Geopolymer concrete and preparation method thereof

Abstract

The invention relates to the technical field of concrete, and particularly discloses geopolymer concrete and a preparation method thereof. The geopolymer concrete is prepared from the following raw materials in parts by weight: 60 to 80 parts of mineral powder, 30 to 40 parts of fly ash, 20 to 25 parts of silica fume, 45 to 55 parts of alkali activator, 150 to 180 parts of aggregate, 1.95 to 2.25 parts of toughening fiber and 40 to 50 parts of water, the toughening fiber is composite toughening agent modified polyvinyl alcohol / polyacrylonitrile composite fiber, and the length of the toughening fiber is 6 to 10 mm; in addition, the preparation method disclosed by the invention has the advantage of improving the brittleness of the geopolymer concrete.

Description

Technical Field

[0001] The present application relates to the technical field of concrete, and more particularly, to a geopolymer concrete and a preparation method thereof. Background Art

[0002] Cement is a powdered, hydraulic, inorganic binder. When mixed with water, it forms a slurry that hardens in air or water, firmly bonding materials like sand and stone. Concrete made from crushed stone is particularly strong after hardening and resistant to erosion by both fresh and salt water. Cement has long been a key binder used in civil engineering, water conservancy, and national defense projects. Geopolymer concrete, a new environmentally friendly building material, has recently garnered widespread attention. It is primarily produced by reacting industrial waste materials like mineral powder and fly ash with an alkali activator.

[0003] Geopolymer concrete has the characteristics of high strength, strong corrosion resistance and relatively easy construction. It is widely used in underground facilities, water conservancy projects and chemical equipment. Compared with traditional concrete, geopolymer concrete has higher strength and is not easily corroded, but it is also a brittle material with poor tensile strength and ductility, which restricts the use of geopolymer concrete. Summary of the Invention

[0004] In order to improve the brittleness of geopolymer concrete, the present application provides a geopolymer concrete and a preparation method thereof.

[0005] In a first aspect, the present application provides a geopolymer concrete, which adopts the following technical solution: A geopolymer concrete comprises the following raw materials in parts by weight: 60-80 parts of mineral powder, 30-40 parts of fly ash, 20-25 parts of silica fume, 45-55 parts of alkali activator, 150-180 parts of aggregate, 1.95-2.25 parts of toughening fiber, and 40-50 parts of water. The toughening fiber is a composite toughening agent-modified polyvinyl alcohol / polyacrylonitrile composite fiber, and the toughening fiber has a length of 6-10 mm.

[0006] By adopting the above technical solution, silicon and aluminum are provided by mineral powder, fly ash and silica fume, and the three are mixed with silica fume and alkali activator. The concrete formed after hydration treatment has high mechanical strength. It can be used as a road surface for paving to obtain a road surface with good crack resistance and high durability. The silica fume has a small particle size and a large specific surface area, which can make the structure of the concrete denser and improve the strength of the concrete. The toughening fiber has a high strength and elastic modulus, which is beneficial to the stress dispersion during the hydration and curing process of the concrete, and effectively improves the crack resistance and brittleness of the concrete. At the same time, polyvinyl alcohol has good hydrophilicity, so that the toughening fiber can reduce the shrinkage of the concrete during the curing and drying process of the concrete, further reducing the damage caused by stress.

[0007] Preferably, the alkaline activator comprises 35 wt% water glass and sodium hydroxide in a mass ratio of (5.9-6.1):(0.95-1.1), and the water glass modulus is 2.9-3.2.

[0008] By adopting the above technical solution, the mass ratio of the alkali activator and the modulus of the water glass are controlled, so that the mixed concrete raw materials have better slurry fluidity, promote the density of the concrete structure, and further improve the strength of the concrete.

[0009] Preferably, the composite toughening agent is graphene oxide-modified carbon nanotubes, and the added amount of the composite toughening agent is 0.76-0.95 wt % of the total mass of the toughened fiber.

[0010] By adopting the above technical solution, the addition of carbon nanotubes can effectively improve the tensile strength and elastic modulus of the toughened fiber. After modification with graphene oxide, the surface of graphene oxide contains more active groups, which effectively improves the dispersibility of the composite toughening agent in the spinning solution and improves the effect of gel spinning. At the same time, it can effectively improve the bonding strength between the toughened fiber and the concrete base, thereby improving the compatibility of the concrete.

[0011] Preferably, the method for preparing the toughened fiber comprises the following steps: (1) Preparation of composite toughening agent: ultrasonically disperse carbon nanotubes in ethanol solution, add graphene oxide suspension, ultrasonicate for 3-4 hours, let stand, filter, and dry to obtain composite toughening agent; (2) Spinning: Add polyvinyl alcohol and polyacrylonitrile to dimethyl sulfoxide, stir and dissolve at high speed at 75-85°C to obtain a spinning solution, add a composite toughening agent, ultrasonicate for 25-30 minutes, perform gel spinning, and perform a coagulation bath and 3-4 stretching to obtain a toughened fiber.

[0012] By adopting the above technical solution, polyvinyl alcohol and polyacrylonitrile are dissolved in dimethyl sulfoxide to form a spinning solution, and carbon nanotubes modified with graphene oxide are dispersed in the spinning solution. Graphene oxide enables the composite toughening agent to have better dispersibility in dimethyl sulfoxide, and the obtained toughened fiber component has a uniform texture and excellent mechanical strength and elastic modulus.

[0013] Preferably, the solid-liquid ratio of the carbon nanotubes to the ethanol solution is 1 g:1 L, the concentration of the graphene oxide suspension is 0.2-0.25 g / L, and the mass ratio of the carbon nanotubes to the graphene oxide is (1.1-1.4):(2.2-2.6).

[0014] By adopting the above technical solution, the concentrations of carbon nanotubes and graphene oxide are controlled, so that graphene oxide is evenly dispersed, and the carbon nanotubes are modified so that the composite toughening agent has good elastic modulus and dispersibility.

[0015] Preferably, the gel spinning conditions are: extrusion diameter of 0.5 mm, extrusion rate of 0.9-1.1 m / min, spinning temperature of 75-80° C., air gap of 1.12-1.35 cm; the coagulation bath uses a dimethyl sulfoxide solution with a volume fraction of 70% and a temperature of 10-15° C.

[0016] By adopting the above technical solution, gel spinning allows the extruded fibers to retain good axial orientation during the cooling process, so that the composite fibers obtained by spinning have higher tensile strength, thereby increasing the degree of improvement of the toughened fibers on the compressive strength of concrete.

[0017] Preferably, the total mass fraction of polyvinyl alcohol and polyacrylonitrile in the spinning solution is 11-13 wt %, and the mass ratio of polyvinyl alcohol to polyacrylonitrile is (2.12-2.35):(1.35-1.54).

[0018] By adopting the above technical solution, the total mass fraction is controlled so that the spinning solution has good viscosity and fluidity, the texture and size of the fibers produced by spinning are uniform, and the mass ratio of polyvinyl alcohol to polyacrylonitrile is controlled so that the composite fiber has high strength and good hydrophilic properties.

[0019] In a second aspect, the present application provides a method for preparing geopolymer concrete, which adopts the following technical solution: A method for preparing geopolymer concrete comprises the following steps: mixing mineral powder, fly ash, silica fume and aggregate at a stirring rate of 150-170 r / min for 6-10 minutes to obtain a solid material; adding an alkali activator to water, stirring and dispersing the mixture at 130-150 r / min for 4-6 minutes to obtain a liquid material; stirring and dispersing the solid material and the liquid material at 140-150 r / min for 5-8 minutes, and then adding toughening fiber at 160-180 r / min while stirring for 4-7 minutes to obtain the geopolymer concrete.

[0020] By adopting the above technical solution, silicon and aluminum react under the action of alkali activator, and the addition of toughening fiber can effectively improve the density of geopolymer concrete structure, while having higher strength and elastic modulus, which can effectively improve the shrinkage and brittleness of concrete.

[0021] In summary, this application has the following beneficial effects: 1. In the present application, silicon and aluminum are provided by mineral powder, fly ash and silica fume, and the three are mixed with silica fume and alkali activator. The concrete formed after hydration treatment has high mechanical strength. When used as a road surface, it can obtain a road surface with good crack resistance and high durability. The silica fume has a small particle size and a large specific surface area, which can make the structure of the concrete denser and improve the strength of the concrete. The toughening fiber has a high strength and elastic modulus, which is beneficial to the stress dispersion during the hydration and curing process of the concrete, and effectively improves the crack resistance and brittleness of the concrete. At the same time, polyvinyl alcohol has good hydrophilicity, so that the toughening fiber can reduce the shrinkage of the concrete during the curing and drying process of the concrete, further reducing the damage caused by stress.

[0022] 2. The addition of carbon nanotubes in this application can effectively improve the tensile strength and elastic modulus of the toughened fiber. After modification with graphene oxide, the surface of graphene oxide contains more active groups, which effectively improves the dispersibility of the composite toughening agent in the spinning solution and improves the effect of gel spinning. At the same time, it can effectively improve the bonding strength between the toughened fiber and the concrete base, thereby improving the compatibility of the concrete.

[0023] 3. In this application, polyvinyl alcohol and polyacrylonitrile are dissolved in dimethyl sulfoxide to form a spinning solution, and carbon nanotubes modified with graphene oxide are dispersed in the spinning solution. Graphene oxide enables the composite toughening agent to have better dispersibility in dimethyl sulfoxide, and the obtained toughened fiber component has a uniform texture and has better mechanical strength and elastic modulus. DETAILED DESCRIPTION

[0024] The present application is further described in detail below with reference to the embodiments.

[0025] Preparation Example 1 The preparation method of the toughened fiber comprises the following steps: (1) Preparation of composite toughening agent: carbon nanotubes were ultrasonically dispersed in an ethanol solution, and a graphene oxide suspension was added. After ultrasonic treatment for 3 h, the composite toughening agent was prepared by standing, filtering, and drying. The material-liquid ratio of carbon nanotubes to ethanol solution was 1 g:1 L, the concentration of graphene oxide suspension was 0.2 g / L, and the mass ratio of carbon nanotubes to graphene oxide was 1.1:2.2. (2) Spinning: Polyvinyl alcohol and polyacrylonitrile were added to dimethyl sulfoxide. The total mass fraction of polyvinyl alcohol and polyacrylonitrile in the spinning solution was 11 wt%, and the mass ratio of polyvinyl alcohol to polyacrylonitrile was 2.12:1.35. The solution was dissolved by high-speed stirring at 75 °C to obtain a spinning solution. A composite toughening agent was added. The amount of the composite toughening agent added was 0.76 wt% of the total mass of the toughened fiber. After ultrasonic treatment for 25 minutes, gel spinning was performed. The conditions for gel spinning were: extrusion diameter of 0.5 mm, extrusion rate of 0.9 m / min, spinning temperature of 75 °C, and air gap of 1.12 cm. A coagulation bath was also performed. The coagulation bath used a dimethyl sulfoxide solution with a volume fraction of 70% at a temperature of 15 °C. After three stretchings, the toughened fiber was obtained.

[0026] Preparation Example 2 The preparation method of the toughened fiber comprises the following steps: (1) Preparation of composite toughening agent: carbon nanotubes were ultrasonically dispersed in an ethanol solution, and a graphene oxide suspension was added. After ultrasonic treatment for 4 h, the composite toughening agent was prepared by standing, filtering, and drying. The material-liquid ratio of carbon nanotubes to ethanol solution was 1 g:1 L, the concentration of graphene oxide suspension was 0.25 g / L, and the mass ratio of carbon nanotubes to graphene oxide was 1.4:2.6. (2) Spinning: Polyvinyl alcohol and polyacrylonitrile were added to dimethyl sulfoxide. The total mass fraction of polyvinyl alcohol and polyacrylonitrile in the spinning solution was 13 wt%, and the mass ratio of polyvinyl alcohol to polyacrylonitrile was 2.35:1.54. The solution was dissolved by high-speed stirring at 85 °C to obtain a spinning solution. A composite toughening agent was added. The amount of the composite toughening agent added was 0.95 wt% of the total mass of the toughened fiber. After ultrasonic treatment for 30 minutes, gel spinning was performed. The conditions for gel spinning were: extrusion diameter of 0.5 mm, extrusion rate of 1.1 m / min, spinning temperature of 80 °C, and air gap of 1.35 cm. A coagulation bath was also performed. The coagulation bath used a dimethyl sulfoxide solution with a volume fraction of 70% at a temperature of 10 °C. After four stretchings, toughened fibers were obtained.

[0027] Preparation Example 3 The difference between Preparation Example 3 and Preparation Example 1 is that in Preparation Example 3, the mass ratio of carbon nanotubes to graphene oxide is 1.1:1.1.

[0028] Preparation Example 4 The difference between Preparation Example 4 and Preparation Example 1 is that in Preparation Example 4, the mass ratio of carbon nanotubes to graphene oxide is 1.1:3.2.

[0029] Preparation Example 5 The difference between Preparation Example 5 and Preparation Example 1 is that in Preparation Example 5, the total mass fraction of polyvinyl alcohol and polyacrylonitrile in the spinning solution is 6 wt %.

[0030] Preparation Example 6 The difference between Preparation Example 6 and Preparation Example 1 is that in Preparation Example 6, the total mass fraction of polyvinyl alcohol and polyacrylonitrile in the spinning solution is 18 wt %.

[0031] Preparation Example 7 The difference between Preparation Example 7 and Preparation Example 1 is that in Preparation Example 7, the mass ratio of polyvinyl alcohol to polyacrylonitrile is 2.12:0.87.

[0032] Preparation Example 8 The difference between Preparation Example 8 and Preparation Example 1 is that in Preparation Example 8, the mass ratio of polyvinyl alcohol to polyacrylonitrile is 2.12:2.12.

[0033] Preparation Example 9 The difference between Preparation Example 9 and Preparation Example 1 is that in Preparation Example 9, the added amount of the composite toughening agent is 0.56 wt % of the total mass of the toughened fiber.

[0034] Preparation Example 10 The difference between Preparation Example 10 and Preparation Example 1 is that in Preparation Example 10, the added amount of the composite toughening agent is 1.52 wt% of the total mass of the toughened fiber.

[0035] Preparation Example 11 The difference between Preparation Example 11 and Preparation Example 1 is that in Preparation Example 11, an equal amount of carbon nanotubes is used instead of the composite toughening agent.

[0036] Preparation Example 12 The difference between Preparation Example 12 and Preparation Example 1 is that in Preparation Example 12, no composite toughening agent is added to the spinning solution before gel spinning.

[0037] In the embodiment of the present application, the mineral powder is selected to have a specific surface area of 430 cm 2 / g S95 grade slag powder, fly ash is grade I fly ash, aggregate is recycled sand with a particle size of 0.25-0.55mm, and the specific surface area of silica fume is 2000cm 2 / g.

[0038] Example 1

[0039] A geopolymer concrete includes the following raw materials by weight: 60 kg of mineral powder, 40 kg of fly ash, 20 kg of silica fume, 45 kg of alkali activator, 150 kg of aggregate, 1.95 kg of toughening fiber, and 40 kg of water. The toughening fiber is the toughening fiber prepared in Preparation Example 1, and the toughening fiber has a length of 6 mm. The alkali activator includes 35 wt% of water glass and sodium hydroxide in a mass ratio of 5.9:0.95, and the water glass modulus is 3.2.

[0040] The preparation method of the above-mentioned geopolymer concrete includes the following steps: mixing mineral powder, fly ash, silica fume and aggregate at a stirring rate of 150 r / min for 10 minutes to obtain a solid material; adding an alkali activator to water, stirring and dispersing it at 130 r / min for 6 minutes to obtain a liquid material; then stirring and dispersing the solid material and the liquid material at 140 r / min for 8 minutes, and then adding toughening fiber at 160 r / min while stirring for 7 minutes to obtain geopolymer concrete.

[0041] Example 2

[0042] A geopolymer concrete includes the following raw materials by weight: 80 kg of mineral powder, 30 kg of fly ash, 25 kg of silica fume, 55 kg of alkali activator, 180 kg of aggregate, 2.25 kg of toughening fiber, and 50 kg of water. The toughening fiber is the toughening fiber prepared in Preparation Example 2, and the toughening fiber has a length of 10 mm. The alkali activator includes 35 wt% of water glass and sodium hydroxide in a mass ratio of 6.1:1.1, and the water glass modulus is 2.9.

[0043] The preparation method of the above-mentioned geopolymer concrete includes the following steps: mixing mineral powder, fly ash, silica fume and aggregate at a stirring rate of 170 r / min for 6 minutes to obtain a solid material; adding an alkali activator to water, stirring and dispersing at 150 r / min for 4 minutes to obtain a liquid material; then stirring and dispersing the solid material and the liquid material at 150 r / min for 5 minutes, and then adding toughening fiber at 180 r / min while stirring for 4 minutes to obtain geopolymer concrete.

[0044] Example 3

[0045] The difference between Example 3 and Example 1 is that in Example 3, the toughening fiber is the toughening fiber prepared in Preparation Example 3.

[0046] Example 4

[0047] The difference between Example 4 and Example 1 is that in Example 4, the toughening fiber is the toughening fiber prepared in Preparation Example 4.

[0048] Example 5 The difference between Example 5 and Example 1 is that in Example 5, the toughening fiber is the toughening fiber prepared in Preparation Example 5.

[0049] Example 6

[0050] The difference between Example 6 and Example 1 is that in Example 6, the toughening fiber is the toughening fiber prepared in Preparation Example 6.

[0051] Example 7

[0052] The difference between Example 7 and Example 1 is that in Example 7, the toughening fiber is the toughening fiber prepared in Preparation Example 7.

[0053] Example 8

[0054] The difference between Example 8 and Example 1 is that in Example 8, the toughening fiber is the toughening fiber prepared in Preparation Example 8.

[0055] Example 9

[0056] The difference between Example 9 and Example 1 is that in Example 9, the toughening fiber is the toughening fiber prepared in Preparation Example 9.

[0057] Example 10 The difference between Example 10 and Example 1 is that in Example 10, the toughening fiber is the toughening fiber prepared in Preparation Example 10.

[0058] Example 11 The difference between Example 11 and Example 1 is that in Example 11, in the alkaline activator, the mass ratio of 35wt% water glass to sodium hydroxide is 5.9:0.54.

[0059] Example 12 The difference between Example 12 and Example 1 is that in Example 12, in the alkaline activator, the mass ratio of 35wt% water glass to sodium hydroxide is 5.9:1.65.

[0060] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that in Comparative Example 1, no toughening fiber is added.

[0061] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that in Comparative Example 2, the toughening fiber is the toughening fiber prepared in Preparation Example 11.

[0062] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that in Comparative Example 3, the toughening fiber is the toughening fiber prepared in Preparation Example 12.

[0063] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that in Comparative Example 4, the length of the toughening fiber is 3 mm.

[0064] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that in Comparative Example 5, the length of the toughening fiber is 15 mm.

[0065] Geopolymer concrete was prepared according to the raw materials and methods of Examples 1-12 and Comparative Examples 1-5, injected into a mold, and demolded after curing at room temperature for 24 hours. Thereafter, the concrete samples were cured for 28 days according to the standard curing conditions in GB / T 50081-2019 "Standard for Test Methods for Physical and Mechanical Properties of Concrete". The compressive strength and tensile strength of the concrete samples were tested and recorded in Table 1.

[0066] Table 1 Concrete strength test project Compressive strength / MPa Tensile strength / MPa Example 1 102.68 12.35 Example 2 103.14 12.68 Example 3 96.35 11.02 Example 4 95.26 10.98 Example 5 93.68 11.18 Example 6 93.12 10.92 Example 7 94.19 11.16 Example 8 93.52 10.86 Example 9 96.57 10.19 Example 10 94.29 11.08 Example 11 93.81 11.16 Example 12 95.16 10.84 Comparative Example 1 59.65 6.12 Comparative Example 2 92.31 9.23 Comparative Example 3 84.26 8.68 Comparative Example 4 93.26 10.15 Comparative Example 5 91.25 10.59 According to Table 1, Examples 1-2 and Comparative Examples 1-3, it can be seen that after the mineral powder, fly ash, silica fume and aggregate are mixed, the silicon aluminum depolymerizes and condenses under the action of the alkali activator to form a Si-O-Al network structure, and then forms a gel structure. After hardening, a geopolymer concrete with higher strength is obtained. Compared with Comparative Example 1, in Example 1-2, toughening fibers are added. The compressive strength and tensile strength of the geopolymer concrete, especially the tensile strength, are greatly improved, indicating that the addition of toughening fibers can effectively improve the brittleness and crack resistance of geopolymer concrete. The toughening fibers have It has high tensile strength and elastic modulus. When added to geopolymer concrete, when the geopolymer concrete is stressed or cracks occur, the toughening fiber can absorb the stress and reduce the damage to the concrete. At the same time, the bonding strength between the toughening fiber and the concrete base is high, and the tensile force required for the toughening fiber and the concrete base to slip is higher, thereby effectively improving the tensile strength of the geopolymer concrete. The toughening fiber is a composite of polyvinyl alcohol and polyacrylonitrile. While having high strength, it also has good hydrophilicity, which can effectively improve the shrinkage of concrete, make the structure of the concrete denser, and improve its crack resistance and strength.

[0067] In Comparative Example 2, carbon nanotubes that have not been modified with graphene oxide are used instead of the composite toughening agent, while in Comparative Example 3, no composite toughening agent is added. The compressive strength and tensile strength of Comparative Examples 2-3 both decrease, indicating that the composite toughening agent can effectively improve the strength and elastic modulus of the toughened fiber, and the carbon nanotubes modified with graphene oxide can further improve the strength of the toughened fiber, thereby improving the strength and crack resistance of the geopolymer concrete. Graphene oxide contains more active groups. The carbon nanotubes modified with graphene oxide have good dispersibility in the spinning solution and are not easy to agglomerate during the gel spinning process, so that the toughened fiber obtained by spinning has a uniform texture. At the same time, the active groups of the toughening fiber are further improved, thereby improving the bonding force between the toughening fiber and the concrete base, improving the compatibility of the concrete, and helping to improve the density of the concrete.

[0068] Compared with Example 1-2, the compressive strength and tensile strength of the geopolymer concrete prepared in Example 3-4 are both reduced. The mass ratio of carbon nanotubes to graphene oxide was changed during the preparation of the toughening fiber selected in Example 3-4, indicating that the mass ratio of carbon nanotubes to graphene oxide affects the strength of the toughening fiber, thereby affecting the strength of the geopolymer concrete. The mass ratio of carbon nanotubes to graphene oxide directly affects the modification of carbon nanotubes by graphene oxide. A decrease in the mass ratio is likely to reduce the amount of graphene oxide attached, reduce the dispersibility of the composite toughening agent, and deteriorate the spinning effect. An increase in the mass ratio is likely to result in an excessively high content of graphene oxide and uneven modification, thereby reducing the adhesion uniformity of graphene oxide and reducing the strength of the toughening fiber.

[0069] Compared with Example 1-2, the compressive strength and tensile strength of the geopolymer concrete prepared in Example 5-8 are both reduced. The total mass fraction of polyvinyl alcohol and polyacrylonitrile was changed during the preparation of the toughening fiber selected in Example 5-6, and the mass ratio of polyvinyl alcohol to polyacrylonitrile was changed during the preparation of the toughening fiber selected in Example 7-8. This shows that the total mass fraction of polyvinyl alcohol and polyacrylonitrile, as well as the mass ratio of polyvinyl alcohol and polyacrylonitrile, have an impact on the strength of the toughening fiber, and thus affect the strength of the geopolymer concrete. The total mass fraction of polyvinyl alcohol and polyacrylonitrile affects the fluidity and viscosity of the spinning solution. Too low a mass fraction can easily make the spinning solution difficult to spin. As the silk component content decreases, the strength of the formed fiber decreases, while if the mass fraction is too high, the viscosity of the spinning solution will increase, extrusion will be difficult, the diameter of the fibers obtained by spinning will be uneven, and the strength will decrease; the addition of polyvinyl alcohol can effectively improve the hydrophilicity of the toughened fiber, and at the same time, polyvinyl alcohol is compounded with polyacrylonitrile to prepare a composite fiber, so that the composite fiber has good hydrophilicity and high strength. Polyvinyl alcohol and polyacrylonitrile are compounded according to the mass ratio, which can make the toughened fiber have high strength. When the mass ratio changes, the synergistic effect of the two is weakened, the strength of the toughened fiber decreases or the hydrophilicity is weakened, thereby reducing the reinforcing effect of the toughened fiber on geopolymer concrete.

[0070] Compared with Examples 1-2, the compressive strength and tensile strength of the geopolymer concrete prepared in Examples 9-10 are decreased. The amount of composite toughening agent added during the preparation of the toughening fibers selected in Examples 9-10 is changed, indicating that the amount of composite toughening agent added affects the strength of the toughening fibers, thereby affecting the strength of the geopolymer concrete. When the amount of composite toughening agent added is reduced, the strength enhancement effect of the composite toughening agent on the toughening fibers is reduced, thereby reducing the strength of the toughening fibers and the elastic modulus. When the amount of composite toughening agent added is increased, the composite toughening agent is unevenly dispersed in the spinning solution, affecting the spinning effect, thereby reducing the uniformity of the toughened fibers, reducing the tensile strength and elastic modulus, and reducing the strength of the geopolymer concrete.

[0071] Compared with Example 1-2, the compressive strength and tensile strength of the geopolymer concrete prepared in Example 11-12 are both reduced. Example 11-12 changes the composition of the alkali activator, indicating that the mass ratio of water glass to sodium hydroxide affects the effect of the alkali activator. Sodium hydroxide can react with silicates in concrete and promote the formation and dispersion of gel, while water glass can condense to form polymer geopolymers, thereby enhancing the strength of the concrete base. When the mass ratio of the two changes, it is easy to affect the reaction and formation of concrete colloids, thereby reducing the strength of the geopolymer concrete.

[0072] Compared with Examples 1-2, the compressive strength and tensile strength of the geopolymer concrete prepared in Comparative Example 4-5 are both decreased. Comparative Example 4-5 changes the length of the toughening fibers, indicating that the length of the toughening fibers affects the strength of the geopolymer concrete. When the length of the toughening fibers is shortened, the complexity of the network structure formed by the toughening fibers in the geopolymer concrete decreases, and the reinforcing effect on the microstructure of the geopolymer concrete is weakened. When the length of the toughening fibers is increased, the number of toughening fibers decreases, and the distribution in the geopolymer concrete is uneven, and the density of the formed fiber network structure decreases, thereby affecting the strength of the concrete.

[0073] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A geopolymer concrete, characterized in that: The invention comprises the following raw materials in parts by weight: 60-80 parts of mineral powder, 30-40 parts of fly ash, 20-25 parts of silica fume, 45-55 parts of alkali activator, 150-180 parts of aggregate, 1.95-2.25 parts of toughening fiber and 40-50 parts of water. The toughening fiber is a composite toughening agent-modified polyvinyl alcohol / polyacrylonitrile composite fiber, and the toughening fiber length is 6-10 mm.

2. The geopolymer concrete according to claim 1, characterized in that: The alkaline activator comprises 35 wt% water glass and sodium hydroxide in a mass ratio of (5.9-6.1):(0.95-1.1), and the water glass modulus is 2.9-3.

2.

3. The geopolymer concrete according to claim 1, characterized in that: The composite toughening agent is carbon nanotubes modified with graphene oxide, and the addition amount of the composite toughening agent is 0.76-0.95wt% of the total mass of the toughened fiber.

4. The geopolymer concrete according to claim 3, characterized in that: The method for preparing the toughened fiber comprises the following steps: (1) Preparation of composite toughening agent: ultrasonically disperse carbon nanotubes in ethanol solution, add graphene oxide suspension, ultrasonicate for 3-4 hours, let stand, filter, and dry to obtain composite toughening agent; (2) Spinning: Add polyvinyl alcohol and polyacrylonitrile to dimethyl sulfoxide, stir and dissolve at high speed at 75-85°C to obtain a spinning solution, add a composite toughening agent, ultrasonicate for 25-30 minutes, perform gel spinning, and perform a coagulation bath and 3-4 stretching to obtain a toughened fiber.

5. The geopolymer concrete according to claim 4, characterized in that: The material-liquid ratio of the carbon nanotubes to the ethanol solution is 1 g:1 L, the concentration of the graphene oxide suspension is 0.2-0.25 g / L, and the mass ratio of the carbon nanotubes to the graphene oxide is (1.1-1.4):(2.2-2.6).

6. The geopolymer concrete according to claim 4, characterized in that: The gel spinning conditions are as follows: extrusion diameter of 0.5 mm, extrusion rate of 0.9-1.1 m / min, spinning temperature of 75-80° C., air gap of 1.12-1.35 cm; coagulation bath using dimethyl sulfoxide solution with a volume fraction of 70% at a temperature of 10-15° C.

7. The geopolymer concrete according to claim 4, characterized in that: The total mass fraction of polyvinyl alcohol and polyacrylonitrile in the spinning solution is 11-13 wt %, and the mass ratio of polyvinyl alcohol to polyacrylonitrile is (2.12-2.35):(1.35-1.54).

8. The method for preparing geopolymer concrete according to any one of claims 1 to 7, characterized in that: The following steps are involved: Mix the slag, fly ash, silica fume and aggregate at a stirring rate of 150-170 r / min for 6-10 minutes to obtain a solid material; add the alkali activator to water and stir and disperse at 130-150 r / min for 4-6 minutes to obtain a liquid material; The solid material and the liquid material are stirred and dispersed at 140-150 r / min for 5-8 minutes, and then toughening fibers are added while stirring at 160-180 r / min for 4-7 minutes to obtain geopolymer concrete.