An anti-cracking concrete and its preparation method

Abstract

This application relates to the technical field of building materials, and particularly relates to a crack-resistant concrete and a preparation method thereof. The crack-resistant concrete is made from the following raw materials in parts by weight: 300-400 parts of cement, 900-1100 parts of stones, 300-400 parts of sand, 90-110 parts of fly ash, 30-50 parts of a modified calcium oxide-based expansive agent, 5-15 parts of a composite fiber material, and 150 parts of water; the composite fiber material is made from a modified polycarboxylate water reducer and modified fibers. In this application, a combination of an organic matrix-silane coupling agent-inorganic matrix formed by the modified polycarboxylate water reducer and the modified fibers improves the dispersibility of the fibers in the system, and at the same time, a modified calcium oxide-based expansive agent is compounded to improve the crack-resistant performance of the concrete.

Description

Technical Field

[0001] This application relates to the technical field of building materials, and particularly relates to a crack-resistant concrete and a preparation method thereof. Background Art

[0002] Concrete is a mixture composed of various materials and is a brittle material. Under the effects of cement hydration heat, internal and external temperature differences, and self-shrinkage, there is a possibility of cracks, which affects its use effect. In the prior art, the preparation of concrete adds fibers to improve the overall tensile stress of the concrete and the crack-resistant performance of the concrete. However, the fibers are prone to knotting in the concrete and it is difficult to achieve uniform dispersion. Therefore, the use of fibers in concrete is subject to certain limitations.

[0003] Therefore, improving the uniform dispersion of fibers in concrete is of great significance for improving the crack-resistant performance of concrete. Summary of the Invention

[0004] In order to improve the uniform dispersion of fibers in concrete, this application provides a crack-resistant concrete and a preparation method thereof.

[0005] In the first aspect, this application provides a crack-resistant concrete, adopting the following technical solution:

[0006] A crack-resistant concrete, comprising raw materials made of the following parts by weight: 300 - 400 parts of cement, 900 - 1100 parts of stones, 300 - 400 parts of sand, 90 - 110 parts of fly ash, 30 - 50 parts of modified calcium oxide-based expansive agent, 5 - 15 parts of composite fiber material, and 150 parts of water;

[0007] The preparation method of the composite fiber material comprises the following steps:

[0008] Mix polycarboxylate superplasticizer and the first solvent, then dropwise add SOCl2, heat under reflux, after obtaining a solid, dissolve it with the second solvent to obtain a mixture; mix silane coupling agent and the second solvent, heat, add an organic weak base, stir in an inert gas atmosphere, and add the mixture, stir and perform post-treatment to obtain a modified polycarboxylate superplasticizer;

[0009] Blend the modified polycarboxylate superplasticizer and the modified fiber in a mass ratio of (1 - 3):(25 - 100) in an aqueous medium, adjust the pH to alkaline, heat and stir, and perform post-treatment to obtain the composite fiber material.

[0010] By adopting the above technical solution, the polycarboxylate superplasticizer is modified with a silane coupling agent. The polycarboxylate superplasticizer, the silane coupling agent, and the modified fiber form a combination of an organic matrix - silane coupling agent - inorganic matrix, enhancing the interaction force between the polycarboxylate superplasticizer and the fiber. Moreover, the silane coupling agent is reactive to the building substrate, enhancing the bonding force between the composite fiber material and other components. At the same time, the dispersibility of the fiber in the system is improved, the internal bonding force of the concrete is increased, and thus the anti-cracking performance of the concrete is improved.

[0011] By adding an appropriate amount of modified calcium oxide-based expansive agent, bubbles and tiny cracks are generated during the formation of the concrete, causing changes in the internal structure of the crystals in the concrete, reducing the internal stress within the crystal lattice, decreasing the shrinkage amount and cracking tendency of the concrete, and improving the anti-cracking performance of the concrete.

[0012] In this application, by adding a composite fiber material and a modified calcium oxide-based expansive agent to the concrete system, the anti-cracking performance of the concrete is improved under the combined action of the two.

[0013] In a specific feasible implementation, the preparation method of the modified fiber is as follows: Mix water and fiber, add an alkali solution to adjust the pH to 8 - 9. After dispersing evenly, filter and dry to obtain pretreated fiber; Add (50 - 150) g of the pretreated fiber to (50 - 150) ml of graphene dispersion with a pH of 6 - 7 and containing an active agent, disperse evenly and filter.

[0014] By adopting the above technical solution, using the ultra-high strength, flexibility, and large specific surface area of graphene, and by opening and roughening the fiber clusters and then grafting a graphene network, a graphene-modified fiber material with high strength and high toughness is obtained, further improving the strength and dispersibility of the fiber material in the concrete system and enhancing the crack resistance of the prepared concrete.

[0015] In a specific feasible implementation, the fiber is glass fiber, cold-drawn stainless steel fiber, or carbon fiber.

[0016] By adopting the above technical solution, glass fiber, cold-drawn stainless steel fiber, and carbon fiber all have relatively high strength and stiffness, can be dispersed in the concrete to form a network structure, and prevent the expansion of concrete cracks; at the same time, when the concrete surface is affected by factors such as temperature change or drying, it is easy to form cracks, and the doped fiber can effectively resist the occurrence of cracks and ensure the overall performance of the concrete.

[0017] In a specific feasible implementation, the modified calcium oxide-based expansive agent is prepared from calcium oxide clinker, phenolic resin, and setting regulator with a mass ratio of (990 - 996):(2 - 8):2. The specific preparation method includes the following steps: Dissolve the phenolic resin in an organic solvent, then add the calcium oxide clinker and stir evenly to form a mixture;

[0018] Dry and grind the mixture to a specific surface area of 500 - 700 m 2 / Kg to obtain modified calcium oxide clinker;

[0019] Mix the modified calcium oxide evenly with the setting regulator to obtain the modified calcium oxide-based expansive agent.

[0020] By adopting the above technical solution, the phenolic resin has a hydrophobic effect on the surface of the calcium oxide-based expansive clinker, reducing the hydration rate of the calcium oxide-based expansive agent, delaying the contact between the expansive agent and water, enabling the expansive agent to be slowly released during the construction process, reducing the ineffective consumption of the expansive agent in the plastic stage of cement concrete, and increasing the effective expansion energy after the concrete hardens; at the same time, using the setting regulator to form a composite system with the released calcium oxide clinker, delaying the hydration process of the calcium oxide clinker in contact with water, achieving the purpose of regulating the expansion process of the calcium oxide expansive agent, making its expansion deformation mainly form in the hardening stage of the concrete, and enhancing the compensating shrinkage effect on the concrete.

[0021] In addition, the phenolic resin can effectively prevent the clinker from absorbing moisture and becoming ineffective during the storage process of the expansive agent, extending the storage period of the clinker, and thus extending the shelf life of the finished expansive agent.

[0022] In a specific feasible implementation, the setting regulator is one or both of boric acid and sodium tartrate.

[0023] By adopting the above technical solution, the reason why the setting regulator can delay the hydration of cement may be as follows: The molecules of the setting regulator precipitate on the surface of cement particles, hindering the contact between cement and water, thus delaying the hydration of cement; The setting regulator forms a complex salt with Ca 2+ in the cement paste system, inhibiting the precipitation of Ca(OH)2 crystals; The surface of cement particles adsorbs the setting regulator, hindering the cement hydration process; From the induction period to the acceleration period of the cement hydration reaction, the setting regulator always hinders the nucleation of Ca(OH)2 crystals precipitated from the liquid phase. After the setting regulator is used in combination with the expansive agent, the hydration rate of the concrete is reduced, the restriction on free expansion is reduced, and its expansion mainly forms in the hardening stage of the concrete, improving the crack prevention performance of the concrete.

[0024] In a specific feasible embodiment, the method for preparing the calcium oxide clinker is as follows: Limestone and mineral filler with a mass ratio of (85-95):(5-15) are mixed and abrasive, and then calcined at a temperature of 1250-1450 °C, and after cooling, abrasive is carried out to prepare calcium oxide clinker with a specific surface area of 500-700 m 2 / Kg.

[0025] By adopting the above technical solution, adding mineral filler in the calcium oxide system can fill the voids in limestone, make the calcium oxide clinker more dense, thereby improving the strength and durability of the calcium oxide clinker; at the same time, the price of mineral filler is relatively low, which can replace part of the use of limestone, thereby reducing the cost of concrete; in addition, the fine particles in the mineral filler can also absorb and fix some harmful substances, thereby reducing environmental pollution.

[0026] In a specific feasible embodiment, the mineral filler is a mixture of gypsum, alumina and aluminum sulfate with a mass ratio of (50-100):(30-50):(10-50).

[0027] In a specific feasible embodiment, the raw materials of the crack-resistant concrete further include 2-4 parts by mass of a mixture of silica fume and shell powder, and the mass ratio of silica fume to shell powder is (1-3):1.

[0028] By adopting the above technical solution, silica fume, shell powder and composite fiber material are combined. Utilizing the connection effect of the composite fiber material and the filling effect of silica fume and shell powder, the fine cracks in the internal structure of the concrete are filled, so that the concrete has a good crack-resistant effect.

[0029] In the second aspect, the present application provides a method for preparing crack-resistant concrete, adopting the following technical solution:

[0030] A method for preparing crack-resistant concrete includes the following steps:

[0031] S1, Mix cement, fly ash, modified calcium oxide-based expansive agent, composite fiber material and water, and stir evenly to obtain cement slurry;

[0032] S2, Add the mixture of sand and gravel into the cement slurry and mix evenly to obtain crack-resistant concrete.

[0033] By adopting the above technical solution, cement, fly ash, modified calcium oxide-based expansive agent, composite fiber material and water are first mixed to facilitate uniform mixing, and then the mixture of sand and stones is added to the cement slurry. During the mixing process of stones and sand, larger particles of stones overlap with each other to form a skeleton, and smaller sand fills between the larger particles of stones, reducing the porosity of the skeleton; in the subsequent blending process, the skeleton is mixed with cement, with good uniformity, and the preparation method is efficient and fast.

[0034] In a specific feasible implementation, in the step S1, a mixture of shell powder and silica fume is also added.

[0035] In summary, the present application includes at least one of the following beneficial technical effects:

[0036] 1. In the present application, the polycarboxylate water reducer is modified by a silane coupling agent, and the polycarboxylate water reducer, silane coupling agent and modified fiber form a combination of organic matrix - silane coupling agent - inorganic matrix, enhancing the interaction force between the polycarboxylate water reducer and the fiber. Moreover, the silane coupling agent is reactive to the building substrate, enhancing the binding force between the composite fiber material and other components, while improving the dispersibility of the fiber in the system, increasing the internal binding force of the concrete, and thus improving the anti-cracking performance of the concrete;

[0037] 2. The present application utilizes the synergistic effect of the composite fiber material and the modified calcium oxide-based expansive agent. Under the combined action of the two, the anti-cracking performance of the concrete is improved;

[0038] 3. The present application utilizes the ultra-high strength, flexibility and large specific surface area of graphene, and by opening and roughening the fiber clusters and then grafting a graphene network, a high-strength and high-toughness graphene-modified fiber material is obtained, further improving the strength and dispersibility of the fiber material in the concrete system and enhancing the crack resistance of the prepared concrete;

[0039] 4. In the present application, through the combined action of phenolic resin and setting regulator on the calcium oxide expansive agent, the purpose of regulating the expansion process and speed of the calcium oxide expansive agent is achieved, enhancing the effect of compensating shrinkage of the concrete and improving the anti-cracking performance of the concrete. Specific Embodiments

[0040] The following further elaborates on the present application with preparation examples and implementation examples.

[0041] Preparation Examples

[0042] Preparation Example 1

[0043] The preparation example of the present application discloses a preparation method of a composite fiber material, including the following steps:

[0044] P1, preparation of modified fiber:

[0045] P11, 50 g of graphene was added to a mixture of 22.5 L of water and 2.5 L of ethanol. Glacial acetic acid was added while stirring to adjust the pH to 6. After stirring, a solution was formed. 30 g of TEC6300 activator was slowly added dropwise to the solution, and ultrasonic dispersion was performed for 40 min to obtain a graphene dispersion.

[0046] P12, weigh 4.5 kg of glass fiber, add it to 10 L of deionized water, adjust the pH to 9 with NaOH solution, ultrasonically disperse it for 60 min, filter it, and dry it in a drying oven at 105°C to constant weight to obtain pretreated glass fiber;

[0047] P13, adding 50 g of the above pretreated glass fiber to 150 ml of graphene dispersion, ultrasonically dispersing for 60 min, filtering, and drying in a drying oven at 105° C. to constant weight to obtain modified glass fiber;

[0048] P2, Preparation of modified polycarboxylate water reducer:

[0049] P21, in a dry, branched bottle equipped with a reflux condenser, add 10 g of polycarboxylate water-reducing agent and 30 ml of anhydrous tetrahydrofuran, stir, add 20 g of SOCl2 dropwise, heat under reflux at 66°C, and distill under reduced pressure to obtain a solid, which is then dissolved in anhydrous toluene to obtain a mixture;

[0050] P22, in a dry, branched flask equipped with a reflux condenser, add γ-aminopropyltrimethoxysilane and anhydrous toluene, heat to 76°C, add pyridine, and stir under a nitrogen atmosphere. Add the above mixture dropwise, heat to 85°C with stirring, and precipitate the product with methanol. After two cycles of dissolution / precipitation in a toluene / methanol mixed solvent, dry under vacuum at 45°C to constant weight to obtain a modified polycarboxylate superplasticizer.

[0051] P3, preparation of composite fiber material: 1 kg of modified polycarboxylate water-reducing agent and 24 kg of modified fiber were added to deionized water and blended for 10 minutes. NaOH solution was added dropwise to adjust the pH to 10. The mixture was heated at 50°C with stirring and continuously washed with trichloroacetic acid / deionized water until the solution pH reached 7 to obtain a composite fiber material.

[0052] Preparation Example 2

[0053] This preparation example is basically the same as Preparation Example 1, except that the preparation method of the modified fiber P1 is different, specifically:

[0054] P11, 50 g of graphene was added to a mixture of 22.5 L of water and 2.5 L of ethanol. Glacial acetic acid was added while stirring to adjust the pH to 7. After stirring, a solution was formed. 30 g of TEC6300 activator was slowly added dropwise to the solution, and ultrasonic dispersion was performed for 40 min to obtain a graphene dispersion.

[0055] P12, Weigh 4.5 Kg of glass fiber, add it to 10 L of deionized water, adjust the pH to 8 with NaOH solution, disperse it by ultrasonic for 60 min, filter it by suction, and then place it in a drying oven to dry at 105 °C until constant weight to obtain pretreated glass fiber;

[0056] P13, Add the above 150 g of pretreated glass fiber to 50 ml of graphene dispersion, disperse it by ultrasonic for 60 min, filter it by suction, and then place it in a drying oven to dry at 105 °C until constant weight to obtain modified glass fiber.

[0057] Preparation Example 3

[0058] This preparation example is basically the same as Preparation Example 1, the difference is that in P3, the preparation of the composite fiber material is different. Specifically: Add 2 Kg of modified polycarboxylate superplasticizer and 62.5 Kg of modified fiber to deionized water and mix for 10 min, add NaOH solution dropwise to adjust to 10, heat and stir at 50 °C, and continuously wash with trichloroacetic acid / deionized water until the pH of the solution is 7 to obtain the composite fiber material.

[0059] Preparation Example 4

[0060] This preparation example is basically the same as Preparation Example 1, the difference is that in P3, the preparation of the composite fiber material is different. Specifically: Add 3 Kg of modified polycarboxylate superplasticizer and 100 Kg of modified fiber to deionized water and mix for 10 min, add NaOH solution dropwise to adjust to 10, heat and stir at 50 °C, and continuously wash with trichloroacetic acid / deionized water until the pH of the solution is 7 to obtain the composite fiber material.

[0061] Preparation Example 5

[0062] This preparation example is basically the same as Preparation Example 3, the difference is that the glass fiber in P1 is replaced with an equal amount of cold-drawn stainless steel fiber.

[0063] Preparation Example 6

[0064] This preparation example is basically the same as Preparation Example 3, the difference is that the glass fiber in P1 is replaced with an equal amount of carbon fiber.

[0065] Preparation Example 7

[0066] This preparation example discloses a preparation method of a modified calcium oxide-based expansive agent, including the following steps:

[0067] P10, Preparation of calcium oxide clinker: Mix 850 g of limestone and 150 g of mineral filler (50 g of gypsum, 50 g of alumina, and 50 g of aluminum sulfate), and grind them in a ball mill to a specific surface area of 500 m 2Raw meal powder of / Kg; the raw meal powder is calcined at 1250 °C for 150 min and then quenched in air, and ground to a specific surface area of 500 m 2 / Kg to obtain calcium oxide clinker;

[0068] P20, Preparation of modified calcium oxide clinker: Dissolve 8 g of phenolic resin in 400 ml of absolute ethanol, stir evenly, add 990 g of the above calcium oxide clinker, stir evenly, dry at 60 °C for 3 h, remove the absolute ethanol, and grind the obtained solid to a specific surface area of 500 m 2 / Kg to obtain modified calcium oxide clinker;

[0069] P30, Preparation of modified calcium oxide expansive agent: Mix the above modified calcium oxide clinker with 2 g of boric acid.

[0070] Preparation Example 8

[0071] This preparation example discloses a preparation method of a modified calcium oxide-based expansive agent, including the following steps:

[0072] P10, Preparation of calcium oxide clinker: Mix 950 g of limestone and 50 g of mineral filler (30 g of gypsum, 15 g of alumina and 5 g of aluminum sulfate), and grind to a specific surface of 700 m 2 / Kg of raw meal powder; the raw meal powder is calcined at 1450 °C for 150 min and then quenched in air, and ground to a specific surface area of 700 m 2 / Kg to obtain calcium oxide clinker;

[0073] P20, Preparation of modified calcium oxide clinker: Dissolve 2 g of phenolic resin in 100 ml of absolute ethanol, stir evenly, add 996 g of the above calcium oxide clinker, stir evenly, dry at 60 °C for 3 h, remove the absolute ethanol, and grind the obtained solid to a specific surface area of 700 m 2 / Kg to obtain modified calcium oxide clinker;

[0074] P30, Preparation of modified calcium oxide expansive agent: Mix the above modified calcium oxide clinker, 1 g of boric acid and 1 g of sodium tartrate.

[0075] Preparation Example 9

[0076] This application's preparation example discloses a preparation method of a composite fiber material, including the following steps:

[0077] P1, Preparation of modified polycarboxylate superplasticizer:

[0078] P11. In a dry side-neck flask equipped with a reflux condenser, add 10 g of polycarboxylate superplasticizer and 30 ml of anhydrous tetrahydrofuran, stir, add dropwise 20 g of SOCl₂, heat under reflux at 66 °C, and distill under reduced pressure to obtain a solid. Dissolve the solid in anhydrous toluene to obtain a mixture;

[0079] P12. In a dry side-neck flask equipped with a reflux condenser, add γ-aminopropyltrimethoxysilane and anhydrous toluene, heat at 76 °C, add pyridine, stir under a nitrogen atmosphere, add dropwise the above mixture, heat and stir at 85 °C. The product is precipitated with methanol, dissolved and precipitated twice with a toluene / methanol mixed solvent, and then dried to constant weight at 45 °C under vacuum to obtain the modified polycarboxylate superplasticizer;

[0080] P2. Preparation of composite fiber material: Add 1 Kg of modified polycarboxylate superplasticizer and 25 Kg of glass fiber to deionized water and mix for 10 min. Add dropwise NaOH solution to adjust to pH 10, heat and stir at 50 °C, and continuously wash with trichloroacetic acid / deionized water until the solution pH is 7 to obtain the composite fiber material.

[0081] Preparation Example 10

[0082] This preparation example discloses a preparation method of a calcium oxide-based expansive agent. The specific process is as follows: Mix 850 g of limestone and 150 g of mineral fillers (50 g of gypsum, 50 g of alumina, and 50 g of aluminum sulfate), and grind them in a ball mill to a raw meal powder with a specific surface area of 500 m 2 / Kg; Calcinate the raw meal powder at 1250 °C for 150 min and then rapidly cool it in air, and grind it to a specific surface area of 500 m 2 / Kg to obtain it.

[0083] Preparation Example 11

[0084] This preparation example discloses a preparation method of a modified calcium oxide-based expansive agent, including the following steps:

[0085] P10. Preparation of calcium oxide clinker: Mix 850 g of limestone and 150 g of mineral fillers (50 g of gypsum, 50 g of alumina, and 50 g of aluminum sulfate), and grind them in a ball mill to a raw meal powder with a specific surface area of 500 m 2 / Kg; Calcinate the raw meal powder at 1250 °C for 150 min and then rapidly cool it in air, and grind it to a specific surface area of 500 m 2 / Kg to obtain calcium oxide clinker;

[0086] P20. Preparation of modified calcium oxide clinker: Dissolve 10 g of phenolic resin in 500 ml of anhydrous ethanol, stir evenly, add 990 g of the above calcium oxide clinker, stir evenly, dry at 60 °C for 3 h, remove anhydrous ethanol, and grind the obtained solid to a specific surface area of 500 m 2Obtain the modified calcium oxide expansive agent by / Kg.

[0087] Preparation Example 12

[0088] This preparation example discloses a preparation method of a modified calcium oxide-based expansive agent, including the following steps:

[0089] P10, Preparation of calcium oxide clinker: Mix 850 g of limestone and 150 g of mineral fillers (50 g of gypsum, 50 g of alumina, and 50 g of aluminum sulfate), and then grind them in a ball mill to a specific surface area of 500 m 2 / Kg of raw meal powder; Calcinate the raw meal powder at 1250 °C for 150 min and then rapidly cool it in air, and grind it to a specific surface area of 500 m 2 / Kg to obtain calcium oxide clinker;

[0090] P20, Preparation of modified calcium oxide expansive agent: Mix the above 990 g of calcium oxide clinker with 10 g of boric acid.

[0091] Examples

[0092] Examples 1 - 13

[0093] As shown in Table 1, the difference between Preparation Examples 1 - 13 lies in the different raw material ratios of the crack-resistant concrete.

[0094] The following takes Example 1 as an illustration. The example of the present application discloses a crack-resistant concrete, which is prepared from 300 Kg of cement, 900 Kg of gravel, 300 Kg of sand, 90 Kg of fly ash, 30 Kg of modified calcium oxide-based expansive agent, 5 Kg of composite fiber material, and 150 Kg of water. Among them, the fineness of the sand is 2.7, the apparent density is, 2650 Kg / m 3 , and the bulk density is 1560 Kg / m 3 ; The cement is P.0425.5; The fly ash is Class I fly ash, with a loss on ignition ≤ 3%, a residue on 45 μm sieve ≤ 10%, a water demand ratio ≤ 95%, and a water content ≤ 1%; The particle size of the gravel is 5 - 25 mm continuous grading, the apparent density is 2650 Kg / m 3 , the loose bulk porosity is 47%, and the loose bulk density is 1575 Kg / m 3 ; The modified calcium oxide-based expansive agent is obtained from Preparation Example 7, and the composite fiber material is obtained from Preparation Example 1.

[0095] Table 1 Raw material ratios of crack-resistant concrete in Examples 1 - 13

[0096]

[0097] The example of the present application also discloses a preparation method of crack-resistant concrete, which specifically adopts the following steps:

[0098] S1. Weigh cement, fly ash, modified calcium oxide-based expansive agent, composite fiber material and water according to the formula, mix them and stir evenly to obtain cement slurry;

[0099] S2. Weigh sand and gravel according to the formula, mix them and then add the above cement slurry, mix evenly to obtain crack-resistant concrete.

[0100] Example 14

[0101] This example is basically the same as Example 12, the difference is that in this example, the raw materials of the crack-resistant concrete further include 1 Kg of silica fume and 1 Kg of shell powder, and the preparation method of the crack-resistant concrete is as follows:

[0102] S1. Weigh cement, fly ash, modified calcium oxide-based expansive agent, composite fiber material and water according to the formula to obtain a mixture, mix silica fume and shell powder and add them to the mixture, stir evenly to obtain cement slurry;

[0103] S2. Weigh sand and gravel according to the formula, mix them and then add the above cement slurry, mix evenly to obtain crack-resistant concrete.

[0104] Example 15

[0105] This example is basically the same as Example 14, the difference is that in this example, the raw materials of the crack-resistant concrete further include 1 Kg of silica fume and 2 Kg of shell powder.

[0106] Example 16

[0107] This example is basically the same as Example 14, the difference is that in this example, the raw materials of the crack-resistant concrete further include 1 Kg of silica fume and 3 Kg of shell powder.

[0108] Example 17

[0109] This example is basically the same as Example 15, the difference is that in this example, the composite fiber material is obtained from Preparation Example 2, and the modified calcium oxide-based expansive agent is obtained from Preparation Example 8.

[0110] Example 18

[0111] This example is basically the same as Example 15, the difference is that in this example, the composite fiber material is obtained from Preparation Example 3.

[0112] Example 19

[0113] This example is basically the same as Example 15, the difference is that in this example, the composite fiber material is obtained from Preparation Example 4.

[0114] Example 20

[0115] This embodiment is basically the same as Embodiment 15, except that the composite fiber material in this embodiment is obtained from Preparation Example 5.

[0116] Embodiment 21

[0117] This embodiment is basically the same as Embodiment 15, except that the composite fiber material in this embodiment is obtained from Preparation Example 6.

[0118] Comparative Example

[0119] Comparative Example 1

[0120] The difference between this comparative example and Embodiment has the following raw material ratio for the anti-cracking concrete: prepared from 300 Kg of cement, 900 Kg of stones, 300 Kg of sand, 90 Kg of fly ash, 35 Kg of modified calcium oxide-based expansive agent, and 150 Kg of water.

[0121] Comparative Example 2

[0122] The difference between this comparative example and Embodiment has the following raw material ratio for the anti-cracking concrete: prepared from 300 Kg of cement, 900 Kg of stones, 300 Kg of sand, 90 Kg of fly ash, 35 Kg of composite fiber material, and 150 Kg of water.

[0123] Comparative Example 3

[0124] The difference between this comparative example and Embodiment has the following raw material ratio for the anti-cracking concrete: prepared from 300 Kg of cement, 900 Kg of stones, 300 Kg of sand, water 150 Kg, 90 Kg of fly ash, 30 Kg of modified calcium oxide-based expansive agent, 0.2 Kg of polycarboxylate water reducer, and 4.8 Kg of modified glass fiber, where the modified glass fiber is obtained from Preparation Example 1.

[0125] Comparative Example 4

[0126] The difference between this comparative example and Comparative Example 1 is that the composite fiber material in the raw materials of the anti-cracking concrete is obtained from Preparation Example 9.

[0127] Comparative Example 5

[0128] The difference between this comparative example and Comparative Example 1 has the following raw material ratio for the anti-cracking concrete: prepared from 300 Kg of cement, 900 Kg of stones, 300 Kg of sand, 90 Kg of fly ash, 30 Kg of calcium oxide-based expansive agent, 5 Kg of composite fiber material, and 150 Kg of water, where the calcium oxide expansive agent is obtained from Preparation Example 10.

[0129] Comparative Example 6

[0130] The difference between this comparative example and comparative example 1 is that the modified calcium oxide expansive agent in the anti-cracking concrete raw material is obtained from Preparation Example 11.

[0131] Comparative Example 7

[0132] The difference between this comparative example and comparative example 1 is that the modified calcium oxide expansion agent in the anti-cracking concrete raw material is obtained from Preparation Example 12.

[0133] Performance testing

[0134] The same weight of concrete obtained from Examples 1-21 and Comparative Examples 1-7 was subjected to performance testing. The results are shown in Table 2.

[0135] The specific test process is as follows: the concrete obtained from the embodiment and the comparative example are respectively loaded into the test mold at one time. When loading, a spatula is used to tamp along the walls of each test mold. Then, the test mold is placed on a vibration table and vibrated twice. The excess anti-cracking concrete at the test mold opening is scraped off. Then, it is smoothed with a spatula and placed in a concrete curing box for curing for 24 hours. Finally, the mold is removed and moved to a standard concrete curing room for curing. After 28 days, it is taken out and the following test is performed.

[0136] Compressive strength and splitting tensile strength: Tested in accordance with GB / T50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete".

[0137] Table 2 Performance test data of Examples 1-21 and Comparative Examples 1-7

[0138]

[0139]

[0140] Referring to Table 2, in conjunction with Example 1 and Comparative Examples 1-2, it can be seen that the simultaneous addition of composite fiber material and modified calcium oxide expansive agent to the concrete system in the present application improves the mechanical strength of the concrete through the combined action of the two, and the anti-cracking performance of the concrete is superior to the anti-cracking performance of the concrete obtained by adding the composite fiber material and modified calcium oxide expansive agent separately. The composite fiber material can utilize its inherent fibrous properties to form a network structure within the concrete, which acts as a link to the concrete matrix, improves the compressive strength and splitting strength of the concrete, and thus improves the anti-cracking performance of the concrete. The modified calcium oxide expansive agent generates bubbles and tiny cracks during the concrete formation process, which changes the internal structure of the crystals in the concrete, reduces internal lattice stress, reduces the shrinkage and cracking tendency of the concrete, and improves the anti-cracking performance of the concrete. It can be seen that the composite fiber material and the modified calcium oxide expansive agent improve the anti-cracking performance of the concrete through different mechanisms, and have a good synergistic effect.

[0141] Referring to Table 2 and combining Example 1 and Comparative Example 3, it can be seen that when the polycarboxylate water reducer is not modified and then blended with modified glass fibers and added to the concrete system, the mechanical properties of the formed concrete decrease, that is, the anti-cracking effect is not good; in this application, after the polycarboxylate water reducer is modified with a silane coupling agent and then reacted with the fibers, the dispersibility of the fibers in the concrete system is improved, the internal bonding force of the concrete is increased, the mechanical strength of the concrete is increased, and thus the anti-cracking performance of the concrete is improved.

[0142] Referring to Table 2 and combining Example 1 and Comparative Example 4, it can be seen that when the glass fibers react with the modified polycarboxylate water reducer to form a composite fiber material (the glass fibers are not modified) and added to the concrete system, the mechanical properties of the concrete decrease; in this application, the glass fibers are modified with graphene. By using the ultra-high strength, flexibility and large specific surface area of graphene, and by opening and roughening the fiber clusters and then grafting the graphene network, a graphene-modified fiber material with high strength and high toughness is obtained, further improving the strength and dispersibility of the fiber material in the concrete system and enhancing the crack resistance of the prepared concrete.

[0143] Referring to Table 2 and combining Example 1 and Comparative Examples 5-7, it can be seen that the modified calcium oxide-based expansive agent formed by modifying the calcium oxide-based expansive agent and compounding a setting regulator in combination in this application has a better anti-seepage effect on concrete compared with the pure calcium oxide-based expansive agent (Comparative Example 5), the calcium oxide-based expansive agent modified with phenolic resin (Comparative Example 6), and the calcium oxide-based expansive agent compounded with a setting regulator (Comparative Example 7). The phenolic resin in this application has a hydrophobic effect on the surface of the inner-expanded clinker of calcium oxide, reducing the hydration rate of the calcium oxide-based expansive agent, delaying the contact between the expansive agent and water, enabling the expansive agent to be slowly released during the construction process, reducing the ineffective consumption of the expansive agent in the plastic stage of cement concrete, and increasing the effective expansion energy after the concrete hardens; at the same time, by using the setting regulator to form a composite system with the released calcium oxide clinker, the hydration process of the calcium oxide clinker in contact with water is delayed, achieving the purpose of regulating the expansion process of the calcium oxide expansive agent, so that its expansion deformation is mainly formed in the hardening stage of the concrete, improving the compensating shrinkage effect on the concrete. Thus, it can be seen that the phenolic resin and the setting regulator have a good synergistic effect. Under the modification effect of the phenolic resin and the regulation effect of the setting regulator, the calcium oxide-based expansive agent improves the anti-seepage effect of the concrete.

[0144] This specific embodiment is only an explanation of this application and is not a limitation of this application. After reading this specification, those skilled in the art can make modifications without creative contributions to this embodiment as needed, but as long as they are within the scope of the claims of this application, they are protected by the patent law.

Claims

1. A crack-resistant concrete, characterized by: The invention is prepared from the following raw materials in parts by weight: 300-400 parts of cement, 900-1100 parts of gravel, 300-400 parts of sand, 90-110 parts of fly ash, 30-50 parts of modified calcium oxide expansion agent, 5-15 parts of composite fiber material and 150 parts of water; The preparation method of the composite fiber material comprises the following steps: After mixing a polycarboxylate water-reducing agent and a first solvent, SOCl2 is added dropwise, heated under reflux, and a solid is obtained, followed by dissolving the solid in a second solvent to obtain a mixture; a silane coupling agent and the second solvent are mixed, heated, an organic weak base is added, and the mixture is stirred under an inert gas atmosphere, and the mixture is added, stirred, and post-treated to obtain a modified polycarboxylate water-reducing agent; The modified polycarboxylate water-reducing agent and the modified fiber in a mass ratio of (1-3): (25-100) are added to deionized water and blended, the pH is adjusted to alkaline, heated and stirred, and continuously washed with trichloroacetic acid / deionized water until the pH of the solution reaches 7 to obtain a composite fiber material; The modified fiber preparation method comprises: mixing water and fiber, adding an alkaline solution to adjust the pH to 8-9, uniformly dispersing, filtering, and drying to obtain pretreated fiber; adding (50-150) g of the pretreated fiber to (50-150) ml of a graphene dispersion liquid containing an active agent and having a pH of 6-7, uniformly dispersing, and filtering; The modified calcium oxide expansion agent is prepared from calcium oxide clinker, phenolic resin and setting agent in a mass ratio of (990-996): (2-8):

2. The specific preparation method includes the following steps: Dissolving phenolic resin in an organic solvent, adding calcium oxide clinker and stirring to form a mixture; The mixture is dried and ground to a specific surface area of 500-700 m 2 / Kg to obtain modified calcium oxide clinker; The modified calcium oxide clinker is mixed evenly with a setting regulator to obtain a modified calcium oxide expansion agent.

2. The anti-cracking concrete according to claim 1, characterized in that: The fibers are glass fibers, cold-drawn stainless steel fibers or carbon fibers.

3. The anti-cracking concrete according to claim 1, characterized in that: The coagulant is one or both of boric acid and sodium tartrate.

4. The anti-cracking concrete according to claim 1, characterized in that: The preparation method of the calcium oxide clinker is as follows: limestone and mineral filler are mixed in a mass ratio of (85-95): (5-15), ground, calcined at a temperature of 1250-1450°C, and ground after cooling to prepare a specific surface area of 500-700m 2 / Kg of calcium oxide clinker.

5. The anti-cracking concrete according to claim 4, characterized in that: The mineral filler is a mixture of gypsum, aluminum oxide and aluminum sulfate in a mass ratio of (50-100): (30-50): (10-50).

6. The anti-cracking concrete according to claim 1, characterized in that: The anti-cracking concrete raw materials also include a mixture of 2-4 parts by mass of silicon micropowder and shell powder, and the mass ratio of silicon micropowder to shell powder is (1-3):

1.

7. The method for preparing the anti-cracking concrete according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, mixing cement, fly ash, modified calcium oxide expansion agent, composite fiber material and water, and stirring uniformly to obtain cement slurry; S2, adding sand and gravel into cement slurry, mixing and stirring evenly to obtain anti-cracking concrete.

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