Ultra-high performance concrete containing coarse aggregate, preparation method of ultra-high performance concrete and abrasion resistance testing method of ultra-high performance concrete

Abstract

The invention relates to the technical field of building materials, and particularly discloses ultra-high performance concrete containing coarse aggregate, a preparation method of the ultra-high performance concrete and a method for testing the abrasion resistance of the ultra-high performance concrete, the ultra-high performance concrete containing the coarse aggregate comprises cement, a mineral admixture, fine aggregate, steel fiber, the coarse aggregate, an additive and water, and the coarse aggregate is pretreated through cationic emulsified asphalt. The coarse aggregate ultra-high performance concrete is subjected to molding preparation, demolding maintenance, vacuum water saturation and other processes to obtain an original test piece for testing the abrasion resistance, two sub test pieces are obtained after radial cutting, and the mass of the test pieces before and after abrasion is weighed to obtain the abrasion resistance strength. According to the testing method, the abrasion resistance of the surface mortar layer and the abrasion resistance of the internal aggregate layer in the same test piece can be compared, and the abrasion resistance of the ultra-high performance concrete containing the coarse aggregate can be evaluated more comprehensively and objectively. The coarse-aggregate ultra-high-performance concrete has excellent mechanical properties, the abrasion resistance is enhanced, the use amount of a cementing material can be effectively reduced, and the production cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and particularly relates to an ultra-high performance concrete containing coarse aggregate, a preparation method thereof, and a method for testing the anti-abrasion performance thereof. Background Art

[0002] The service environment of the flow surface of hydraulic structures is often relatively harsh. They are subjected to the abrasive effects of water flow carrying sand, stones and other abrasive debris for a long time. The surface wear of hydraulic structures is very serious, the service life of the structure is shortened, and maintenance is frequent, resulting in huge economic losses and operational safety hazards. The problem of abrasive damage to concrete is a major engineering problem commonly faced by hydraulic structures in my country. This has greatly stimulated the demand for the application of high-performance new materials to resist abrasion. However, the current research on the abrasion resistance of cement-based materials is still at the stage of high-performance concrete, and the performance characteristics of ultra-high performance concrete show that it has the potential to be used as a highly abrasion-resistant material for hydraulic structures.

[0003] Ultra-high-performance concrete (UHPC) is a new cement-based composite material that differs from conventional concrete and high-strength concrete in terms of material composition, mix design, and microstructure. It boasts ultra-high strength, high impact resistance, and excellent durability. While UHPC possesses excellent mechanical and durability properties, conventional ultra-high-performance concrete uses high amounts of high-grade cement, highly reactive mineral powder, silica fume, and other cementitious materials. Furthermore, it incorporates special materials such as quartz sand, steel fiber, and high-performance water-reducing agents. As a result, the unit price of UHPC is typically much higher than that of conventional high-performance concrete. These drawbacks, such as the high amount of cementitious materials used and the high material cost, have limited the further promotion and application of UHPC.

[0004] To address these issues, researchers proposed incorporating coarse aggregate into ultra-high performance concrete (UHPC), thus creating coarse aggregate ultra-high performance concrete (CA-UHPC). Numerous studies have shown that coarse aggregate UHPC, while retaining many of the advantages of UHPC, improves the elastic modulus of concrete and further enhances its compressive strength. For example, Chinese patent application CN115925371A discloses an ultra-high performance concrete containing coarse aggregate and its preparation method. This high-performance concrete is composed of the following ingredients by weight: 625-675 parts cement; 145-190 parts fly ash; 90-145 parts silica fume; 600-840 parts fine aggregate; 480-720 parts coarse aggregate; 16.9-20.9 parts water reducer; 0.19-0.48 parts defoamer; 0.014-0.028 parts air entraining agent; 0.10-0.30 parts suspending agent; 160-200 parts steel fiber; and 156-166 parts water. This concrete combines the high strength, ductility, and durability of traditional ultra-high performance concrete. Furthermore, by incorporating high-quality aggregates and designing a mix ratio based on the closest packing principle, it further enhances the interface transition zone between cement paste and aggregate, improving its compressive strength and elastic modulus, while reducing shrinkage creep and material preparation costs. However, this concrete requires raw materials such as defoamers and air entraining agents. Adding too much raw materials and in large quantities will lead to a decrease in the working performance of the concrete and an increase in material costs.

[0005] For the determination of the anti-abrasion performance of ultra-high performance concrete, the two determination methods proposed in the existing test procedures (SL-T 352 and DL / T 5150) are currently commonly used: the ring method and the underwater steel ball method. However, since UHPC is denser and has higher anti-abrasion strength than ordinary concrete, the standard test method can only evaluate the anti-abrasion performance of the shallow surface layer (i.e., the cement mortar layer) of the UHPC specimen. The surface performance of the specimen is easily affected by factors such as the forming and finishing process and curing conditions, making it difficult to accurately evaluate the internal anti-abrasion performance of UHPC containing coarse aggregate. For example, Chinese patent application CN114477896A discloses an ultra-high performance anti-impact and wear-resistant concrete and its preparation method. This patent is based on the "Test Procedure for Hydraulic Concrete" DL / T 5150-2017 for anti-impact performance testing, and cannot truly reflect the anti-impact and wear performance of UHPC containing coarse aggregate. At present, there is no test method that can comprehensively, objectively and truly evaluate the impact and abrasion resistance of ultra-high performance concrete containing coarse aggregate, and it is impossible to effectively characterize the impact and abrasion resistance of ultra-high performance concrete containing coarse aggregate.

[0006] Therefore, there is an urgent need for a method for testing the abrasion resistance of ultra-high performance concrete that can reduce experimental errors and more realistically reflect the anti-erosion damage and true abrasion resistance of ultra-high performance concrete containing coarse aggregate. Summary of the Invention

[0007] The present invention addresses the problems of the prior art by providing an ultra-high performance concrete containing coarse aggregate, a preparation method thereof, and a method for testing its abrasion resistance. By incorporating high-quality, pretreated coarse aggregate of appropriate dosage and particle size specifications, the coarse aggregate ultra-high performance concrete maintains its original mechanical properties while reducing the amount of cementitious materials used, saving production costs, and improving economic scalability while also enhancing its abrasion resistance. This testing method enables comparative testing of the abrasion resistance of the "surface mortar layer" and the "actual internal structure" within the same specimen, providing a more intuitive and comprehensive characterization of the abrasion resistance of ultra-high performance concrete containing coarse aggregate.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] The invention provides an ultra-high performance concrete containing coarse aggregate. The raw materials include cement, mineral admixture, fine aggregate, coarse aggregate, steel fiber, admixture and water. The coarse aggregate needs to be pretreated with cationic emulsified asphalt.

[0010] Preferably, the ultra-high performance concrete is composed of the following raw materials per cubic meter of ultra-high performance concrete:

[0011]

[0012] The mineral admixture is composed of fly ash microbeads, microsilica powder and slag powder, and the fly ash microbeads, microsilica powder and slag powder account for 40%, 40% and 20% of the total mass of the mineral admixture respectively; the amount of the coarse aggregate accounts for 10%, 20% or 30% of the total solid amount of cement, mineral admixture, fine aggregate, coarse aggregate and steel fiber; the solid content of the cationic emulsified asphalt is 50%-60%, the demulsification speed is slow cracking or medium cracking, the particle polarity is cationic, and the Enn viscosity is 8-12.

[0013] Further preferably, the amount of the coarse aggregate accounts for 20% of the total solid amount of cement, mineral admixture, fine aggregate, coarse aggregate and steel fiber.

[0014] Preferably, the fly ash microspheres have a water requirement ratio of 100%-110% and a 28d activity index of 105%-110%; the microsilica powder has a silicon dioxide content of 90%-95%, a water requirement ratio of 115%-120%, and a 28d activity index of 110%-130%; the slag powder has a specific surface area of ​​450m 2 / kg-490m 2 / kg, and the activity index was greater than 95% at 28 days.

[0015] Preferably, the coarse aggregate is any one of basalt, granite and quartzite, the parent rock strength is greater than 150 MPa, the total content of needle-like particles does not exceed 4.5%, and the mud content does not exceed 0.2%; the particle size of the coarse aggregate is any one of 5mm-10mm, 10mm-20mm and 5mm-20mm.

[0016] Preferably, the steel fiber includes at least one of a copper-plated straight steel fiber and an end hook steel fiber; the copper-plated straight steel fiber has a length of 10mm-15mm, a diameter of 0.2mm, and an aspect ratio of 60-70; the end hook steel fiber has a length of 30mm-35mm, a diameter of 0.55mm, and an aspect ratio of 55-60.

[0017] Preferably, the fine aggregate is quartz sand with a particle size of 0.16-0.63 mm and a fineness modulus of 2.3; the admixture is a polycarboxylic acid high-performance water-reducing agent with a solid content greater than 25% and a water-reducing rate greater than 30%.

[0018] The present invention also provides a method for preparing the above-mentioned ultra-high performance concrete containing coarse aggregate, comprising the following steps:

[0019] S1. Using cationic emulsified asphalt to perform surface modification pretreatment on coarse aggregate to obtain pretreated coarse aggregate;

[0020] S2. Mix cement, mineral admixture, fine aggregate, and steel fiber and add them to a mixing device for dry premixing to obtain a uniformly mixed premix;

[0021] S3, premixing part of the water, the water reducing agent, and the premix to form a fresh ultra-high performance concrete slurry without coarse aggregate;

[0022] S4. Add the pretreated coarse aggregate and the remaining water to the fresh ultra-high performance concrete slurry without coarse aggregate and stir them thoroughly to obtain ultra-high performance concrete containing coarse aggregate.

[0023] Preferably, the preparation method of the ultra-high performance concrete comprises the following steps: S1, uniformly mixing the coarse aggregate and cationic emulsified asphalt by mechanical mixing, wherein the amount of cationic emulsified asphalt is 3%-5% of the mass of the coarse aggregate, and then curing under the conditions of relative humidity of 90±5% and temperature of 20±2°C to promote the rapid and uniform demulsification of the cationic emulsified asphalt on the surface of the coarse aggregate, forming a thin layer of uniform texture on the surface of the coarse aggregate, and obtaining pretreated coarse aggregate; S2, mixing cement, fly ash microbeads, microsilica powder, slag powder, fine aggregate, and steel fiber, and adding them to a mixing equipment for dry premixing to fully mix them to obtain a premix; S3, premixing 50% by volume of water, a water reducer, and the premix to form a fresh ultra-high performance concrete slurry without coarse aggregate; S4, adding the pretreated coarse aggregate and the remaining 50% by volume of water to the fresh ultra-high performance concrete slurry without coarse aggregate and fully stirring to obtain ultra-high performance concrete.

[0024] In another aspect, the present invention provides a method for testing the abrasion resistance of ultra-high performance concrete containing coarse aggregate, comprising the following steps:

[0025] S1. Preparation before the impact and abrasion resistance test: (1) The above-mentioned ultra-high performance concrete containing coarse aggregate is cured and vacuum-saturated to obtain an original specimen; (2) The original specimen is cut to obtain a test specimen;

[0026] S2. Impact and abrasion resistance test: Measure the mass of the test specimen before and after impact and abrasion, and calculate it according to the impact and abrasion resistance formula to obtain the impact and abrasion resistance of ultra-high performance concrete containing coarse aggregate.

[0027] Preferably, the anti-wear formula in step S2 includes:

[0028]

[0029] A=πD 2 / 4(Formula 3)

[0030] ΔM1=M 10 -M 1f (Formula 4)

[0031] ΔM2=M 20 -M 2f (Formula 5)

[0032]

[0033] Where, f a1 is the abrasion resistance of the lower specimen, h / (kg / m 2 );f a2 is the abrasion resistance of the upper specimen, h / (kg / m 2); t is the cumulative abrasion time, h = 72h; ΔM1 is the cumulative abrasion amount of the lower specimen, kg; ΔM2 is the cumulative abrasion amount of the upper specimen, kg; M 10 is the initial mass of the lower specimen, kg; M 20 is the initial mass of the upper specimen, kg; M 1f is the mass of the lower specimen after wear, kg; M 2f is the mass of the upper specimen after wear, kg; A is the wear area of ​​the specimen, m 2 ; D is the specimen diameter, m; L av1 is the wear rate of the lower specimen; L av2 is the wear rate of the upper specimen; M0 is the initial mass of the specimen, kg.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The ultra-high performance concrete of the present invention realizes a dual-threshold design of particle size and dosage through the coordinated optimization of aggregate particle size classification and dosage, and obtains pretreated coarse aggregate through interface strengthening technology, which significantly improves the impact and abrasion resistance. At the same time, it effectively reduces the amount of cementitious materials used, achieves a balance between economy and high performance, and has good engineering scalability.

[0036] The ultra-high performance concrete of the present invention adopts a specific composite mineral admixture system. Through active complementarity and micro-aggregate filling effects, it optimizes the matrix density and interface transition zone performance, ensuring the mechanical strength after the incorporation of coarse aggregate. It adopts a steel fiber composite design, and differentiates the configuration of copper-plated straight and end-hook steel fibers to address the differences in coarse aggregate particle size (≤10mm and >10mm). The spatial distribution and anchoring effect of the fibers are utilized to inhibit crack expansion and enhance impact and abrasion toughness.

[0037] The present invention proposes a single-specimen dual-interface partitioning design, and finds that the internal interface of concrete has more realistic and better anti-abrasion performance, which meets the enterprise production standards; and the testing method of the present invention can realize the comparative test of the anti-abrasion performance of the "surface mortar layer" and the "internal aggregate layer" in the same specimen, which more intuitively and comprehensively characterizes the anti-abrasion performance of ultra-high performance concrete containing coarse aggregate, breaking through the limitation of traditional methods that can only evaluate the surface layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is the image processing flow chart of the present invention.

[0039] Figure 2 This is a diagram showing the influence of coarse aggregate content and particle size on the impact and abrasion resistance in the examples.

[0040] Figure 3 This is a graph showing the effect of coarse aggregate content and particle size on wear rate in the examples. DETAILED DESCRIPTION

[0041] The present invention is described below through specific embodiments to make the technical solution of the present invention easier to understand and grasp, but the present invention is not limited thereto. The described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0042] The endpoints and any value of the scope disclosed in this article are not limited to this accurate scope or value, and these scopes or values ​​should be understood as comprising values ​​close to these scopes or values.For numerical range, between the endpoint values ​​of each scope, between the endpoint values ​​of each scope and a separate point value, and between the separate point value, can be combined with each other and obtain one or more new numerical ranges, and these numerical ranges should be considered as specifically disclosed in this article. Unless the context clearly indicates otherwise, the singular form "one", "a kind of" and "described" as used herein include singular and plural indicators. The numerical range stated by endpoint is included in all numerical values ​​and fractions within the corresponding range, and the stated endpoint.

[0043] Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without inventive effort shall fall within the scope of protection of the present invention. The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0044] The following raw material characteristics are illustrative:

[0045] The cement used in this example is PO 42.5 cement with a specific surface area of ​​345m 2 / kg, 3d flexural strength is 5.9MPa, 28d flexural strength is 8.8MPa, 3d compressive strength is 29.5MP, 28d compressive strength is 51.3Mpa; fly ash microspheres are hollow glass microspheres generated by melting and cooling of minerals during coal combustion, with smooth surface and high sphericity, water requirement ratio of 105%, and 28d activity index of 108%; microsilica is produced by oxidation and condensation of SiO2 and Si gas produced by electric furnace in the process of smelting ferrosilicon or industrial silicon in the air, with a silicon dioxide content of 93.1%, a water requirement ratio of 118%, and a 28d activity index of 115%; slag powder is obtained by drying and grinding blast furnace slag, with a specific surface area of ​​470m 2 / kg, density is 2.87g / cm 3, 28d activity index is 100%; the steel fibers used include two types, one is a copper-plated straight steel fiber with a length of 13mm, a diameter of 0.2mm, and an aspect ratio of 65, and the other is a hook-type steel fiber with a length of 30mm-35mm, a diameter of 0.55mm, and an aspect ratio of 55-60; the fine aggregate is quartz sand with a particle size of 0.16-0.63mm and a fineness modulus of 2.3; the water reducer used is a polycarboxylic acid high-performance water reducer that meets the requirements of "Concrete Admixtures" (GB 8076-2008), with a solid content of 25.5% and a water reduction rate of 33%.

[0046] The high-quality coarse aggregate used in this example is granite crushed stone, with a parent rock strength of 212 MPa and a total content of 4.5% needle-shaped particles. The crushed stone is cleaned to a mud content of ≤0.2%. Based on the closest packing theory and the characteristics of coarse aggregate particle size and dosage, a maximum coarse aggregate particle size greater than 20 mm or a coarse aggregate dosage exceeding 30% will significantly adversely affect the workability and mechanical strength of the concrete.

[0047] The coarse aggregate used in this example was pretreated with cationic emulsified asphalt before incorporation. The pretreatment method involved thoroughly mixing the cationic emulsified asphalt and coarse aggregate using high-speed mechanical mixing. The amount of cationic emulsified asphalt used was 3%-5% of the coarse aggregate mass, ensuring that after curing and demulsification, the cationic emulsified asphalt was evenly coated on the coarse aggregate surface, forming a stable asphalt film. The cationic emulsified asphalt used in this example was PC-1, a light brown liquid with a uniform texture and no impurities. Its evaporation residue content was 51.8%, its demulsification rate was slow-cracking (SS), its particle polarity was cationic, its Engler viscosity (25°C) was 10.6, and its adhesion test showed that the crushed stone coating area exceeded two-thirds.

[0048] The specific compositions of basic examples 1-11 are shown in Table 1.

[0049] Basic Example 1: A conventional ultra-high performance concrete benchmark control group without coarse aggregate;

[0050] Basic Example 2: The coarse aggregate particle size is 5-10 mm and the admixture amount is 10%;

[0051] Basic Example 3: The coarse aggregate particle size is 5-10 mm and the admixture amount is 20%;

[0052] Basic Example 4: The coarse aggregate particle size is 5-10 mm and the dosage is 30%;

[0053] Basic Example 5: The coarse aggregate particle size is 10-20 mm and the dosage is 10%;

[0054] Basic Example 6: The coarse aggregate particle size is 10-20 mm and the admixture amount is 20%;

[0055] Basic Example 7: The coarse aggregate particle size is 10-20 mm and the dosage is 30%;

[0056] Basic Example 8: The coarse aggregate particle size is 5-20 mm and the dosage is 10%;

[0057] Basic Example 9: The coarse aggregate particle size is 5-20 mm and the dosage is 20%;

[0058] Basic Example 10: The coarse aggregate particle size is 5-20 mm and the dosage is 30%;

[0059] Basic Example 11: The coarse aggregate particle size specification is 5-20 mm, and the admixture amount is 30%.

[0060] The amount of coarse aggregate refers to the amount of cement, fly ash microbeads, microsilica, slag powder, fine aggregate, coarse aggregate and steel fiber added compared to the total amount of solids in Basic Example 1. For example, the total solids in Basic Example 1 is 883 kg / m 3 +118kg / m 3 +118kg / m 3 +59kg / m 3 +1023kg / m 3 +126k g / m 3 =2327kg / m 3 , then the coarse aggregate dosage is 10%, which means adding 233kg / m 3 coarse aggregate; the dosage of 20% and 30% shall be deduced in proportion with reference to the dosage of 10%.

[0061] Compared with Basic Example 1, the amounts of cement, fly ash microbeads, microsilica powder, slag powder, fine aggregate and steel fiber used in other groups can be reduced accordingly due to the addition of coarse aggregate, which can effectively reduce the amount of cementitious materials used. The specific amounts are shown in Table 1.

[0062] Table 1 Basic Example Proportions

[0063]

[0064] A test method for the abrasion resistance of ultra-high performance concrete containing coarse aggregate:

[0065] S1: Prepare fresh ultra-high performance concrete slurry containing coarse aggregate according to the mix ratio shown in Table 1:

[0066] 1) The cationic emulsified asphalt and coarse aggregate are thoroughly mixed by high-speed mechanical mixing, with the amount of cationic emulsified asphalt being 3%-5% of the mass of the coarse aggregate. Subsequently, after curing and demulsification under the conditions of relative humidity of 90±5% and temperature of 20±2°C, the cationic emulsified asphalt is promoted to demulsify quickly and evenly on the surface of the coarse aggregate, so as to ensure that the cationic emulsified asphalt forms a uniform film on the surface of the coarse aggregate particles, thereby obtaining pretreated coarse aggregate;

[0067] 2) Cement, fly ash microbeads, microsilica fume, slag powder, fine aggregate, and steel fiber were mixed and added to a mixing device for dry premixing for 4 minutes to fully mix and obtain a premix;

[0068] 3) Premixing 50% of the volume of water, the water reducing agent, and the premix for 2 minutes to form a fresh ultra-high performance concrete slurry without coarse aggregate;

[0069] 4) adding the pretreated coarse aggregate and the remaining 50% of the volume of water to the fresh ultra-high performance concrete slurry without coarse aggregate, and stirring thoroughly for 4 minutes so that the slurry fully covers the surface of the coarse aggregate, thereby obtaining an ultra-high performance concrete containing coarse aggregate;

[0070] S2: Preparation before impact and abrasion resistance test:

[0071] 1) Specimen preparation: The ultra-high performance concrete containing coarse aggregate obtained in S1 was poured into a test mold coated with a release agent. The dimensions of the impact and abrasion strength test mold were (300 ± 2) mm in diameter and (100 ± 1) mm in height. Three specimens were tested in each group.

[0072] 2) Specimen curing: After being compacted by manual and mechanical vibration, the specimens were placed in a curing room (temperature 20°C ± 2°C, relative humidity ≥ 95%) and taken out after curing to the test age of 28 days;

[0073] 3) Vacuum saturation: Place the specimen in a vacuum saturation device, seal it, and evacuate it to 133 Pa. Maintain the vacuum for 3 hours. Then, maintain this vacuum and automatically suck in enough deionized water to completely submerge the specimen. After soaking for 1 hour, return the specimen to normal pressure and continue soaking at normal pressure for 18±2 hours. Remove the saturated specimen, clean any debris from the surface, and wipe it dry with a damp cloth. Record the initial mass M0 of the specimen to the nearest 0.001 kg.

[0074] 4) Specimen cutting: The original cylindrical specimen (diameter D = 300 mm, height H0 = 100 mm) was radially cut to form two sub-specimens (diameter D = 300 mm, height H1 = 50 ± 5 mm). The bottom surface of the lower specimen was tested to test and characterize the abrasion resistance of the concrete surface mortar layer. The initial mass M after saturation was weighed before the test. 10The upper specimen is tested on its cut surface to test and characterize the abrasion resistance of the real structure inside the concrete. The initial mass M after saturation is weighed before the test. 20 ;

[0075] S3: Test on the abrasion resistance of ultra-high performance concrete containing coarse aggregate:

[0076] After curing to 28 days, the abrasion resistance of the ultra-high performance concrete containing coarse aggregate was tested;

[0077] 1) Place the test block in the concrete abrasion resistance testing machine, raise the test block to the original test block height and then conduct the abrasion test. After a cumulative abrasion of 72 hours, take it out and add water to the steel drum to the initial water level every 24 hours;

[0078] 2) Take out the specimen, rinse it, wipe it dry with a damp cloth, and record the mass M of the specimen after wear. 1f and M 2f ;

[0079] 3) Use a camera to obtain images of the specimen surface after the abrasion test. Through image grayscale conversion, image filtering and denoising, image binarization, morphological processing, and contour extraction, the texture distribution of the concrete surface after the abrasion test is extracted to preliminarily determine the correlation between aggregate distribution and abrasion resistance.

[0080] 4) According to the mass of the specimen before and after the abrasion test, calculate the concrete abrasion strength f according to the following formula: a and wear rate L av .

[0081]

[0082] A=πD 2 / 4(Formula 3)

[0083] ΔM1=M 10 -M 1f (Formula 4)

[0084] ΔM2=M 20 -M 2f (Formula 5)

[0085]

[0086] Where, f a1 is the abrasion resistance of the lower specimen, h / (kg / m 2 );f a2 is the abrasion resistance of the upper specimen, h / (kg / m 2); t is the cumulative abrasion time, h = 72h; ΔM1 is the cumulative abrasion amount of the lower specimen, kg; ΔM2 is the cumulative abrasion amount of the upper specimen, kg; M 10 is the initial mass of the lower specimen, kg; M 20 is the initial mass of the upper specimen, kg; M 1f is the mass of the lower specimen after wear, kg; M 2f is the mass of the upper specimen after wear, kg; A is the wear area of ​​the specimen, m 2 ; D is the diameter of the specimen, which can be calculated as 0.3m, m; L av1 is the wear rate of the lower specimen; L av2 is the wear rate of the upper specimen; M0 is the initial mass of the specimen, kg.

[0087] Examples 1-11

[0088] The raw materials were weighed according to the mix ratios in Table 1. The 28-day abrasion resistance and wear rate of the upper specimens with the formed finish were tested using the aforementioned test method for the abrasion resistance of ultra-high performance concrete containing coarse aggregate. The results are shown in Table 2 below.

[0089] Table 2 Abrasion resistance and wear rate of Examples 1-11

[0090] Group <![CDATA[Abrasion and impact resistance strength h / (kg / m 2 )]]> Wear rate (%) Example 1 62.80 0.442 Example 2 84.78 0.329 Example 3 89.25 0.309 Example 4 77.08 0.361 Example 5 80.75 0.345 Example 6 86.22 0.320 Example 7 75.93 0.367 Example 8 90.84 0.302 Example 9 95.98 0.289 Example 10 83.39 0.334 Example 11 73.72 0.381

[0091] Examples 12-22

[0092] Raw materials were weighed according to the proportions shown in Table 1. Examples 12-22 corresponded to Basic Examples 1-11, respectively. The 28-day abrasion resistance and wear rate of the lower specimens after directionally cutting were tested according to the aforementioned test method for the abrasion resistance of ultra-high performance concrete containing coarse aggregate. The raw materials for the ultra-high performance concrete containing coarse aggregate in Examples 12-22 remained consistent with those in Examples 1-11, with the only difference being the abrasion resistance test specimens. The results are shown in Table 3 below.

[0093] Table 3 Abrasion resistance and wear rate of Examples 12-22

[0094] Group <![CDATA[Abrasion and impact resistance strength h / (kg / m 2 )]]> Wear rate (%) Example 12 55.90 0.509 Example 13 65.22 0.426 Example 14 67.83 0.408 Example 15 61.29 0.448 Example 16 63.59 0.432 Example 17 66.06 0.417 Example 18 60.56 0.459 Example 19 67.83 0.407 Example 20 70.65 0.392 Example 21 65.22 0.427 Example 22 61.29 0.462

[0095] According to the above results, the addition of coarse aggregate has a significant effect on improving the abrasion resistance of ultra-high performance concrete, and the abrasion resistance of Example 9 reaches 95.98h / (kg / m 2), the wear rate is only 0.289%, which is the largest improvement in the impact and wear resistance test results compared to Example 1 without coarse aggregate, with the impact and wear resistance increased by 52.79% and the wear rate reduced by 34.62%. By comparing Example 11 and Example 10, it can be found that compared with the untreated coarse aggregate, the pretreated coarse aggregate has a more significant effect on improving the impact and wear resistance. By pretreating the coarse aggregate, the cationic emulsified asphalt evenly wraps the surface of the coarse aggregate particles, giving it a certain viscosity, which can effectively improve the concrete interface transition zone and effectively inhibit the spread of fine cracks generated by stress. In summary, the impact and wear resistance of Examples 2-3, 5-6, and 8-10 is greater than 80h / (kg / m 2 ) and the wear rate is less than 0.35%, which are improved to varying degrees compared with Example 1 and meet the engineering design requirements.

[0096] The present invention also found that for the examples 13-21 whose test surface is the surface mortar layer of the specimen, the abrasion resistance is between 60-70h / (kg / m 2 ), the impact and abrasion resistance of Example 12 without coarse aggregate was improved by 8%-25%; and for Examples 2-10 where the test surface was the inner aggregate layer, the impact and abrasion resistance was between 75-95h / (kg / m 2 ), the improvement in impact and abrasion resistance is between 20% and 55% compared with Example 1 without coarse aggregate. In general, the test surface of Examples 1-10 is the surface mortar surface of the specimen, and the improvement in impact and abrasion resistance is between 25% and 35% compared with Examples 12-21, and the wear rate reduction rate is between 20% and 30%, which has better impact and abrasion resistance. The existing underwater steel ball method for testing the impact and abrasion resistance of ultra-high performance concrete with coarse aggregate can only test its surface mortar layer, and the surface mortar area mainly relies on the wear resistance of the matrix itself due to the lack of rigid support of coarse aggregate, and cannot reflect the key role of coarse aggregate in the impact and abrasion resistance system of ultra-high performance concrete with coarse aggregate. The internal aggregate layer after cutting can more effectively resist impact and abrasion damage through the "structural armor" effect formed by three-dimensional interlacing. The testing method of the present invention can more truly reflect the impact and abrasion resistance of ultra-high performance concrete containing coarse aggregate, and can better reflect the effect of improving the impact and abrasion resistance of ultra-high performance concrete by adding coarse aggregate.

[0097] According to actual production and existing technology, the specific coarse aggregate ultra-high performance concrete of the present invention shows more outstanding anti-abrasion performance on the basis of traditional ultra-high performance concrete which already has good anti-abrasion performance, and overcomes the contradiction between high anti-abrasion performance and economy. This marks the leap of coarse aggregate ultra-high performance concrete from material innovation to engineering topology optimization design, and provides a new paradigm for improving the anti-abrasion performance of major water conservancy infrastructure. Moreover, the improved anti-abrasion performance test method of the present invention separates the upper specimen for testing the cutting surface and the lower specimen for testing the bottom surface by radially cutting the original specimen, thereby realizing the comparative test of the anti-abrasion performance of the "surface mortar layer" and the "internal aggregate layer" in the same specimen, and more intuitively and comprehensively characterizing the anti-abrasion performance of ultra-high performance concrete containing coarse aggregate, breaking through the limitation that the traditional method can only evaluate the surface layer.

[0098] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. An ultra-high performance concrete containing coarse aggregate, characterized by: The raw materials include cement, mineral admixtures, fine aggregate, coarse aggregate, steel fiber, admixture and water. The coarse aggregate needs to be pretreated with cationic emulsified asphalt.

2. The ultra-high performance concrete according to claim 1, characterized in that: Calculated per cubic meter of ultra-high performance concrete, the ultra-high performance concrete is composed of the following raw materials: The mineral admixture is composed of fly ash microbeads, microsilica powder and slag powder, and the fly ash microbeads, microsilica powder and slag powder account for 40%, 40% and 20% of the total mass of the mineral admixture respectively; the amount of the coarse aggregate accounts for 10%, 20% or 30% of the total solid amount of cement, mineral admixture, fine aggregate, coarse aggregate and steel fiber; the solid content of the cationic emulsified asphalt is 50%-60%, the demulsification speed is slow cracking or medium cracking, the particle polarity is cationic, and the Enn viscosity is 8-12.

3. The ultra-high performance concrete according to claim 1, wherein: The coarse aggregate is any one of basalt, granite and quartzite, the parent rock strength is greater than 150MPa, the total content of needle-like particles does not exceed 4.5%, and the mud content does not exceed 0.2%; the particle size of the coarse aggregate is any one of 5mm-10mm, 10mm-20mm and 5mm-20mm.

4. The ultra-high performance concrete according to claim 1, wherein: The steel fiber includes at least one of a copper-plated straight steel fiber and an end hook steel fiber; the copper-plated straight steel fiber has a length of 10 mm to 15 mm, a diameter of 0.2 mm, and an aspect ratio of 60 to 70; the end hook steel fiber has a length of 30 mm to 35 mm, a diameter of 0.55 mm, and an aspect ratio of 55 to 60.

5. The ultra-high performance concrete according to claim 1, wherein: The fine aggregate is quartz sand with a particle size of 0.16-0.63 mm and a fineness modulus of 2.3; the admixture is a polycarboxylic acid high-performance water-reducing agent with a solid content greater than 25% and a water-reducing rate greater than 30%.

6. The ultra-high performance concrete according to claim 2, characterized in that: The fly ash microspheres have a water requirement of 100%-110% and a 28-day activity index of 105%-110%; the microsilica powder has a silicon dioxide content of 90%-95%, a water requirement of 115%-120%, and a 28-day activity index of 110%-130%; the slag powder has a specific surface area of ​​450m 2 / kg-490m 2 / kg, and the activity index was greater than 95% at 28 days.

7. The ultra-high performance concrete according to claim 2, characterized in that: The amount of the coarse aggregate accounts for 20% of the total solid amount of cement, mineral admixture, fine aggregate, coarse aggregate and steel fiber.

8. The method for preparing ultra-high performance concrete according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Using cationic emulsified asphalt to perform surface modification pretreatment on coarse aggregate to obtain pretreated coarse aggregate; S2. Mix cement, mineral admixture, fine aggregate, and steel fiber and add them to a mixing device for dry premixing to obtain a uniformly mixed premix; S3, premixing part of the water, the water reducing agent, and the premix to form a fresh ultra-high performance concrete slurry without coarse aggregate; S4. Add the pretreated coarse aggregate and the remaining water to the fresh ultra-high performance concrete slurry without coarse aggregate and stir them thoroughly to obtain ultra-high performance concrete containing coarse aggregate.

9. A method for testing the abrasion resistance of ultra-high performance concrete containing coarse aggregate, characterized by: The following steps are involved: S1. Preparation before the impact and abrasion resistance test: (1) The ultra-high performance concrete containing coarse aggregate according to any one of claims 1 to 7 is cured and vacuum-saturated to obtain an original specimen; (2) The original specimen is cut to obtain a test specimen; S2. Impact and abrasion resistance test: Measure the mass of the test specimen before and after impact and abrasion, and calculate it according to the impact and abrasion resistance formula to obtain the impact and abrasion resistance of ultra-high performance concrete containing coarse aggregate.

10. The method for testing the abrasion resistance according to claim 9, wherein: The anti-wear formula in step S2 includes: A=πD 2 / 4(Formula 3) ΔM1=M 10 -M 1f (Formula 4) ΔM2=M 20 -M 2f (Formula 5) Where, f a1 is the abrasion resistance of the lower specimen, h / (kg / m 2 );f a2 is the abrasion resistance of the upper specimen, h / (kg / m 2 ); t is the cumulative abrasion time, h = 72h; ΔM1 is the cumulative abrasion amount of the lower specimen, kg; ΔM2 is the cumulative abrasion amount of the upper specimen, kg; M 10 is the initial mass of the lower specimen, kg; M 20 is the initial mass of the upper specimen, kg; M 1f is the mass of the lower specimen after wear, kg; M 2f is the mass of the upper specimen after wear, kg; A is the wear area of ​​the specimen, m 2 ; D is the specimen diameter, m; L av1 is the wear rate of the lower specimen; L av2 is the wear rate of the upper specimen; M0 is the initial mass of the specimen, kg.

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