the crack-resistant precast concrete in Comparative Example 5 was obtained by treating the pre-oxidized fiber with γ-aminopropyltriethoxysilane, trimethylolpropane triacrylate, and sodium hydroxide; the modified pre-oxidized fiber in the raw material of the crack-resistant precast concrete in Example 1 was obtained by treating the pre-oxidized fiber with γ-aminopropyltriethoxysilane, trimethylolpropane triacrylate, tetraethylenediamine, and sodium hydroxide. This demonstrates that modifying pre-oxidized fibers, and through the synergistic effect of γ-aminopropyltriethoxysilane, trimethylolpropane triacrylate, tetraethylenediamine, and sodium hydroxide, increases the number of branches and active groups, enhances the interaction between the phase change material and the modified pre-oxidized fibers, reduces the total crack area, improves compressive strength and flexural strength, and improves the performance of the modified pre-oxidized fibers.

[0106] It should be noted that the embodiments described above are only for explaining this application and do not constitute any limitation on this application. This application has been described with reference to typical embodiments, but it should be understood that the terms used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to this application within the scope of the claims, and revisions can be made to the invention without departing from the scope and spirit of this application. Although the application described herein relates to specific methods, materials, and embodiments, it does not mean that this application is limited to the specific examples disclosed herein; on the contrary, this application can be extended to all other methods and applications with the same function.

Claims

1. A crack-resistant precast concrete component, characterized in that: It is mainly made from the following raw materials in parts by weight: 150-160 parts water, 240-270 parts cement, 95-115 parts fly ash, 60-70 parts slag powder, 730-780 parts sand, 980-1100 parts crushed stone, 3-5 parts phase change material, 5-10 parts modified pre-oxidized fiber, and 6-7 parts water-reducing agent; the modified pre-oxidized fiber is obtained by treating the pre-oxidized fiber with γ-aminopropyltriethoxysilane, trimethylolpropane triacrylate, tetraethylenediamine, and sodium hydroxide. The modified pre-oxidized fiber was prepared using the following method: T1. Add pre-oxidized fiber to water and mix, then add γ-aminopropyltriethoxysilane, stir for 3-5 hours, filter, and obtain grafted pre-oxidized fiber a. T2. Add grafted pre-oxidized fiber a to an organic solvent and mix. Then add the first part of trimethylolpropane triacrylate and stir for 24-26 hours. Then add tetraethylenediamine triacrylate and stir for 24-26 hours. Then add the second part of trimethylolpropane triacrylate and stir for 24-26 hours. Filter to obtain grafted pre-oxidized fiber b. T3. At a temperature of 70-80℃, add grafted pre-oxidized fiber b to water and mix. Then add sodium hydroxide, stir for 1-3 hours, adjust the pH to 5-6, filter, wash, and dry to obtain modified pre-oxidized fiber.

2. The crack-resistant precast concrete component according to claim 1, characterized in that: The phase change material is a phase change microcapsule, and the phase change temperature of the phase change microcapsule is 40-70℃.

3. The crack-resistant precast concrete component according to claim 1, characterized in that: The weight ratio of the pre-oxidized filament fiber, γ-aminopropyltriethoxysilane, the first part of trimethylolpropane triacrylate, tetraethylenediamine triacrylate, the second part of trimethylolpropane triacrylate, and sodium hydroxide is (9-11):(3-5):(3-4):(6.5-7.5):(17-25):(7-10).

4. A crack-resistant precast concrete component according to claim 1, characterized in that: In step T1, the weight ratio of the pre-oxidized fiber to water is (9-11):(50-150); in step T2, the weight ratio of the first part of trimethylolpropane triacrylate to organic solvent is (3-4):(100-200); in step T3, the weight ratio of sodium hydroxide to water is (7-10):(50-150).

5. A crack-resistant precast concrete component according to claim 1, characterized in that: The organic solvent is one or more of methanol, ethanol, propanol, n-butanol, n-pentanol, and isoamyl alcohol.

6. A crack-resistant precast concrete component according to claim 1, characterized in that: The pre-oxidized filaments have an average fineness of 0.5-3D and an average length of 1-100mm.

7. A crack-resistant precast concrete component according to claim 1, characterized in that: The cement is silicate cement; the fly ash is Grade II fly ash; the slag powder is Grade S95 slag powder; and the water-reducing agent is polycarboxylate water-reducing agent.

8. A crack-resistant precast concrete component according to claim 1, characterized in that: The fineness modulus of the sand is 2.3-3.0 and the mud content is ≤2%; the particle size of the crushed stone is 5-25mm with continuous gradation.

9. A method for preparing a crack-resistant precast concrete component as described in any one of claims 1-8, characterized in that: Includes the following steps: S1. Mix water, cement, fly ash, slag powder, sand, crushed stone, phase change material, modified pre-oxygenated fiber, and water-reducing agent to obtain crack-resistant concrete. S2. At a temperature of 20-30℃ and a relative humidity of ≥95%, the crack-resistant concrete is poured into the mold and cured for 2-3 hours. Then, the temperature is raised to 50-60℃ and cured for 5-6 hours. After cooling, the concrete is demolded to obtain the crack-resistant concrete precast component.

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