Low-cost low-carbon ultra-high performance concrete

Abstract

The invention discloses low-cost low-carbon ultra-high performance concrete, and relates to the field of concrete materials. The concrete is prepared by mixing the following raw materials in parts by weight: 360 to 465 parts of cement, 50 to 105 parts of silica fume, 100 to 260 parts of fine limestone powder, 205 to 260 parts of superfine limestone powder, 100 to 155 parts of an aluminum-rich cementing material, 10 to 15 parts of a water reducing agent, 1200 to 1250 parts of quartz sand, 80 to 240 parts of a fiber material and 150 to 175 parts of water. According to the concrete, the proportion of quartz sand with different particle sizes is specifically optimized according to a close packing theory, so that the physical packing result of a concrete system is improved, and the compressive strength of the concrete is remarkably improved; on the basis of the physical stacking and filling principle of the system, the fine limestone powder and the superfine limestone powder with specific particle sizes are used for replacing part of the silica fume and the cement in the system, so that the proportion of the limestone powder can be remarkably increased and the cost and the carbon emission of the concrete can be reduced under the condition that the performance and the stacking density of the concrete are not influenced.

Description

Technical Field

[0001] The present invention relates to the field of concrete materials, in particular to the field of ultra-high performance concrete materials, and specifically to a low-cost, low-carbon, ultra-high performance concrete. Background Art

[0002] Ultra-High Performance Concrete (UHPC) is a new building material composed of Portland cement, silica fume, quartz powder, steel fiber or synthetic fiber, high-efficiency water reducer, and water. UHPC is a cement-based composite material with an optimally graded particle size, a water-cement ratio of less than 0.25, and a high proportion of fine short steel fiber reinforcement. It exhibits ultra-high strength (compressive strength of at least 100 MPa), high toughness (tensile strength of at least 5 MPa), and exceptional durability (service life exceeding 50 years).

[0003] In existing UHPC, the cement dosage is mostly between 900 and 1100 kg / m 3 , the amount of silica fume also accounts for 10% to 20% of the cementitious materials. Therefore, cement and silica fume in UHPC account for a large proportion, which is also the reason why UHPC has ultra-high performance; but the large amount of silica fume and cement will also cause the reaction heat and shrinkage of UHPC to increase during curing, making UHPC prone to cracks and high cost, seriously affecting the performance and application of UHPC materials; at the same time, the study also found that due to the low water-cement ratio of UHPC, part of the cement in the UHPC matrix failed to participate in hydration and only played the role of filler. This also provides a theoretical basis for replacing unhydrated cement as a filler by adding cheap admixtures of a specific particle size without affecting the performance of UHPC.

[0004] Limestone powder is a powdered substance made from natural limestone through crushing and grinding. Its primary component is calcium carbonate, often containing small amounts of impurities such as magnesium, iron, and silicon. This makes it inexpensive and commonly used as a filler in various applications. In the concrete industry, limestone powder is used as an admixture to improve concrete's workability and mechanical properties. In high-performance concrete, limestone powder can be used as a relatively inert filler to reduce concrete shrinkage and improve durability.

[0005] However, in existing concrete materials, the amount and gradation of raw materials such as limestone powder have not been specifically optimized, resulting in the inability to maximize the utilization of the added limestone powder. Consequently, the large amount of limestone powder added to concrete significantly reduces the mechanical properties of the concrete, ultimately resulting in a generally low amount of limestone powder used in concrete, which only has a small cost-reduction effect. Therefore, in ultra-high performance concrete, how to specifically optimize the amount and gradation of raw materials such as limestone powder, so that limestone powder can replace unhydrated cement and silica fume without significantly reducing the performance of ultra-high performance concrete, is of great significance for reducing the cost of UHPC and expanding the application range of UHPC. Summary of the Invention

[0006] The purpose of the present invention is to overcome the defect in existing ultra-high performance concrete that the amount and gradation of raw materials are not optimized in a targeted manner, resulting in a significant reduction in UHPC performance when a large amount of limestone powder is added to replace part of the cement and silica fume, and to propose a low-cost, low-carbon ultra-high performance concrete.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] A low-cost, low-carbon, ultra-high-performance concrete is prepared by mixing the following raw materials in parts by weight: 360-465 parts of cement, 50-105 parts of silica fume, 100-260 parts of fine limestone powder, 205-260 parts of ultrafine limestone powder, 100-155 parts of aluminum-rich cementitious material, 10-15 parts of a water reducer, 1200-1250 parts of quartz sand, 80-240 parts of a fiber material, and 150-175 parts of water;

[0009] The particle size of the fine limestone powder is 1-100 μm, and the particles with a particle size of 5-90 μm account for no less than 80 wt%;

[0010] The particle size of the ultrafine limestone powder is 0.5-10 μm, and the particles with a particle size of 1-8 μm account for no less than 90 wt%;

[0011] The quartz sand is composed of two or more types of quartz sands with different gradations in a particle size range of 10-100 meshes. When the number of gradations of the quartz sand is two, the ratio of the two gradations of the quartz sands is obtained through a stacking experiment. When the number of gradations of the quartz sand is three or more, the ratio of the different gradations of the quartz sands is calculated through an improved Anderson model equation with a distribution modulus value of 0.5-0.7.

[0012] The low-cost, low-carbon ultra-high performance concrete of the present invention not only optimizes the proportion of quartz sand of different particle sizes (gradations) according to the close packing theory, thereby improving the physical packing result of the concrete system and significantly improving the compressive strength of the concrete; but also, based on the physical packing filling principle of the system, utilizes fine limestone powder and ultrafine limestone powder of a specific particle size to replace part of the silica fume and cement in the replacement system (silicon fume and cement that do not participate in hydration and exist only as fillers), thereby significantly increasing the proportion of limestone powder without affecting the performance and packing density of the concrete, thereby reducing the cost and carbon emissions of the concrete; at the same time, by adding aluminum-rich cementitious materials, during the secondary hydration process, the limestone can undergo a chemical reaction to generate carbon aluminate that is beneficial to the strength of the concrete, thereby facilitating the improvement of the strength of the UHPC and significantly reducing the deterioration effect of the limestone on the performance of the concrete; the ultra-high performance concrete has the advantages of good performance, low cost and low carbon emissions, and is suitable for large-scale promotion and application.

[0013] Among them, preferably, the cement is silicate cement; the preferred cement type is PO52.5 cement, which has lower UHPC cost and wider application range.

[0014] Among them, preferably, in the ultra-high performance concrete, the ratio of glue (cement + silica fume + aluminum-rich cementitious material + fine limestone powder + ultrafine limestone powder) to sand (quartz sand) is 0.8-0.9; the preferred mortar-sand ratio can ensure the maximum contact surface between the gel material and the sand to the greatest extent, facilitate the bonding and curing of the cementitious material, and thus help improve the performance of UHPC.

[0015] Among them, preferably, the fine limestone powder and / or ultrafine limestone powder is machine-made sand tailings; machine-made sand tailings are waste materials, are inexpensive, and are widely available, which can reduce UHPC costs and reduce carbon emissions.

[0016] Preferably, the particle size distribution of the fine limestone powder is: D 50 (median particle size) 9-14 μm, D 90 (90% cumulative particle size) is between 26-55 μm; the preferred fine lime powder particle size distribution is closer to the particle size distribution of some cement and silica fume, which is conducive to the replacement of silica fume and cement and has less deterioration effect on concrete performance.

[0017] Preferably, the particle size distribution of the ultrafine limestone powder is: D 50 (median particle size) 2-4 μm, D 90 (90% cumulative particle size) is between 4-8 μm; the preferred ultrafine lime powder particle size distribution is closer to the particle size distribution of some cement and silica fume, which is conducive to the replacement of silica fume and cement and has less deterioration effect on concrete performance.

[0018] Among them, preferably, the maximum particle size of the aluminum-rich cementitious material is not greater than 35 μm; the preferred particle size range can make the concrete system more consistent with the close packing theory, and the obtained UHPC has better performance.

[0019] Preferably, the aluminum-rich gelling material is one or more of mineral powder, fly ash, metakaolin, and fly ash microbeads.

[0020] Preferably, the mineral powder is of S95 grade; the preferred mineral powder has higher activity and a particle size that is more consistent with the stacking theory, resulting in better performance of the ultra-high performance concrete.

[0021] Preferably, the silica fume is of 95U grade. The preferred silica fume has higher activity and a particle size that is more consistent with the stacking theory, and the obtained ultra-high performance concrete has better performance.

[0022] Among them, preferably, the length of the fiber material is 10±5 mm and the diameter is 0.1-0.2 mm; more preferably, the aspect ratio of the fiber material is 50-100; the preferred fiber material size has better dispersibility and better toughness enhancement effect on concrete.

[0023] Preferably, the fiber material is at least one of steel fiber or composite fiber.

[0024] Among them, preferably, the method of obtaining the quartz sand ratio through the stacking experiment includes: first setting the basic ratio of coarse sand to 1, then adding fine sand from a small proportion to a large proportion, and obtaining a ratio of coarse sand to fine sand at the maximum stacking density, which is the optimal ratio of the two particle sizes of quartz sand;

[0025] More preferably, during the stacking experiment, the ratio interval is 0.05-0.1;

[0026] Most preferably, during the stacking experiment, first select a larger ratio for experimentation, determine a ratio with the maximum density, and then take a similar ratio before and after the ratio value for experimentation, and take the ratio with the largest density as the optimal ratio; such as: the ratio interval is 0.1, after the maximum value appears, take it and the two values ​​before and after ±0.05 for testing. For example, when the maximum value appears at the ratio of fine sand: coarse sand = 0.5, then do two stacking densities of 0.45 and 0.55, and the maximum of these three values ​​is taken as the optimal ratio.

[0027] Wherein, preferably, the improved Anderson model equation is:

[0028] P(D) is the mass fraction of quartz sand smaller than particle size D;

[0029] D is the particle size of quartz sand (μm);

[0030] D max is the maximum particle size of quartz sand;

[0031] D min is the minimum particle size of quartz sand;

[0032] q is the distribution modulus.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The low-cost, low-carbon, ultra-high performance concrete of the present invention optimizes the ratio of quartz sand of different particle sizes based on the close packing theory, thereby improving the physical packing result of the concrete system and significantly improving the compressive strength of the concrete.

[0035] 2. The low-cost, low-carbon, ultra-high performance concrete of the present invention is based on the physical stacking and filling principle of the system. It uses fine limestone powder and ultra-fine limestone powder of a specific particle size to replace part of the silica fume and cement in the replacement system, thereby significantly increasing the proportion of limestone powder without affecting the performance and bulk density of the concrete, thereby reducing the cost and carbon emissions of the concrete.

[0036] 3. The low-cost, low-carbon, ultra-high-performance concrete of the present invention, by adding aluminum-rich cementitious materials, can react chemically with limestone during the secondary hydration process to generate carbon aluminates that are beneficial to the strength of concrete, thereby improving the strength of UHPC and significantly reducing the deterioration effect of limestone on the performance of concrete.

[0037] 4. The low-cost, low-carbon ultra-high performance concrete of the present invention has the advantages of good performance, low cost and low carbon emissions, and is suitable for large-scale promotion and application. DETAILED DESCRIPTION

[0038] The present invention will be described in further detail below in conjunction with specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments, as all technologies implemented based on the present invention fall within the scope of the present invention.

[0039] In the specific implementation manner of the present invention, the specific models of the raw materials in the examples and comparative examples (unless otherwise specified) are as follows:

[0040] Cement type is PO52.5, D 50 (median particle size) is 18.70 μm, D 90 (90% cumulative particle size) is 41.52 μm;

[0041] The mineral powder model is S95, D 50 11.14μm, D 90 28.28μm;

[0042] Fly ash is Class C first-class fly ash, with particle size less than 10μm, D 50 2.95μm, D 90 7.38μm;

[0043] The silica fume model is 95U, the particle size is less than 10μm, D 50 2.18μm, D 90 7.52μm;

[0044] Ultrafine limestone powder A (Examples 1-6, Comparative Examples 1-10, Comparative Example 13): Particle size is between 0.5-10 μm, particles with a particle size of 1-8 μm account for 93.3 wt%, and D 50 2.83μm, D 90 5.33μm;

[0045] Ultrafine limestone powder B (Examples 7 and 8): particle size is between 0.5-10 μm, particle size between 1-8 μm accounts for 90.3 wt%, and D 50 3.75μm, D 90 5.82μm;

[0046] Ultrafine limestone powder C (Comparative Examples 11 and 12): Particle size is between 0.5-10 μm, particles with a particle size of 1-8 μm account for 87.5 wt%, and D 50 3.96μm, D 90 6.43μm;

[0047] Fine limestone powder A (Examples 1-4, Comparative Examples 1-10, Comparative Example 13): Particle size is between 1-100 μm, with particles of 5-90 μm accounting for 86.5 wt%, and D 50 11.88μm, D 90 29.56μm;

[0048] Fine limestone powder B (Examples 7 and 8): particle size is between 1-100 μm, with particles between 5-90 μm accounting for 80.1 wt%, and D 50 12.57 μm, D 90 35.21μm;

[0049] Fine limestone powder C (Comparative Examples 11 and 12): Particle size is between 1-100 μm, with particles of 5-90 μm accounting for 78.6 wt%, and D 50 13.12μm, D 90 41.72μm;

[0050] The diameter of the steel fiber is 0.2 ± 0.02 mm and the length is 13 ± 1 mm;

[0051] Water reducing agent: polycarboxylate water reducing agent (NC-100(F)).

[0052] The prices and carbon emissions of various raw materials are as follows:

[0053]

[0054] Example: A low-cost, low-carbon, ultra-high-performance concrete is prepared by mixing the following raw materials in parts by weight: Steel fiber can be added according to the flexural performance requirements. In the embodiments of the present invention, the amount of steel fiber used is 160 parts. The ratio of glue (cement + silica fume + aluminum-rich cementitious material + fine limestone powder + ultrafine limestone powder) to sand (quartz sand) in the embodiments is 0.85. The specific weight parts of each raw material in the embodiment are as follows:

[0055]

[0056]

[0057] Among them, the improved Anderson model equation is

[0058] P(D) is the mass fraction of quartz sand smaller than particle size D;

[0059] D is the particle size of quartz sand (μm);

[0060] D max is the maximum particle size of quartz sand;

[0061] D min is the minimum particle size of quartz sand;

[0062] q is the distribution modulus, which ranges from 0.5 to 0.7.

[0063] Comparative Example: A concrete was prepared by mixing the following raw materials in parts by weight. The ratio of glue (cement + silica fume + fine limestone powder + aluminum-rich cementitious material + ultrafine limestone powder) to sand (quartz sand) in the comparative example was 0.85. The incorporation fraction of steel fiber was the same as in the example, both being 160 parts. The specific parts by weight of the raw materials in the comparative example are as follows:

[0064]

[0065]

[0066] In comparative example 1, when the q value is 0.4, according to the ternary sand design, the result calculated by the Anderson model shows that the usage of 26-46 mesh sand is 0%.

[0067] Experimental example:

[0068] The compressive strength test of the concrete prepared in the above examples 1-8 and comparative examples 1-13 was carried out (tested according to the relevant provisions of the national standard GB / T31387-2015 reactive powder concrete), raw materials (per m 3 concrete) costs and carbon emissions (e -CO2 kg / m 3 ) statistics (steel fiber is not included in the cost), the results are as follows:

[0069]

[0070]

[0071] Analysis of the experimental results above shows that the present invention, by optimizing the proportion, particle size, and type of raw materials in ultra-high performance concrete, can significantly reduce the cost and carbon emissions of concrete compared to conventional UHPC while ensuring the compressive strength of the concrete system, making it suitable for large-scale promotion and application.

[0072] The above-described embodiments merely represent specific implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of protection of the present application. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the technical concept of the present application, and all such variations and improvements fall within the scope of protection of the present application.

Claims

1. An ultra-high performance concrete, characterized in that: The invention is prepared from the following raw materials in parts by weight: 360-465 parts of cement, 50-105 parts of silica fume, 100-260 parts of fine limestone powder, 205-260 parts of ultrafine limestone powder, 100-155 parts of aluminum-rich cementitious material, 10-15 parts of water reducing agent, 1200-1250 parts of quartz sand, 80-240 parts of fiber material, and 150-175 parts of water; wherein the particle size of the fine limestone powder is 1-100 μm, and the particle size of 5-90 μm accounts for no less than 80 wt%. %; the particle size of the ultrafine limestone powder is 0.5-10μm, and the proportion of particles with a particle size of 1-8μm is not less than 90wt%; the quartz sand is composed of 2 or more quartz sands with different gradations in the particle size range of 10-100 mesh, and when the number of gradations of quartz sand is 2, the ratio of the two gradations of quartz sand is obtained by stacking experiments, and when the number of gradations of quartz sand is 3 or more, the ratio of quartz sands with different gradations is calculated by the improved Anderson model equation with a distribution modulus value of 0.5-0.

7.

2. The ultra-high performance concrete according to claim 1, characterized in that: In the ultra-high performance concrete, the mortar-sand ratio is 0.8-0.

9.

3. The ultra-high performance concrete according to claim 1, characterized in that: The particle size distribution of the fine limestone powder is: 50 At 9-14 μm, D 90 Between 26-55μm.

4. The ultra-high performance concrete according to claim 1, characterized in that: The particle size distribution of the ultrafine limestone powder is: 50 At 2-4 μm, D 90 Between 4-8μm.

5. The ultra-high performance concrete according to claim 1, characterized in that: The particle size of the aluminum-rich gelling material is not greater than 45 μm.

6. The ultra-high performance concrete according to claim 1, characterized in that: The aluminum-rich gelling material is one or more of mineral powder, fly ash, metakaolin, and fly ash microbeads.

7. The ultra-high performance concrete according to claim 1, characterized in that: The fiber material has a length of 10±5 mm and a diameter of 0.1-0.2 mm.

8. The ultra-high performance concrete according to claim 7, characterized in that: The aspect ratio of the fiber material is 50-100.

9. The ultra-high performance concrete according to claim 1, characterized in that: The method of obtaining the proportion of quartz sand through stacking experiments includes: first setting the basic proportion of coarse sand to 1, and then adding fine sand from a small proportion to a large proportion to obtain a ratio of coarse sand to fine sand at the maximum stacking density, which is the optimal ratio of the two particle sizes of quartz sand.

10. The ultra-high performance concrete according to claim 1, characterized in that: The improved Anderson model equation is: P(D) is the mass fraction of quartz sand smaller than particle size D; D is the particle size of quartz sand (um); D max is the maximum particle size of quartz sand; D min It is the minimum particle size of quartz sand; q is the distribution modulus.

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