Low-modulus high-ductility super-retarded concrete and preparation method thereof

Abstract

The application discloses a kind of low modulus high ductility super-retarding concrete, the concrete includes by weight ratio: cement 254~360 parts, fly ash 68~108 parts, slag powder 68~70 parts, 5~16mm gravel 352~393 parts, 16~25mm gravel 660~729 parts, medium sand 669~705 parts, rubber powder 20 parts, polystyrene plastic 15 parts, water 150 parts, water reducing agent 5.9~7.5 parts, super-retarding agent 3.1~4.0 parts, water-based polyurethane 15 parts, nano composite hydrogel 15 parts, polyolefin elastomer 5 parts, polypropylene fiber 1.0 part, can have higher toughness, lower elastic modulus, and can reach design requirement strength and durability, simultaneously, when practical application, first, a layer of low modulus high ductility super-retarding concrete is poured, then continue to pour ordinary concrete, combined with other anti-cracking measures, can effectively reduce the constraint degree of bottom plate to upper portion, prevent temperature cracks.

Description

Technical Field

[0001] This invention relates to the field of hydraulic engineering materials technology, specifically to a low-modulus, high-ductility, ultra-retarded concrete and its preparation method. Background Technology

[0002] Hydraulic concrete has a wide range of applications in water conservancy construction. It is often used in hydraulic structures such as sluice gates and gate piers that are subjected to severe water scouring, as well as in areas with frequent water level fluctuations such as dams and canals. It is a major material in water conservancy engineering construction and belongs to the category of mass concrete. At present, due to the large-scale application of pumped concrete and ready-mixed concrete, as well as the accelerated construction progress and the decline in the quality of raw materials, concrete is prone to problems such as early temperature rise, rapid increase in elastic modulus, and large temperature deformation. The problem of temperature cracking in hydraulic concrete is becoming increasingly prominent, and crack prevention has become more difficult, posing a serious threat to the durability and structural safety of concrete.

[0003] To address the problem of temperature cracking, current technical measures mainly include arranging anti-crack reinforcement, using mineral admixtures to replace cement to reduce the heat of hydration of concrete, and incorporating anti-crack fibers to reduce early shrinkage of concrete, disperse cracks, and reduce crack width. However, the mechanism of temperature cracking is complex, and addressing it from only one aspect cannot effectively control the generation and development of cracks. Currently, a large number of hydraulic concrete structures still exhibit temperature cracks, and some are even quite severe. Summary of the Invention

[0004] The purpose of this invention is to provide a low-modulus, high-ductility, ultra-retarded concrete and its preparation method, which can have high toughness, low modulus of elasticity, and achieve the design requirements for strength and durability. In practical applications, a layer of low-modulus, high-ductility, ultra-retarded concrete is first poured, followed by ordinary concrete. When used in combination with other anti-cracking measures, it can effectively reduce the degree of constraint of the base plate on the upper part and prevent temperature cracks.

[0005] According to the present invention, a low-modulus, high-ductility, super-retarded concrete comprises, by weight: 254-360 parts cement, 68-108 parts fly ash, 68-70 parts slag powder, 352-393 parts 5-16mm crushed stone, 660-729 parts 16-25mm crushed stone, 669-705 parts medium sand, 20 parts rubber powder, 15 parts polystyrene plastic, 150 parts water, 5.9-7.5 parts water-reducing agent, 3.1-4.0 parts super-retarder, 15 parts waterborne polyurethane, 15 parts nano-composite hydrogel, 5 parts polyolefin elastomer, and 1.0 part polypropylene fiber.

[0006] Furthermore, P·O 52.5 grade cement with a specific surface area of ​​340 m² is used. 2 / kg.

[0007] Furthermore, the fly ash used is Class F, Grade II fly ash, with a specific surface area of ​​303 m². 2 / kg, water requirement ratio is 94%.

[0008] Furthermore, the slag powder used is S95 grade slag powder, with a specific surface area of ​​449 m2 / kg, a 7-day activity index of 81%, a 28-day activity index of 96%, and a fluidity ratio of 107%.

[0009] Furthermore, the apparent density of the crushed stone is 2950 kg / m³. 3 It has a mud content of 0.5%, a needle-like and flaky content of 4%, and a crushing value of 8%.

[0010] Furthermore, the medium sand used is zone II medium sand, with an apparent density of 2620 kg / m³. 3 The mud content is 1.2%, and the fineness modulus is 2.6.

[0011] Furthermore, the rubber powder is made from waste tires through processing. It is granular with a fineness of 50 mesh and an apparent density of 1050 kg / m³. 3 .

[0012] Furthermore, polystyrene plastic is a rigid, transparent solid with an apparent density of 1040 kg / m³. 3 .

[0013] Furthermore, the water-reducing agent is a polycarboxylate high-efficiency water-reducing agent with a water reduction rate of 20%~30% and a solid content of 20.44%.

[0014] Furthermore, the super retarder is a hydroxycarboxylic acid retarder with a solid content of 18.9%, a density of 1.08 g / cm3, and a pH value of 7.28.

[0015] Furthermore, the waterborne polyurethane is synthesized from raw materials such as toluene diisocyanate, polyol, dihydroxypropionic acid, and diluent, with a solid content of 55%.

[0016] Furthermore, the nanocomposite hydrogel is an organosilicon-polyvinyl alcohol nanocomposite hydrogel, prepared by the sol-gel method, with a tensile strength of not less than 1.6 MPa, a compressive strength of not less than 0.6 MPa, and a water content of greater than 82%.

[0017] Furthermore, the polyolefin elastomer is a copolymer of ethylene and octene, with a melt flow rate of 28 g / 10 min.

[0018] Furthermore, the polypropylene fibers have a length of 12 mm, a diameter of 31 μm, and a density of 0.91 g / cm³. 3 Its elastic modulus is 4.65 GPa and its elongation is 19.69%.

[0019] A method for preparing low-modulus, high-ductility, ultra-slow-release concrete as described above includes the following steps: Step 1: Mix the coarse aggregate and fine aggregate evenly in the mixing device; then add the cement, fly ash and slag powder to the mixing device and mix evenly. Step 2: Add the rice composite hydrogel and polyolefin elastomer to the mixing device and stir evenly; then add the water-reducing agent, super retarder, waterborne polyurethane, and water evenly to the mixing device and stir evenly. Step 3: Add polypropylene fibers to a mixing device and mix evenly to obtain pre-concrete; Step 4: After the pre-mixed concrete is thoroughly stirred, it is transferred to a mold and poured to form a specimen; Step 5: Cur the specimens in a standard curing chamber at a temperature of 20±2℃ and a relative humidity of 95% until the specified age to obtain the low modulus of elasticity, high ductility, and ultra-retarded concrete.

[0020] The beneficial effects of this invention are as follows: 1. In this invention, industrial solid wastes such as fly ash and slag powder are used to replace part of the cement. This reduces engineering costs, enables the reuse of solid waste, improves the workability of concrete, reduces the heat of hydration of concrete, and reduces the occurrence of temperature cracks.

[0021] 2. In this invention, rubber powder is added to concrete to realize the resource utilization of solid waste, reduce land occupation, save natural resources, improve the environment, and at the same time improve the toughness and crack resistance of concrete, reduce the elastic modulus of concrete, and improve the brittle failure characteristics of traditional concrete.

[0022] 3. Compared to traditional methods that control the generation and development of temperature cracks from a single aspect, this invention starts from the crack prevention mechanism of concrete. By adjusting the concrete mix ratio, replacing part of the cement with fly ash and slag powder reduces the heat of hydration and decreases the formation of early temperature cracks. Polypropylene fibers and organosilicon-polyvinyl alcohol nanocomposite hydrogels are added to enhance the toughness and crack resistance of concrete. Rubber powder, polystyrene plastic, waterborne polyurethane, and polyolefin elastomers are added to enhance and reduce the elastic modulus of concrete. This achieves effective prevention and control of temperature cracks in concrete from multiple aspects. At the same time, the concrete prepared by this invention is carried out at room temperature, which requires less mixing equipment, is simple to operate, and has a lower cost. Attached Figure Description

[0023] Figure 1 The diagram shows the characteristic values ​​of bending toughness for Embodiment 1 and Comparative Example 1 of the present invention.

[0024] Figure 2 The diagram shows the characteristic values ​​of bending toughness for Embodiment 2 and Comparative Example 2 of the present invention.

[0025] Figure 3 The diagram shows the characteristic values ​​of bending toughness for Embodiment 3 and Comparative Example 3 of the present invention.

[0026] Figure 4 The diagram shows the characteristic values ​​of bending toughness in Examples 1-3 and Comparative Examples 1-3 of the present invention.

[0027] Figure 5 The diagram shows the condensation time of Examples 1-3 and Comparative Examples 1-3 of the present invention.

[0028] Figure 6 The elastic modulus diagrams are for Embodiments 1-3 and Comparative Examples 1-3 of the present invention. Detailed Implementation To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0029] A low-modulus, high-ductility, ultra-retarded concrete comprises, by weight, 254-360 parts cement, 68-108 parts fly ash, 68-70 parts slag powder, 352-393 parts 5-16mm crushed stone, 660-729 parts 16-25mm crushed stone, 669-705 parts medium sand, 20 parts rubber powder, 15 parts polystyrene plastic, 150 parts water, 5.9-7.5 parts water-reducing agent, 3.1-4.0 parts ultra-retarding agent, 15 parts waterborne polyurethane, 15 parts nano-composite hydrogel, 5 parts polyolefin elastomer, and 1.0 part polypropylene fiber.

[0030] The cement used is P·O 52.5 grade cement with a specific surface area of ​​340 m2 / kg.

[0031] The fly ash used is Class F, Grade II fly ash, with a specific surface area of ​​303 m² / kg and a water requirement ratio of 94%.

[0032] The slag powder used is S95 grade slag powder, with a specific surface area of ​​449 m2 / kg, a 7-day activity index of 81%, a 28-day activity index of 96%, and a fluidity ratio of 107%.

[0033] The crushed stone is 5~25mm continuously graded crushed stone, with an apparent density of 2950kg / m3, a mud content of 0.5%, a needle-like and flaky content of 4%, and a crushing value of 8%.

[0034] The medium sand used is zone II medium sand, with an apparent density of 2620 kg / m3, a mud content of 1.2%, and a fineness modulus of 2.6.

[0035] The rubber powder is made from waste tires and is in granular form with a fineness of 50 mesh and an apparent density of 1050 kg / m3.

[0036] Polystyrene plastic is a rigid, transparent solid with an apparent density of 1040 kg / m³.

[0037] The water-reducing agent is a polycarboxylate high-efficiency water-reducing agent with a water reduction rate of 20%~30% and a solid content of 20.44%.

[0038] The super retarder is a hydroxycarboxylic acid retarder with a solid content of 18.9%, a density of 1.08 g / cm3, and a pH of 7.28.

[0039] Waterborne polyurethane is synthesized from raw materials such as toluene diisocyanate, polyol, dihydroxypropionic acid, and diluent, with a solid content of 55%.

[0040] The nanocomposite hydrogel is an organosilicon-polyvinyl alcohol nanocomposite hydrogel, prepared by the sol-gel method, with a tensile strength of not less than 1.6 MPa, a compressive strength of not less than 0.6 MPa, and a water content of more than 82%.

[0041] The polyolefin elastomer is a copolymer of ethylene and octene, with a melt flow rate of 28 g / 10 min.

[0042] The polypropylene fiber has a length of 12 mm, a diameter of 31 μm, a density of 0.91 g / cm3, an elastic modulus of 4.65 GPa, and an elongation of 19.69%.

[0043] A method for preparing the above-mentioned low-modulus, high-ductility, ultra-slow-release concrete includes the following steps: Step 1: Mix the coarse aggregate and fine aggregate evenly in the mixing device; then add the cement, fly ash and slag powder to the mixing device and mix evenly. Step 2: Add the rice composite hydrogel and polyolefin elastomer to the mixing device and stir evenly; then add the water-reducing agent, super retarder, waterborne polyurethane, and water evenly to the mixing device and stir evenly. Step 3: Add polypropylene fibers to a mixing device and mix evenly to obtain pre-concrete; Step 4: After the pre-mixed concrete is thoroughly stirred, it is transferred to a mold and poured to form a specimen; Step 5: Cur the specimens in a standard curing chamber at a temperature of 20±2℃ and a relative humidity of 95% until the specified age to obtain low modulus of elasticity, high toughness, and ultra-retarded concrete.

[0044] The beneficial effects of this invention are as follows: 1. In this invention, industrial solid wastes such as fly ash and slag powder are used to replace part of the cement. This reduces engineering costs, enables the reuse of solid waste, improves the workability of concrete, reduces the heat of hydration of concrete, and reduces the occurrence of temperature cracks.

[0045] 2. In this invention, rubber powder is added to concrete to realize the resource utilization of solid waste, reduce land occupation, save natural resources, improve the environment, and at the same time improve the toughness and crack resistance of concrete, reduce the elastic modulus of concrete, and improve the brittle failure characteristics of traditional concrete.

[0046] 3. Compared to traditional methods that control the generation and development of temperature cracks from a single aspect, this invention starts from the crack prevention mechanism of concrete. By adjusting the concrete mix ratio, replacing part of the cement with fly ash and slag powder reduces the heat of hydration and decreases the formation of early temperature cracks. Polypropylene fibers and organosilicon-polyvinyl alcohol nanocomposite hydrogels are added to enhance the toughness and crack resistance of concrete. Rubber powder, polystyrene plastic, waterborne polyurethane, and polyolefin elastomers are added to enhance and reduce the elastic modulus of concrete. This achieves effective prevention and control of temperature cracks in concrete from multiple aspects. At the same time, the concrete prepared by this invention is carried out at room temperature, which requires less mixing equipment, is simple to operate, and has a lower cost.

[0047] It is worth noting that the specific explanation of "low elastic modulus, high ductility, and ultra-retarded setting" in the title of this invention is as follows: The elastic modulus is lower than the 30.0 GPa requirement in the "Code for Design of Concrete Structures" (GB 50010-2010), classifying it as low elastic modulus concrete; the flexural toughness is greater than the 5 MPa requirement in the "Technical Standard for Application of High Ductility Concrete" (DB62T 3159-2019), classifying it as high ductility concrete. Ultra-retarded setting refers to a significant extension of the setting time of cement-based materials, far exceeding the level of ordinary retarded concrete. Currently, according to GB / T 50080 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures," the initial setting time of ordinary concrete is around 6 hours, and the final setting time is around 10 hours. According to the group standard "Technical Specification for Design and Construction of Ultra-Retarded Concrete" (T / CI) issued by the China International Association for the Promotion of Science and Technology,... —2024), the initial setting time should be greater than 60 h, the final setting time should be less than 120 h, and the difference between the initial and final setting times should be less than 20 h.

[0048] It is worth noting that when the setting time is mentioned separately in this invention, it always refers to the initial setting time.

[0049] Example 1: Concrete was prepared by mixing 254 parts cement, 68 parts fly ash, 68 parts slag powder, 729 parts 16-25mm crushed stone, 393 parts 5-16mm crushed stone, 688 parts medium sand, 20 parts rubber powder, 15 parts polystyrene plastic, 150 parts water, 5.9 parts water-reducing agent, 3.1 parts super retarder, 15 parts waterborne polyurethane, 15 parts organosilicon-polyvinyl alcohol nanocomposite hydrogel, 5 parts polyolefin elastomer, and 1.0 part polypropylene fiber using the preparation method provided in this invention. The slump and setting time were then tested.

[0050] Specimens of 100mm×100mm×100mm, 100mm×100mm×300mm, and 100mm×100mm×400mm were formed and cured for 28 days in a standard curing room at 20±2℃ and 95% relative humidity. The setting time of the concrete was measured to be 72.3h, the slump to be 225mm, the compressive strength at 7 days and 28 days to be 21.3MPa and 42.1MPa, the flexural strength at 7 days and 28 days to be 2.8MPa and 4.5MPa, the splitting tensile strength at 7 days and 28 days to be 3.1MPa and 4.5MPa, and the elastic modulus to be 24.2GPa, which is less than that specified in the "Code for Design of Concrete Structures" (GB). The elastic modulus requirement of 30.0 GPa in the "Technical Standard for Application of High Ductility Concrete" (DB62T3159-2019) indicates that it belongs to low elastic modulus concrete. The characteristic value of flexural toughness is 5.24 MPa, which is greater than the flexural toughness requirement of 5 MPa in the "Technical Standard for Application of High Ductility Concrete" (DB62T3159-2019). It belongs to high ductility concrete. The setting time is 72.3 h, which belongs to ultra-slow setting concrete.

[0051] Example 2: Concrete was prepared by mixing 264 parts cement, 108 parts fly ash, 68 parts slag powder, 709 parts 16-25mm crushed stone, 382 parts 5-16mm crushed stone, 669 parts medium sand, 20 parts rubber powder, 15 parts polystyrene plastic, 150 parts water, 6.6 parts water-reducing agent, 3.5 parts super retarder, 15 parts waterborne polyurethane, 15 parts organosilicon-polyvinyl alcohol nanocomposite hydrogel, 5 parts polyolefin elastomer, and 1.0 part polypropylene fiber. Its slump and setting time were then tested.

[0052] Specimens of 100mm×100mm×100mm, 100mm×100mm×300mm, and 100mm×100mm×400mm were formed and cured for 28 days in a standard curing room at 20±2℃ and 95% relative humidity. The setting time of the concrete was measured to be 74.4 hours, the slump to be 220mm, the compressive strength at 7 days and 28 days to be 30.4MPa and 43.3MPa, the flexural strength at 7 days and 28 days to be 3.9MPa and 5.6MPa, the splitting tensile strength at 7 days and 28 days to be 4.0MPa and 4.6MPa, and the modulus of elasticity to be 24.3GPa, which is less than that specified in the "Code for Design of Concrete Structures" (GB). The elastic modulus requirement of 32.5 GPa in the "Technical Standard for Application of High Ductility Concrete" (DB62T3159-2019) indicates that it belongs to low elastic modulus concrete. The characteristic value of flexural toughness is 6.40 MPa, which is greater than the flexural toughness requirement of 5 MPa in the "Technical Standard for Application of High Ductility Concrete" (DB62T3159-2019). It belongs to high ductility concrete. The setting time is 72.3 h, which belongs to ultra-slow-setting concrete.

[0053] Example 3: Concrete was prepared by mixing 360 parts cement, 70 parts fly ash, 70 parts slag powder, 660 parts 16-25mm crushed stone, 355 parts 5-16mm crushed stone, 705 parts medium sand, 20 parts rubber powder, 15 parts polystyrene plastic, 150 parts water, 7.5 parts water-reducing agent, 4.0 parts super retarder, 15 parts waterborne polyurethane, 15 parts organosilicon-polyvinyl alcohol nanocomposite hydrogel, 5 parts polyolefin elastomer, and 1.0 part polypropylene fiber. Its slump and setting time were then tested.

[0054] Specimens of 100mm×100mm×100mm, 100mm×100mm×300mm, and 100mm×100mm×400mm were formed and cured for 28 days in a standard curing room at 20±2℃ and 95% relative humidity. The setting time of the concrete was measured to be 75.2 hours, the slump to be 225mm, the compressive strength at 7 days and 28 days to be 41.1MPa and 53.9MPa, the flexural strength at 7 days and 28 days to be 4.1MPa and 6.4MPa, the splitting tensile strength at 7 days and 28 days to be 4.4MPa and 5.2MPa, and the modulus of elasticity to be 26.4GPa, which is less than that specified in the "Code for Design of Concrete Structures" (GB). The elastic modulus requirement of 34.5 GPa in the "50010-2010" indicates that the flexural toughness characteristic value of low elastic modulus concrete is 7.81 MPa, which is greater than the flexural toughness requirement of 5 MPa in the "Technical Standard for Application of High Ductility Concrete" (DB62T3159-2019). Therefore, it belongs to high ductility concrete. The setting time is 72.3 h, which belongs to ultra-slow-setting concrete.

[0055] Comparative Example 1: Concrete was prepared by mixing 390 parts cement, 660 parts 16-25mm crushed stone, 355 parts 5-16mm crushed stone, 705 parts medium sand, 150 parts water, and 7.5 parts water-reducing agent, and its slump and setting time were tested.

[0056] Specimens of 100mm×100mm×100mm, 100mm×100mm×300mm, and 100mm×100mm×400mm were formed and cured for 28 days in a standard curing room at 20±2℃ and 95% relative humidity. The concrete setting time was measured to be 5.2h, the slump to be 200mm, the compressive strength at 7 days and 28 days to be 37.8MPa and 43.3MPa, the flexural strength at 7 days and 28 days to be 3.4MPa and 4.7MPa, the splitting tensile strength at 7 days and 28 days to be 4.2MPa and 4.6MPa, the elastic modulus to be 32.3GPa, the characteristic value of flexural toughness to be 1.35MPa, and the setting time to be 5.2h, classifying it as ordinary concrete.

[0057] Comparative Example 2: Concrete was prepared by mixing 440 parts cement, 660 parts 16-25mm crushed stone, 355 parts 5-16mm crushed stone, 705 parts medium sand, 150 parts water, and 7.5 parts water-reducing agent, and its slump and setting time were tested.

[0058] Specimens of 100mm×100mm×100mm, 100mm×100mm×300mm, and 100mm×100mm×400mm were formed and cured for 28 days in a standard curing room at 20±2℃ and 95% relative humidity. The concrete setting time was measured to be 5.3h, the slump to be 210mm, the compressive strength at 7 days and 28 days to be 40.7MPa and 45.5MPa, the flexural strength at 7 days and 28 days to be 4.3MPa and 5.9MPa, the splitting tensile strength at 7 days and 28 days to be 4.3MPa and 4.8MPa, the elastic modulus to be 33.1GPa, the characteristic value of flexural toughness to be 2.53MPa, and the setting time to be 5.3h, classifying it as ordinary concrete.

[0059] Comparative Example 3: Concrete was prepared by mixing 500 parts cement, 660 parts 16-25mm crushed stone, 355 parts 5-16mm crushed stone, 705 parts medium sand, 150 parts water, and 7.5 parts water-reducing agent, and its slump and setting time were tested.

[0060] Specimens of 100mm×100mm×100mm, 100mm×100mm×300mm, and 100mm×100mm×400mm were formed and cured for 28 days in a standard curing room at 20±2℃ and 95% relative humidity. The concrete setting time was measured to be 5.5h, the slump to be 220mm, the compressive strength at 7 days and 28 days to be 46.2MPa and 56.3MPa, the flexural strength at 7 days and 28 days to be 5.3MPa and 6.7MPa, the splitting tensile strength at 7 days and 28 days to be 4.6MPa and 5.4MPa, the elastic modulus to be 35.4GPa, the characteristic value of flexural toughness to be 1.39MPa, and the setting time to be 5.5h, classifying it as ordinary concrete.

[0061] In accordance with national standards, the workability and mechanical properties of the concrete in Examples 1-3 and Comparative Examples 1-3 were tested. The test results are shown in Table 1. Table 1 shows the test results of the workability and mechanical properties of the concrete.

[0062] As can be seen from the data in Table 1, compared with Comparative Examples 1-3, the workability of concrete in Examples 1-3 is improved to a certain extent, the early strength is reduced to a certain extent, the later strength remains basically the same, the elastic modulus is reduced to a certain extent, and the flexural toughness is significantly improved.

[0063] Compared to Comparative Examples 1-3, the concrete setting time of Examples 1-3 was extended by more than 10 times, and the slump was slightly improved. It can be seen that the low modulus of elasticity and high toughness concrete provided by the present invention is more suitable for large-volume, long-distance pumping or special construction needs. The compressive strength at 7 days was reduced by about 26%, the flexural strength at 7 days was reduced by about 17%, the splitting tensile strength at 7 days was reduced by about 12%, the compressive strength at 28 days was reduced by about 4%, the flexural strength at 28 days was reduced by about 4%, the splitting tensile strength at 28 days was reduced by about 3%, the modulus of elasticity was reduced by about 25%, and the flexural toughness was increased by about 3 times.

[0064] Compared to Comparative Examples 1-3, Examples 1-3 used fly ash and slag powder to replace part of the cement, which improved some of the workability of the concrete and increased the slump; the addition of super retarder extended the setting time of the concrete, which also led to an increase in the molding time of the concrete specimens, slowed down the early hydration process, and resulted in a significant reduction in the early strength of the concrete; the addition of polypropylene fiber and organosilicon-polyvinyl alcohol nanocomposite hydrogel enhanced the toughness and crack resistance of the concrete; the addition of rubber powder, polystyrene plastic, waterborne polyurethane, and polyolefin elastomers reduced the elastic modulus of the concrete.

[0065] The bending toughness characteristic value in the examples is as high as 5.24-7.81 MPa, while that in the comparative examples is only 1.35-2.53 MPa, indicating that polypropylene fibers, polyolefin elastomers, rubber powders and other materials play a good toughening and crack-resistant role.

[0066] The elastic modulus of the example is 24-26 GPa, which is significantly lower than that of the comparative example, indicating that the rigidity of the concrete is reduced and the flexibility is enhanced, making it more suitable for occasions that require impact resistance and deformation resistance.

[0067] In summary, this invention significantly prolongs the setting time and retains water through the use of super retarder and organosilicon-polyvinyl alcohol nanocomposite hydrogel. It also significantly improves flexural toughness through the composite toughening of polypropylene fiber, rubber powder, and polyolefin elastomer. Furthermore, it optimizes the microstructure by combining fly ash, slag powder, and waterborne polyurethane to enhance later-stage strength and durability.

[0068] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A low-modulus, high-ductility, ultra-retarded concrete, characterized in that, The concrete comprises, by weight, 254-360 parts cement, 68-108 parts fly ash, 68-70 parts slag powder, 352-393 parts 5-16mm crushed stone, 660-729 parts 16-25mm crushed stone, 669-705 parts medium sand, 20 parts rubber powder, 15 parts polystyrene plastic, 150 parts water, 5.9-7.5 parts water-reducing agent, 3.1-4.0 parts super retarder, 15 parts waterborne polyurethane, 15 parts nano-composite hydrogel, 5 parts polyolefin elastomer, and 1.0 part polypropylene fiber.

2. The low-modulus, high-ductility, ultra-slow-release concrete according to claim 1, characterized in that, The cement used is P·O 52.5 grade cement with a specific surface area of ​​340 m². 2 / kg.

3. The low-modulus, high-ductility, ultra-slow-release concrete according to claim 1, characterized in that, The fly ash used is Class F, Grade II fly ash, with a specific surface area of ​​303 m². 2 / kg, water requirement ratio is 94%.

4. The low-modulus, high-ductility, ultra-slow-release concrete according to claim 1, characterized in that, The slag powder used is S95 grade slag powder with a specific surface area of ​​449 m². 2 / kg, the 7-day activity index was 81%, the 28-day activity index was 96%, and the mobility ratio was 107%.

5. The low-modulus, high-ductility, ultra-slow-release concrete according to claim 1, characterized in that, The apparent density of the crushed stone is 2950 kg / m³. 3 It has a mud content of 0.5%, a needle-like and flaky content of 4%, and a crushing value of 8%.

6. The low-modulus, high-ductility, ultra-slow-release concrete according to claim 1, characterized in that, The medium sand used is from Zone II, with an apparent density of 2620 kg / m³. 3 The mud content is 1.2%, and the fineness modulus is 2.

6.

7. The low-modulus, high-ductility, ultra-slow-release concrete according to claim 1, characterized in that, The rubber powder is made from waste tires through processing. It is in granular form with a fineness of 50 mesh and an apparent density of 1050 kg / m³. 3 .

8. The low-modulus, high-ductility, ultra-slow-release concrete according to claim 1, characterized in that, Polystyrene plastic is a rigid, transparent solid with an apparent density of 1040 kg / m³.

9. The low-modulus, high-ductility, ultra-slow-release concrete according to claim 1, characterized in that, The water-reducing agent is a polycarboxylate high-efficiency water-reducing agent with a water reduction rate of 20%~30% and a solid content of 20.44%.

10. The low-modulus, high-ductility, ultra-slow-release concrete according to claim 1, characterized in that, The super-retarder uses a hydroxycarboxylic acid retarder with a solid content of 18.9% and a density of 1.08 g / cm³. 3 The pH value is 7.

28.

11. The low-modulus, high-ductility, ultra-slow-release concrete according to claim 1, characterized in that, Waterborne polyurethane is synthesized from raw materials such as toluene diisocyanate, polyol, dihydroxypropionic acid, and diluent, with a solid content of 55%.

12. The low-modulus, high-ductility, ultra-slow-release concrete according to claim 1, characterized in that, The nanocomposite hydrogel is an organosilicon-polyvinyl alcohol nanocomposite hydrogel, prepared by the sol-gel method, with a tensile strength of not less than 1.6 MPa, a compressive strength of not less than 0.6 MPa, and a water content of more than 82%.

13. The low-modulus, high-ductility, ultra-slow-release concrete according to claim 1, characterized in that, The polyolefin elastomer is a copolymer of ethylene and octene, with a melt flow rate of 28 g / 10 min.

14. The low-modulus, high-ductility, ultra-slow-release concrete according to claim 1, characterized in that, The polypropylene fibers are 12 mm long, 31 μm in diameter, and have a density of 0.91 g / cm³. 3 Its elastic modulus is 4.65 GPa and its elongation is 19.69%.

15. A method for preparing low-modulus, high-ductility, ultra-slow-release concrete as described in any one of claims 1-14, characterized in that, Includes the following steps: Step 1: Mix the coarse aggregate and fine aggregate evenly in the mixing device; then add the cement, fly ash and slag powder to the mixing device and mix evenly. Step 2: Add the rice composite hydrogel and polyolefin elastomer to the mixing device and stir evenly; then add the water-reducing agent, super retarder, waterborne polyurethane, and water evenly to the mixing device and stir evenly. Step 3: Add polypropylene fibers to a mixing device and mix evenly to obtain pre-concrete; Step 4: After the pre-mixed concrete is thoroughly stirred, it is transferred to a mold and poured to form a specimen; Step 5: Cur the specimens in a standard curing chamber at a temperature of 20±2℃ and a relative humidity of 95% until the specified age to obtain the low modulus of elasticity, high ductility, and ultra-retarded concrete.

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