Wading anti-cavitation engineering cement-based composite material as well as preparation method and application thereof

Abstract

The invention discloses a wading anti-cavitation engineering cement-based composite material as well as a preparation method and application thereof, and belongs to the technical field of hydraulic construction materials. The wading anti-cavitation engineering cement-based composite material disclosed by the invention has high strength, high ductility and good cavitation resistance, and has a good application prospect in hydraulic runner engineering in the Qinghai-Tibet Plateau region; the composite material with the strength higher than 80 MPa and the ultimate tensile strain of 2.6-3.9% is designed on the basis of the ECC theory, meanwhile, after an ultrasonic vibration test for one hour, the quality damage of the composite material is reduced by 55.7%-57.9% compared with that of traditional high-strength mortar, the average cavitation erosion depth is reduced by 47.3%-48.2% compared with that of the high-strength mortar, and the cavitation erosion resistance is superior to that of ultra-high performance concrete. Therefore, when the composite material is applied to the hydraulic structure in the wading area of the Qinghai-Tibet Plateau, the cavitation erosion resistance and the anti-seismic property of the hydraulic structure can be improved, and the service life of the hydraulic structure in the wading environment of the Plateau is prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydraulic construction materials, and in particular relates to a water-related anti-cavitation engineering cement-based composite material and a preparation method and application thereof. Background Art

[0002] Hydraulic concrete flood discharge structures in the Qinghai-Tibet Plateau often suffer cavitation damage from high-velocity water flows, leading to a gradual loss of concrete quality and a collapse of bearing capacity. According to my country's current anti-cavitation design standard, "DL / T 5207-2021," cavitation damage caused by inherent bubbles in concrete under high-velocity water flows can be reduced by increasing concrete strength (>40 MPa). Although material-level anti-cavitation design has the potential to reduce the complexity of dam structures and reduce operation and maintenance costs, it is still in its early stages of development. A deep understanding of the performance behavior of cementitious materials under cavitation is key to achieving efficient anti-cavitation design. Furthermore, as a seismic zone with frequent seismic activity, the Qinghai-Tibet Plateau requires cement-based composites to possess not only environmental durability but also significant seismic toughness.

[0003] Engineered cementitious composites (ECC) have high ductility and excellent crack control capabilities, making them promising as seismic materials. Previous studies have suggested that shock waves, microjets, and high temperatures are typical effects of cavitation. These effects are typically triggered by the collapse of bubbles near the solid surface. Under cavitation damage, corrosion first occurs in the interstitial zone (ITZ) region, which has numerous microcracks and high porosity. Although the incorporation of silica fume into the cementitious system can effectively slow the erosion rate of the interfacial transition zone under cavitation, or the use of metal coatings can alleviate cavitation damage to the concrete surface caused by bubbles, cavitation can cause the evolution of the concrete pore structure and make it more susceptible to failure under tensile stress, the specific cavitation damage mechanism remains unclear.

[0004] Notably, engineering cementitious composites (ECCs) exhibit excellent tensile ductility and are able to maintain excellent energy dissipation capacity under fatigue loading. ECCs have been applied in a variety of engineering structures. Specifically, ECCs demonstrate excellent resistance to shear, cyclic, impact, and blast loads—load types commonly found in cavitation research. In addition to their superior tensile properties, ECCs exhibit exceptional durability and self-healing capabilities under harsh service conditions, thanks to their excellent crack width control. Steel fiber-reinforced ultra-high performance concrete (UHPC) has been successfully applied in hydraulic structures as a material for resisting abrasion and cavitation erosion. UHPC can serve as a benchmark for evaluating the cavitation erosion behavior of hydraulic cementitious materials. Therefore, ECCs may also provide valuable engineering insights for the use of fiber-reinforced concrete to repair cavitation damage in hydraulic structures. Although these materials have been extensively studied for improving their mechanical properties, the relationship between ECC's cavitation resistance and its mechanical properties remains understudied. Summary of the Invention

[0005] In response to the above-mentioned existing technologies, the present invention provides a water-related cavitation-resistant engineering cement-based composite material and its preparation method and application, so as to solve the technical problem that hydraulic concrete flood discharge structures in the Qinghai-Tibet Plateau are easily damaged by cavitation.

[0006] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is to provide a water-related anti-cavitation engineering cement-based composite material, including mortar and reinforcing fiber; the components of the mortar include cement, silica fume, fine sand, water, water reducer and defoamer; the reinforcing fiber is PE fiber.

[0007] On the basis of the above technical solution, the present invention can also be improved as follows.

[0008] Furthermore, the mortar includes the following components in parts by mass: 138-142 parts of cement, 15-20 parts of silica fume, 45-50 parts of fine sand, 30-35 parts of water, 1-3 parts of water reducing agent, and 0.5-1 part of defoaming agent.

[0009] Furthermore, the mass ratio of the reinforcing fiber to the mortar is 0.5~2:240~242.

[0010] Furthermore, the cement is silicate cement with a strength grade of 42.5R or 52.5R; and the silica content in the silica fume is not less than 92%.

[0011] Furthermore, the fine sand is quartz sand having a particle size of 0.075-0.38 mm and a fineness modulus of 1.4-1.6.

[0012] Furthermore, the water reducer is a polycarboxylic acid type water reducer.

[0013] Furthermore, the defoaming agent is a polyether defoaming agent.

[0014] Furthermore, the length of PE fiber is 12~18mm, the equivalent diameter is 26~40μm, and the specific gravity is 0.95~0.97g / cm 3 .

[0015] The present invention also discloses a method for preparing the above-mentioned water-related anti-cavitation engineering cement-based composite material, comprising the following steps: S1: Mix cement, silica fume, fine sand and defoamer, and stir at a speed of 300-360 rpm for 5-8 minutes to obtain a mixture; S2: Mix the water reducer with water, then mix the mixed liquid with the mixture, and stir at a speed of 300-360 rpm for 3-5 minutes to obtain mortar; S3: Add the reinforcing fiber to the mortar and stir at a speed of 540-600 rpm for 5-6 minutes to obtain a slurry; S4: Fill the slurry into a mold, demould after 45-50 hours, and then cure it at a temperature of 18-22°C and a humidity of >95% for 25-30 days.

[0016] The present invention also discloses the application of the above-mentioned water-related anti-cavitation engineering cement-based composite material in hydraulic flow channel projects in the Qinghai-Tibet Plateau area.

[0017] The beneficial effects of the present invention are: The compressive strength of the water-resistant cavitation engineering cement-based composite material prepared by the present invention ranges from 84 to 88 MPa, while its tensile strength and ultimate tensile strain are 9.0 to 9.6 MPa and 2.6 to 3.9%, respectively. Its ultimate tensile strain is 130 to 195 times that of ordinary concrete. Meanwhile, the crack width produced by the tensile specimen under tensile load ranges from 47 to 72 μm. This means that the water-resistant cavitation engineering cement-based composite material of this application has excellent mechanical properties and can meet the needs of specific applications.

[0018] 2. The water-resistant cavitation-resistant cementitious composite material prepared by the present invention exhibited a mass loss of 0.77-0.81g after a one-hour cavitation test, significantly lower than the 1.83g of conventional high-strength mortar and the 1.05g of ultra-high-performance concrete. Furthermore, the average cavitation depth of the specimens was 0.58-0.59mm, lower than the 1.12mm of conventional high-strength mortar and the 0.62mm of ultra-high-performance concrete. This demonstrates that the water-resistant cavitation-resistant cementitious composite material of the present invention possesses superior cavitation resistance and can address the challenge of rapidly decreasing durability of concrete in hydraulic conduits under high-speed water flow in the Qinghai-Tibet Plateau.

[0019] 3. The expansion degree of the cement-based composite material slurry for water-related anti-cavitation engineering prepared by the present invention is 210~230mm, and its working performance meets the requirements of on-site casting. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The 28-day compressive strength comparison of the products obtained in Comparative Examples 1-2 and Examples 1-4 is shown; Figure 2 1-2 and Examples 1-4 are uniaxial tensile stress-strain curves of the products obtained; Figure 3 is the cumulative cavitation mass loss-time curve of the products obtained in Examples 1 to 4 and Comparative Examples 1 to 2; Figure 4 is the cavitation mass loss rate of the products obtained in Examples 1 to 4 and Comparative Examples 1 to 2; Figure 5 This is a comparison of the apparent morphologies of the products obtained in Examples 1 to 4 and Comparative Examples 1 to 2 after cavitation for 1 hour; Figure 6 This is a graph showing the average cavitation depth of the products obtained in Examples 1 to 4 and Comparative Examples 1 to 2 after cavitation for 1 hour. DETAILED DESCRIPTION

[0021] The specific implementation methods of the present invention are described in detail below with reference to the embodiments.

[0022] Example 1 A water-resistant cavitation-resistant engineering cement-based composite material (SA-ECC) is disclosed. The components and weight fractions of the SA-ECC are shown in the following table.

[0023] The cement used is ordinary Portland cement with a strength grade of 52.5R; the silica content in the silica fume is not less than 96%; the particle size of the quartz sand is 0.075-0.38mm, and the fineness modulus is 1.5; the reinforcing fiber is polyethylene fiber with a length of 12-18mm, an equivalent diameter of 26-40μm, and a specific gravity of 0.96g / cm 3 The water reducer is a polycarboxylic acid type water reducer (DC-1059, water reduction rate 40%); the defoamer is a polyether type defoamer (Rilian DC-5700); and the water is tap water.

[0024] The water-resistant cavitation engineering cement-based composite material in this embodiment is prepared by the following steps: S1: Add cement, silica fume, quartz sand and defoamer into a mixing bucket and dry mix at 300 rpm for 5 min to obtain a mixture; S2: Mix the water reducer with water, then mix the mixed liquid with the mixture, and stir at a speed of 360 rpm for 5 min to obtain mortar; S3: Add the reinforcing fibers to the mortar and stir at 540 rpm for 5 min to obtain a slurry; S4: Fill the slurry into a mold, demould after 48 hours, and then cure it at a temperature of 20°C and a humidity of >95% for 28 days.

[0025] Example 2 A water-resistant cavitation-resistant engineering cement-based composite material (SA-ECC) is disclosed. The components and weight fractions of the SA-ECC are shown in the following table.

[0026] The cement used is ordinary Portland cement with a strength grade of 52.5R; the silica content in the silica fume is not less than 96%; the particle size of the quartz sand is 0.075-0.38mm, and the fineness modulus is 1.5; the reinforcing fiber is polyethylene fiber with a length of 12-18mm, an equivalent diameter of 26-40μm, and a specific gravity of 0.96g / cm 3 The water reducer is a polycarboxylic acid type water reducer (DC-1059, water reduction rate 40%); the defoamer is a polyether type defoamer (Rilian DC-5700); and the water is tap water.

[0027] The water-resistant cavitation engineering cement-based composite material in this embodiment is prepared by the following steps: S1: Add cement, silica fume, quartz sand and defoamer into a mixing bucket and dry mix at 350 rpm for 8 min to obtain a mixture; S2: Mix the water reducer with water, then mix the mixed liquid with the mixture, and stir at a speed of 300 rpm for 5 min to obtain mortar; S3: Add the reinforcing fibers to the mortar and stir at 540 rpm for 6 min to obtain a slurry; S4: Fill the slurry into a mold, demould after 48 hours, and then cure it at a temperature of 20°C and a humidity of >95% for 28 days.

[0028] Example 3 A water-resistant cavitation-resistant engineering cement-based composite material (SA-ECC) is disclosed. The components and weight fractions of the SA-ECC are shown in the following table.

[0029] The cement used is ordinary Portland cement with a strength grade of 52.5R; the silica content in the silica fume is not less than 96%; the particle size of the quartz sand is 0.075-0.38mm, and the fineness modulus is 1.5; the reinforcing fiber is polyethylene fiber with a length of 12-18mm, an equivalent diameter of 26-40μm, and a specific gravity of 0.96g / cm 3 The water reducer is a polycarboxylic acid type water reducer (DC-1059, water reduction rate 40%); the defoamer is a polyether type defoamer (Rilian DC-5700); and the water is tap water.

[0030] The water-resistant cavitation engineering cement-based composite material in this embodiment is prepared by the following steps: S1: Add cement, silica fume, quartz sand and defoamer into a mixing bucket and dry mix at 360 rpm for 5 min to obtain a mixture; S2: Mix the water reducer with water, then mix the mixed liquid with the mixture, and stir at a speed of 360 rpm for 3 min to obtain mortar; S3: Add the reinforcing fibers to the mortar and stir at 600 rpm for 5 min to obtain a slurry; S4: Fill the slurry into a mold, demould after 48 hours, and then cure it at a temperature of 20°C and a humidity of >95% for 28 days.

[0031] Example 4 A water-resistant cavitation-resistant engineering cement-based composite material (SA-ECC) is disclosed. The components and weight fractions of the SA-ECC are shown in the following table.

[0032] The cement used is ordinary Portland cement with a strength grade of 52.5R; the silica content in the silica fume is not less than 96%; the particle size of the quartz sand is 0.075-0.38mm, and the fineness modulus is 1.5; the reinforcing fiber is polyethylene fiber with a length of 12-18mm, an equivalent diameter of 26-40μm, and a specific gravity of 0.96g / cm 3 The water reducer is a polycarboxylic acid type water reducer (DC-1059, water reduction rate 40%); the defoamer is a polyether type defoamer (Rilian DC-5700); and the water is tap water.

[0033] The water-resistant cavitation engineering cement-based composite material in this embodiment is prepared by the following steps: S1: Add cement, silica fume, quartz sand and defoamer into a mixing bucket and dry mix at 300 rpm for 5 min to obtain a mixture; S2: Mix the water reducer with water, then mix the mixed liquid with the mixture, and stir at a speed of 360 rpm for 5 min to obtain mortar; S3: Add the reinforcing fibers to the mortar and stir at 540 rpm for 5 min to obtain a slurry; S4: Fill the slurry into a mold, demould after 48 hours, and then cure it at a temperature of 20°C and a humidity of >95% for 28 days.

[0034] Comparative Example 1 The components and mass fractions of traditional hydraulic C40 concrete are shown in the following table: The cement used is ordinary Portland cement with a strength grade of 42.5R; the fly ash is Class I fly ash; the silica fume is Class 98 silica fume; the river sand has a fineness modulus of 2.5; the steel fiber is copper-coated steel fiber, 13mm long and 0.2mm in diameter; and the water reducer is solid polycarboxylate high-efficiency water reducer powder. All of these raw materials can be purchased at building materials markets.

[0035] Comparative Example 2 A water-resistant cavitation-resistant engineering cement-based composite material (HP-ECC) is disclosed. The components and weight fractions of the HP-ECC are shown in the following table.

[0036] Among them, the cement used is ordinary Portland cement with a strength grade of 52.5R; the silicon dioxide content in the silica fume is not less than 96%; the particle size of the quartz sand is 0.075~0.38mm, and the fineness modulus is 1.5; the water reducer is a polycarboxylic acid type water reducer (DC-1059, water reduction rate 40%); the defoamer is a polyether type defoamer (Rilian DC-5700); and the water is tap water.

[0037] The water-resistant cavitation engineering cement-based composite material in this comparative example is prepared by the following steps: S1: Add cement, silica fume, quartz sand and defoamer into a mixing bucket and dry mix at 300 rpm for 5 min to obtain a mixture; S2: Mix the water reducer with water, then mix the mixed liquid with the mixture, and stir at a speed of 360 rpm for 5 min to obtain mortar; S3: Fill the slurry into a mold, demould after 48 hours, and then cure it at a temperature of 20°C and a humidity of >95% for 28 days.

[0038] Experimental example The relevant properties of the products obtained in Examples 1 to 4 and Comparative Examples 1 to 2 were tested, and the results were as follows: Figures 1 to 6 And as shown in Table 1. Among them, Figure 1 The 28-day compressive strength comparison of the products obtained in Comparative Examples 1-2 and Examples 1-4 is shown; Figure 2 1-2 and Examples 1-4 are uniaxial tensile stress-strain curves of the products obtained; Figure 3 is the cumulative cavitation mass loss-time curve of the products obtained in Examples 1 to 4 and Comparative Examples 1 to 2; Figure 4 is the cavitation mass loss rate of the products obtained in Examples 1 to 4 and Comparative Examples 1 to 2; Figure 5 This is a comparison of the apparent morphologies of the products obtained in Examples 1 to 4 and Comparative Examples 1 to 2 after cavitation for 1 hour; Figure 6 This is a graph showing the average cavitation depth of the products obtained in Examples 1 to 4 and Comparative Examples 1 to 2 after cavitation for 1 hour.

[0039] Table 1 Test results of relevant performance tests of products of Examples 1 to 4 and Comparative Examples 1 to 2 from Figures 1 to 6 As can be seen from Table 1, with the increase of PE fiber content, the compressive strength of the four embodiments shows a trend of first increasing and then decreasing. The compressive strength of Example 1, Example 2, Example 3 and Example 4 increased by 7.8%, 40.4%, 26.5% and 31.7% compared with that of Comparative Example 2. The tensile strength of the four groups of embodiments after 28 days all exceeded 9MPa, which was higher than the tensile strength of Comparative Examples 1 and 2. With the increase of PE fiber content, the ultimate tensile strain of the embodiment after 28 days gradually increased. This is because PE fiber has a higher elastic modulus and tensile strength, which can play a bridging role in the matrix, thereby increasing the ultimate tensile strain of the matrix. The ultimate tensile strain of Example 3 and Example 4 is 3.9% and 2.6% respectively, which is 390 and 260 times that of the ultimate tensile strain of Comparative Example 2. From the perspective of mass loss rate and average cavitation depth, with the increase of fiber content, the fiber can be evenly dispersed in the mortar, and the tensile strain energy is increased by improving the tensile ductility of the matrix, and the mass loss of the specimen after cavitation gradually decreases. By comparing Examples 1 to 4 with Comparative Example 2, it can be seen that, from the perspective of mass loss rate and average cavitation depth, as the fiber content increases, the fibers can be evenly dispersed in the mortar, and by improving the tensile ductility of the matrix, its tensile strain energy increases. The mass loss of the specimen after cavitation gradually decreases, and the average cavitation depth decreases. This shows that the incorporation of PE fibers significantly improves the cavitation resistance of the matrix; in addition, compared with Comparative Example 1, the mass loss rate and average cavitation depth of Examples 3 and 4 are lower. The compressive strength of Comparative Example 1 is higher than that of Examples 3 and 4, while its ultimate tensile strain is much lower than that of Examples 3 and 4. From this, it can be inferred that the cavitation resistance of the specimen is related to the tensile properties of the specimen. Therefore, the water-related anti-cavitation engineering cement-based composite material of the present invention has good tensile ductility and excellent cavitation resistance, which can greatly improve the durability of hydraulic channels in the Qinghai-Tibet Plateau and extend their service life.

[0040] Although the specific embodiments of the present invention have been described in detail in conjunction with the embodiments, this should not be construed as limiting the scope of protection of this patent. Within the scope described by the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A cement-based composite material for water-related cavitation-resistant engineering, characterized by: The invention comprises mortar and reinforcing fibers; the components of the mortar include cement, silica fume, fine sand, water, a water reducing agent and a defoaming agent; and the reinforcing fibers are PE fibers.

2. The cement-based composite material for water-related cavitation resistance engineering according to claim 1, characterized in that: The mortar comprises the following components in parts by mass: 138-142 parts of cement, 15-20 parts of silica fume, 45-50 parts of fine sand, 30-35 parts of water, 1-3 parts of water reducing agent, and 0.5-1 part of defoaming agent.

3. The cement-based composite material for water-related anti-cavitation engineering according to claim 2, characterized in that: The mass ratio of the reinforcing fiber to the mortar is 0.5-2:240-242.

4. The cement-based composite material for water-related cavitation-resistant engineering according to claim 1 or 2, characterized in that: The cement is silicate cement with a strength grade of 42.5R or 52.5R; the silicon dioxide content in the silica fume is not less than 92%.

5. The cement-based composite material for water-related cavitation-resistant engineering according to claim 1 or 2, characterized in that: The fine sand is quartz sand with a particle size of 0.075-0.38 mm and a fineness modulus of 1.4-1.

6.

6. The cement-based composite material for water-related cavitation-resistant engineering according to claim 1 or 2, characterized in that: The water reducer is a polycarboxylic acid type water reducer.

7. The cement-based composite material for water-related cavitation resistance engineering according to claim 1 or 2, characterized in that: The defoamer is a polyether defoamer.

8. The cement-based composite material for water-related cavitation resistance engineering according to claim 1, characterized in that: The PE fiber has a length of 12-18 mm, an equivalent diameter of 26-40 μm, and a specific gravity of 0.95-0.97 g / cm 3 .

9. The method for preparing the water-related anti-cavitation engineering cement-based composite material according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1: Mix cement, silica fume, fine sand and defoamer, and stir at a speed of 300-360 rpm for 5-8 minutes to obtain a mixture; S2: Mix the water reducer with water, then mix the mixed liquid with the mixture, and stir at a speed of 300-360 rpm for 3-5 minutes to obtain mortar; S3: Add the reinforcing fiber to the mortar and stir at a speed of 540-600 rpm for 5-6 minutes to obtain a slurry; S4: Fill the slurry into a mold, demould after 45-50 hours, and then cure it at a temperature of 18-22°C and a humidity of >95% for 25-30 days.

10. Use of the water-related anti-cavitation engineering cement-based composite material according to any one of claims 1 to 8 in hydraulic channel projects in the Qinghai-Tibet Plateau.

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