A concrete for precast members, and a method of producing and using the same

Abstract

The application relates to the technical field of fabricated building, and particularly discloses a concrete for prefabricated components and a preparation method and application thereof. The concrete for prefabricated components is mainly made of the following raw materials: water, cement, fly ash, slag, silica fume, gravel, sand, graphite powder, modified calcium sulfate whisker and water reducing agent. The modified calcium sulfate whisker is obtained by treating calcium sulfate whisker with 3-aminopropyl triethoxysilane, trimethylolpropane triacrylate, tetraethylenepentamine and acryloyl carboxybetaine. The concrete has the characteristics of high early compressive strength, high long-term compressive strength and high flexural strength, and the 8h compressive strength is more than 60% of the 28d compressive strength, which meets the stripping requirement, shortens the stripping cycle, improves the mold turnover rate and production efficiency.

Description

Technical Field

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

[0002] With the development of modern industry, prefabricated buildings have emerged. Prefabricated buildings involve prefabricating components in a factory, then transporting these components to the construction site for assembly. Prefabricated components enable standardized design, factory production, and assembly construction, offering advantages such as high quality, high efficiency, and fast construction. They overcome the disadvantages of traditional construction, such as low production efficiency, slow construction speed, long construction period, and high labor intensity. Prefabricated buildings achieve energy conservation, environmental protection, and maximize their full-lifecycle value, and have become a trend in the industrialization of the construction industry.

[0003] Existing precast components are made from concrete, whose raw materials generally include water, cement, fly ash, gravel, sand, and water-reducing agents. The raw materials are mixed to obtain concrete, which is then poured into molds and cured at around 25°C for 28 days before demolding to obtain the precast component. This demolding cycle is long, and the mold turnover rate is low. To shorten the demolding cycle, some manufacturers cure the concrete at around 55°C after pouring it into the mold, allowing it to solidify quickly and meet demolding requirements. While high-temperature curing increases early compressive strength and improves mold turnover rate, it is detrimental to the long-term compressive strength of the precast component. Summary of the Invention

[0004] In order to improve the long-term compressive strength of concrete, this application provides concrete for precast components, its preparation method and application.

[0005] In a first aspect, this application provides concrete for precast components, employing the following technical solution:

[0006] A type of concrete for precast components is mainly made from the following raw materials in parts by weight: 145-180 parts water, 160-180 parts cement, 80-100 parts fly ash, 55-65 parts slag, 13-17 parts silica fume, 1200-1400 parts gravel, 1000-1200 parts sand, 4-6 parts graphite powder, 4-6 parts modified calcium sulfate whiskers, and 2-5 parts water-reducing agent; wherein the modified calcium sulfate whiskers are obtained by treating calcium sulfate whiskers with 3-aminopropyltriethoxysilane, trimethylolpropane triacrylate, tetraethylenepentamine, and acryloylcarboxylic acid betaine.

[0007] The concrete used in this application for precast components, through the mutual combination of raw materials, achieves an 8-hour compressive strength > 34 MPa, a 28-day compressive strength > 56 MPa, a 56-day compressive strength > 58 MPa, and a 28-day flexural strength > 8 MPa. This gives the concrete not only the advantages of high early-stage compressive strength but also high long-term compressive strength. The 8-hour compressive strength reaches more than 60% of the 28-day compressive strength, meeting demolding requirements, improving mold turnover rate and production efficiency. At the same time, it also has the characteristic of high flexural strength, meeting market demand.

[0008] Adding graphite powder and modified calcium sulfate whiskers to concrete raw materials achieves a synergistic effect, reducing the internal and external temperature differences and thermal stress during the concrete curing process. This enhances the hydration degree and stability of hydration products, improving the early compressive strength, long-term compressive strength, and flexural strength of the concrete. Simultaneously, the calcium sulfate whiskers are modified by introducing numerous active groups such as siloxy groups, tertiary amine groups, secondary amine groups, amide groups, carboxylic acid anions, and quaternary ammonium cations onto their surface. This significantly increases grafting stability, grafting amount, and grafted branching, strengthening the interfacial bonding strength between the calcium sulfate whiskers and the raw materials. Ultimately, this improves the performance of the modified calcium sulfate whiskers, resulting in superior mechanical properties in the concrete.

[0009] Optionally, the modified calcium sulfate whiskers are prepared using the following method:

[0010] S1. Add 3-aminopropyltriethoxysilane to an ethanol solution and mix. Then add calcium sulfate whiskers, stir for 3-5 hours, filter, and obtain solid a.

[0011] S2. Add trimethylolpropane triacrylate to ethanol and mix, then add solid a, stir for 24-26 hours, filter to obtain solid b;

[0012] S3. Add tetraethylenepentamine to ethanol and mix, then add solid b, stir for 24-26 hours, filter, and obtain solid c;

[0013] S4. Add acryloyl carboxylate betaine to ethanol and mix, then add solid c, stir for 24-26 hours, filter, wash, and dry to obtain modified calcium sulfate whiskers.

[0014] Optionally, the weight ratio of the calcium sulfate whiskers, 3-aminopropyltriethoxysilane, trimethylolpropane triacrylate, tetraethylenepentamine, and acryloylcarboxylic acid betaine is (9-11):(3-5):(3-4):(6.5-7.5):(16-17).

[0015] By employing the above technical solution, 3-aminopropyltriethoxysilane and calcium sulfate whiskers are added to an ethanol solution. 3-aminopropyltriethoxysilane contains three siloxy groups and a primary amine group. The siloxy groups hydrolyze upon contact with water and are grafted onto the surface of the calcium sulfate whiskers, introducing siloxy groups and primary amine groups onto the surface of the calcium sulfate whiskers. Then, trimethylolpropane triacrylate, containing three carbon-carbon double bonds and three ester groups, is added. The carbon-carbon double bonds undergo an addition reaction with the primary amine groups on the surface of the calcium sulfate whiskers, introducing multiple tertiary amine groups and multiple ester groups onto the surface of the calcium sulfate whiskers. Subsequently, tetraethylenepentamine, containing two primary amine groups and three secondary amine groups, is added. One of the primary amine groups in tetraethylenepentamine undergoes an amidation reaction with the ester groups on the surface of the calcium sulfate whiskers, introducing multiple amide groups, multiple primary amine groups, and multiple secondary amine groups onto the surface of the calcium sulfate whiskers. Then, acryloylcarboxylate betaine, which contains carbon-carbon double bonds, amide groups, carboxylic acid anions, and quaternary ammonium cations, is added. The carbon-carbon double bonds undergo an addition reaction with the primary amine groups on the surface of the calcium sulfate whiskers, introducing multiple tertiary amine groups and multiple amide groups onto the surface of the calcium sulfate whiskers. A grafting reaction is then carried out stepwise on the surface of the calcium sulfate whiskers using 3-aminopropyltriethoxysilane, trimethylolpropane triacrylate, tetraethylenepentamine, and acryloylcarboxylate betaine. This grafts dendritic polymers onto the surface of the calcium sulfate whiskers and introduces a large number of active groups such as siloxy groups, tertiary amine groups, secondary amine groups, amide groups, carboxylic acid anions, and quaternary ammonium cations, increasing the amount of polymer groups and branching, improving the performance of the modified calcium sulfate whiskers, and enhancing the early compressive strength, long-term compressive strength, and flexural strength of concrete.

[0016] In step S1, the weight ratio of calcium sulfate whiskers to ethanol solution is (9-11):(50-150), for example, a weight ratio of 1:10, 9:50, 9:150, 11:50, or 11:150, but not limited to the listed values; other unlisted values ​​within this range also apply. The mass concentration of ethanol in the ethanol solution is 80-90%, for example, 85%, 80%, 83%, 88%, or 90%, but not limited to the listed values; other unlisted values ​​within this range also apply.

[0017] In step S2, the weight ratio of trimethylolpropane triacrylate to ethanol is (3-4):(50-150), for example, the weight ratio is 3.6:100, 3:50, 3:150, 4:50, 4:150, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0018] In step S3, the weight ratio of tetraethylenepentamine to ethanol is (6.5-7.5):(50-150), for example, the weight ratio is 6.8:100, 6.5:50, 6.5:150, 7.5:50, 7.5:150, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] In step S4, the weight ratio of acryloylcarboxylate betaine to ethanol is (16-17):(50-150), for example, 16.5:100, 16:50, 16:150, 17:50, 17:150, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0020] Optionally, the calcium sulfate whiskers are calcium sulfate dihydrate whiskers, and the average diameter of the calcium sulfate whiskers is 1-5 μm and the average length is 20-60 μm.

[0021] By adopting the above technical solution, the average diameter and average length of calcium sulfate whiskers are limited, facilitating the selection of calcium sulfate whiskers. In several embodiments, the average diameter of the calcium sulfate whiskers is 3 μm, but it can also be set to 1 μm, 2 μm, 4 μm, 5 μm, etc., as needed. In several embodiments, the average length of the calcium sulfate whiskers is 50 μm, but it can also be set to 20 μm, 30 μm, 40 μm, 60 μm, etc., as needed.

[0022] Optionally, the average particle size of the graphite powder is 10-50 μm.

[0023] By adopting the above technical solution, the average particle size of the graphite powder is limited, which facilitates the selection of graphite powder. In several embodiments, the average particle size of the graphite powder is 25 μm, but it can also be set to 10 μm, 15 μm, 20 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, etc., as needed.

[0024] Optionally, the cement is silicate cement, the water-reducing agent is polycarboxylate water-reducing agent, the fly ash is Class I fly ash, the slag is blast furnace slag, and the silica content in the silica fume is ≥95%.

[0025] By adopting the above technical solution, the selection of cement, water-reducing agent, fly ash, slag, and silica fume is limited, which facilitates the selection of cement, water-reducing agent, fly ash, slag, and silica fume, and also facilitates the preparation of concrete.

[0026] Optionally, the cement is one or more of silicate cement P.O32.5R, silicate cement P.O42.5R, and silicate cement P.O52.5R. The water-reducing agent is one or more of polycarboxylate superplasticizer PC-1009, polycarboxylate superplasticizer AN4000, and polycarboxylate superplasticizer 540P. The slag is one or more of S95 grade slag powder, S105 grade slag powder, and S75 grade slag powder.

[0027] Optionally, the gravel has a continuous gradation of 5-25mm, and the sand has a fineness modulus of 2.1-3.3.

[0028] By adopting the above technical solutions, the particle size of gravel and sand is optimized, increasing the bulk density and compactness of concrete, thus enabling the concrete to exhibit better mechanical properties.

[0029] Secondly, this application provides a method for preparing concrete for precast components, which adopts the following technical solution:

[0030] A method for preparing concrete for precast components includes the following steps: mixing water, cement, fly ash, slag, silica fume, gravel, sand, graphite powder, modified calcium sulfate whiskers, and water-reducing agent to obtain concrete.

[0031] By adopting the above technical solution, the preparation of concrete becomes easier.

[0032] Thirdly, this application provides a prefabricated component, which adopts the following technical solution:

[0033] A precast component, which is made of concrete using the aforementioned precast component.

[0034] Fourthly, this application provides a method for preparing the precast component, which adopts the following technical solution: A method for preparing the precast component includes the following steps: at a temperature of 20-30℃ and a relative humidity of ≥95%, concrete is poured into a mold and cured for 2-3 hours, then the temperature is raised to 50-60℃ at a rate of 3-7℃ / min and cured for 5-6 hours, and then the temperature is lowered to 20-30℃ at a rate of 3-7℃ / min, and the component is demolded to obtain the precast component.

[0035] By adopting the above technical solution, the concrete is first cured at room temperature and then cured at high temperature to obtain precast components. This not only facilitates the preparation of precast components, but also, through the combination of room temperature curing and high temperature curing, the compressive strength of the precast components reaches more than 60% of the 28-day compressive strength in 8 hours. While ensuring the quality of precast components, the demolding cycle is shortened, and the mold turnover rate and production efficiency are improved.

[0036] In summary, this application has at least the following beneficial effects:

[0037] 1. The concrete used in the precast components of this application, through the mutual combination of raw materials, has an 8-hour compressive strength > 34MPa, a 28-day compressive strength > 56MPa, and a 28-day flexural strength > 8MPa, giving the concrete the characteristics of high early-term compressive strength, high long-term compressive strength, and high flexural strength. Moreover, the 8-hour compressive strength reaches more than 60% of the 28-day compressive strength, meeting the demolding requirements, shortening the demolding cycle, and improving mold turnover rate and production efficiency.

[0038] 2. In the preparation method of modified calcium sulfate whiskers, 3-aminopropyltriethoxysilane is first grafted onto the surface of calcium sulfate whiskers, then trimethylolpropane triacrylate is grafted through an addition reaction, followed by tetraethylenepentamine grafted through an amidation reaction, and then acryloylcarboxylate betaine grafted through an addition reaction. A large number of active groups such as siloxy groups, tertiary amine groups, secondary amine groups, amide groups, carboxylic acid anions, and quaternary ammonium cations are introduced onto the surface of calcium sulfate whiskers, which greatly increases the grafting stability, grafting amount, and grafted branch amount, improves the performance of modified calcium sulfate whiskers, and makes concrete exhibit better mechanical properties. Detailed Implementation

[0039] To make this application easier to understand, the following detailed description is provided in conjunction with 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.

[0040] Preparation Example

[0041] Preparation Example 1

[0042] A modified calcium sulfate whisker is prepared by the following method:

[0043] S1. Add 4g of 3-aminopropyltriethoxysilane to 100g of ethanol solution and stir for 3min. Then add 10g of calcium sulfate whiskers, stir for 4h, filter, and obtain solid a.

[0044] The calcium sulfate whiskers are dihydrate calcium sulfate whiskers, with an average diameter of 3 μm and an average length of 50 μm; the ethanol solution has a mass concentration of 85%.

[0045] S2. Add 3.6g of trimethylolpropane triacrylate to 100g of ethanol and stir for 3min. Then add solid a, stir for 25h, filter, and obtain solid b.

[0046] S3. Add 6.8g of tetraethylenepentamine to 100g of ethanol and stir for 3min. Then add solid b, stir for 25h, filter, and obtain solid c.

[0047] S4. Add 16.5g of acryloylcarboxylic acid betaine to 100g of ethanol and stir for 3min. Then add solid c and stir for 25h. Filter, wash once with ethanol, wash three times with water, and dry to obtain modified calcium sulfate whiskers.

[0048] Preparation Example 2

[0049] A modified calcium sulfate whisker is prepared by the following method:

[0050] S1. Add 3g of 3-aminopropyltriethoxysilane to 100g of water and stir for 3min. Then add 9g of calcium sulfate whiskers, stir for 3h, filter, and obtain solid a.

[0051] The calcium sulfate whiskers are dihydrate calcium sulfate whiskers, with an average diameter of 3 μm and an average length of 50 μm; the ethanol solution has a mass concentration of 85%.

[0052] S2. Add 3g of trimethylolpropane triacrylate to 100g of ethanol and stir for 3min. Then add solid a, stir for 24h, filter, and obtain solid b.

[0053] S3. Add 7.5g of tetraethylenepentamine to 100g of ethanol and stir for 3min. Then add solid b, stir for 26h, filter, and obtain solid c.

[0054] S4. Add 17g of acryloylcarboxylate betaine to 100g of ethanol and stir for 3min. Then add solid c and stir for 26h. Filter, wash once with ethanol, wash three times with water, and dry to obtain modified calcium sulfate whiskers.

[0055] Preparation Example 3

[0056] A modified calcium sulfate whisker is prepared by the following method:

[0057] S1. Add 5g of 3-aminopropyltriethoxysilane to 100g of water and stir for 3min. Then add 11g of calcium sulfate whiskers, stir for 5h, filter, and obtain solid a.

[0058] The calcium sulfate whiskers are dihydrate calcium sulfate whiskers, with an average diameter of 3 μm and an average length of 50 μm; the ethanol solution has a mass concentration of 85%.

[0059] S2. Add 4g of trimethylolpropane triacrylate to 100g of ethanol and stir for 3min. Then add solid a, stir for 26h, filter, and obtain solid b.

[0060] S3. Add 6.5g of tetraethylenepentamine to 100g of ethanol and stir for 3min. Then add solid b, stir for 24h, filter, and obtain solid c.

[0061] S4. Add 16g of acryloylcarboxylate betaine to 100g of ethanol and stir for 3min. Then add solid c and stir for 24h. Filter, wash once with ethanol, wash three times with water, and dry to obtain modified calcium sulfate whiskers.

[0062] Example

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

[0064] Example Example 1 Example 2 Example 3 water 163 145 180 cement 170 160 180 fly ash 90 100 80 slag 58 55 65 silica ash 15 17 13 pebbles 1300 1400 1200 sand 1080 1000 1200 Graphite powder 5 4 6 Modified calcium sulfate whiskers 5 6 4 Water reducing agent 3.5 2 5

[0065] Example 1

[0066] A type of concrete for precast components, the raw material proportions of which are shown in Table 1.

[0067] The cement used was silicate cement P.O42.5R; the fly ash was Grade I fly ash; the slag was Grade S95 slag powder; the silica content in the silica fume was 95%; the gravel was crushed pebbles with a continuous gradation of 5-25 mm; the sand was river sand with a fineness modulus of 2.6; the graphite powder had an average particle size of 25 μm and was selected from Shijiazhuang Jingsheng Mineral Products Co., Ltd.; the water-reducing agent was polycarboxylate superplasticizer PC-1009; and the modified calcium sulfate whiskers were prepared using the method described in Preparation Example 1.

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

[0069] Add sand to the aggregate and mix for 3 minutes. Then add cement, fly ash, slag, and silica fume, and mix for 5 minutes. Next, add graphite powder and modified calcium sulfate whiskers, and mix for 5 minutes. Finally, add water and water-reducing agent, and mix for 10 minutes to obtain concrete.

[0070] Example 2

[0071] A type of concrete for precast components differs from that in Example 1 in that the raw material ratio of the concrete is different, and the raw material ratio is shown in Table 1.

[0072] Example 3

[0073] A type of concrete for precast components differs from that in Example 1 in that the raw material ratio of the concrete is different, and the raw material ratio is shown in Table 1.

[0074] Example 4

[0075] A type of precast concrete differs from Example 1 in that the source of the modified calcium sulfate whiskers in the raw materials of the concrete is different, and the modified calcium sulfate whiskers are prepared by the method of Preparation Example 2.

[0076] Example 5

[0077] A type of precast concrete differs from Example 1 in that the source of the modified calcium sulfate whiskers in the raw materials of the concrete is different, and the modified calcium sulfate whiskers are prepared by the method of Preparation Example 3.

[0078] Comparative Example

[0079] Comparative Example 1

[0080] A type of precast concrete differs from Example 1 in that, in the raw materials of the concrete, an equal amount of sand replaces graphite powder and modified calcium sulfate whiskers.

[0081] Comparative Example 2

[0082] A type of precast concrete differs from Example 1 in that, in the concrete raw materials, an equal amount of graphite powder replaces the modified calcium sulfate whiskers.

[0083] Comparative Example 3

[0084] A type of precast concrete differs from Example 1 in that the graphite powder is replaced with an equal amount of modified calcium sulfate whiskers in the raw materials of the concrete.

[0085] Comparative Example 4

[0086] A type of precast concrete differs from Example 1 in that the source of the modified calcium sulfate whiskers in the concrete raw materials is different, and the modified calcium sulfate whiskers are obtained by treating calcium sulfate whiskers with 3-aminopropyltriethoxysilane.

[0087] Specifically, modified calcium sulfate whiskers are prepared using the following method:

[0088] Add 30.9 g of 3-aminopropyltriethoxysilane to 100 g of ethanol solution and stir for 3 min. Then add 10 g of calcium sulfate whiskers, stir for 4 h, filter, wash once with ethanol, wash three times with water, and dry to obtain modified calcium sulfate whiskers.

[0089] The calcium sulfate whiskers are dihydrate calcium sulfate whiskers, with an average diameter of 3 μm and an average length of 50 μm; the ethanol solution has a mass concentration of 85%.

[0090] Comparative Example 5

[0091] A type of precast concrete differs from Example 1 in that the modified calcium sulfate whiskers in the concrete raw materials are from a different source, and the modified calcium sulfate whiskers are obtained by treating calcium sulfate whiskers with 3-aminopropyltriethoxysilane and trimethylolpropane triacrylate.

[0092] Specifically, modified calcium sulfate whiskers are prepared using the following method:

[0093] S1. Add 16.3g of 3-aminopropyltriethoxysilane to 100g of ethanol solution and stir for 3min. Then add 10g of calcium sulfate whiskers, stir for 4h, filter, and obtain solid a.

[0094] The calcium sulfate whiskers are dihydrate calcium sulfate whiskers, with an average diameter of 3 μm and an average length of 50 μm; the ethanol solution has a mass concentration of 85%.

[0095] S2. Add 14.6g of trimethylolpropane triacrylate to 100g of ethanol and stir for 3min. Then add solid a, stir for 25h, filter, wash once with ethanol, wash three times with water, and dry to obtain modified calcium sulfate whiskers.

[0096] Comparative Example 6

[0097] A type of precast concrete differs from Example 1 in that the modified calcium sulfate whiskers in the concrete raw materials are from a different source, and the modified calcium sulfate whiskers are obtained by treating calcium sulfate whiskers with 3-aminopropyltriethoxysilane, trimethylolpropane triacrylate, and tetraethylenepentamine.

[0098] Specifically, modified calcium sulfate whiskers are prepared using the following method:

[0099] S1. Add 8.6 g of 3-aminopropyltriethoxysilane to 100 g of ethanol solution and stir for 3 min. Then add 10 g of calcium sulfate whiskers, stir for 4 h, filter, and obtain solid a.

[0100] The calcium sulfate whiskers are dihydrate calcium sulfate whiskers, with an average diameter of 3 μm and an average length of 50 μm; the ethanol solution has a mass concentration of 85%.

[0101] S2. Add 7.7g of trimethylolpropane triacrylate to 100g of ethanol and stir for 3min. Then add solid a, stir for 25h, filter, and obtain solid b.

[0102] S3. Add 14.6g of tetraethylenepentamine to 100g of ethanol and stir for 3min. Then add solid b and stir for 25h. Filter, wash once with ethanol, wash three times with water, and dry to obtain modified calcium sulfate whiskers.

[0103] Comparative Example 7

[0104] A type of precast concrete differs from Example 1 in that the source of the modified calcium sulfate whiskers in the concrete raw materials is different.

[0105] Specifically, modified calcium sulfate whiskers are prepared using the following method:

[0106] Add 4g of 3-aminopropyltriethoxysilane, 3.6g of trimethylolpropane triacrylate, 6.8g of tetraethylenepentamine, and 16.5g of acryloylcarboxylic acid betaine to 100g of ethanol solution, and stir for 3min. Then add 10g of calcium sulfate whiskers, stir for 25h, filter, wash once with ethanol, wash three times with water, and dry to obtain modified calcium sulfate whiskers.

[0107] The calcium sulfate whiskers are dihydrate calcium sulfate whiskers, with an average diameter of 3 μm and an average length of 50 μm; the ethanol solution has a mass concentration of 85%.

[0108] Comparative Example 8

[0109] A precast concrete component differs from Example 1 in that, in the preparation method of modified calcium sulfate whiskers in the concrete raw materials, an equal amount of propyltrimethoxysilane is used to replace 3-aminopropyltriethoxysilane.

[0110] Application examples

[0111] Application Example 1

[0112] A precast component is made of concrete, which is prepared using the method of Example 1.

[0113] A method for preparing a precast component includes the following steps:

[0114] Concrete was poured into molds at 25°C and 98% relative humidity and cured for 3 hours. The temperature was then increased to 55°C at a rate of 5°C / min and cured for 5 hours. The temperature was then decreased to 25°C at a rate of 5°C / min, and the concrete was demolded to obtain precast components. Curing continued for 56 days.

[0115] Application Example 2-5

[0116] A precast component differs from Application Example 1 in that the source of the concrete in the raw materials of the precast component is different, and the concrete in Application Examples 2-5 is prepared sequentially using the methods of Examples 2-5.

[0117] Comparative Application Examples

[0118] Compare and contrast examples 1-8

[0119] A precast component differs from Application Example 1 in that the source of the concrete in the raw materials of the precast component is different, and the concrete in Comparative Application Examples 1-8 is prepared by the methods of Comparative Examples 1-8 respectively.

[0120] Performance testing

[0121] Precast components obtained from Application Examples 1-5 and Comparative Application Examples 1-8 were used as test specimens, and the compressive strength and flexural strength of the specimens were tested according to GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". The test results are shown in Table 2.

[0122] Table 2 Detection Results

[0123]

[0124] As shown in Table 2, the concrete of this application exhibits an 8-hour compressive strength of 34.4-35.7 MPa, a 3-day compressive strength of 43.6-45.5 MPa, a 28-day compressive strength of 56.2-58.6 MPa, and a 56-day compressive strength of 58.6-61.3 MPa. This gives the concrete the advantage of high early-stage compressive strength while maintaining relatively high long-term compressive strength. Furthermore, the 8-hour compressive strength reaches over 60% of the 28-day compressive strength, meeting demolding requirements, shortening the demolding cycle, and improving mold turnover rate and production efficiency. Simultaneously, the 8-hour flexural strength is 5.01-5.11 MPa, and the 28-day flexural strength is 8.15-8.46 MPa, demonstrating high flexural strength and meeting market demands.

[0125] Comparing Application Example 1 with Comparative Application Examples 1-3, Comparative Application Example 1 did not contain graphite powder or modified calcium sulfate whiskers in its concrete raw materials; Comparative Application Example 2 contained graphite powder in its concrete raw materials; Comparative Application Example 3 contained modified calcium sulfate whiskers in its concrete raw materials; and Application Example 1 contained both graphite powder and modified calcium sulfate whiskers in its concrete raw materials. This demonstrates that simultaneously adding graphite powder and modified calcium sulfate whiskers to the raw materials, and through their synergistic effect, can increase the compressive and flexural strength of concrete.

[0126] Comparing Application Example 1 with Comparative Application Examples 4-6, the modified calcium sulfate whiskers in the concrete raw material of Comparative Application Example 4 were obtained by treating calcium sulfate whiskers with 3-aminopropyltriethoxysilane; the modified calcium sulfate whiskers in the concrete raw material of Comparative Application Example 5 were obtained by treating calcium sulfate whiskers with 3-aminopropyltriethoxysilane and trimethylolpropane triacrylate; the modified calcium sulfate whiskers in the concrete raw material of Comparative Application Example 6 were obtained by treating calcium sulfate whiskers with 3-aminopropyltriethoxysilane, trimethylolpropane triacrylate, and tetraethylenepentamine; and the modified calcium sulfate whiskers in the concrete raw material of Application Example 1 were obtained by treating calcium sulfate whiskers with 3-aminopropyltriethoxysilane, trimethylolpropane triacrylate, tetraethylenepentamine, and acryloylcarboxylic acid betaine. This demonstrates that treating calcium sulfate whiskers with 3-aminopropyltriethoxysilane, trimethylolpropane triacrylate, tetraethylenepentamine, and acryloylcarboxylic acid betaine can introduce a large number of active groups such as siloxy groups, tertiary amine groups, secondary amine groups, amide groups, carboxylic acid anions, and quaternary ammonium cations onto the surface of calcium sulfate whiskers, thereby enhancing the interfacial bonding strength between calcium sulfate whiskers and raw materials and improving the performance of modified calcium sulfate whiskers.

[0127] Comparing Application Example 1 and Comparative Application Example 7, it can be seen that the step-by-step grafting and reaction on the surface of calcium sulfate whiskers in the modified calcium sulfate whisker preparation method can form a dendritic polymer on the surface of the calcium sulfate whiskers, increasing the number of functional groups and branches, thus improving the performance of the modified calcium sulfate whiskers. Furthermore, in Comparative Application Example 8, it can be seen that compared to propyltrimethoxysilane, the grafting treatment of calcium sulfate whiskers with 3-aminopropyltriethoxysilane, combined with the synergistic effect of trimethylolpropane triacrylate, tetraethylenepentamine, and acryloylcarboxylic acid betaine, results in concrete exhibiting superior mechanical properties.

[0128] 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 type of concrete for precast components, characterized in that: It is mainly made from the following raw materials in parts by weight: 145-180 parts water, 160-180 parts cement, 80-100 parts fly ash, 55-65 parts slag, 13-17 parts silica fume, 1200-1400 parts gravel, 1000-1200 parts sand, 4-6 parts graphite powder, 4-6 parts modified calcium sulfate whiskers, and 2-5 parts water-reducing agent; the modified calcium sulfate whiskers are obtained by treating calcium sulfate whiskers with 3-aminopropyltriethoxysilane, trimethylolpropane triacrylate, tetraethylenepentamine, and acryloylcarboxylic acid betaine. The weight ratio of the calcium sulfate whiskers, 3-aminopropyltriethoxysilane, trimethylolpropane triacrylate, tetraethylenepentamine, and acryloylcarboxylate betaine is (9-11):(3-5):(3-4):(6.5-7.5):(16-17). The calcium sulfate whiskers are dihydrate calcium sulfate whiskers, and the average diameter of the calcium sulfate whiskers is 1-5 μm and the average length is 20-60 μm.

2. The concrete for precast components according to claim 1, characterized in that: The modified calcium sulfate whiskers were prepared using the following method: S1. Add 3-aminopropyltriethoxysilane to an ethanol solution and mix. Then add calcium sulfate whiskers, stir for 3-5 hours, filter, and obtain solid a. S2. Add trimethylolpropane triacrylate to ethanol and mix, then add solid a, stir for 24-26 hours, filter to obtain solid b; S3. Add tetraethylenepentamine to ethanol and mix, then add solid b, stir for 24-26 hours, filter, and obtain solid c; S4. Add acryloyl carboxylate betaine to ethanol and mix, then add solid c, stir for 24-26 hours, filter, wash, and dry to obtain modified calcium sulfate whiskers.

3. The concrete for precast components according to claim 1, characterized in that: The average particle size of the graphite powder is 10-50 μm.

4. The concrete for precast components according to claim 1, characterized in that: The cement is silicate cement, the water-reducing agent is polycarboxylate water-reducing agent, the fly ash is Grade I fly ash, the slag is blast furnace slag, and the silica content in the silica fume is ≥95%.

5. The concrete for precast components according to claim 1, characterized in that: The gravel has a continuous gradation of 5-25mm, and the fineness modulus of the sand is 2.1-3.

3.

6. A method for preparing concrete for precast components as described in any one of claims 1-5, characterized in that: The process includes the following steps: mixing water, cement, fly ash, slag, silica fume, gravel, sand, graphite powder, modified calcium sulfate whiskers, and water-reducing agent to obtain concrete.

7. A prefabricated component, characterized in that: It is made of concrete using precast components as described in any one of claims 1-5.

8. A method for preparing a precast component as described in claim 7, characterized in that: The process includes the following steps: at a temperature of 20-30℃ and a relative humidity of ≥95%, concrete is poured into a mold and cured for 2-3 hours. Then, the temperature is increased to 50-60℃ at a rate of 3-7℃ / min and cured for 5-6 hours. After that, the temperature is decreased to 20-30℃ at a rate of 3-7℃ / min, and the concrete is demolded to obtain the precast component.

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