Early-stage crack-resistant hydraulic concrete and preparation method thereof

Abstract

The invention discloses early-stage crack-resistant hydraulic concrete and a preparation method thereof, and relates to the technical field of hydraulic concrete.The early-stage crack-resistant hydraulic concrete is prepared from volcanic ash, basalt fiber, filler, a dispersing agent, a foaming agent, cement and water. The early-stage crack-resistant concrete has the advantages of excellent construction performance, mechanical property, volume stability and the like, the problem that more cracks are generated in the early stage of the concrete can be effectively solved, the durability is improved, the overall engineering quality is improved, and the later-stage operation and maintenance cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of hydraulic concrete, and in particular to an early-stage anti-cracking hydraulic concrete and a preparation method thereof. Background Art

[0002] Hydraulic concrete is the most widely used building material in water conservancy project construction. However, it will inevitably produce a certain number of microcracks or even macrocracks in actual engineering applications. These cracks will not only reduce the aesthetics of hydraulic structures, but also affect the safety of the structure over time. Studies have shown that the early cracking of concrete is one of the main reasons affecting the durability of concrete structures, and temperature stress and shrinkage stress are the main causes of early cracking. Therefore, improving the early crack resistance of concrete and controlling its cracking degree to a minimum has become an important topic in current concrete research. The early crack resistance of concrete can be effectively improved by optimizing mix design, adding mineral admixtures and other technical means.

[0003] In recent years, researchers have carried out a lot of exploratory work to improve the early crack resistance of hydraulic concrete. Among them, adding mineral admixtures such as fly ash and slag to reduce the amount of cement, reduce the internal hydration heat of concrete, enhance volume stability, and thus inhibit concrete shrinkage has become an effective way to control concrete cracking and improve durability. Engineering practice shows that the use of fly ash, fine aggregate, air entraining agent, water reducer and basalt fiber alone or in combination can improve the early crack resistance of concrete to varying degrees and significantly reduce the occurrence of small cracks. However, it often leads to fluctuations in early crack resistance, and the current research on the comprehensive use of admixtures, admixtures and fibers to prepare early hydraulic high crack resistance concrete still lacks systematicity, and has not yet formed a practical engineering solution.

[0004] Therefore, it is urgent to develop an early crack-resistant hydraulic concrete and a preparation method thereof to solve the above-mentioned technical problems. Summary of the invention

[0005] The main purpose of the present invention is to provide an early-stage crack-resistant hydraulic concrete and a preparation method thereof, aiming to solve the technical problem in the prior art that hydraulic concrete produces many cracks at an early stage and has poor durability.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides an early-stage anti-cracking hydraulic concrete. The raw materials of each cubic meter of the early-stage anti-cracking hydraulic concrete include the following components:

[0008] 63.3 to 141.8 kg of volcanic ash, 4.0 to 6.0 kg of basalt fiber, 1660 to 2000 kg of filler, 2.1 to 4.2 kg of dispersant, 0.02 to 0.03 kg of foaming agent, 253.3 to 330.9 kg / m of cement 3 and 133 to 155 kg of water.

[0009] Preferably, the diameter of the basalt fiber is 6 to 13 μm and the length is 18 mm.

[0010] Specifically, adding basalt fiber to concrete can increase the strength, durability and toughness of the concrete, thereby improving the early cracking resistance and tensile properties of the concrete.

[0011] Preferably, the filler is basalt aggregate, and the basalt aggregate includes large stones with a particle size of 80 to 90 mm, medium stones with a particle size of 30 to 50 mm, and small stones with a particle size of 0.35 to 0.5 mm; the ratio of small stones: medium stones: large stones = 1:(0.8 to 0.9):(0.6 to 0.7).

[0012] Preferably, the dispersant is a naphthalene-based dispersant, and the naphthalene-based dispersant is sodium methylene bisnaphthalene sulfonate dispersant.

[0013] Preferably, the foaming agent is ML-301 foaming agent.

[0014] Specifically, the addition of the dispersant and the foaming agent can improve the workability and strength of the concrete.

[0015] Preferably, the cement is P·MH 42.5 grade cement.

[0016] Specifically, P·MH 42.5 grade cement can improve the strength of the concrete.

[0017] The present invention also provides a preparation method of early cracking resistance hydraulic concrete, comprising the following steps:

[0018] S1. Process the basalt aggregate into large stones with a particle size of 80 to 90 mm, medium stones with a particle size of 30 to 50 mm, and small stones with a particle size of 0.35 to 0.5 mm respectively, and set aside;

[0019] S2. Prepare the filler according to the ratio of small stones: medium stones: large stones = 1:(0.8 to 0.9):(0.6 to 0.7);

[0020] S3. Mix the filler, cement, volcanic ash and basalt fiber evenly to fully disperse the basalt fiber, and obtain a dry mix;

[0021] S4. Mix the dispersant and the foaming agent with water evenly to obtain an external mixture;

[0022] S5. Add the external mixture in S4 to the dry mixture. After being stirred evenly, early crack-resistant hydraulic concrete is obtained.

[0023] Specifically, the basalt fiber has good compatibility and bonding performance with fillers, cement, and volcanic ash matrix, can be evenly dispersed in the concrete to form a stable reinforcing phase, and fully exerts its reinforcing effect.

[0024] Preferably, the stirring time in step S5 is 115 - 125 s, and the stirring rate is 60 - 70 revolutions per minute.

[0025] The beneficial effects of the present invention are as follows:

[0026] 1. In the present invention, by incorporating basalt fiber and designing the optimal dosage according to the characteristics and functions of various materials. Firstly, the incorporation of high-strength and high-modulus basalt fiber can form a three-dimensional reinforcing network inside the concrete. When the concrete is subjected to tensile stress, these fibers can effectively bear and disperse the stress, preventing the expansion of cracks. The high strength and toughness of basalt fiber enable the concrete to withstand greater deformation without cracking when subjected to external loads or internal stresses. Secondly, the basalt fiber is evenly dispersed in the concrete, can fill the pores and micro-cracks inside the concrete, and improve the density of the concrete. This improvement in the microstructure helps to improve the early crack resistance and freeze-thaw resistance of the concrete, further enhancing its durability. Finally, during the hardening process of the concrete, the basalt fiber can inhibit the formation of early plastic cracks. Due to the presence of basalt fiber, the crack resistance of the concrete in the plastic stage is significantly improved. When the concrete begins to harden, the fiber can effectively restrain the shrinkage of the concrete, reducing the cracks caused by shrinkage.

[0027] 2. By using P·MH 42.5 cement in the present invention, the hydration heat of the cement can be reduced, which is particularly important in the construction of mass concrete. Since the temperature rise caused by hydration heat is one of the main reasons for the early cracking of concrete, using P·MH 42.5 cement can effectively reduce the formation of temperature cracks. The hydration heat of P·MH 42.5 cement is about 10% - 20% lower than that of ordinary Portland cement, which helps to reduce the temperature gradient inside the concrete and reduce the stress caused by temperature differences.

[0028] 3. The concrete strength grade provided by the present invention is not less than C20, and can meet the requirements of different construction processes, including a concrete with different fluidities, that is, the slump is 50 - 70 mm.

[0029] 4. The hydraulic concrete with early crack resistance of the present invention is used in dams, reservoirs, tunnels, water diversion supports, sluice gates and other buildings with strict requirements for cracks in water conservancy and hydropower projects. It is particularly important for face slab concrete, and has the advantages of good mechanical properties, deformation properties, construction properties and durability. At the same time, it improves the crack resistance of the concrete itself. The concrete with early crack resistance takes into account the excellent construction properties, mechanical properties and volume stability, etc., and can effectively solve the problem of more cracks generated in the early stage of concrete, improve durability, improve the overall project quality, reduce construction costs and reduce the later operation and maintenance costs. Detailed implementation mode

[0030] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the embodiments of the present application.

[0031] To verify the effects such as the early high crack resistance of the early crack-resistant hydraulic concrete of the present invention, a comparative test was conducted between the early crack-resistant hydraulic concrete of the present invention and the existing concrete. There are many actual embodiments, and only the following representative embodiments are selected.

[0032] Embodiment 1

[0033] The early crack-resistant hydraulic concrete provided in this embodiment, the raw materials per cubic meter of the early crack-resistant hydraulic concrete include the following components:

[0034] Water: 133 kg / m 3 ; P·MH 42.5 grade cement: 253.3 kg / m 3 ; Pozzolan: 63.3 kg / m 3 ; Basalt fiber: 4.0 kg / m 3 ; Filler 1666 kg / m 3 ; Methylene bisnaphthalenesulfonate dispersant: 4.2 kg / m 3 ; ML-301 foaming agent: 0.02 kg / m 3 .

[0035] Among them, the diameter of the basalt fiber is 6 - 13 μm and the length is 18 mm; the basalt aggregate filler is composed of large stones with a particle size of 80 - 90 mm, medium stones with a particle size of 30 - 50 mm and small stones with a particle size of 0.35 - 0.5 mm mixed in a ratio of 1:0.9:0.7.

[0036] The preparation method of the early crack-resistant hydraulic concrete is prepared according to the above raw material components, and includes the following steps:

[0037] S1. Process the basalt aggregates into large stones with a particle size of 80 - 90 mm, medium stones with a particle size of 30 - 50 mm and small stones with a particle size of 0.35 - 0.5 mm respectively, and set aside;

[0038] S2. Prepare the filler according to the ratio of small stones: medium stones: large stones = 1:0.9:0.7;

[0039] S3. Mix the filler, cement, volcanic ash and basalt fiber evenly to fully disperse the basalt fiber, obtaining the dry mix;

[0040] S4. Mix the dispersant and foaming agent with water evenly to obtain the external mixture;

[0041] S5. Add the external mixture in S4 to the dry mix, stir at a stirring rate of 60 revolutions per minute for 120 s, and obtain the early crack-resistant hydraulic concrete after stirring evenly.

[0042] The test results of the performance of the prepared early crack-resistant hydraulic concrete are shown in Table 1.

[0043] Table 1

[0044]

[0045] Example 2:

[0046] For the early crack-resistant hydraulic concrete provided in this example, the raw materials per cubic meter of the early crack-resistant hydraulic concrete include the following components:

[0047] Water: 145 kg / m 3 ; P·MH 42.5-grade cement: 287.2 kg / m 3 ; Volcanic ash: 67.5 kg / m 3 ; Basalt fiber: 5.0 kg / m 3 ; Filler 1855 kg / m 3 ; Methylene bisnaphthalenesulfonate dispersant: 3.1 kg / m 3 ; ML-301 foaming agent: 0.025 kg / m 3 .

[0048] Among them, the diameter of the basalt fiber is 6 - 13 μm and the length is 18 mm; the basalt aggregate filler is composed of large stones with a particle size of 80 - 90 mm, medium stones with a particle size of 30 - 50 mm and small stones with a particle size of 0.35 - 0.5 mm mixed in a ratio of 1:0.8:0.6.

[0049] The preparation method of the early crack-resistant hydraulic concrete is prepared according to the above raw material components, including the following steps:

[0050] S1. Process the basalt aggregate into large stones with a particle size of 80 - 90 mm, medium stones with a particle size of 30 - 50 mm and small stones with a particle size of 0.35 - 0.5 mm respectively, and set aside;

[0051] S2. Prepare the filler by mixing small stones, medium stones, and large stones in a ratio of 1:0.8:0.6;

[0052] S3. Mix the filler, cement, pozzolan, and basalt fibers evenly to fully disperse the basalt fibers and obtain the dry mix;

[0053] S4. Mix the dispersant and foaming agent evenly with water to obtain the external admixture mix;

[0054] S5. Add the external admixture mix in S4 to the dry mix and stir at a speed of 70 revolutions per minute for 115 s. After stirring evenly, obtain the early crack-resistant hydraulic concrete.

[0055] The test results of the performance of the prepared early crack-resistant hydraulic concrete are shown in Table 2.

[0056] Table 2

[0057]

[0058] Example 3:

[0059] For the early crack-resistant hydraulic concrete provided in this example, the raw materials per cubic meter of the early crack-resistant hydraulic concrete include the following components:

[0060] Water: 155 kg / m 3 ; P·MH 42.5 grade cement: 330.9 kg / m 3 ; Pozzolan: 69.5 kg / m 3 ; Basalt fibers: 6.0 kg / m 3 ; Filler 1975 kg / m 3 ; Sodium methylene bisnaphthalene sulfonate dispersant: 2.1 kg / m 3 ; ML-301 foaming agent: 0.03 kg / m 3 .

[0061] Among them, the diameter of the basalt fibers is 6 - 13 μm and the length is 18 mm; the basalt aggregate filler is composed of large stones with a particle size of 80 - 90 mm, medium stones with a particle size of 30 - 50 mm, and small stones with a particle size of 0.35 - 0.5 mm, mixed in a ratio of 1:0.85:0.65.

[0062] The preparation method of the early crack-resistant hydraulic concrete is prepared according to the above raw material components and includes the following steps:

[0063] S1. Process the basalt aggregates into large stones with a particle size of 80 - 90 mm, medium stones with a particle size of 30 - 50 mm, and small stones with a particle size of 0.35 - 0.5 mm respectively, and set aside;

[0064] S2. Prepare the filler by mixing small stones, medium stones, and large stones at a ratio of 1:0.85:0.65;

[0065] S3. Mix the filler, cement, volcanic ash, and basalt fibers evenly to fully disperse the basalt fibers and obtain the dry mix;

[0066] S4. Mix the dispersant and foaming agent with water evenly to obtain the external admixture mix;

[0067] S5. Add the external admixture mix in S4 to the dry mix and stir at a rate of 65 revolutions per minute for 125 s. After stirring evenly, obtain the early crack-resistant hydraulic concrete.

[0068] The performance test results of the prepared early crack-resistant hydraulic concrete are shown in Table 3.

[0069]

[0070] Comparative Example 1

[0071] The difference between Comparative Example 1 and Example 1 is that no basalt fibers are added.

[0072] Comparative Example 2

[0073] The difference between Comparative Example 1 and Example 3 is that the basalt fibers are replaced with PVA fibers, and the PVA dosage is 6.0 kg / m 3 .

[0074] The performance test results of the concrete prepared in Comparative Example 1 and Comparative Example 2 are shown in Table 4.

[0075] Table 4

[0076]

[0077] It can be seen from Tables 1, 2, 3, and 4 that the early crack-resistant hydraulic concrete of Examples 1-3 of the present invention is significantly superior to the corresponding concrete of Comparative Examples 1-2 in terms of compressive strength and early crack resistance. It shows that the concrete prepared by the above raw materials and preparation method has excellent high-strength early crack resistance. The hydraulic crack-resistant concrete described in the present invention is superior to the concrete prepared without adding fibers or adding PVA fibers in the prior art.

[0078] Example 4

[0079] The early crack-resistant hydraulic concrete provided in this example, the raw materials per cubic meter of the early crack-resistant hydraulic concrete include the following components:

[0080] Water: 141 kg / m 3 ; P·MH 42.5 grade cement: 289.6 kg / m 3; Volcanic ash: 141.8 kg / m 3 ; Basalt fiber: 5.0 kg / m 3 ; Filler 2000 kg / m 3 ; Sodium methylene bisnaphthalene sulfonate dispersant: 3.0 kg / m 3 ; ML-301 foaming agent: 0.02 kg / m 3 。

[0081] Among them, the diameter of the basalt fiber is 6 - 13 μm and the length is 18 mm; the basalt stone filler is composed of large stones with a particle size of 80 - 90 mm, medium stones with a particle size of 30 - 50 mm, and small stones with a particle size of 0.35 - 0.5 mm, which are mixed in a ratio of 1:0.9:0.7.

[0082] The preparation method of early crack-resistant hydraulic concrete is prepared according to the above raw material components, including the following steps:

[0083] S1. Process the basalt stones into large stones with a particle size of 80 - 90 mm, medium stones with a particle size of 30 - 50 mm, and small stones with a particle size of 0.35 - 0.5 mm respectively, and set aside;

[0084] S2. Prepare the filler according to the ratio of small stones: medium stones: large stones = 1:0.8:0.7;

[0085] S3. Mix the filler, cement, volcanic ash and basalt fiber evenly to fully disperse the basalt fiber and obtain a dry mix;

[0086] S4. Mix the dispersant and the foaming agent with water evenly to obtain an external mixture;

[0087] S5. Add the external mixture in S4 to the dry mix, stir at a stirring rate of 60 revolutions per minute for 120 s, and after stirring evenly, obtain the early crack-resistant hydraulic concrete.

[0088] In addition, the concrete formulas with different components other than Examples 1 - 4 are designed and selected according to the requirements of specific projects and the actual site conditions. The optimal mix ratio of the concrete needs to be comprehensively considered and designed based on multiple factors such as the load that the concrete will bear, the use environment, and the construction technology; therefore, the optimal mix ratio design of the concrete needs to be adjusted and optimized in combination with specific situations to meet the needs of actual projects.

[0089] In summary, in the present invention, by incorporating basalt fibers and designing the optimal dosage according to the characteristics and functions of various materials. The incorporation of high-strength and high-modulus basalt fibers can first form a three-dimensional reinforcement network inside the concrete. When the concrete is subjected to tensile stress, these fibers can effectively bear and disperse the stress, preventing the expansion of cracks. The high strength and toughness of basalt fibers enable the concrete to withstand greater deformation without fracture when subjected to external loads or internal stresses. Secondly, the basalt fibers are evenly dispersed in the concrete, which can fill the pores and micro-cracks inside the concrete, improving the compactness of the concrete. This improvement in the micro-structure helps to enhance the early anti-cracking and freeze-thaw resistance of the concrete, further strengthening its durability. Finally, during the hardening process of the concrete, the basalt fibers can inhibit the formation of early plastic cracks. Due to the presence of basalt fibers, the anti-cracking performance of the concrete in the plastic stage is significantly improved. When the concrete begins to harden, the fibers can effectively restrain the shrinkage of the concrete, reducing the cracks caused by shrinkage. By using P·MH 42.5 cement, the heat of hydration of the cement can be reduced, which is particularly important in the construction of mass concrete. Since the temperature rise caused by the heat of hydration is one of the main reasons for the early cracking of concrete, using P·MH 42.5 cement can effectively reduce the formation of temperature cracks. The heat of hydration of P·MH 42.5 cement is about 10% - 20% lower than that of ordinary Portland cement, which helps to reduce the temperature gradient inside the concrete and the stress caused by temperature differences.

[0090] The specific embodiments of the invention have been described in detail above, but they are only examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modification or substitution of the invention is also within the scope of the present invention. Therefore, equivalent transformations, modifications, improvements, etc. made without departing from the spirit and principles of the present invention should all be covered by the scope of the present invention.

Claims

1. An early anti-cracking hydraulic concrete, characterized in that, The raw materials of per cubic meter of the early crack-resistant hydraulic concrete include the following components: 63.3 to 141.8 kg of volcanic ash, 4.0 to 6.0 kg of basalt fiber, 1660 to 2000 kg of filler, 2.1 to 4.2 kg of dispersant, 0.02 to 0.03 kg of foaming agent, 253.3 to 330.9 kg / m of cement 3 , 133 to 155 kg of water.

2. The early crack-resistant hydraulic concrete according to claim 1, wherein, The diameter of the basalt fiber is 6 - 13 μm and the length is 18 mm.

3. The early crack-resistant hydraulic concrete according to claim 1, characterized in that The filler is basalt aggregate, and the basalt aggregate includes large stones with a particle size of 80 - 90 mm, medium stones with a particle size of 30 - 50 mm, and small stones with a particle size of 0.35 - 0.5 mm; the ratio of small stones: medium stones: large stones = 1:(0.8 - 0.9):(0.6 - 0.7).

4. The early anti-cracking hydraulic concrete according to claim 1, characterized in that The dispersant is a naphthalene-based dispersant, and the naphthalene-based dispersant is sodium methylene bisnaphthalene sulfonate dispersant.

5. The early anti-cracking hydraulic concrete according to claim 1, characterized in that, The foaming agent is ML-301 foaming agent.

6. The early anti-cracking hydraulic concrete according to claim 1, characterized in that, The cement is P·MH 42.5 grade cement.

7. A preparation method of the early crack-resistant hydraulic concrete according to any one of claims 1-6, characterized in that, It includes the following steps: S1. Process the basalt aggregate into large stones with a particle size of 80 - 90 mm, medium stones with a particle size of 30 - 50 mm, and small stones with a particle size of 0.35 - 0.5 mm respectively, and set aside; S2. Prepare the filler according to the ratio of small stones: medium stones: large stones = 1:(0.8 - 0.9):(0.6 - 0.7); S3. Mix the filler, cement, volcanic ash, and basalt fiber evenly to fully disperse the basalt fiber and obtain the dry mix; S4. Mix the dispersant and the foaming agent with water evenly to obtain the external admixture; S5. Add the external admixture in S4 to the dry mix, and after stirring evenly, obtain the early crack-resistant hydraulic concrete.

8. The preparation method of the early crack-resistant hydraulic concrete according to claim 7, characterized in that, In step S5, the stirring time is 115 - 125 s and the stirring rate is 60 - 70 revolutions per minute.

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