Hybrid fiber reinforced ultrahigh-performance geopolymer concrete as well as preparation method and application thereof

Abstract

The invention relates to hybrid fiber reinforced ultrahigh-performance geopolymer concrete as well as a preparation method and application thereof. Slag, metakaolin and silica fume are used as precursor materials of geopolymer concrete, a sodium hydroxide-water glass solution is adopted to compound an alkali activator, and steel fibers, polyvinyl alcohol fibers and modified glass chopped fibers of different sizes are mixed and doped, so that the brittleness of the geopolymer concrete is remarkably improved, and the service life of the geopolymer concrete is prolonged. The early strength and the high temperature resistance are improved. The hybrid fiber reinforced ultrahigh-performance geopolymer concrete has the characteristics of low carbon emission, ultrahigh strength, high temperature resistance, high durability and the like, and can meet the use of the geopolymer concrete in actual engineering. According to the ultrahigh-performance geopolymer concrete, solid waste resources are utilized at the same time, carbon emission in the concrete production process is reduced, and the ultrahigh-performance geopolymer concrete is environmentally friendly, low in carbon, ultrahigh in strength, easy to prepare and capable of being suitable for complex environmental engineering structures such as tunnels, bridges and high-rise buildings.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, in particular to a hybrid fiber reinforced ultra-high performance geopolymer concrete and a preparation method and application thereof. BACKGROUND

[0002] In recent years, ultra-high performance concrete (UHPC) has been widely used in complex engineering structures such as submarine tunnels, cross-sea bridges, high-rise buildings, etc. due to its excellent mechanical properties and durability. However, compared with ordinary concrete, the preparation of UHPC requires more cement consumption, about 3-4 times that of ordinary concrete, which means higher carbon emissions, which is not conducive to the sustainable development of the economy and society. In addition, it is proposed to comprehensively improve the level of green manufacturing and strengthen the research and development and application of low-carbon building materials products such as new types of cementitious materials and low-carbon concrete. Therefore, it is urgent to reduce the carbon emissions of UHPC.

[0003] According to statistics, the cumulative stock of bulk solid waste in China is about 60 billion tons, and the annual increase is close to 3 billion tons, which poses a serious threat to the ecological environment. Improving the resource utilization rate of solid waste is a problem that needs to be solved urgently. Industrial solid wastes such as slag, kaolin, fly ash, and red mud are used as precursors of geopolymer concrete to replace cement, and a green and low-carbon ultra-high performance geopolymer concrete is prepared after alkali activation, realizing the synergy of high strength and low carbon of concrete.

[0004] Ultra-high performance geopolymer concrete has the characteristics of high early strength, good durability, and high brittleness, which is prone to cracking or even explosion under high temperature, limiting its application in practical engineering. The incorporation of hybrid fibers can improve the strength of geopolymer concrete while improving its brittleness, inhibiting its high-temperature cracking, and avoiding explosive damage, which has a significant effect on improving the high-temperature performance of ultra-high performance geopolymer concrete.

[0005] Chinese patent CN115321891A discloses a hybrid fiber toughened high-ductility geopolymer material and a preparation method thereof, which comprises the following preparation raw materials by weight: fly ash 30-40 parts; granulated blast furnace slag 50-60 parts; steel slag powder 20-30 parts; anhydrous sodium silicate 7-10 parts; fine sand 35-40 parts; steel fiber 5-10 parts; polyethylene fiber 1-2 parts; water 35-40 parts; the average particle size of the steel slag powder is 10-50 μm, preferably the average particle size of the steel slag powder is 10.1-15.3 μm; the length of the PE fiber is 15-18 mm, and the diameter is 10-25 μm; the length of the steel fiber is 20-23 mm, and the diameter is 0.1-0.5 mm.

[0006] Chinese patent CN119409453A discloses a self-healing high-toughness concrete and a preparation method thereof, in particular relates to a method for realizing self-healing of high-toughness concrete by using an excess precursor alkali activated cementitious system. The method realizes self-repair of concrete after cracking by configuring an excess precursor of cementitious material, and realizes toughness enhancement of concrete by combining with hybrid fibers, thereby realizing low-cost configuration of concrete and new self-healing concrete integrating control and repair. Although the above-mentioned scheme improves the brittleness of concrete and improves the strength of concrete at room temperature by using PE fibers and PP fibers, the melting point is low, and the strength cannot be provided after high temperature, and even the internal defects and pores of the matrix are increased, and the residual strength is significantly deteriorated. SUMMARY

[0007] The purpose of the present application is to provide a hybrid fiber reinforced ultra-high performance geopolymer concrete and its preparation method and application to solve the problems of high carbon emission, low early strength and poor high temperature resistance of traditional concrete. The hybrid fiber reinforced ultra-high performance geopolymer concrete has the characteristics of low carbon emission, ultra-high strength, high temperature resistance and high durability, and can meet the use of geopolymer concrete in actual engineering. The ultra-high performance geopolymer concrete of the present application simultaneously utilizes solid waste resources, reduces carbon emission in the production process of concrete, has green low carbon and ultra-high strength, is simple to prepare, and can be suitable for complex environment engineering structures such as tunnels, bridges and high-rise buildings.

[0008] The purpose of the present application can be realized by the following technical solutions:

[0009] A hybrid fiber reinforced ultra-high performance geopolymer concrete is composed of the following raw materials in parts by weight:

[0010]

[0011] Further, the multi-component solid waste-based precursor material comprises the following components in parts by weight:

[0012] blast furnace slag 429-932 parts,

[0013] metakaolin 86-518 parts,

[0014] silica fume 86-311 parts.

[0015] Further, the blast furnace slag is S95 grade slag powder, the 28d activity coefficient is greater than or equal to 95, and the specific surface area is greater than or equal to 400 m 2 / kg.

[0016] Further, the metakaolin is calcined at 600 DEG C, and the maximum particle size is less than or equal to 10 microns.

[0017] Further, the 28d activity coefficient of the silica ash is greater than or equal to 115, the specific surface area is greater than or equal to 15000 m 2 / kg, the SiO2 content is greater than or equal to 92%, and the average particle size is 0.1-0.3 μm.

[0018] Further, the particle size of the quartz sand is 26-70 mesh.

[0019] Further, the alkali activator is a NaOH solution-water glass composite activator.

[0020] Further, the NaOH solution is configured by using an industrial-grade flaky sodium hydroxide solid with a purity of 99%, and the concentration of the NaOH solution is 15-17 mol / L, preferably 16 mol / L.

[0021] The SiO2 content in the water glass solution is 29.9%, the Na2O content is 13.75%, and the modulus is 2.25.

[0022] Further, the water reducing agent is a polycarboxylic acid high-performance water reducing agent, and the water reducing rate is greater than or equal to 45%.

[0023] Further, the steel fiber is a copper-plated micro-wire steel fiber or an end-hook steel fiber, the diameter is 0.18-0.23 mm, the length is 12-14 mm, and the volume fraction is 1%-2%.

[0024] Further, the polyvinyl alcohol fiber has a diameter of 15-30 μm, a length of 12 mm, a tensile strength greater than or equal to 1550 Mpa, and a volume fraction of 0.5%-1%.

[0025] Further, the modified glass short-cut fiber has a diameter of 15-17 μm, a length of 3 mm, and a volume fraction of 0.5%-1.

[0026] The application also provides a preparation method of the hybrid fiber reinforced ultra-high performance geopolymer concrete.

[0027] S1, configuring an alkali activator;

[0028] S2, performing silane coupling agent modification treatment on the surface of the glass fiber to obtain modified glass short-cut fiber;

[0029] S3, weighing polybasic solid waste-based precursor materials, quartz sand and water reducing agent according to weight parts, and slowly stirring in a mixer to obtain a mixture A;

[0030] S4, weighing water and an alkali activator according to weight parts, and mixing the water and the alkali activator with the mixture A obtained in step S3 to obtain a mixture B through medium-speed mechanical stirring;

[0031] S5, the mixture B obtained in step S4 is added with steel fiber, polyvinyl alcohol fiber and modified glass fiber in sequence in proportion by weight, and high-speed mechanical stirring is performed to uniformly disperse the fibers, thereby obtaining mixture C;

[0032] S6, the mixture C stirred in step S5 is transferred into a mold, vibrated and formed, and a surface film is coated thereon, thereby obtaining hybrid fiber reinforced ultra-high performance polymer concrete after demolding and curing.

[0033] Further, in step S1, the specific steps for preparing the alkali activator are as follows:

[0034] S1-1, preparing NaOH solution: dissolving flaky sodium hydroxide solid in water, stirring to obtain NaOH solution, and standing for 24 h for use;

[0035] S1-2, mixing the NaOH solution obtained in step S1-1 with water glass solution according to a mass ratio of (103-124):(206-248) to obtain an alkali activator.

[0036] Further, in step S2, the specific steps for modifying the surface of the glass fiber with silane coupling agent are as follows:

[0037] S2-1, calcining the glass fiber at high temperature to remove the wetting agent on the surface thereof;

[0038] S2-2, mixing water and silane coupling agent to obtain a coupling agent solution;

[0039] S2-3, soaking the calcined glass fiber in step S2-1 in the coupling agent solution obtained in step S2-2, and drying to obtain modified glass short-cut fiber.

[0040] Further, in step S2-1, the high temperature is 300-500°C, preferably 400°C.

[0041] Further, in step S2-2, the silane coupling agent is γ-aminopropyl triethoxysilane (KH550),

[0042] The concentration of the coupling agent solution is 1.5%-2.5%, preferably 2%.

[0043] Further, in step S2-2, the soaking time is 10-20 min,

[0044] The drying temperature is 120°C, and the drying time is 4 h.

[0045] Further, in step S3, the rotation speed of the slow stirring is 70-90 r / min, and the stirring time is 1-3 min, preferably 1 min.

[0046] Further, in step S4, the rotation speed of the medium-speed stirring is 90-140 r / min, and the stirring time is 3-5 min.

[0047] Further, in step S5, the rotation speed of the high-speed stirring is greater than 140 r / min, and the stirring time is 2-4 min.

[0048] Further, in step S5, the vibration time is 30-60 s, and the demolding time is 24 h, and the curing time at normal temperature after demolding is 3-28 d.

[0049] In addition, the application also provides an application of the hybrid fiber reinforced ultra-high performance geopolymer concrete in a complex environment engineering structure.

[0050] Compared with the prior art, the application has the following beneficial effects:

[0051] 1) The early-strength high-temperature-resistant hybrid fiber reinforced ultra-high performance geopolymer concrete provided by the application does not need cement, reduces the huge energy consumption and carbon emission of cement production, and effectively improves the resource utilization rate by using solid wastes such as slag and kaolin;

[0052] 2) The ultra-high performance geopolymer concrete has high strength and fast setting and hardening speed, and the early compressive strength can reach 120 MPa, and the 28d compressive strength can reach 140 MPa, and can be used for repairing and reinforcing engineering structures;

[0053] 3) The ultra-high performance geopolymer concrete has good high-temperature resistance, can avoid high-temperature burst damage, effectively inhibits high-temperature cracking, has high residual strength, and the compressive strength after 400 DEG C can reach 70 MPa, and the compressive strength after 800 DEG C can reach 40 MPa;

[0054] 4) The glass short-cut fiber is modified by a silane coupling agent, the interfacial bonding performance of the glass fiber is improved, the melting point is high, the glass fiber has good high-temperature resistance and acid and alkali resistance, and the residual strength of the geopolymer concrete is effectively improved;

[0055] 5) The application adopts steel fibers, polyvinyl alcohol fibers and glass short-cut fibers, and the hybrid fibers with different diameters and lengths are used to enhance the geopolymer concrete at different scales, inhibit crack propagation, significantly improve the brittleness of the ultra-high performance geopolymer concrete, and improve the residual strength;

[0056] 6) The material source is wide, the preparation method is simple, and the application can be applied to engineering structures such as tunnels, bridges and high-rise buildings.

[0057] 7) The present application uses slag, metakaolin, silica fume as the precursor material of geopolymer concrete, adopts sodium hydroxide-sodium silicate solution composite alkali activator, and mixes and adds different sizes of steel fiber, polyvinyl alcohol fiber and modified glass short fiber, which significantly improves the brittleness of geopolymer concrete, and improves the early strength and high temperature resistance.

[0058] 8) Compared with the prior art, the present application relates to a kind of hybrid fiber reinforced ultra-high performance geopolymer concrete, which uses steel fiber, polyvinyl alcohol fiber and glass short fiber of different sizes and different melting points to mix well with the matrix, effectively inhibits the macro-micro crack propagation, improves the brittleness of geopolymer concrete, significantly improves its residual strength and high temperature resistance, and has the advantages of low carbon emission, ultra-high strength and high temperature resistance. DETAILED DESCRIPTION

[0059] The present application will be described in detail below in conjunction with specific examples. The present embodiment is implemented on the premise of the technical solution of the present application, and detailed implementation and specific operation process are given, but the protection scope of the present application is not limited to the following examples.

[0060] Unless otherwise specified, the raw materials used in the examples of the present application are conventional commercially available raw materials in the art. Some embodiments of the present application will be described in detail below. In the case of no conflict, the following examples and features in the examples can be combined with each other.

[0061] Example 1

[0062] The present embodiment provides a kind of hybrid fiber reinforced ultra-high performance geopolymer concrete, which is composed of raw materials in the following weight fractions:

[0063]

[0064] In the present embodiment, the multi-element solid waste-based precursor material includes the following components in the following weight fractions:

[0065] blast furnace slag 524 parts,

[0066] metakaolin 175 parts,

[0067] silica fume 175 parts.

[0068] In the present embodiment, the blast furnace slag is S95 grade slag powder, the metakaolin is calcined at 600 DEG C, the maximum particle size is ≤10 μm, and the average particle size of the silica fume is 0.1-0.3 μm, and the SiO2 content is ≥92%.

[0069] In the present embodiment, the particle size of the quartz sand is 26-70 mesh.

[0070] In the embodiment, the alkali activator is composed of 105 parts of NaOH solution and 210 parts of water glass composite activator,

[0071] The concentration of the NaOH solution is 16 mol / L, and the modulus of the water glass solution is 2.25.

[0072] In the embodiment, the water reducing agent is a polycarboxylic acid high-performance water reducing agent, and the water reducing rate is greater than or equal to 45%.

[0073] In the embodiment, the steel fiber is a copper-plated micro-wire straight steel fiber, with a diameter of 0.22 mm, a length of 13 mm, and a volume fraction of 1%.

[0074] The polyvinyl alcohol fiber has a diameter of 30 μm, a length of 12 mm, and a volume fraction of 0.5%.

[0075] The modified glass short fiber has a diameter of 17 μm, a length of 3 mm, and a volume fraction of 0.5%.

[0076] In addition, the embodiment also provides a preparation method of the hybrid fiber reinforced ultra-high performance polymer concrete, and the specific steps are as follows:

[0077] (1) configuring an alkali activator:

[0078] First, the flaky sodium hydroxide solid is dissolved in water, stirred for 30 s, and a NaOH solution with a concentration of 16 mol / L is prepared, and the solution is left to stand for 24 h for use, to obtain the NaOH solution; the NaOH solution and the water glass solution are mixed according to a mass ratio of 103:206 to obtain the alkali activator.

[0079] (2) The glass fiber is modified by a silane coupling agent. First, the glass fiber is calcined at a high temperature of 400°C to remove the wetting agent on the surface of the glass fiber. Then, water and a silane coupling agent (KH550) are mixed to prepare a coupling agent solution with a concentration of 2%. The calcined glass fiber is then soaked in the coupling agent solution for 10-20 min. After taking out the glass fiber, the surface liquid is wiped off and the glass fiber is placed in a drying oven at 120°C for 4 h. After cooling, the modified glass short fiber is obtained and ready for use.

[0080] (3) The slag, metakaolin, silica fume, quartz sand, and water reducing agent are weighed according to the weight parts, and added to the mixer. The dry materials are slowly stirred for 1 min at a speed of 70 r / min.

[0081] (4) The water and the alkali activator are weighed according to the weight parts, mixed, and then slowly poured into the mixer. The mixture is mechanically stirred at medium speed for 4 min at a speed of 90 r / min.

[0082] (5) The steel fiber, polyvinyl alcohol fiber, and modified glass fiber are added in the order of weight parts, and mechanically stirred at high speed for 3 min to make the fibers uniformly dispersed, at a speed of 150 r / min.

[0083] (6) The stirred fresh mixture is transferred to the mold (cubes with a side length of 70.7 mm), vibrated for 30-60 s to form, coated with a surface film, and demolded and cured after 24 h to obtain the hybrid fiber reinforced ultra-high performance geopolymer concrete.

[0084] It is detected that the 3d compressive strength of the test piece prepared in Example 1 is 114.4 MPa, the 28d compressive strength at room temperature is 131.6 MPa, the compressive strength after high temperature of 400℃ is 52.8 MPa, and the compressive strength after high temperature of 800℃ is 41.6 MPa.

[0085] Example 2

[0086] The present embodiment provides a hybrid fiber reinforced ultra-high performance geopolymer concrete, which is composed of the following raw materials in parts by weight:

[0087]

[0088]

[0089] In the present embodiment, the multi-element solid waste-based precursor material comprises the following components in parts by weight:

[0090] Blast furnace slag 711 parts,

[0091] Metakaolin 89 parts,

[0092] Silica fume 89 parts.

[0093] In the present embodiment, the alkali activator is composed of 107 parts of NaOH solution and 214 parts of water glass composite activator.

[0094] In the present embodiment, the volume content of the steel fiber is 1%, and the volume content of the modified glass short-cut fiber is 1%.

[0095] The volume content of the polyvinyl alcohol fiber is 0.5%.

[0096] In addition to the above parts by weight, the preparation method and material properties in the present embodiment are the same as those in Example 1.

[0097] It is detected that the 3d compressive strength of the test piece prepared in Example 2 is 121.8 MPa, the 28d compressive strength at room temperature is 140.7 MPa, the compressive strength after high temperature of 400℃ is 73.3 MPa, and the compressive strength after high temperature of 800℃ is 45.6 MPa.

[0098] Example 3

[0099] The embodiment provides a hybrid fiber reinforced ultra-high performance geopolymer concrete, which is composed of raw materials in the following proportions by weight:

[0100]

[0101] In the embodiment, the multi-element solid waste-based precursor material comprises the following components in proportions by weight:

[0102] blast furnace slag 711 parts,

[0103] metakaolin 89 parts,

[0104] silica fume 89 parts.

[0105] In the embodiment, the alkali activator is composed of 107 parts of NaOH solution and 214 parts of water glass composite activator.

[0106] In the embodiment, the volume content of the steel fiber is 1%, and the volume content of the polyvinyl alcohol fiber is 1%.

[0107] The volume content of the modified glass short-cut fiber is 0.5%.

[0108] In addition to the proportions by weight described above, the preparation method and material properties in the embodiment are the same as those in Embodiment 1.

[0109] It is detected that the 3d compressive strength of the test piece prepared in Embodiment 3 is 108.2 MPa, the 28d compressive strength at room temperature is 127.7 MPa, the compressive strength after high temperature of 400 DEG C is 52.5 MPa, and the compressive strength after high temperature of 800 DEG C is 39.4 MPa.

[0110] Comparative Example 1

[0111] The comparative example provides a slag-based ultra-high performance geopolymer concrete, which is composed of raw materials in the following proportions by weight:

[0112]

[0113] In the embodiment, the alkali activator is composed of 107 parts of NaOH solution and 214 parts of water glass composite activator.

[0114] In addition to the proportions by weight and composition of the concrete described above, the preparation method and material properties in the comparative example are the same as those in Embodiment 1.

[0115] It is detected that the 3d compressive strength of the test piece prepared in Comparative Example 1 is 95.3 MPa, the 28d compressive strength at room temperature is 115.7 MPa, the compressive strength after high temperature of 400 DEG C is 51.4 MPa, and the compressive strength after high temperature of 800 DEG C is 36.7 MPa.

[0116] Comparative Example 2

[0117] The comparative example provides a fiber reinforced geopolymer concrete, which is composed of raw materials in the following weight fractions:

[0118]

[0119]

[0120] In this example, the alkali activator is composed of 122 parts of NaOH solution and 244 parts of water glass composite activator.

[0121] In this example, the volume fraction of the glass fiber is 2%.

[0122] Except for the weight fractions and compositions of the above concrete, the preparation method and material properties in this comparative example are the same as those in Example 1.

[0123] It is detected that the 3d compressive strength of the test piece prepared in Comparative Example 2 is 77.6 MPa, the 28d compressive strength at room temperature is 110.4 MPa, the compressive strength of the test piece after high temperature of 400℃ is 55.2 MPa, and the compressive strength of the test piece after high temperature of 800℃ is 31.2 MPa.

[0124] Comparative Example 3

[0125] The comparative example provides a fiber reinforced geopolymer concrete, which is composed of raw materials in the following weight fractions:

[0126]

[0127] In this example, the alkali activator is composed of 122 parts of NaOH solution and 244 parts of water glass composite activator.

[0128] In this example, the volume fraction of the steel fiber is 1%, and the volume fraction of the modified glass short-cut fiber is 1%.

[0129] Except for the weight fractions and compositions of the above concrete, the preparation method and material properties in this comparative example are the same as those in Example 1.

[0130] It is detected that the 3d compressive strength of the test piece prepared in Comparative Example 3 is 97.6 MPa, the 28d compressive strength at room temperature is 115.2 MPa, the compressive strength of the test piece after high temperature of 400℃ is 65.2 MPa, and the compressive strength of the test piece after high temperature of 800℃ is 37.3 MPa.

[0131] Comparative Example 4

[0132] The comparative example provides a fiber reinforced geopolymer concrete, which is composed of raw materials in the following weight fractions:

[0133]

[0134] In the present embodiment, the alkali activator is composed of 105 parts of NaOH solution and 210 parts of water glass composite activator.

[0135] In the present embodiment, the volume content of polyvinyl alcohol fiber is 2%.

[0136] In addition to the weight parts and composition of the above concrete, the preparation method and material properties in the present comparative example are the same as those in Example 1.

[0137] It is detected that the 3d compressive strength of the test piece prepared in Comparative Example 4 is 83.4 MPa, the 28d compressive strength at room temperature is 107.2 MPa, the compressive strength of the test piece after high temperature of 400℃ is 35.7 MPa, and the compressive strength of the test piece after high temperature of 800℃ is 28.5 MPa.

[0138] It is found by comparing the hybrid fiber reinforced ultra-high performance geopolymer concrete prepared in Examples 1-3 with the slag-based ultra-high performance geopolymer concrete prepared in Comparative Example 1 that the 3d and 28d compressive strengths of the hybrid fiber reinforced ultra-high performance geopolymer concrete prepared in Examples 1-3 are significantly greater than those of the slag-based ultra-high performance geopolymer concrete prepared in Comparative Example 1, and the hybrid fiber reinforced ultra-high performance geopolymer concrete prepared in Examples 1-3 has higher compressive performance under high temperature of 400℃ and 800℃; however, the absence of metakaolin and silica fume in the components results in poor fluidity, large shrinkage of geopolymer concrete, increased cracks, and insufficient pozzolanic reaction, and the residual compressive strength is lower than that of the multi-solid waste hybrid fiber reinforced ultra-high performance geopolymer concrete.

[0139] It is found by comparing the hybrid fiber reinforced ultra-high performance geopolymer concrete prepared in Examples 1-3 with the fiber reinforced geopolymer concrete prepared in Comparative Example 2 that when only a single glass fiber is added to the geopolymer concrete, the 28d strength is only 110.4 MPa, which is lower than the strength of the hybrid fiber reinforced ultra-high performance geopolymer concrete prepared in Examples 1-3, and the room temperature strength is insufficient, indicating that the single fiber has low toughening efficiency; since the glass fiber softens and loses the reinforcing effect above 700℃, the high temperature strength is less than that of the hybrid fiber reinforced ultra-high performance geopolymer concrete prepared in Examples 1-3, and the high temperature performance degrades; the absence of silica fume in the components results in poor fluidity of the geopolymer concrete, fast setting and hardening, and poor matrix density. Therefore, a single fiber cannot balance the room temperature / high temperature performance, and an excessive volume content of a single fiber may cause agglomeration.

[0140] Comparing the hybrid fiber reinforced ultra-high performance geopolymer concrete prepared in Examples 1-3 with the fiber reinforced geopolymer concrete prepared in Comparative Example 3, it is found that when only steel fibers and modified glass chopped fibers are added to the geopolymer concrete, the 3d strength of the geopolymer concrete is 97.6 MPa, which is significantly lower than 121.8 MPa of Example 2, the early strength development is slow due to the lack of PVA fibers to inhibit plastic shrinkage cracks; the high temperature strength is less than that of the hybrid fiber reinforced ultra-high performance geopolymer concrete prepared in Examples 1-3 due to the lack of micro-pore channels left by PVA fibers to release steam pressure, and the high temperature residual strength is low; when only slag and metakaolin are used in the components, the SiO2 / Al2O3 ratio is unbalanced, resulting in insufficient activity of the matrix. Therefore, the absence of PVA fibers leads to weak micro-crack control ability and decreased high temperature anti-spalling performance.

[0141] Comparing the hybrid fiber reinforced ultra-high performance geopolymer concrete prepared in Examples 1-3 with the fiber reinforced geopolymer concrete prepared in Comparative Example 4, it is found that when only polyvinyl alcohol fibers are added to the geopolymer concrete, the 28d strength of the geopolymer concrete is 107.2 MPa, the modulus of PVA fibers is low, and it is easy to agglomerate, so it is difficult to effectively bear load, and therefore the normal temperature strength is the lowest; the strength at 400℃ drops to 35.7 MPa due to the melting of PVA at 250℃ to form pore channels, weakening the matrix. Therefore, single PVA fibers cannot provide effective reinforcement, and even accelerate performance degradation at high temperatures.

[0142] In summary, by hybridly incorporating steel fibers, polyvinyl alcohol fibers and modified glass chopped fibers of different sizes, the brittleness of the geopolymer concrete is significantly improved, and the early strength and high temperature resistance are improved.

[0143] The above description of the examples is for the convenience of the ordinary skilled person in the art to understand and use the invention. Those skilled in the art can easily make various modifications to these examples, and apply the general principles described herein to other examples without having to go through creative labor. Therefore, the present application is not limited to the above examples, and those skilled in the art can make improvements and modifications within the scope of the present application without departing from the scope of the present application.

Claims

1. A hybrid fiber reinforced ultra-high performance geopolymer concrete, characterized in that: It is composed of the following raw materials in parts by weight:

2. The hybrid fiber reinforced ultra-high performance geopolymer concrete according to claim 1, characterized in that: The multi-solid waste-based precursor material includes the following components in parts by weight: 429-932 parts of blast furnace slag, 86-518 parts of metakaolin, 86-311 parts of silica fume.

3. The hybrid fiber reinforced ultra-high performance geopolymer concrete according to claim 2, characterized in that: The blast furnace slag is S95 grade slag powder, with a 28d activity coefficient of ≥95 and a specific surface area of ​​≥400m 2 / kg; The metakaolin is calcined at 600°C and has a maximum particle size of ≤10 μm; The silica fume has a 28d activity coefficient of ≥115 and a specific surface area of ​​≥15000m 2 / kg, SiO2 content ≥92%, average particle size 0.1-0.3μm.

4. The hybrid fiber reinforced ultra-high performance geopolymer concrete according to claim 1, characterized in that: The alkaline activator is a NaOH solution-water glass composite activator; The NaOH solution is prepared from industrial-grade flaky sodium hydroxide solid with a purity of 99%, and the concentration of the NaOH solution is 15-17 mol / L. The water glass solution has a SiO2 content of 29.9%, a Na2O content of 13.75%, and a modulus of 2.

25.

5. The hybrid fiber reinforced ultra-high performance geopolymer concrete according to claim 1, characterized in that: The particle size of the quartz sand is 26-70 mesh; The water reducing agent is a polycarboxylic acid high performance water reducing agent with a water reducing rate of ≥45%.

6. The hybrid fiber reinforced ultra-high performance geopolymer concrete according to claim 1, characterized in that: The steel fiber is a copper-plated microfilament steel fiber or an end hook steel fiber, with a diameter of 0.18-0.23 mm, a length of 12-14 mm, and a volume fraction of 1%-2%; The polyvinyl alcohol fiber has a diameter of 15-30 μm, a length of 12 mm, a tensile strength of ≥1550 MPa, and a volume fraction of 0.5%-1%; The modified glass chopped fibers have a diameter of 15-17 μm, a length of 3 mm, and a volume fraction of 0.5%-1.

7. A method for preparing the hybrid fiber reinforced ultra-high performance geopolymer concrete according to any one of claims 1 to 6, characterized in that: The specific steps are as follows: S1. Prepare alkaline activator; S2, modifying the surface of the glass fiber with a silane coupling agent to obtain modified glass chopped fibers; S3. Weigh the multi-solid waste-based precursor material, quartz sand, and water reducer in parts by weight, add them into a blender, and slowly stir to obtain a mixture A; S4, weighing water and an alkaline activator in parts by weight, mixing them with the mixture A obtained in step S3, and mechanically stirring at a medium speed to obtain a mixture B; S5. Add steel fiber, polyvinyl alcohol fiber and modified glass fiber to the mixture B obtained in step S4 in order according to the weight ratio, and stir at high speed to evenly disperse the fibers to obtain a mixture C; S6. Transfer the mixture C stirred in step S5 into a mold, vibrate it into shape, and coat the surface with a film. After demolding and curing, a hybrid fiber reinforced ultra-high performance geopolymer concrete is obtained.

8. The method for preparing hybrid fiber reinforced ultra-high performance geopolymer concrete according to claim 7, characterized in that: In step S1, the specific steps of preparing the alkaline activator are: S1-1, prepare NaOH solution: dissolve flaky sodium hydroxide solid in water, stir to obtain NaOH solution, and let it stand for 24 hours before use; S1-2, mixing the NaOH solution obtained in step S1-1 with the water glass solution in a mass ratio of (103-124): (206-248) to obtain an alkaline activator; In step S2, the specific steps of modifying the glass fiber surface with a silane coupling agent are as follows: S2-1, calcining the glass fiber at a high temperature to remove the impregnation agent on its surface; S2-2, mixing water and a silane coupling agent to obtain a coupling agent solution; S2-3, soaking the glass fiber calcined in step S2-1 in the coupling agent solution obtained in step S2-2, and drying to obtain modified glass chopped fibers.

9. The method for preparing hybrid fiber reinforced ultra-high performance geopolymer concrete according to claim 7, characterized in that: In step S3, the rotation speed of the slow stirring is 70-90 r / min, and the stirring time is 1-3 min; In step S4, the speed of the medium-speed stirring is 90-140 r / min, and the stirring time is 3-5 min; In step S5, the rotation speed of the high-speed stirring is greater than 140 r / min, and the stirring time is 2-4 min.

10. Use of the hybrid fiber reinforced ultra-high performance geopolymer concrete according to any one of claims 1 to 6 in complex environmental engineering structures.

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