C700-grade anti-instantaneous high-temperature burst ultra-high performance concrete as well as preparation and application thereof

Abstract

The invention discloses C700-grade anti-instantaneous high temperature burst ultra-high performance concrete as well as preparation and application thereof. The components of the C700-grade anti-instantaneous high temperature burst ultra-high performance concrete comprise a mixture and hybrid steel fibers, the mixture is prepared from the following components in parts by mass: 400 to 450 parts of cement, 90 to 120 parts of silica fume, 45 to 60 parts of fly ash microbeads, 50 to 70 parts of inorganic temperature regulating and reinforcing agent, 30 to 40 parts of hydration rate regulating and reinforcing agent, 65 to 85 parts of water, 6.5 to 8 parts of polycarboxylate superplasticizer and 1000 parts of metal aggregate; the hybrid steel fibers account for 7-8% of the volume of the mixture; the C700-grade instantaneous high temperature burst resistant UHPC is obtained by adjusting the components and combining a vibration pressurization process with gradient curing, and the strength, impact resistance and high temperature stability of the material are synergistically improved.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and in particular to a C700-grade instantaneous high-temperature burst-resistant ultra-high performance concrete and its preparation and application. Background Art

[0002] Ultra-high-performance concrete (UHPC), with its exceptional strength, toughness, and durability, has become a key candidate material for major national frontier projects. However, the emergence of extreme and complex applications in major national frontier projects, particularly those requiring protection against robust earth-penetrating weapons, requires UHPC to withstand the extreme demands of high strain rate impact, transient high temperatures, and high-velocity loads. This places even higher demands on UHPC's strength and high-temperature resistance.

[0003] In existing technologies, to significantly enhance the strength of UHPC, nanomaterials are often added for modification, such as nano-SiO2 and carbon nanotubes. While these can improve UHPC strength to a certain extent, the water-cement ratio of UHPC itself (0.16-0.18) is lower than that of ordinary concrete. These nanomaterials are difficult to disperse in UHPC, resulting in limited reinforcement effects and a high risk of rapid loss of the UHPC slurry state. Alternatively, the strength can be improved by increasing the curing temperature, but high-temperature curing can easily lead to internal defects due to an imbalance between the hydration rate and temperature stress, making it difficult for UHPC strength to exceed 300 MPa. Alternatively, the strength of UHPC can be enhanced by increasing the fiber content, but numerous studies have shown that when the fiber content exceeds 4%, it becomes difficult to disperse in the UHPC, significantly affecting the overlap between the fibers and limiting the maximum strength increase. Moreover, due to the extremely dense internal structure of UHPC, the internal steam pressure cannot be effectively released under high temperature conditions, resulting in poor high temperature resistance.

[0004] Therefore, there is an urgent need for a technical solution to improve the mechanical properties and transient high temperature and explosion-proof performance of ultra-high performance concrete. Summary of the Invention

[0005] In view of this, the present application provides a C700 grade ultra-high performance concrete resistant to instantaneous high temperature bursting and its preparation method and application, which are used to solve the problem of how to improve the mechanical properties of ultra-high performance concrete and resist instantaneous high temperature explosion.

[0006] In order to achieve the above technical objectives, this application adopts the following technical solutions: In a first aspect, the present application provides a C700-grade instantaneous high-temperature burst-resistant ultra-high performance concrete, comprising a mixture and mixed steel fibers, wherein the mixture comprises the following components by mass: 400-450 parts of cement, 90-120 parts of silica fume, 45-60 parts of fly ash microspheres, 50-70 parts of an inorganic temperature control-reinforcement agent, 30-40 parts of a hydration rate control-reinforcement agent, 65-85 parts of water, 6.5-8 parts of a polycarboxylate water-reducing agent, and 1000 parts of a metal aggregate; the mixed steel fibers account for 7-8% of the mixture by volume; The preparation method of C700 grade instantaneous high temperature burst resistant ultra-high performance concrete comprises the following steps: Cement, silica fume, fly ash microbeads, inorganic temperature control-enhancing agent, hydration rate control-enhancing agent, polycarboxylate water-reducing agent, metal aggregate, and mixed steel fiber are uniformly mixed and poured into a test mold. After vibration and pressure molding, standard curing and demolding are performed, and gradient high-temperature curing is performed in sequence. The concrete is cooled to obtain the C700 grade instantaneous high-temperature burst-resistant ultra-high performance concrete.

[0007] The present invention optimizes the composition of the cementitious material system and adds a hydration rate control-enhancing agent to control the state of the entire slurry, making it feasible to vibrate and pressurize, and ensures the effective dispersion of the subsequent steel fibers in the slurry during the stirring and vibration molding process, thereby improving its overlapping effect; by optimizing the composition of the cementitious material system and adding an inorganic temperature control-enhancing agent and a hydration rate control-enhancing agent, the Ca-Si-Al ratio of the entire cementitious system and the hydration process of the cementitious material under high-temperature thermal excitation are controlled, thereby improving its hydration reaction efficiency and hydration reaction degree, and optimizing the morphology and quantity of the internal hydration products of the UHPC specimen under high-temperature curing, making the microstructure of the hydration product more dense and stable.

[0008] This application uses metal aggregates and hybrid steel fibers as the skeleton of the entire cementitious material system. On the one hand, fibers of different sizes in the hybrid fibers can form a gradient overlap, strengthening the bridging effect between the fibers in the slurry system. Combined with metal aggregates with higher hardness, it can provide a solid skeleton foundation for the entire matrix. On the other hand, the effective bridging between the hybrid fibers, the metal aggregates with a thermal expansion coefficient similar to that of the matrix, and the inorganic temperature control-enhancing agent with higher high-temperature stability can play a multi-dimensional heat conduction role, avoiding uneven heating inside the specimen under high-temperature thermal excitation, affecting its thermal excitation effect, and also enhancing the instantaneous high-temperature burst resistance of the obtained UHPC at high temperatures.

[0009] The present invention adopts a vibration pressurization process to form the specimen, which can not only effectively solve the problem of the forward distribution of steel fibers in the slurry under the condition of single pressurization, resulting in a decrease in the compressive strength of the specimen, but also effectively eliminate the pores in the specimen, so that the specimen has an extremely dense internal structure, and can effectively improve the interlacing and overlapping effect of the mixed fibers in the three-dimensional space of the entire system, thereby improving the ability of the entire system to resist external impact; through a maintenance strategy of gradually increasing the temperature in stages, the hydration reaction process of the cementitious system is dynamically matched with the temperature field, which not only avoids the accumulation of internal defects caused by a single high temperature, but also fully stimulates the secondary reaction activity of the mineral admixture.

[0010] Based on the existing UHPC closest packing theory, the present invention innovatively combines the coordinated control technology of high-temperature thermal excitation and cementitious material hydration process, the coordinated balance technology of temperature stress formation rate and strength formation rate, the coordinated control technology of high-strength skeleton interface reinforcement and fiber three-dimensional spatial interlacing and overlapping, the coordinated balance technology of fiber three-dimensional spatial distribution and vibration-compression compaction, and high-temperature heat conduction control technology to produce C700-grade ultra-high performance concrete that is resistant to instantaneous high-temperature bursting.

[0011] Preferably, the hybrid steel fiber includes a first fiber and a second fiber, the first fiber has a diameter of 0.20-0.30 mm and a length of 13-15 mm; the second fiber has a diameter of 0.20-0.22 mm and a length of 4-6 mm.

[0012] The hybrid steel fiber of the present application includes a first fiber (long fiber) and a second fiber (short fiber). The long fiber provides macroscopic crack resistance, and the short fiber fills microscopic defects. The two are gradiently overlapped to form a spatial bridging system, thereby improving compressive strength and impact resistance. At the same time, the matching of the thermal expansion coefficients of the metal aggregate and the matrix reduces the interfacial thermal stress. The hybrid fiber and the inorganic temperature control-reinforcement agent can synergistically construct a "fiber-interface-matrix" three-dimensional heat conduction path, thereby improving the uniformity of the thermal stress distribution of the material under instantaneous high temperature and reducing the risk of bursting.

[0013] Preferably, the mass ratio of the first fiber to the second fiber is (2-3):1.

[0014] Preferably, the hydration rate regulating and enhancing agent comprises boric acid and anhydrite in a mass ratio of (0.01-0.02):1.

[0015] Preferably, the cement is ordinary Portland cement with a grade of ≥52.5 or Portland cement with a grade of ≥52.5.

[0016] Preferably, the inorganic temperature regulating and reinforcing agent comprises calcined high-alumina bauxite powder and / or metakaolin powder; the fineness of the inorganic temperature regulating and reinforcing agent is ≥325 mesh.

[0017] Preferably, the water demand ratio of the fly ash microbeads is ≤95%, and the 28d compressive activity index is ≥110%.

[0018] Preferably, the water demand ratio of silica fume is ≤125%, and the 28d activity index is ≥105%.

[0019] Preferably, the metal aggregate is steel sand, and the particle size of the steel sand is 0.3-1.0 mm.

[0020] Preferably, the vibration frequency of the vibration press molding is 50-70 Hz, the vibration time is 10-13 min, and the pressurization pressure is 4-6 MPa.

[0021] Preferably, the steps of gradient high temperature curing are: first steam curing at 90°C for 48 hours, then autoclaving curing at 185-200°C for 6-8 hours, and then high temperature dry curing at 280-300°C for 6-8 hours.

[0022] In a second aspect, the present application provides a method for preparing C700 grade instantaneous high temperature burst resistant ultra-high performance concrete, comprising the following steps: Mixing cement, silica fume, fly ash microbeads, an inorganic temperature control-enhancing agent, a hydration rate control-enhancing agent, a polycarboxylate water reducer, and metal aggregate to obtain a mixture; Adding water to the mixture and stirring evenly to obtain a slurry; Mixed steel fibers are added to the slurry, stirred evenly, poured into a test mold, vibrated and pressed into shape, and then subjected to standard curing and demolding. Gradient high-temperature curing and cooling are then performed in sequence to obtain the C700 grade instantaneous high-temperature burst-resistant ultra-high performance concrete.

[0023] The beneficial effects of this application are as follows: the present invention constructs a gradient skeleton by metal aggregate and mixed steel fiber, suppresses high-temperature bursting through thermal expansion matching and multi-dimensional heat transfer, and strengthens mechanical properties at the same time; breaks the fiber directional distribution and eliminates pores through the vibration pressurization process, realizes three-dimensional uniform dispersion and matrix densification, and combines gradient curing to obtain C700 grade instantaneous high-temperature burst-resistant UHPC, which synergistically improves the strength, impact resistance and instantaneous high-temperature stability of the material, and its impact strength can reach 60KJ / m 2 The strength loss rate of the steel sheet after being placed at 1000°C for 10 minutes is less than 18%. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a picture of the unbroken test piece before calcination at 1000℃; Figure 2 This is a picture of the broken test piece before calcination at 1000℃; Figure 3 This is a picture of the test piece after calcination at 1000℃ for 10min; Figure 4 This is a picture of a test piece that did not break after calcining at 1000℃ for 10 minutes; Figure 5 This is a picture of the broken test piece after calcination at 1000℃ for 10 minutes. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0026] The present invention is further described below through specific examples.

[0027] Example 1 A C700 grade instantaneous high-temperature burst resistant ultra-high performance concrete comprises the following components by mass: 400 parts of cement, 90 parts of silica fume, 45 parts of fly ash microspheres, 50 parts of inorganic temperature control-reinforcement agent, 30 parts of hydration rate control-reinforcement agent, 65 parts of water, 6.5 parts of polycarboxylate water reducer, 1000 parts of metal aggregate, and mixed steel fiber accounting for 7% of the volume of the C700 grade instantaneous high-temperature burst resistant ultra-high performance concrete; wherein the hydration rate control-reinforcement agent is a mixture of boric acid and anhydrite in a mass ratio of 0.015:1; the cement is PII52.5 grade ordinary silica fume. cement; the water requirement of silica fume is 115%, and the 28-day activity index is 118%; the water requirement of fly ash microbeads is 91%, and the 28-day compressive activity index is 112%; the inorganic temperature control-reinforcement agent is 325-mesh calcined high-alumina bauxite powder with an alumina content of 80.3%; the metal aggregate is a mixture of steel grit with particle sizes of 0.7 mm and 0.5 mm in a mass ratio of 2:8; the mixed steel fiber is a mixture of steel fiber with a diameter of 0.2 mm and a length of 13 mm and steel fiber with a diameter of 0.2 mm and a length of 6 mm in a mass ratio of 2:1.

[0028] The above-mentioned C700 grade instantaneous high temperature burst resistance ultra-high performance concrete is produced by the following method: According to the above raw material ratio, cement, silica fume, fly ash microspheres, inorganic temperature control-enhancing agent, hydration rate control-enhancing agent, polycarboxylate water reducer, and metal aggregate were mixed and stirred for 1 minute to obtain a mixture; Add water to the mixture and continue stirring for 3 minutes to obtain a slurry; Mixed steel fibers were added to the slurry, stirred for 2 minutes, poured into a test mold, placed under a vibration frequency of 60 Hz and a pressurized pressure of 5 MPa while vibrating and pressurizing for 12 minutes, then placed in a standard curing room for curing for 1 day, and demolded. The specimen was then steam-cured at 90°C for 48 hours. After cooling, it was autoclaved at 185°C for 8 hours. After cooling, it was dry-cured at 300°C for 8 hours. After cooling, C700 grade ultra-high performance concrete resistant to instantaneous high-temperature bursting was obtained.

[0029] Example 2 A C700 grade instantaneous high-temperature burst resistant ultra-high performance concrete comprises the following components by mass: 410 parts of cement, 100 parts of silica fume, 50 parts of fly ash microspheres, 70 parts of inorganic temperature control-reinforcement agent, 35 parts of hydration rate control-reinforcement agent, 80 parts of water, 7.5 parts of polycarboxylate water reducer, 1000 parts of metal aggregate, and mixed steel fiber accounting for 7% of the volume of the C700 grade instantaneous high-temperature burst resistant ultra-high performance concrete; wherein the hydration rate control-reinforcement agent is a mixture of boric acid and anhydrite in a mass ratio of 0.015:1; the cement is PII52.5 grade ordinary silica fume. The water requirement of silica fume is 115%, and the 28-day activity index is 118%; the water requirement of fly ash microbeads is 91%, and the 28-day compressive activity index is 112%; the inorganic temperature control-reinforcement agent is 325-mesh calcined high-alumina bauxite powder with an alumina content of 80.3%; the metal aggregate is a mixture of steel grit with particle sizes of 0.7 mm and 0.5 mm in a mass ratio of 2:8; the mixed steel fiber is a mixture of steel fiber with a diameter of 0.2 mm and a length of 13 mm and steel fiber with a diameter of 0.2 mm and a length of 6 mm in a mass ratio of 3:1.

[0030] The above-mentioned C700 grade instantaneous high temperature burst resistance ultra-high performance concrete is produced by the following method: According to the above raw material ratio, cement, silica fume, fly ash microspheres, inorganic temperature control-enhancing agent, hydration rate control-enhancing agent, polycarboxylate water reducer, and metal aggregate were mixed and stirred for 1 minute to obtain a mixture; Add water to the mixture and continue stirring for 3 minutes to obtain a slurry; Mixed steel fibers were added to the slurry, stirred for 2 minutes, poured into a test mold, placed under a vibration frequency of 60 Hz and a pressurized pressure of 5 MPa while vibrating and pressurizing for 12 minutes, then placed in a standard curing room for curing for 1 day, and demolded. The specimen was then steam-cured at 90°C for 48 hours. After cooling, it was autoclaved at 185°C for 8 hours. After cooling, it was dry-cured at 300°C for 8 hours. After cooling, C700 grade ultra-high performance concrete resistant to instantaneous high-temperature bursting was obtained.

[0031] Example 3 A C700 grade instantaneous high temperature burst resistance ultra-high performance concrete comprises the following components by mass: 430 parts of cement, 120 parts of silica fume, 50 parts of fly ash microspheres, 50 parts of an inorganic temperature control-reinforcer, 35 parts of a hydration rate control-reinforcer, 80 parts of water, 8 parts of a polycarboxylate water reducer, 1000 parts of a metal aggregate, and mixed steel fibers accounting for 8% of the volume of the C700 grade instantaneous high temperature burst resistance ultra-high performance concrete; wherein the hydration rate control-reinforcer is a mixture of boric acid and anhydrite in a mass ratio of 0.015:1; the cement is PII5 2.5 grade ordinary Portland cement; the water requirement ratio of silica fume is 115%, and the 28d activity index is 118%; the water requirement ratio of fly ash microbeads is 91%, and the 28d compressive activity index is 112%; the inorganic temperature control-reinforcement agent is 325 mesh high-grade territorial micropowder; the metal aggregate is a mixture of steel grit with particle sizes of 0.7mm and 0.5mm in a mass ratio of 2:8; the mixed steel fiber is a mixture of steel fiber with a diameter of 0.3mm and a length of 13mm, and steel fiber with a diameter of 0.2mm and a length of 6mm in a mass ratio of 2:1.

[0032] The above-mentioned C700 grade instantaneous high temperature burst resistance ultra-high performance concrete is produced by the following method: According to the above raw material ratio, cement, silica fume, fly ash microspheres, inorganic temperature control-enhancing agent, hydration rate control-enhancing agent, polycarboxylate water reducer, and metal aggregate were mixed and stirred for 1 minute to obtain a mixture; Add water to the mixture and continue stirring for 3 minutes to obtain a slurry; Mixed steel fibers were added to the slurry, stirred for 2 minutes, poured into a test mold, placed under a vibration frequency of 60 Hz and a pressurized pressure of 5 MPa while vibrating and pressurizing for 12 minutes, then placed in a standard curing room for curing for 1 day, and demolded. The specimen was then steam-cured at 90°C for 48 hours. After cooling, it was autoclaved at 185°C for 8 hours. After cooling, it was dry-cured at 300°C for 8 hours. After cooling, C700 grade ultra-high performance concrete resistant to instantaneous high-temperature bursting was obtained.

[0033] Example 4 A C700-grade instantaneous high-temperature burst-resistant ultra-high performance concrete comprising the following components in parts by mass: 4,350 parts of cement, 120 parts of silica fume, 60 parts of fly ash microspheres, 70 parts of an inorganic temperature control-reinforcement agent, 40 parts of a hydration rate control-reinforcement agent, 85 parts of water, 8 parts of a polycarboxylate water-reducing agent, 1,000 parts of a metal aggregate, and mixed steel fibers accounting for 8% by volume of the C700-grade instantaneous high-temperature burst-resistant ultra-high performance concrete; Among them, the hydration rate control-reinforcement agent is a mixture of boric acid and anhydrite in a mass ratio of 0.015:1; the cement is PII52.5 grade ordinary Portland cement; the water demand ratio of silica fume is 115%, and the 28d activity index is 118%; the water demand ratio of fly ash microbeads is 91%, and the 28d compressive activity index is 112%; the inorganic temperature control-reinforcement agent is 325 mesh high-grade territorial micropowder; the metal aggregate is a mixture of steel sand with a particle size of 0.7mm and 0.5mm in a mass ratio of 2:8; the mixed steel fiber is a mixture of steel fiber with a diameter of 0.3mm and a length of 13mm and steel fiber with a diameter of 0.2mm and a length of 6mm in a mass ratio of 3:1.

[0034] The above-mentioned C700 grade instantaneous high temperature burst resistance ultra-high performance concrete is produced by the following method: According to the above raw material ratio, cement, silica fume, fly ash microspheres, inorganic temperature control-enhancing agent, hydration rate control-enhancing agent, polycarboxylate water reducer, and metal aggregate were mixed and stirred for 1 minute to obtain a mixture; Add water to the mixture and continue stirring for 3 minutes to obtain a slurry; Mixed steel fibers were added to the slurry, stirred for 2 minutes, poured into a test mold, placed under a vibration frequency of 60 Hz and a pressurized pressure of 5 MPa while vibrating and pressurizing for 12 minutes, then placed in a standard curing room for curing for 1 day, and demolded. The specimen was then steam-cured at 90°C for 48 hours. After cooling, it was autoclaved at 185°C for 8 hours. After cooling, it was dry-cured at 300°C for 8 hours. After cooling, C700 grade ultra-high performance concrete resistant to instantaneous high-temperature bursting was obtained.

[0035] Comparative Example 1 An ultra-high performance concrete, the other contents of which are the same as those of Example 1, except that no hydration rate regulating and reinforcing agent is added, and the usage ratio of cement, silica fume, fly ash microbeads, and inorganic temperature regulating and reinforcing agent remains unchanged, and the sum of their mass fractions is the sum of the mass of the hydration rate regulating and reinforcing agent, cement, silica fume, fly ash microbeads, and inorganic temperature regulating and reinforcing agent in Example 1.

[0036] Comparative Example 2 An ultra-high performance concrete, the other contents of which are the same as those of Example 1, except that the S105 grade mineral powder is replaced by an inorganic temperature regulating and enhancing agent.

[0037] Comparative Example 3 An ultra-high performance concrete, the other contents are the same as those of Example 1, except that: Cement, silica fume, fly ash microbeads, inorganic temperature control-enhancing agent, hydration rate control-enhancing agent, polycarboxylate water reducer, and metal aggregate were mixed and stirred for 1 minute to obtain a mixture; Add water to the mixture and continue stirring for 3 minutes to obtain a slurry; Mixed steel fibers were added to the slurry, stirred for 2 minutes, poured into a test mold, and placed under a vibration frequency of 60 Hz and a pressurized pressure of 5 MPa while vibrating and pressurizing for 2 minutes. The slurry was then placed in a standard curing room for curing for 1 day, and the mold was removed. The specimen was then steam-cured at 90°C for 48 hours. After cooling, it was autoclaved at 185°C for 8 hours. After cooling, it was dry-cured at 300°C for 8 hours. After cooling, ultra-high performance concrete was obtained.

[0038] Comparative Example 4 An ultra-high performance concrete, the other contents are the same as those of Example 1, except that: Cement, silica fume, fly ash microbeads, inorganic temperature control-enhancing agent, hydration rate control-enhancing agent, polycarboxylate water reducer, and metal aggregate were mixed and stirred for 1 minute to obtain a mixture; Add water to the mixture and continue stirring for 3 minutes to obtain a slurry; Mixed steel fibers were added to the slurry, stirred for 2 minutes, poured into a test mold, and vibrated at a vibration frequency of 60 Hz for 12 minutes. The slurry was then placed in a standard curing room for 1 day and removed from the mold. The specimen was then steam-cured at 90°C for 48 hours. After cooling, the specimen was autoclaved at 185°C for 8 hours. After cooling, the specimen was dry-cured at 300°C for 8 hours. After cooling, ultra-high performance concrete was obtained.

[0039] Comparative Example 5 An ultra-high performance concrete, the other contents are the same as those of Example 1, except that: Cement, silica fume, fly ash microbeads, inorganic temperature control-enhancing agent, hydration rate control-enhancing agent, polycarboxylate water reducer, and metal aggregate were mixed and stirred for 1 minute to obtain a mixture; Add water to the mixture and continue stirring for 3 minutes to obtain a slurry; Mixed steel fibers were added to the slurry, stirred for 2 minutes, poured into a test mold, and placed under a vibration frequency of 60 Hz and a pressurized pressure of 5 MPa for 12 minutes while vibrating. The slurry was then placed in a standard curing room for 1 day and the mold was removed. The specimen was then steam cured at 90°C for 48 hours. After cooling, it was dry-cured at 200°C for 8 hours. After cooling, it was dry-cured at 300°C for 8 hours. After cooling, ultra-high performance concrete was obtained.

[0040] Comparative Example 6 An ultra-high performance concrete, the other contents are the same as those of Example 1, except that: Cement, silica fume, fly ash microbeads, inorganic temperature control-enhancing agent, hydration rate control-enhancing agent, polycarboxylate water reducer, and metal aggregate were mixed and stirred for 1 minute to obtain a mixture; Add water to the mixture and continue stirring for 3 minutes to obtain a slurry; Mixed steel fibers were added to the slurry, stirred for 2 minutes, poured into a test mold, and placed under a vibration frequency of 60 Hz and a pressurized pressure of 5 MPa while vibrating and pressurizing for 12 minutes. The slurry was then placed in a standard curing room for curing for 1 day, and the mold was removed. The specimen was then steam-cured at 90°C for 48 hours. After cooling, it was autoclaved and cured at 185°C for 4 hours. After cooling, it was dry-cured at 300°C for 8 hours. After cooling, ultra-high performance concrete was obtained.

[0041] Comparative Example 7 An ultra-high performance concrete, the other contents are the same as those of Example 1, except that: Cement, silica fume, fly ash microbeads, inorganic temperature control-enhancing agent, hydration rate control-enhancing agent, polycarboxylate water reducer, and metal aggregate were mixed and stirred for 1 minute to obtain a mixture; Add water to the mixture and continue stirring for 3 minutes to obtain a slurry; Mixed steel fibers were added to the slurry, stirred for 2 minutes, poured into a test mold, and placed under a vibration frequency of 60 Hz and a pressurized pressure of 5 MPa while vibrating and pressurizing for 12 minutes. The slurry was then placed in a standard curing room for curing for 1 day, and the mold was removed. The specimen was then steam-cured at 90°C for 48 hours, autoclaved at 185°C for 8 hours, cooled, and dry-cured at 300°C for 4 hours. After cooling, ultra-high performance concrete was obtained.

[0042] Comparative Example 8 An ultra-high performance concrete, the other contents are the same as those of Example 1, except that: Cement, silica fume, fly ash microbeads, inorganic temperature control-enhancing agent, hydration rate control-enhancing agent, polycarboxylate water reducer, and metal aggregate were mixed and stirred for 1 minute to obtain a mixture; Add water to the mixture and continue stirring for 3 minutes to obtain a slurry; Mixed steel fibers were added to the slurry, stirred for 2 minutes, poured into a test mold, pressurized at 50 MPa for 30 minutes, and then cured in a standard curing room for 1 day. The mold was removed, and then the specimen was steam-cured at 90°C for 48 hours, autoclaved and cured at 185°C for 8 hours, cooled, and dry-cured at 300°C for 8 hours. After cooling, ultra-high performance concrete was obtained.

[0043] Comparative Example 9 An ultra-high performance concrete comprises the following components by weight: 400 parts of cement, 90 parts of silica fume, 125 parts of quartz powder, 68 parts of water, 6.5 parts of polycarboxylate superplasticizer, 1000 parts of metal aggregate, and steel fibers accounting for 7% of the volume of the ultra-high performance concrete; wherein the steel fibers have a diameter of 0.2 mm and a length of 3 mm.

[0044] The preparation method of the above-mentioned ultra-high performance concrete is as follows: According to the above raw material ratio, cement, silica fume, quartz powder, polycarboxylate water reducer and metal aggregate were mixed and stirred for 1 minute to obtain a mixture; Add water to the mixture and continue stirring for 3 minutes to obtain a slurry; Steel fiber was added to the slurry, stirred for 2 minutes, poured into a test mold, pressurized at 50 MPa for 30 minutes, and then cured in a standard curing room for 1 day. The mold was removed, and then the specimen was dry-cured at 300°C for 8 hours. After cooling, ultra-high performance concrete was obtained.

[0045] Testing and Evaluation The mechanical properties, impact resistance, and high-temperature burst resistance of the ultra-high performance concrete obtained in different embodiments and comparative examples, and the ultra-high performance concrete of comparative examples 1-7 were tested. The mechanical properties were tested using 40×40×160 mm specimens, the impact resistance was tested with reference to GB / T15231 "Test Method for Properties of Glass Fiber Reinforced Cement", and the high-temperature burst resistance was characterized by measuring the strength loss rate of the formed 40×40×160 mm specimens after curing at 1000°C for 10 minutes. The test results are shown in Table 1.

[0046] Table 1 Test results

[0047] As shown in Table 1, the C700 grade instantaneous high temperature burst resistance ultra-high performance concrete of the present invention has a compressive strength of more than 700 MPa and an impact strength of 60 KJ / m 2 As shown above, when treated at 1000℃ for 10min, the strength loss is very small, below 1.5%, and the strength loss rate can be kept below 18% after 30min.

[0048] Compared with Example 1, Comparative Example 1 does not add the hydration rate regulating-enhancing agent of the present invention, and the compressive strength is significantly reduced, the strength is reduced, and the impact resistance and high-temperature burst resistance are also reduced to varying degrees; Compared with Example 1, Comparative Example 2 replaces the inorganic temperature regulating-enhancing agent with S105 grade mineral powder, and the mechanical properties, impact strength and instantaneous high-temperature burst resistance of the specimen are all reduced, but the reduction in instantaneous high-temperature burst resistance is very significant; Compared with Example 1, Comparative Example 3 puts the stirred slurry into the mold and only pressurizes and vibrates for 2 minutes, the compressive strength is reduced, the impact strength is reduced, and the high-temperature burst resistance is also reduced; Compared with Example 1, Comparative Example 4 only vibrates for 12 minutes without pressurization, and the compressive strength, impact strength and high-temperature burst resistance of the specimen are also reduced to varying degrees; Compared with Example 1, Comparative Example 5 adopts 200°C high-temperature dry curing and 300°C high-temperature dry curing during gradient high-temperature curing, and Comparative Example 6 reduces the gradient high-temperature curing temperature to 185°C. The test specimens were autoclaved and cured, so that the test specimens did not form sufficient initial strength to resist the temperature stress of curing at 300°C, and the compressive strength, impact strength and high-temperature burst resistance of the test specimens were reduced to varying degrees; relative to Example 1, Comparative Example 7 reduced the curing time at 300°C in the gradient high-temperature curing, which resulted in the hydration activity of the cementitious material in the test specimen not being fully stimulated, causing the compressive strength, impact strength and high-temperature burst resistance of the test specimen to decrease; relative to Example 1, Comparative Example 8 used a method of maintaining the pressure at 50 MPa for 30 minutes to form the test specimen, which easily caused the steel fibers in the slurry to be distributed in the forward direction, causing the compressive strength, impact strength and high-temperature burst resistance of the test specimen to decrease; relative to Example 1, Comparative Example 9 used short fibers and a conventional cementitious material system to prepare the slurry, and used a method of maintaining the pressure at 50 MPa for 30 minutes to form the test specimen and directly dry-cured it at high temperature, which greatly reduced the mechanical properties and instantaneous high-temperature burst resistance of the test specimen.

[0049] Photos of the test process are as follows Figure 1-5 shown. Figure 1 This is a picture of the unbroken test piece before calcination at 1000℃; Figure 2 This is a picture of the broken test piece before calcination at 1000℃; Figure 3 This is a picture of the test piece after calcination at 1000℃ for 10min; Figure 4 This is a picture of a test piece that did not break after calcining at 1000℃ for 10 minutes; Figure 5 Figures 1-5 show a broken specimen after calcining at 1000°C for 10 minutes. As shown in Figures 1-5, the specimens prepared according to the present invention exhibit no cracking or other phenomena after calcining at 1000°C for 10 minutes. Furthermore, after calcining at 1000°C for 10 minutes, the specimens retain their morphology better than the broken specimens before calcining at 1000°C, demonstrating that the specimens prepared according to the present invention exhibit excellent resistance to transient high-temperature bursting.

[0050] The above are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A C700 grade ultra-high performance concrete resistant to instantaneous high temperature bursting, characterized in that: The invention comprises a mixture and mixed steel fibers, wherein the mixture comprises the following components by mass: 400-450 parts of cement, 90-120 parts of silica fume, 45-60 parts of fly ash microspheres, 50-70 parts of an inorganic temperature control-reinforcement agent, 30-40 parts of a hydration rate control-reinforcement agent, 65-85 parts of water, 6.5-8 parts of a polycarboxylate water reducer, and 1000 parts of a metal aggregate; the mixed steel fibers account for 7-8% of the volume of the mixture; and the preparation process of C700 grade instantaneous high temperature burst resistance ultra-high performance concrete is as follows: Cement, silica fume, fly ash microbeads, inorganic temperature control-enhancing agent, hydration rate control-enhancing agent, polycarboxylate water-reducing agent, metal aggregate, and mixed steel fiber are uniformly mixed and poured into a test mold. After vibration and pressure molding, standard curing and demolding are performed, and gradient high-temperature curing is performed in sequence. The concrete is cooled to obtain the C700 grade instantaneous high-temperature burst-resistant ultra-high performance concrete.

2. The C700 grade instantaneous high temperature burst resistance ultra-high performance concrete according to claim 1 is characterized in that: The hybrid steel fibers include first fibers and second fibers. The first fibers have a diameter of 0.20-0.30 mm and a length of 13-15 mm. The second fibers have a diameter of 0.20-0.22 mm and a length of 4-6 mm.

3. The C700 grade instantaneous high temperature burst resistance ultra-high performance concrete according to claim 2, characterized in that: The mass ratio of the first fiber to the second fiber is (2-3):

1.

4. The C700 grade instantaneous high temperature burst resistance ultra-high performance concrete according to claim 1, characterized in that: The hydration rate regulating and enhancing agent comprises boric acid and anhydrite in a mass ratio of (0.01-0.02):

1.

5. The C700 grade instantaneous high temperature burst resistance ultra-high performance concrete according to claim 1 is characterized in that: The inorganic temperature regulating and reinforcing agent comprises calcined high-alumina bauxite powder and / or metakaolin powder; the fineness of the inorganic temperature regulating and reinforcing agent is ≥325 mesh.

6. The C700 grade instantaneous high temperature burst resistance ultra-high performance concrete according to claim 1, characterized in that: The fly ash microbeads have a water demand ratio of ≤95% and a 28d compressive activity index of ≥110%.

7. The C700 grade instantaneous high temperature burst resistance ultra-high performance concrete according to claim 1 is characterized in that: The vibration frequency of the vibration pressurization molding is 50-70 Hz, the vibration time is ≥10 min, and the pressurization pressure is 4-6 MPa.

8. The C700 grade instantaneous high temperature burst resistance ultra-high performance concrete according to claim 1 is characterized in that: The steps of the gradient high temperature curing are: first steam curing at 90°C for 48 hours, then autoclaving curing at 185-200°C for 6-8 hours, and then high temperature dry curing at 280-300°C for 6-8 hours.

9. A method for preparing C700 grade instantaneous high temperature burst resistant ultra-high performance concrete according to any one of claims 1 to 8, characterized in that: The following steps are involved: Mixing cement, silica fume, fly ash microbeads, an inorganic temperature control-enhancing agent, a hydration rate control-enhancing agent, a polycarboxylate water reducer, and metal aggregate to obtain a mixture; Adding water to the mixture and stirring evenly to obtain a slurry; Mixed steel fibers are added to the slurry, stirred evenly, poured into a test mold, vibrated and pressed into shape, and then subjected to standard curing and demolding. Gradient high-temperature curing and cooling are then performed in sequence to obtain the C700 grade instantaneous high-temperature burst-resistant ultra-high performance concrete.

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