Strain hardening ultra-high performance concrete and preparation method thereof
By enhancing the combination of modified polymers and low-heat cementitious materials and optimizing the composition ratio of ultra-high performance concrete, the problems of difficult pumping and insufficient durability under high fiber content were solved, strain hardening under low fiber content was achieved, the toughness and microcrack control ability of the material were improved, and the production cost was reduced.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-18
- Publication Date
- 2026-04-14
AI Technical Summary
Existing ultra-high performance concrete is difficult and costly to pump with high steel fiber content, and conventional strain-hardening cement-based composite materials have insufficient durability under high strength and long-term service conditions, making it difficult to meet the application requirements of complex structures.
By enhancing the synergistic effect of modified polymers, low-heat cementitious materials, and steel fibers, and optimizing the component ratio, a strain-hardening ultra-high performance concrete was prepared. This enhanced the bonding force between the polymer and steel fibers, optimized the microstructure, reduced the heat of hydration, and achieved tensile strain hardening with low fiber content.
Achieving tensile strain hardening of ultra-high performance concrete with low fiber content improves the material's toughness and microcrack control capabilities, while reducing production costs and expanding its application range.
Smart Images
Figure CN121850492A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of building materials technology, specifically relating to a strain-hardening ultra-high performance concrete and its preparation method. Background Technology
[0002] Ultra-high performance concrete (UHPC), as a new type of concrete material, has excellent workability, higher mechanical strength and durability, and has been widely used in bridge, municipal and other engineering fields.
[0003] With the development of engineering structural systems, higher requirements are being placed on the performance of UHPC materials. Standard DB65 / T8014-2024, "Test Standard for Ultra-High Performance Concrete," stipulates that the ultimate tensile strain of strain-hardening UHPC must reach at least 0.2%. Steel fibers are key to toughening UHPC, and current technologies require an addition volumetric dosage of over 2% (160 kg / m³). 3 Only steel fibers can make the tensile properties of UHPC approach strain hardening, but excessive steel fiber content increases the pumping difficulty of UHPC and is not conducive to cost control.
[0004] In the context of adjacent technologies, strain-hardening cementitious composites (SHCCs), as a novel fiber-reinforced cementitious material, possess excellent tensile ductility, microcrack control, and workability, showing broad application prospects in engineering structures subjected to cyclic and fatigue loads. However, conventional SHCC materials have strength grades below C100, water-cement ratios greater than 0.30, and primarily use organic fibers such as polypropylene and polyethylene. For applications with complex structural stresses and high durability requirements under long-term service, technological barriers still need to be overcome.
[0005] Therefore, developing a strain-hardening ultra-high performance concrete that combines the advantages of both UHPC and SHCC is of great significance for expanding the application fields of UHPC and SHCC technologies and promoting the efficient development of the building materials industry. Summary of the Invention
[0006] The purpose of this invention is to provide a strain-hardening ultra-high performance concrete and its preparation method. By combining enhanced modified polymers, low-heat cementitious materials and steel fibers, ultra-high performance concrete exhibits tensile strain hardening characteristics with low fiber content and without changing the original strength properties, thus opening up a new technical approach for the strain hardening of ultra-high performance concrete.
[0007] Specifically, the present invention provides the following technical solutions: A strain-hardening ultra-high performance concrete comprises the following components: low-heat cementitious material, reinforcing modified polymer, manufactured sand, steel fiber, water, and water-reducing agent; The enhanced modified polymer is prepared by mixing, grinding, and spray drying 87-94 wt% polymer emulsion, 5-10 wt% aluminate carbonate seed crystals, and 1-3 wt% silane coupling agent. The aluminate carbonate seed crystals are prepared by mixing 100 parts by weight of nano-calcium carbonate, 20-40 parts by weight of aluminum phase minerals, 5-10 parts by weight of gypsum and / or cement clinker, then adding water at a liquid-solid ratio of 0.3-0.4:1 and stirring to form a paste, which is then cured at 5-15°C for more than 7 days.
[0008] In this invention, the reinforcing modified polymer is a compound of polymer emulsion, aluminate seed crystals, and silane coupling agent. The polymer emulsion, as a flexible component of UHPC, optimizes the UHPC matrix, enhancing its adhesion to steel fibers and thus improving the tensile properties of UHPC. The aluminate seed crystals primarily accelerate hydration and fill pores, addressing the adverse effects of polymer film formation on the microstructure of UHPC by strengthening the overall microstructure and compensating for compressive strength. The silane coupling agent improves the compatibility between the organic components of the polymer and the inorganic components of UHPC. This reinforcing modified polymer, by coordinating the properties of different materials and optimizing the mix ratio, allows each component to complement each other, achieving concrete toughening and microcrack control while overcoming negative impacts on strength.
[0009] Preferably, the composition, by weight, includes the following components: 900-1200 parts of low-heat cementitious material, 20-100 parts of reinforcing modified polymer, 900-1200 parts of manufactured sand, 60-200 parts of steel fiber, 110-180 parts of water, and 10-20 parts of water-reducing agent. Studies have found that, with the above-mentioned proportions, the resulting ultra-high performance concrete exhibits superior strain hardening properties.
[0010] More preferably, by weight, it comprises the following components: 900-1200 parts of low-heat cementitious material, 20-50 parts of reinforcing modified polymer, 900-1200 parts of manufactured sand, 60-200 parts of steel fiber, 110-180 parts of water, and 10-20 parts of water-reducing agent.
[0011] Preferably, the low-heat cementitious material comprises 40-60 wt% cement, 10-15 wt% silica fume, and 25-50 wt% other admixtures; the other admixtures are at least two of limestone powder, electric furnace phosphorus slag powder, and lithium slag powder. More preferably, the specific surface area of the limestone powder, electric furnace phosphorus slag powder, and lithium slag powder all exceed 600 m². 2 / kg; and the CaCO3 content in limestone powder is greater than 95wt%, the total SiO2 and CaO content in electric furnace phosphorus slag powder is greater than 80wt%, and the total SiO2 and Al2O3 content in lithium slag powder is greater than 80wt%.
[0012] This invention reduces the heat release during hydration of UHPC by more than 20% through the design of the above-mentioned low-heat gelling material components, and further suppresses the negative impact of accelerated polymer demulsification and film formation process on the strength of UHPC caused by the internal temperature rise of UHPC.
[0013] Preferably, the polymer emulsion is at least one of acrylate emulsion, styrene-butadiene latex, and vinyl acetate-ethylene copolymer emulsion; and the glass transition temperature is below 15°C, and the content of emulsion particles with a diameter of less than 300 nm is greater than 50 wt%.
[0014] Preferably, the particle size of the nano-calcium carbonate is 10-200 nm; And / or, the aluminum phase mineral is at least one of high-alumina cement, tricalcium aluminate, and dodecacalcium heptaaluminate.
[0015] And / or, the grinding is grinding to a particle size D50 of less than 5 μm.
[0016] Preferably, the manufactured sand is limestone and / or quartz, and the content of fine powder below 0.075 μm reaches more than 10 wt%.
[0017] Preferably, the steel fiber is a copper-plated microfiber steel fiber with a length of 12-20 mm and a single filament diameter of 100-300 μm.
[0018] Preferably, the water-reducing agent is a polycarboxylate-type water-reducing agent with a water reduction rate exceeding 35%.
[0019] The present invention also provides a method for preparing the above-mentioned ultra-high performance concrete, comprising the following steps: S1. Mix the low-heat cementitious material, reinforcing modified polymer, manufactured sand, water-reducing agent and water. After the mixture forms a fluid state, add steel fibers and continue stirring for a period of time to ensure that the steel fibers are fully coated. S2. Pour the material obtained in step S1 into the mold, shape and demold, and then cure to obtain the final product.
[0020] The beneficial effects of this invention are at least as follows: (1) The present invention provides a strain-hardening ultra-high performance concrete, which, through the synergistic combination of enhanced modified polymer, low-heat cementitious material and steel fiber, enables ultra-high performance concrete to exhibit tensile strain hardening characteristics on the basis of low steel fiber content and without changing the original strength properties, thus opening up a new technical approach for strain hardening of ultra-high performance concrete. (2) The present invention provides a strain-hardening ultra-high performance concrete, wherein the reinforcing modified polymer is composed of polymer emulsion, aluminate carbon crystal seed and silane coupling agent. Each component plays a complementary role, thereby achieving concrete toughening and microcrack control while overcoming the negative impact on strength. (3) The present invention provides a strain-hardening ultra-high performance concrete, which further improves the strain hardening performance of ultra-high performance concrete by optimizing the proportion of each component. (4) The strain-hardening ultra-high performance concrete provided by the present invention has a simple production process and is easy to use; in addition, it has low economic cost and has high social and economic benefits. Attached Figure Description
[0021] Figure 1 The results of tensile stress-strain tests on the UHPC prepared in Example 1 are shown.
[0022] Figure 2 The results of tensile stress-strain tests on the UHPC prepared in Example 2 are shown.
[0023] Figure 3 The results of tensile stress-strain tests on the UHPC prepared for Comparative Example 1 are shown.
[0024] Figure 4 SEM image of the aluminate carbonaceous seed crystals prepared in Example 1.
[0025] Figure 5 The image is a SEM image of the UHPC prepared in Example 1. Detailed Implementation
[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the art, or in accordance with the product manual.
[0027] Example 1 A strain-hardening ultra-high performance concrete comprises the following components in parts by weight: 1100 parts of low-heat cementitious material, 20 parts of reinforcing modified polymer, 1000 parts of manufactured sand, 60 parts of steel fiber, 130 parts of water, and 12 parts of water-reducing agent; wherein, The low-heat cementitious material is composed of 60wt% P·O52.5 cement, 15% silica fume and 25wt% other admixtures; the other admixtures are electric furnace phosphorus slag powder and lithium slag powder, with a corresponding mass ratio of 3:2; The specific surface area of the limestone powder is 600 m². 2 / kg, the limestone powder contains 95wt% CaCO3; the electric furnace phosphorus slag powder has a specific surface area of 600m². 2 / kg, the total SiO2 and CaO content in the electric furnace phosphorus slag powder is 85wt%; the specific surface area of the lithium slag powder is 600m². 2 / kg, the total content of SiO2 and Al2O3 in lithium slag powder is 85wt%.
[0028] The enhanced modified polymer is prepared by mixing 94 wt% polymer emulsion, 5 wt% aluminate carbonate seed crystals and 1 wt% silane coupling agent, grinding the mixture to a particle size D50 of less than 5 μm, and then spray drying. The aluminate carbonate seed crystals are prepared by mixing 100 parts by mass of nano-calcium carbonate with a particle size of 10-200 nm, 30 parts by mass of aluminum phase minerals and 5 parts by mass of cement clinker, then adding water at a liquid-solid ratio of 0.35:1 and stirring to form a paste, which is then cured at 5-15℃ for 7 days. The polymer emulsion is an acrylic emulsion with a glass transition temperature of 10°C and a particle size content of 55 wt% below 300 nm; the aluminum phase mineral is high-alumina cement.
[0029] The manufactured sand is limestone, and the content of fine powder below 0.075 μm reaches 15 wt%.
[0030] The steel fiber is a 12-20 mm copper-plated microfiber steel fiber with a single filament diameter of approximately 200 μm.
[0031] The water-reducing agent is a JS-type polycarboxylate water-reducing agent with a water reduction rate of 40%.
[0032] The preparation method of this ultra-high performance concrete is as follows: S1. Mix the low-heat cementitious material, reinforcing modified polymer, manufactured sand, water-reducing agent and water. After it forms a fluid state, add steel fiber and continue stirring so that the steel fiber is fully coated. S2. Pour the material obtained in step S1 into the mold, shape and demold, and then cure to obtain the final product. Performance Testing: The process described in Example 1 was repeated three times (resulting in specimen 1, specimen 2, and specimen 3). Tensile and compressive strength tests were conducted on the UHPC after 28 days of curing, according to DB65 / T 8014-2024 "Standard for Testing Ultra-High Performance Concrete" and GB / T 31387-2015 "Reactive Powder Concrete". The stress-strain curves were recorded. Figure 1 As shown in the figure, the tensile strength and peak tensile strain are obtained from it, as shown in Table 1 below.
[0033] Table 1 Test Results of Mechanical Properties of UHPC
[0034] Example 2 A strain-hardening ultra-high performance concrete is composed of the following components in parts by weight: 1100 parts of low-heat cementitious material, 20 parts of reinforcing modified polymer, 1000 parts of manufactured sand, 120 parts of steel fiber, 130 parts of water, and 12 parts of water-reducing agent. The low-heat cementitious material is the same as in Example 1; The limestone powder, electric furnace phosphorus slag powder, and lithium slag powder are the same as in Example 1; The enhanced modified polymer is the same as in Example 1; The manufactured sand is the same as in Example 1; The steel fiber is the same as in Example 1; The water-reducing agent is the same as in Example 1; The preparation method and performance testing of this ultra-high performance concrete are the same as in Example 1; the obtained stress-strain relationship curve is shown below. Figure 2 As shown in Table 2 below, the tensile strength and peak tensile strain are obtained from the results.
[0035] Table 2 Test Results of Mechanical Properties of UHPC
[0036] Example 3 A strain-hardening ultra-high performance concrete is composed of the following components in parts by weight: 900 parts of low-heat cementitious material, 100 parts of reinforcing modified polymer, 1200 parts of manufactured sand, 200 parts of steel fiber, 110 parts of water, and 10 parts of water-reducing agent. The low-heat cementitious material is the same as in Example 1; The limestone powder, electric furnace phosphorus slag powder, and lithium slag powder are the same as in Example 1; The enhanced modified polymer is the same as in Example 1; The manufactured sand is the same as in Example 1; The steel fiber is the same as in Example 1; The water-reducing agent is the same as in Example 1; The preparation method and performance testing of this ultra-high performance concrete are the same as in Example 1; the results of the test, such as tensile strength and peak tensile strain, are shown in Table 3 below.
[0037] Table 3 Test Results of Mechanical Properties of UHPC
[0038] Comparative Example 1 A commercially available UHPC premix (a commercially available UHPC cementitious material) with a strength grade of UC120 was used as a control.
[0039] An ultra-high performance concrete is composed of the following components in parts by weight: 1100 parts of commercially available UHPC premix, 1000 parts of manufactured sand, 60 parts of steel fiber, 130 parts of water, and 12 parts of water-reducing agent. The manufactured sand is the same as in Example 1; The steel fiber is the same as in Example 1; The water-reducing agent is the same as in Example 1; The preparation method and performance testing of this ultra-high performance concrete are the same as in Example 1; the obtained stress-strain relationship curve is shown below. Figure 3 As shown in the figure, the tensile strength and peak tensile strain are obtained from it, as shown in Table 4 below.
[0040] Table 4 Test Results of Mechanical Properties of UHPC
[0041] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the enhanced modified polymer does not contain aluminate carbon crystals. It is prepared by mixing 99wt% polymer emulsion and 1wt% silane coupling agent, grinding it to a particle size D50 of less than 5 μm, and then spray drying.
[0042] The preparation method and performance testing of this ultra-high performance concrete are the same as in Example 1. The results of the test, such as tensile strength and peak tensile strain, are shown in Table 5 below.
[0043] Table 5 Test Results of Mechanical Properties of UHPC
[0044] Analysis of the results of Examples 1-2 and Comparative Example 1 shows that the strain-hardening ultra-high performance concrete provided by the present invention achieves an average tensile strength of 8.1 MPa with a minimum fiber content of 60 kg, which is at the strain-hardening level. This breaks through the limitations of existing technologies that rely on high fiber content and are not economical, and expands the technical approach to achieve low-cost strain-hardening of UHPC materials.
[0045] Analysis of the results from Examples 1-3 shows that when the amount of the reinforcing modified polymer is 100 parts, the compressive and tensile strength properties of UHPC decrease. This is because the hydration process of UHPC releases a large amount of heat, which accelerates the demulsification and film formation of the polymer, thus affecting the early strength development of UHPC. However, since the amount of fiber in this experimental group is relatively high (the amount of steel fiber is 200 parts), it can still maintain a strain hardening level with an average ultimate tensile strain of 0.26%.
[0046] Analysis of the results from Example 1 and Comparative Example 2 shows that when the reinforced modified polymer does not contain aluminate carbonate seeds, the compressive and tensile properties of the corresponding UHPC also decrease significantly. This demonstrates the strength enhancement effect of introducing aluminate carbonate seeds into the reinforced modified polymer of this invention on UHPC. By introducing aluminate carbonate seeds to accelerate hydration and fill pores, the adverse effects of accelerated polymer demulsification and film formation on the microstructure of UHPC are overcome. The microstructure of the aluminate carbonate seeds is as follows: Figure 4 As shown, the microstructure of the UHPC containing aluminate carbohydrate seeds prepared in Example 1 is as follows. Figure 5 As shown, aluminate carbon crystals enhance the integrity of the microstructure of the polymer UHPC system and compensate for compressive strength.
[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A strain-hardening ultra-high performance concrete, characterized in that, It includes the following components: low-heat cementitious material, reinforcing modified polymer, manufactured sand, steel fiber, water and water-reducing agent; The enhanced modified polymer is prepared by mixing, grinding, and spray drying 87-94 wt% polymer emulsion, 5-10 wt% aluminate carbonate seed crystals, and 1-3 wt% silane coupling agent. The aluminate carbonate seed crystals are prepared by mixing 100 parts by weight of nano-calcium carbonate, 20-40 parts by weight of aluminum phase minerals, 5-10 parts by weight of gypsum and / or cement clinker, then adding water at a liquid-solid ratio of 0.3-0.4:1 and stirring to form a paste, which is then cured at 5-15°C for more than 7 days.
2. The strain-hardening ultra-high performance concrete according to claim 1, characterized in that, By weight, it includes the following components: 900-1200 parts of low-heat cementitious material, 20-100 parts of reinforcing modified polymer, 900-1200 parts of manufactured sand, 60-200 parts of steel fiber, 110-180 parts of water, and 10-20 parts of water-reducing agent. Preferably, the composition includes the following components: 900-1200 parts of low-heat cementitious material, 20-50 parts of reinforcing modified polymer, 900-1200 parts of manufactured sand, 60-200 parts of steel fiber, 110-180 parts of water, and 10-20 parts of water-reducing agent.
3. The strain-hardening ultra-high performance concrete according to claim 1 or 2, characterized in that, The low-heat cementitious material comprises 40-60 wt% cement, 10-15 wt% silica fume, and 25-50 wt% other admixtures; the other admixtures are at least two of limestone powder, electric furnace phosphorus slag powder, and lithium slag powder.
4. The strain-hardening ultra-high performance concrete according to claim 3, characterized in that, The specific surface area of the limestone powder, electric furnace phosphorus slag powder, and lithium slag powder all exceed 600 m². 2 / kg; and the CaCO3 content in limestone powder is greater than 95wt%, the total SiO2 and CaO content in electric furnace phosphorus slag powder is greater than 80wt%, and the total SiO2 and Al2O3 content in lithium slag powder is greater than 80wt%.
5. A strain-hardening ultra-high performance concrete according to claim 1 or 2, characterized in that, The polymer emulsion is at least one of acrylate emulsion, styrene-butadiene latex, and vinyl acetate-ethylene copolymer emulsion; and has a glass transition temperature below 15°C and an emulsion particle size content below 300 nm greater than 50 wt%.
6. A strain-hardening ultra-high performance concrete according to claim 1 or 2, characterized in that, The particle size of the nano-calcium carbonate is 10-200 nm; And / or, the aluminum phase mineral is at least one of high-alumina cement, tricalcium aluminate, and dodecacalcium heptaaluminate. And / or, the grinding is grinding to a particle size D50 of less than 5 μm.
7. A strain-hardening ultra-high performance concrete according to claim 1 or 2, characterized in that, The manufactured sand is limestone and / or quartz, and the content of fine powder below 0.075 μm reaches more than 10 wt%. And / or, the steel fiber is a copper-plated microfiber steel fiber with a length of 12~20 mm and a single filament diameter of 100~300 μm; And / or, the water-reducing agent is a polycarboxylate-type water-reducing agent, and the water reduction rate exceeds 35%.
8. The method for preparing ultra-high performance concrete according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Mix the low-heat cementitious material, reinforcing modified polymer, manufactured sand, water-reducing agent and water. After the mixture forms a fluid state, add steel fibers and continue stirring for a period of time to ensure that the steel fibers are fully coated. S2. Pour the material obtained in step S1 into the mold, shape and demold, and then cure to obtain the final product.