High-temperature-resistant ultra-high performance concrete and preparation method thereof

Abstract

This application relates to the field of building materials technology, specifically disclosing a high-temperature resistant ultra-high performance concrete and its preparation method. The high-temperature resistant ultra-high performance concrete raw materials consist of cementitious materials, composite heat-stabilized aggregates, hydration product modifiers, nanomaterials, multifunctional composite fibers, steel fibers, water-reducing agents, and water in a mass ratio of (800-1000):(900-1100):(50-100):(1-2):(1-2):(78-156):(10-20):(160-180); the composite heat-stabilized aggregates consist of five aggregates including: 1.18 The mixture comprises: 35-50% basalt manufactured sand (~2.36mm), 5-10% waste aerated concrete particles (0.6-1.18mm), 35-50% modified steel slag particles (0.3-1.18mm), 5-10% hollow alumina spheres (0.075-0.3mm), and 5-10% hollow glass microspheres (0.075-0.15mm). The modified steel slag particles are obtained by coating aggregate with steel slag and using an aggregate modification liquid, which is one or a combination of potassium dihydrogen phosphate, sodium dihydrogen phosphate, and ammonium dihydrogen phosphate. This application can reduce fiber content and avoid using expensive synthetic organic fibers, while fully utilizing solid waste from various industries. The resulting concrete has good high-temperature explosion-proof and mechanical strength properties, and the preparation process is simple and the curing method is convenient.

Description

Technical Field

[0001] This application relates to the field of building materials technology, and more specifically, to a high-temperature resistant ultra-high performance concrete and its preparation method. Background Technology

[0002] Ultra-high performance concrete (UHPC), as a special fiber-reinforced cementitious composite material, possesses excellent mechanical and durability properties. However, under fire conditions, UHPC faces challenges such as susceptibility to high-temperature cracking and irreversible degradation of its mechanical properties, limiting its application in specific fire-resistant applications.

[0003] Currently, incorporating a sufficient amount of low-melting-point organic fibers is an effective way to suppress high-temperature cracking of UHPC (Ultra-High-Pressure Polymer). The principle is based on the characteristic that low-melting-point organic fibers melt under high temperatures, thereby releasing the vapor pressure inside the UHPC and reducing or even eliminating the risk of high-temperature cracking. However, incorporating large amounts of organic fibers can severely affect the workability of UHPC and even damage its mechanical properties. Patents CN105693166 and CN111099865 avoid incorporating organic fibers and instead adopt a special dry-heat combined curing method to improve the high-temperature cracking resistance of concrete, which has some merit. However, the cumbersome curing system not only consumes a large amount of energy but is also only effective for precast components. In addition, regarding the improvement of the high-temperature mechanical properties of UHPC, patent CN115784682 solves the problem of the deterioration of the interface transition zone of conventional aggregates in high-temperature environments by calcining high-alumina bauxite clinker, iron filings, and anthracite coal at a high temperature of 2250℃ to obtain a refractory and explosion-proof ultra-high performance concrete. However, the calcination temperature of this aggregate is high, which is too costly for concrete, a material with large production volume and wide application, and does not comply with environmental and energy conservation policies.

[0004] Furthermore, with socio-economic development, various types of waste are constantly being generated, such as steel slag from the metallurgical industry, waste concrete from the construction industry, rice husks and straw from agriculture, and discarded masks from the medical industry. Currently, the main methods for dealing with such waste are simple dumping, burying, and burning, which not only wastes precious land resources but also harms the ecological environment. UHPC, as a new type of building material, is an excellent choice for consuming solid waste from various industries due to its designability and wide availability of raw materials.

[0005] Therefore, minimizing fiber content and avoiding the use of expensive synthetic organic fibers, while fully utilizing solid waste from various industries to prepare a high-temperature resistant ultra-high-performance concrete with excellent construction performance, convenient curing methods, and stable high-temperature mechanical properties, is of great significance for broadening its application range. Summary of the Invention

[0006] This application provides a high-temperature resistant ultra-high performance concrete and its preparation method, which can reduce the fiber content and avoid the use of expensive synthetic organic fibers, while making full use of solid waste from various industries. The concrete prepared has good high-temperature explosion-proof and mechanical strength properties, and the preparation process is simple and the curing method is convenient.

[0007] In the first aspect, this application provides a high-temperature resistant ultra-high performance concrete, which adopts the following technical solution:

[0008] A high-temperature resistant ultra-high performance concrete, the raw materials of which are composed of cementitious materials, composite heat-stabilized aggregates, hydration product modifiers, nano-functional materials, multifunctional composite fibers, steel fibers, water-reducing agents and water in a mass ratio of (800~1000):(900~1100):(50~100):(1~2):(1~2):(78~156):(10~20):(160~180);

[0009] The composite heat-stabilized aggregate is composed of the following five types of aggregate:

[0010] 1.18–2.36 mm basalt manufactured sand 35–50%

[0011] 0.6–1.18 mm waste aerated concrete particles 5–10%

[0012] 0.3–1.18 mm modified steel slag particles 35–50%

[0013] 0.075~0.3mm alumina hollow spheres 5~10%

[0014] 5-10% of 0.075-0.15mm hollow glass microspheres; the modified steel slag particles are prepared by steel slag coating aggregate modification liquid, wherein the aggregate modification liquid is one or more of potassium dihydrogen phosphate, sodium dihydrogen phosphate, and ammonium dihydrogen phosphate.

[0015] By adopting the above technical solutions, steel slag, due to its low-activity magnesium oxide content, is difficult to reuse because the low-activity magnesium oxide will expand later, leading to cracking in buildings. In the modified steel slag particles of this application, the phosphate in the aggregate modification liquid not only neutralizes the low-activity magnesium oxide to solve its volume stability problem, but also forms struvite on its surface to enhance its high-temperature resistance, minimizing the inconsistency in thermal deformation between the aggregate and the paste, and significantly improving the high-temperature residual strength of the concrete. In addition, the various aggregate particle sizes in this application are reasonably matched, which not only forms more uniform and dense struvite, but also allows each aggregate to fully exert its comprehensive effects of strength, high-temperature resistance, and ball bearing properties, ensuring that the ultra-high performance concrete has good workability, mechanical properties, and high-temperature resistance. At the same time, the aggregate sources are wide-ranging. Compared with the traditional ultra-high performance concrete that requires a large amount of precious quartz sand and river sand, this application can make extensive use of solid waste from industrial and construction industries. The prepared concrete has good high-temperature explosion-proof and mechanical strength properties, and the preparation process is simple and the curing method is convenient.

[0016] Furthermore, the modified steel slag particles are obtained by the following steps:

[0017] Aggregate modification solution is prepared at a concentration of 5-20% by mass, and the aggregate modification solution is continuously sprayed to coat the steel slag particles, with a total spraying time of 5-30 minutes. After spraying ends, the aggregate is rinsed 30-60 minutes later to obtain modified steel slag particles. The amount of aggregate modification solution used is 0.05%-0.1% of the mass of the modified steel slag.

[0018] Further, the nanofunctional material comprises a composition of nano-hydrated calcium aluminosilicate and nano-hydrated calcium silicate, and nano-titanium dioxide, with a mass ratio of 0.5 to 1:1; the particle size of the nanofunctional material is no greater than 500 nm. The composition of nano-hydrated calcium aluminosilicate and nano-hydrated calcium silicate is prepared by the following steps:

[0019] (1) Weighing: Weigh sodium silicate solution, metakaolin, and water in a mass ratio of 1:2 to 3:15 to 30, and then weigh 0.02 to 0.05% of the metakaolin mass of melamine.

[0020] (2) Reaction: The weighed material in (1) is reacted, the temperature is controlled at 40-90℃, the stirring rate is 100-300r / min, and the reaction time is 12-24h;

[0021] (3) Grinding: The reactants in (2) are vacuum filtered, dried and finely ground to obtain a combination of nano-hydrated calcium aluminosilicate and nano-hydrated calcium silicate.

[0022] Furthermore, the cementitious material is composed of cement and mineral admixtures in a mass ratio of 1:0.3 to 0.4, wherein the comprehensive specific surface area of ​​the mineral admixtures is not less than 8000 m². 2 / kg. The mineral admixture comprises silica fume, rice husk ash, and other mineral admixtures in a mass ratio of 1:1 to 2:2 to 4; the other mineral admixtures include one or more combinations of mineral powder, fly ash, quartz powder, zeolite powder, and ultrafine calcium carbonate. The hydration product modifier comprises aluminosilicate minerals with a particle size of less than 3μm. The aluminosilicate minerals include metakaolin and / or finely ground coal gangue powder, and the alumina content is not less than 38%.

[0023] By adopting the above technical solutions, nanomaterials can not only promote cement hydration through the nucleation effect, but also effectively improve the high-temperature resistance of UHPC. Specifically, the combination of nano-hydrated calcium aluminosilicate and nano-hydrated calcium silicate, along with the hydration product modifier, can promote the conversion of conventional cement hydration product CSH to CASH, increasing both chain length and thermal decomposition temperature, resulting in superior high-temperature stability. Furthermore, nano-titanium dioxide can also protect against heat radiation and reduce thermal damage to concrete.

[0024] Furthermore, the multifunctional composite fiber comprises natural fiber, waste mask fiber, and basalt fiber, with a mass ratio of 1:1 to 2:1 to 2. The natural fiber includes one or more combinations of abaca fiber, pineapple fiber, and jute fiber. The natural fiber has a diameter of 30–200 μm and a length of 6–20 mm; the waste mask fiber has a length of 6–20 mm and a diameter of 0.1–0.2 mm; and the basalt fiber has a length of 6–20 mm and a diameter of 30–100 μm.

[0025] By adopting the above technical solution, multifunctional composite fibers can interact with some aggregates in composite heat-stabilized aggregates. Specifically, molten waste mask fibers, natural fibers that shrink radially due to shrinkage, molten hollow glass microspheres, and porous waste aerated concrete together form a network system that releases steam, exhibiting excellent high-temperature explosion-proof performance. Compared to the approach that requires the addition of a large amount of one-dimensional fiber material to form a three-dimensional pressure-relief network, this application creatively utilizes the combined action of various "points" and "lines" to form a "three-dimensional pressure-relief system." In reality, waste mask fibers with slightly larger diameters (few in number at the same dosage) and natural fibers cannot effectively form a pressure-relief network through their own action alone. However, by introducing uniformly distributed "pressure-relief grid" materials (i.e., hollow glass microspheres and porous waste aerated concrete in this application), a coupling effect can be cleverly generated. This avoids the disadvantages of conventional UHPC explosion-proof technology, such as decreased workability, reduced mechanical properties, and increased costs caused by the addition of a large amount of organic fibers, and especially avoids the need to use expensive synthetic organic fibers.

[0026] Furthermore, the steel fiber is a heat-resistant stainless steel fiber with a length of 6–20 mm and a diameter of 0.2 ± 0.02 mm.

[0027] Secondly, this application provides a method for preparing high-temperature resistant ultra-high performance concrete, which adopts the following technical solution:

[0028] A method for preparing high-temperature resistant ultra-high performance concrete includes the following steps: dry mixing powder materials, composite heat-stabilized aggregates, and multifunctional composite fibers, then adding water and water-reducing agent and mixing, and finally adding steel fibers and continuing to stir to obtain the final product.

[0029] In summary, this application has the following beneficial effects:

[0030] (1) This application modifies steel slag by modifying it with aggregate modifying liquid, which not only allows waste steel slag to be reused, but also allows it to be mixed with other aggregates of suitable particle size and proportion after the formation of guano on the surface of the modified steel slag. This results in a combination of strength and high temperature stability, avoiding the problem that conventional UHPC aggregates (river sand or quartz sand) will undergo crystal transformation at 573℃, thus expanding and deteriorating the interface transition zone. This makes the concrete of this application have good high temperature explosion-proof and mechanical strength properties, and the preparation process is simple and the curing method is convenient.

[0031] (2) In addition to using composite heat-stabilized aggregates to improve the performance of concrete, the use of hydration product modifiers and nano-functional materials can further enhance the high-temperature stability of hydration products. In addition, the use of multifunctional composite fibers, in conjunction with the composite heat-stabilized aggregates of this application, can further improve the high-temperature explosion-proof performance of the concrete of this application.

[0032] (3) The high-temperature resistant ultra-high performance concrete of this application can effectively dissipate internal steam pressure when facing fire, so it does not need to be dry heat curing to eliminate internal moisture, that is, it has low humidity sensitivity. Compared with complex dry heat curing, it saves a lot of energy and can be extended to cast-in-place ultra-high performance concrete components, which is highly feasible.

[0033] (4) The high-temperature resistant ultra-high performance concrete of this application can effectively utilize solid wastes in the metallurgical, agricultural, construction and medical industries, such as steel slag, rice husk ash, waste masks and waste aerated concrete. This is of great significance for reducing the cost of UHPC, saving energy in society and protecting the environment. It is green, low-carbon and energy-saving. Detailed Implementation

[0034] The present application will be further described in detail below with reference to the embodiments.

[0035] Example

[0036] This application discloses a high-temperature resistant ultra-high-performance concrete. The raw materials consist of cementitious materials, composite heat-stabilized aggregates, hydration product modifiers, nanomaterials, multifunctional composite fibers, steel fibers, a water-reducing agent, and water, in a mass ratio of (800-1000):(900-1100):(50-100):(1-2):(1-2):(78-156):(10-20):(160-180). The water-reducing agent is PCE high-performance water-reducing agent provided by Jiangsu Subote New Material Co., Ltd.

[0037] The cementitious material is composed of cement and mineral admixtures at a mass ratio of 1:0.3 to 0.4, wherein the comprehensive specific surface area of ​​the mineral admixtures is not less than 8000 m². 2 / kg, the comprehensive specific surface area in this embodiment is 8000-9000m² 2 / kg. The cement is Conch P·II 525 grade cement. Further, the mineral admixtures include silica fume, rice husk ash, and other mineral admixtures in a mass ratio of 1:1 to 2:2 to 4; the other mineral admixtures include one or more combinations of mineral powder, fly ash, quartz powder, zeolite powder, and ultrafine calcium carbonate. Provided by Jiangsu Subote New Material Co., Ltd.

[0038] The composite heat-stabilized aggregate consists of the following five types of aggregates:

[0039] 1.18–2.36 mm basalt manufactured sand 35–50%

[0040] 0.6–1.18 mm waste aerated concrete particles 5–10%

[0041] 0.3–1.18 mm modified steel slag particles 35–50%

[0042] 0.075~0.3mm alumina hollow spheres 5~10%

[0043] 5-10% of hollow glass microspheres with a diameter of 0.075-0.15mm; of which the hollow alumina spheres are provided by Sanmenxia Ultra-Long New Materials Technology Co., Ltd., and the remainder are provided by Jiangsu Subote New Materials Co., Ltd.

[0044] Furthermore, the modified steel slag particles are obtained by coating aggregate with steel slag and using an aggregate modification liquid, wherein the aggregate modification liquid is one or more combinations of potassium dihydrogen phosphate, sodium dihydrogen phosphate, and ammonium dihydrogen phosphate. Further still, the modified steel slag particles are obtained by the following steps:

[0045] Prepare aggregate modification solution at a concentration of 5-20% by mass, and continuously spray the solution to coat the steel slag particles. The total spraying time is 5-30 minutes. After spraying ends, rinse the aggregate 30-60 minutes later to obtain modified steel slag particles. The amount of aggregate modification solution used is 0.05%-0.1% of the mass of the modified steel slag.

[0046] The hydration product modifier includes aluminosilicate minerals with a particle size of less than 3 μm, and in this embodiment, the particle size is 2 μm. The aluminosilicate minerals include metakaolin and / or finely ground coal gangue powder, and the alumina content is not less than 38%, and in this embodiment, the alumina content is 41%, provided by Jiangsu Subote New Material Co., Ltd.

[0047] The multifunctional composite fiber includes natural fibers, waste mask fibers, and basalt fibers, with a mass ratio of 1:1 to 2:1 to 2. Further, the natural fibers include one or more combinations of abaca fiber, pineapple fiber, and jute fiber. The natural fibers have a diameter of 30–200 μm and a length of 6–20 mm; the waste mask fibers have a length of 6–20 mm and a diameter of 0.1–0.2 mm; and the basalt fibers have a length of 6–20 mm and a diameter of 30–100 μm. Additionally, the waste mask fibers can be obtained from one or more of the following: shredded waste mask fibers, such as those from non-woven disposable medical masks, activated carbon masks, and N95 masks, after disinfection, removal of nose pads and ear loops, and pulverization.

[0048] The steel fiber is a heat-resistant stainless steel fiber with a length of 6-20 mm and a diameter of 0.2±0.02 mm.

[0049] The nanofunctional materials include a composition of nano-hydrated calcium aluminosilicate and nano-hydrated calcium silicate, and nano-titanium dioxide, with a mass ratio of 0.5 to 1:1; the particle size of the nanofunctional materials is no greater than 500 nm, and the particle size in this embodiment is 500-800 nm.

[0050] Furthermore, the composition of nano-hydrated calcium aluminosilicate and nano-hydrated calcium silicate is prepared by the following steps:

[0051] (1) Weighing: Weigh sodium silicate solution, metakaolin, and water in a mass ratio of 1:2 to 3:15 to 30, and then weigh 0.02 to 0.05% of melamine by mass of metakaolin; the solid content of sodium silicate solution is 35%.

[0052] (2) Reaction: The weighed material in (1) is reacted, the temperature is controlled at 40-90℃, the stirring rate is 100-300r / min, and the reaction time is 12-24h;

[0053] (3) Grinding: The reactants in (2) are vacuum filtered, dried and finely ground to obtain a combination of nano-hydrated calcium aluminosilicate and nano-hydrated calcium silicate.

[0054] This application also provides a method for preparing high-temperature resistant ultra-high performance concrete, including the following steps: first, dry mix powder materials, aggregates, and composite fibers for 30 seconds, then add water and water-reducing agent and mix for 4 minutes, and finally add steel fibers and continue stirring for 3 minutes to obtain the final product.

[0055] The following is an illustration through specific examples.

[0056] Example 1

[0057] This embodiment provides a high-temperature resistant ultra-high performance concrete composition, the raw materials of which are cementitious materials, composite heat-stabilized aggregates, hydration product modifiers, nano-functional materials, multifunctional composite fibers, steel fibers, water-reducing agents and water in a mass ratio of 950:1050:75:2:2:141:15:170.

[0058] The cementitious material consists of cement and mineral admixtures in a mass ratio of 1:0.3. The mineral admixtures include silica fume, rice husk ash, and mineral powder in a mass ratio of 1:1:2.

[0059] Composite heat-stabilized aggregates consist of the following five types of aggregates:

[0060] 1.18–2.36 mm basalt manufactured sand 45%

[0061] 5% of waste aerated concrete particles (0.6–1.18 mm)

[0062] 40% modified steel slag particles (0.3–1.18 mm)

[0063] 0.075~0.3mm hollow alumina spheres (5%)

[0064] 5% of 0.075-0.15mm hollow glass microspheres.

[0065] The modified steel slag particles are prepared as follows:

[0066] Aggregate modification solution was prepared at a concentration of 15% by mass, and the steel slag particles were continuously coated with the modified solution by spraying for a total spraying time of 20 minutes. After 50 minutes of spraying, the aggregate was rinsed to obtain modified steel slag particles. The aggregate modification solution was sodium dihydrogen phosphate. The amount of aggregate modification solution used was 0.08% of the mass of the modified steel slag.

[0067] The hydration product modifier is composed of metakaolin.

[0068] The multifunctional composite fiber includes jute fiber, waste non-woven disposable medical mask shredded fiber, and basalt fiber in a mass ratio of 1:1:1. The jute fiber has a diameter of 50μm and a length of 6mm, the waste non-woven disposable medical mask shredded fiber has a length of 6mm and a diameter of 0.1mm, and the basalt fiber has a length of 6mm and a diameter of 50μm.

[0069] The steel fiber is a straight, heat-resistant stainless steel fiber with a length of 6mm and a diameter of 0.2mm.

[0070] The nanomaterial comprises a composition of nano-hydrated calcium aluminosilicate and nano-hydrated calcium silicate, and nano-titanium dioxide, in a mass ratio of 1:1. The composition of nano-hydrated calcium aluminosilicate and nano-hydrated calcium silicate is prepared by the following steps:

[0071] (1) Weighing: Weigh sodium silicate solution, metakaolin, and water in a mass ratio of 1:3:20, and then weigh 0.05% of the metakaolin mass of melamine.

[0072] (2) Reaction: The weighed material in (1) is reacted, the temperature is controlled at 80℃, the stirring rate is 300r / min, and the reaction time is 24h;

[0073] (3) Grinding: The reactants in (2) are vacuum filtered, dried and finely ground to obtain a combination of nano-hydrated calcium aluminosilicate and nano-hydrated calcium silicate.

[0074] Example 2

[0075] This embodiment provides a high-temperature resistant ultra-high performance concrete composition, the raw materials of which are cementitious materials, composite heat-stabilized aggregates, hydration product modifiers, nano-functional materials, multifunctional composite fibers, steel fibers, water-reducing agents and water in a mass ratio of 800:900:50:1:1:78:10:160.

[0076] The cementitious material consists of cement and mineral admixtures in a mass ratio of 1:0.4. The mineral admixtures include silica fume, rice husk ash, and mineral powder in a mass ratio of 1:2:4.

[0077] Composite heat-stabilized aggregates consist of the following five types of aggregates:

[0078] 1.18–2.36 mm basalt manufactured sand 35%

[0079] 10% of waste aerated concrete particles (0.6–1.18 mm)

[0080] 35% modified steel slag particles (0.3–1.18 mm)

[0081] 10% of 0.075-0.3mm alumina hollow spheres

[0082] 10% hollow glass microspheres, ranging from 0.075 to 0.15 mm.

[0083] The modified steel slag particles are prepared as follows:

[0084] Aggregate modification solution was prepared at a concentration of 5% by mass, and the steel slag particles were continuously coated with the solution by spraying for a total spraying time of 30 minutes. After 60 minutes of spraying, the aggregate was rinsed to obtain modified steel slag particles. The aggregate modification solution was ammonium dihydrogen phosphate. The amount of aggregate modification solution used was 0.05% of the mass of the modified steel slag.

[0085] The hydration product modifier is composed of metakaolin.

[0086] The multifunctional composite fiber includes abaca fiber, waste nonwoven disposable medical mask shredded fiber, and basalt fiber in a mass ratio of 1:2:2. Among them, the jute fiber has a diameter of 200μm and a length of 20mm, the waste nonwoven disposable medical mask shredded fiber has a length of 20mm and a diameter of 0.2mm, and the basalt fiber has a length of 20mm and a diameter of 100μm.

[0087] The steel fiber is a straight, heat-resistant stainless steel fiber with a length of 20mm and a diameter of 0.2mm.

[0088] The nanomaterial comprises a composition of nano-hydrated calcium aluminosilicate and nano-hydrated calcium silicate, and nano-titanium dioxide, with a mass ratio of 0.5:1. The composition of nano-hydrated calcium aluminosilicate and nano-hydrated calcium silicate is prepared by the following steps:

[0089] (1) Weighing: Weigh sodium silicate solution, metakaolin, and water in a mass ratio of 1:2:15, and then weigh 0.02% of melamine by mass of metakaolin.

[0090] (2) Reaction: The weighed material in (1) is reacted, the temperature is controlled at 50℃, the stirring rate is 300r / min, and the reaction time is 24h.

[0091] (3) Grinding: The reactants in (2) are vacuum filtered, dried and finely ground to obtain a combination of nano-hydrated calcium aluminosilicate and nano-hydrated calcium silicate.

[0092] Example 3

[0093] This embodiment provides a high-temperature resistant ultra-high performance concrete composition, the raw materials of which are cementitious materials, composite heat-stabilized aggregates, hydration product modifiers, nano-functional materials, multifunctional composite fibers, steel fibers, water-reducing agents and water in a mass ratio of 1000:1100:100:2:1.5:156:20:180.

[0094] The cementitious material consists of cement and mineral admixtures in a mass ratio of 1:0.4. The mineral admixtures include silica fume, rice husk ash, and fly ash in a mass ratio of 1:2:2.

[0095] Composite heat-stabilized aggregates consist of the following five types of aggregates:

[0096] 50% manufactured basalt sand, 1.18–2.36 mm.

[0097] 5% of waste aerated concrete particles (0.6–1.18 mm)

[0098] 35% modified steel slag particles (0.3–1.18 mm)

[0099] 0.075~0.3mm hollow alumina spheres (5%)

[0100] 5% of 0.075-0.15mm hollow glass microspheres.

[0101] The modified steel slag particles are prepared as follows:

[0102] Aggregate modification solution was prepared at a concentration of 20% by mass, and the steel slag particles were continuously coated with the modified solution by spraying for a total spraying time of 30 minutes. After 60 minutes from the end of spraying, the aggregate was rinsed to obtain modified steel slag particles. The aggregate modification solution was potassium dihydrogen phosphate. The amount of aggregate modification solution used was 0.1% of the mass of the modified steel slag.

[0103] The hydration product modifier is composed of metakaolin.

[0104] The multifunctional composite fiber includes abaca fiber, waste nonwoven disposable medical mask shredded fiber, and basalt fiber in a mass ratio of 1:2:2. Among them, the jute fiber has a diameter of 180μm and a length of 15mm, the waste nonwoven disposable medical mask shredded fiber has a length of 15mm and a diameter of 0.2mm, and the basalt fiber has a length of 15mm and a diameter of 100μm.

[0105] The steel fiber is a straight, heat-resistant stainless steel fiber with a length of 16mm and a diameter of 0.2mm.

[0106] The nanomaterial comprises a composition of nano-hydrated calcium aluminosilicate and nano-hydrated calcium silicate, and nano-titanium dioxide, with a mass ratio of 0.8:1. The composition of nano-hydrated calcium aluminosilicate and nano-hydrated calcium silicate is prepared by the following steps:

[0107] (1) Weighing: Weigh sodium silicate solution, metakaolin, and water in a mass ratio of 1:3:30, and then weigh 0.04% of melamine by mass of metakaolin.

[0108] (2) Reaction: The weighed material in (1) is reacted, the temperature is controlled at 60℃, the stirring rate is 300r / min, and the reaction time is 24h;

[0109] (3) Grinding: The reactants in (2) are vacuum filtered, dried and finely ground to obtain a combination of nano-hydrated calcium aluminosilicate and nano-hydrated calcium silicate.

[0110] Example 4

[0111] The difference between Example 4 and Example 1 is that the modified steel slag particles are prepared as follows:

[0112] Aggregate modification solution was prepared at a concentration of 30% by mass, and the steel slag particles were continuously coated with the modified solution by spraying for a total spraying time of 20 minutes. After 50 minutes of spraying, the aggregate was rinsed to obtain modified steel slag particles. The aggregate modification solution was sodium dihydrogen phosphate. The amount of aggregate modification solution used was 0.08% of the mass of the modified steel slag.

[0113] Example 5

[0114] The difference between Example 5 and Example 1 is that the modified steel slag particles are prepared as follows:

[0115] Aggregate modification solution was prepared at a concentration of 1% by mass, and the steel slag particles were continuously coated with the modified solution by spraying for a total spraying time of 20 minutes. After 50 minutes of spraying, the aggregate was rinsed to obtain modified steel slag particles. The aggregate modification solution was sodium dihydrogen phosphate. The amount of aggregate modification solution used was 0.08% of the mass of the modified steel slag.

[0116] Comparative Example

[0117] Comparative Example 1

[0118] The difference between this comparative example and Example 1 is that 50% of each aggregate in the composite heat-stabilized aggregate is replaced with river sand of the same particle size and gradation.

[0119] Comparative Example 2

[0120] The difference between this comparative example and Example 1 is that all the aggregates in the composite heat-stabilized aggregate are replaced with river sand of the same particle size and gradation.

[0121] Comparative Example 3

[0122] The difference between this comparative example and Example 1 is that all the aggregates in the composite heat-stabilized aggregate are replaced with river sand of the same particle size and gradation, and two additional parts of polypropylene fibers with a length of 12 mm and a diameter of 40 μm are added to inhibit its high-temperature cracking.

[0123] Comparative Example 4

[0124] The difference between this comparative example and Example 1 is that the hydration product modifier is replaced with fly ash with the same particle size distribution.

[0125] Comparative Example 5

[0126] The difference between this comparative example and Example 1 is that no nanofunctional materials are added.

[0127] Comparative Example 6

[0128] The difference between this comparative example and Example 1 is that the modified steel slag in the composite heat-stabilized aggregate is replaced in equal amounts by waste aerated concrete particles with the same particle size distribution.

[0129] Comparative Example 7

[0130] The difference between this comparative example and Example 1 is that hollow alumina spheres are replaced in equal amounts with hollow glass microspheres of the same particle size distribution in the composite heat-stabilized aggregate.

[0131] Comparative Example 8

[0132] The difference between this comparative example and Example 1 is that the composite heat-stabilized aggregate consists of the following five aggregates:

[0133] 1.18–2.36 mm basalt manufactured sand 45%

[0134] 5% of waste aerated concrete particles (0.6–1.18 mm)

[0135] 40% modified steel slag particles, 1.18–2.36 mm

[0136] 0.075~0.3mm hollow alumina spheres (5%)

[0137] 5% of 0.075-0.15mm hollow glass microspheres.

[0138] Comparative Example 9

[0139] The difference between this comparative example and Example 1 is that the composite heat-stabilized aggregate consists of the following five aggregates:

[0140] 0.3–1.18 mm basalt manufactured sand 45%

[0141] 5% of waste aerated concrete particles (0.6–1.18 mm)

[0142] 40% modified steel slag particles, 1.18–2.36 mm

[0143] 0.075~0.3mm hollow alumina spheres (5%)

[0144] 5% of 0.075-0.15mm hollow glass microspheres.

[0145] Performance testing

[0146] Various performance tests were conducted on the concrete samples from each embodiment and comparative example. For the high-temperature test, the concrete specimens were cured for 28 days, then placed in a ventilated area for 56 days. Finally, a high-temperature test was conducted in a high-temperature furnace using the ISO 834 heating curve. The total duration of the high-temperature test was 2 hours. Following the high-temperature test, relevant mechanical properties were tested. The test methods followed the standard T / CECS864-2021: Test Methods for Ultra-High Performance Concrete. The results are as follows:

[0147] As shown in Table 1.

[0148]

[0149]

[0150] As shown by the performance tests of Examples 1-3, the concrete of this application achieves both high-temperature explosion-proof properties and high residual mechanical properties. This is because the steel slag particles in this application are modified, which not only avoids the volume stability problem caused by the low-activity magnesium oxide they contain, but also enhances their high-temperature resistance by forming struvite on their surface. Furthermore, the reasonable particle size distribution of various aggregates in this application not only forms more uniform and dense struvite, but also allows each aggregate to fully exert its comprehensive effects of strength, high-temperature resistance, and ball bearing properties, ensuring that the ultra-high performance concrete has good workability, mechanical properties, and high-temperature resistance. Further analysis of the performance of Examples 4 and 5 reveals that the strength of the concrete in Examples 4 and 5 decreases to some extent after high-temperature treatment. This is because, although the amount of aggregate modification liquid remains unchanged in Examples 4 and 5, its concentration during the spraying process is either too high or too low. This affects the interaction between the aggregate modification liquid and the steel slag, potentially preventing the formation of high-performance struvite and also affecting the synergistic effect with other components.

[0151] Comparative Examples 1 and 2 all exhibited high-temperature cracking after varying degrees of replacement of the composite heat-stabilized aggregate. This is partly because the reduction in glass hollow microspheres and waste aerated concrete in the composite heat-stabilized aggregate reduced the number of "pressure relief grid points" in the UHPC system, making it impossible for the limited number of fibers to connect with the "pressure relief grid points" to form a pressure relief network. On the other hand, the composite heat-stabilized aggregate containing modified steel slag particles not only neutralizes the low-activity magnesium oxide it contains to solve its volume stability problem, but also forms struvite on its surface to enhance its high-temperature resistance.

[0152] Comparative Example 3 achieved high-temperature explosion-proof function only after adding two additional parts of waste mask fibers to Comparative Example 2. The above test results prove the "point" and "line" joint pressure relief principle of this application. At the same time, although Comparative Example 3 has a certain degree of high-temperature stability, its high-temperature residual strength is only 45.0% of that of Example 1. This is because the replaced river sand will undergo a crystal transformation at 573℃, causing severe deterioration of the interface transition zone, and ultimately significantly reducing the high-temperature residual strength. The heat-stabilized aggregate in Example 1 effectively improves this defect.

[0153] Compared to Comparative Example 4, the high-temperature residual strength in Example 1 increased by 34.5%. This is because the hydration product modifier promotes the formation of more high-temperature stable CASH and calcium aluminum feldspar, ensuring the load-bearing capacity requirements of UHPC under high-temperature conditions. Compared to Comparative Example 5, the high-temperature residual strength in Example 1 increased by 30.6%. This is because the nanofunctional material can both promote the formation of aluminum-doped CSH gel (which is more stable at high temperatures) and has a certain function of preventing high-temperature radiation, which can reduce the high-temperature thermal damage of UHPC.

[0154] Comparative Examples 6 and 7 both involved changes in the aggregate composition of the composite heat-stabilized aggregate. Although Comparative Examples 6 and 7 did not experience spalling after high-temperature treatment compared to Example 7, their strength decreased both at room temperature and after high temperature, with a significant drop in strength after high temperature. Furthermore, Comparative Examples 8 and 9 showed changes in the aggregate gradation of the composite heat-stabilized aggregate. It was found that Comparative Examples 8 and 9 exhibited a significant decrease in room temperature strength, and further, a significant decrease in strength after high temperature. In summary, the type and gradation of composite heat-stabilized aggregate affect its blending effect with other components, as well as the formation of struvite, thus impacting the performance of concrete.

[0155] In summary, this application overcomes the shortcomings of current ultra-high performance concrete, such as easy cracking in high-temperature environments and low residual strength at high temperatures, and has broad application prospects and industrial utilization value.

[0156] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high-temperature resistant ultra-high performance concrete, characterized in that, The raw materials consist of cementitious materials, composite heat-stabilized aggregates, hydration product modifiers, nano-functional materials, multifunctional composite fibers, steel fibers, water-reducing agents, and water in a mass ratio of (800~1000):(900~1100):(50~100):(1~2):(1~2):(78~156):(10~20):(160~180); The composite heat-stabilized aggregate is composed of the following five types of aggregate: 1.18~2.36mm basalt manufactured sand 35~50% 0.6~1.18mm waste aerated concrete particles 5~10% 0.3~1.18mm modified steel slag particles 35~50% 0.075~0.3mm alumina hollow spheres 5~10% 5-10% of 0.075-0.15mm hollow glass microspheres; the modified steel slag particles are prepared by coating aggregate modification liquid with steel slag, wherein the aggregate modification liquid is one or more of potassium dihydrogen phosphate, sodium dihydrogen phosphate, and ammonium dihydrogen phosphate.

2. The high-temperature resistant ultra-high performance concrete according to claim 1, characterized in that, The modified steel slag particles are obtained by the following steps: Prepare aggregate modification liquid at a mass concentration of 5-20%, and continuously spray the aggregate modification liquid to coat the steel slag particles. The total spraying time is 5-30 minutes. After the spraying ends, rinse the aggregate 30-60 minutes later to obtain modified steel slag particles.

3. The high-temperature resistant ultra-high performance concrete according to claim 2, characterized in that, The amount of aggregate modification liquid used is 0.05% to 0.1% of the mass of modified steel slag.

4. The high-temperature resistant ultra-high performance concrete according to claim 1, characterized in that, The nanofunctional material includes a composition of nano-hydrated calcium aluminosilicate and nano-hydrated calcium silicate, and nano-titanium dioxide, with a mass ratio of 0.5 to 1:1; the particle size of the nanofunctional material is 500-800 nm.

5. The high-temperature resistant ultra-high performance concrete according to claim 4, characterized in that, The composition of nano-hydrated calcium aluminosilicate and nano-hydrated calcium silicate is prepared by the following steps: (1) Weighing: Weigh sodium silicate solution, metakaolin, and water in a mass ratio of 1:2~3:15~30, and then weigh 0.02~0.05% of the mass of metakaolin in melamine; (2) Reaction: The weighed material in (1) is reacted, the temperature is controlled at 40~90℃, the stirring rate is 100~300r / min, and the reaction time is 12~24h; (3) Grinding: The reactants in (2) are vacuum filtered, dried and finely ground to obtain a combination of nano-hydrated calcium aluminosilicate and nano-hydrated calcium silicate.

6. The high-temperature resistant ultra-high performance concrete according to claim 1, characterized in that, The cementitious material is composed of cement and mineral admixtures in a mass ratio of 1:0.3~0.4, wherein the comprehensive specific surface area of ​​the mineral admixtures is not less than 8000m2 / kg.

7. The high-temperature resistant ultra-high performance concrete according to claim 6, characterized in that, The mineral admixtures include silica fume, rice husk ash, and other mineral admixtures in a mass ratio of 1:1 to 2:2 to 4; the other mineral admixtures include one or more combinations of mineral powder, fly ash, quartz powder, zeolite powder, and ultrafine calcium carbonate.

8. The high-temperature resistant ultra-high performance concrete according to claim 1, characterized in that, The hydration product modifier includes aluminosilicate minerals with a particle size of less than 3 μm.

9. The high-temperature resistant ultra-high performance concrete according to claim 8, characterized in that, The aluminum-rich silicate minerals include metakaolin and / or finely ground coal gangue powder, and the alumina content is not less than 38%.

10. The high-temperature resistant ultra-high performance concrete according to claim 1, characterized in that, The multifunctional composite fiber includes natural fiber, waste mask fiber and basalt fiber, with a mass ratio of 1:1~2:1~2.

11. The high-temperature resistant ultra-high performance concrete according to claim 10, characterized in that, The natural fibers include one or more combinations of abaca fiber, pineapple fiber, and jute fiber.

12. The high-temperature resistant ultra-high performance concrete according to claim 10, characterized in that, The natural fiber has a diameter of 30~200μm and a length of 6~20mm; the waste mask fiber has a length of 6~20mm and a diameter of 0.1~0.2mm; the basalt fiber has a length of 6~20mm and a diameter of 30~100μm.

13. The high-temperature resistant ultra-high performance concrete according to claim 1, characterized in that, The steel fiber is a heat-resistant stainless steel fiber with a length of 6~20mm and a diameter of 0.2±0.02mm.

14. A method for preparing high-temperature resistant ultra-high performance concrete as described in any one of claims 1 to 13, characterized in that, The preparation method includes the following steps: dry mixing powder materials, composite heat-stabilized aggregates, and multifunctional composite fibers, then adding water and water-reducing agent and mixing, and finally adding steel fibers and continuing to stir to obtain the final product.

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