A high-toughness frost-resistant concrete block for high-altitude infrastructure projects and its preparation method

Abstract

The present invention relates to the field of high-altitude infrastructure projects, and discloses a high-toughness frost-resistant concrete block for high-altitude infrastructure projects and a preparation method thereof. The preparation method of the concrete block comprises: preparing modified rubber basalt fiber and modified basalt ore sand; after cement and water reducer are fully mixed, mixing water is added and continuously mixed until an obvious adhesive state is obtained, then river sand and modified basalt ore sand are added and mixed to obtain mortar, thickener is added to the mortar to adjust the mortar consistency, and then modified rubber basalt fiber is added to the mortar and mixed evenly to obtain concrete slurry; the concrete slurry is formed to obtain high-toughness frost-resistant concrete blocks for high-altitude infrastructure projects. The present invention carries out orthogonal experimental design and analysis and mix ratio optimization, and obtains the optimal mix ratio of concrete with the best flexural strength and flexural toughness index, further improving the toughness of the concrete blocks.

Description

Technical Field

[0001] The present invention relates to the field of high-altitude infrastructure projects, and in particular to a high-toughness frost-resistant concrete block for high-altitude infrastructure projects and a preparation method thereof. Background Art

[0002] ECC stands for Engineered Cementations Composite, which refers to a high-toughness cement-based composite material. It is composed of cement, fillers or fine aggregates with a particle size of less than 5mm as the matrix, and an appropriate amount of fiber reinforcement is added to the concrete. Through some means, the matrix and fiber interface is effectively ensured to form a cement-based composite material that meets higher requirements. Compared with ordinary concrete, ECC has higher deformation capacity and stronger bending strength and longer fatigue life under the action of bending beam toughness and tensile strain. However, with the rapid development of construction in the western region, the performance requirements for concrete are increasing. In particular, the rapid development of infrastructure projects in high-altitude and low-temperature areas requires the concrete blocks used to have higher toughness and frost resistance.

[0003] Existing patent CN110218030A discloses a frost-resistant concrete comprising the following components by weight: 432-486 parts cement, 551-620 parts ceramsite, 707-744 parts river sand, 141-162 parts water, 3.24-6.48 parts water reducer, 0.1-0.9 parts organic fiber, 1.33-5.3 parts inorganic fiber, and 2.5-4.5 parts modified gas-generating additive. Lightweight aggregate (ceramsite) is mixed with hybrid fiber and other additives to form hybrid fiber ceramsite concrete. Basalt fiber and polypropylene fiber are added to LC50 ceramsite concrete to prepare frost-resistant concrete, which has good frost resistance. However, due to the surface finish and radial brittleness of the fibers, the hybrid fibers in the concrete have poor bonding with the concrete gel material and are prone to radial shear failure. For high-altitude infrastructure projects, the toughness and frost resistance of concrete blocks need to be further improved.

[0004] Based on this, the development of a high-toughness frost-resistant concrete block and its preparation method for high-altitude infrastructure projects has high industrial value and practical significance. Summary of the Invention

[0005] In view of the problems and shortcomings of the existing technology, the present invention provides a high-toughness frost-resistant concrete block for high-altitude infrastructure projects and a preparation method thereof.

[0006] Based on the above purpose, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing high-toughness frost-resistant concrete blocks for high-altitude infrastructure projects, comprising the following steps:

[0008] (1) After the surface of the basalt fiber is covered with a rubber layer, the basalt fiber is cut into basalt fiber fragments, the basalt fiber fragments are subjected to plasma modification treatment, and then soaked, rinsed, dried, placed in a coupling agent, and allowed to stand, taken out and dried to obtain modified rubber basalt fiber;

[0009] (2) placing basalt sand in a coupling agent and allowing it to stand, taking it out and drying it to obtain modified basalt sand;

[0010] (3) After cement and water reducer are fully mixed, mixing water is added and continuously mixed until a noticeable adhesive state is achieved. Then river sand and modified basalt sand are added to mix to prepare mortar. Thickener is added to the mortar to adjust the consistency of the mortar. Modified rubber basalt fiber is then added to the mortar and mixed evenly to prepare concrete slurry.

[0011] (4) The concrete slurry is molded to obtain high-toughness frost-resistant concrete blocks for high-altitude infrastructure projects.

[0012] Furthermore, the basalt fiber in step (1) is drawn by melting basalt.

[0013] Furthermore, the drawing process uses a platinum-rhodium alloy drawing plate.

[0014] Furthermore, the plasma modification method in step (1) is as follows: under the conditions of an air flow rate of 25 to 35 mL / min, a voltage of 60 to 75 V, and a current of 2 to 3 A, the basalt fiber fragments are treated at a distance of 1 to 2 cm from the plasma flame for 5 to 15 seconds.

[0015] Furthermore, the coupling agent in step (1) and step (2) is KH550 complex coupling agent.

[0016] Furthermore, the coupling time in step (1) and step (2) is 48 to 72 hours.

[0017] Furthermore, in step (1) and step (2), the drying is performed until the moisture content is lower than 0.3%, and the drying temperature is 40-60°C.

[0018] Preferably, the apparent density of the basalt sand in step (2) is 2620 Kg·m -3 , bulk density 1520Kg·m -3 , porosity 42%, mud content 3%, crushing index 19%.

[0019] Preferably, the amount of the water reducer in step (3) is 1% to 1.5% of the mass of the cement, and the amount of the modified basalt sand is 25% to 100% of the total mass of the river sand and the modified basalt sand; in the concrete slurry, the mass fraction of the modified rubber basalt fiber is 0.3% to 1.5%, the water-binder ratio is 0.15 to 0.25, and the sand-binder ratio is 0.3 to 0.4.

[0020] More preferably, the active ingredient of the water reducer is greater than 90%, the residual moisture is less than 3%, the bulk density is 500-700 g / L, and the mortar water reduction rate is greater than 23%.

[0021] More preferably, the modified rubber basalt fiber is a mixture of modified rubber basalt fibers having lengths of 6 mm, 9 mm, 12 mm, and 18 mm in equal proportions.

[0022] Furthermore, the mortar consistency in step (3) is a truncated cone expansion method fluidity of less than 17 cm.

[0023] Furthermore, the mixing process in step (3) uses a concrete mortar mixer.

[0024] Furthermore, the cement and water reducing agent are mixed at a speed of 15 r / min for 5 to 10 minutes.

[0025] Furthermore, the modified rubber basalt fiber mixing process is first stirring at a rotation speed of 15 r / min for 10 to 18 minutes, and then stirring at a rotation speed of 40 r / min for 20 to 30 minutes.

[0026] Furthermore, in step (4), the curing temperature is 20-30° C., the humidity is 90%-95%, and the curing time is 28-40 days.

[0027] In a second aspect, the present invention provides a high-toughness frost-resistant concrete block for high-altitude infrastructure projects, which is prepared by the method of the first aspect.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. In the present invention, the surface of the basalt fiber is covered with a rubber layer, which enhances the toughness and pressure resistance of the basalt fiber, effectively avoiding the radial brittleness and damage caused by radial shear in the basalt fiber in the prior art, and improving the physical properties of the basalt fiber. The basalt fiber covered with the rubber layer is plasma-modified, and the plasma etches the fiber surface, creating pits, etc., thereby enhancing the bond between the hybrid fiber and the concrete gel material. The basalt fiber and basalt sand are further modified with a coupling agent to further form modified particles attached to their surfaces, thereby reducing the surface smoothness of the basalt fiber and basalt sand.

[0030] 2. The present invention adds an appropriate amount of basalt sand to the concrete mortar. Basalt sand has the characteristics of high strength, high density, low saturation rate and good frost resistance. It changes the original pore structure and interface structure of the concrete, giving the concrete advantages such as frost resistance.

[0031] 3. The present invention improves the uniformity of the mixed fiber dispersion in the concrete mortar by adding a thickener. In particular, when the mortar fluidity measured by the truncated cone expansion method is less than 17 cm, the basalt fiber dispersion is close to optimal, and the resulting mixed fiber ECC has the highest mechanical properties.

[0032] The present invention carries out orthogonal test design and analysis and mix ratio optimization, obtains the optimal mix ratio of concrete with the best flexural strength and flexural toughness index, and further improves the toughness of concrete blocks. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention clearer and more specific, the present invention is further described in detail below through examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] In order to explore the effects of three factors, namely, rubber basalt fiber dosage, water-binder ratio and sand-binder ratio, on the 28d flexural strength and flexural toughness index of hybrid fiber ECC in modified concrete slurry, the mix proportion was designed based on the 28d flexural strength criterion of hybrid fiber ECC, and orthogonal experimental design and analysis as well as mix proportion optimization were carried out.

[0035] This orthogonal test was designed according to orthogonal table L18 (3.6.6.1), as shown in Table 1. A total of 18 groups of tests were required. Due to some errors that cannot be ignored in the test and the discreteness of the test results, three groups of test blocks were grouped together in this test. The size of the test blocks was 40 mm × 40 mm × 160 mm.

[0036]

[0037] Example 1

[0038] A high-toughness frost-resistant concrete block for high-altitude infrastructure projects, the preparation method of which comprises the following steps:

[0039] (1) The basalt is crushed and ground and heated in an incinerator until it melts. A platinum-rhodium alloy drawing plate is used to draw it into continuous fibers. The continuous fibers are covered with a rubber layer on the surface of a softened rubber pool and cut into basalt fiber fragments. The basalt fiber fragments are modified using plasma. The plasma modification method is as follows: under the conditions of an air flow rate of 25-35 mL / min, a voltage of 60-75 V, and a current of 2-3 A, the basalt fiber fragments are placed 1-2 cm away from the plasma flame for 5-15 seconds, then rinsed with clean water, dried, and completely immersed in a KH550 complex coupling agent for 48 hours. After being taken out, they are placed in a vacuum constant temperature drying oven and dried at 40-60 ° C until the moisture content is less than 0.3%, thereby obtaining modified rubber basalt fiber.

[0040] (2) Basalt sand (apparent density 2620Kg·m -3 , bulk density 1520Kg·m -3 , porosity 42%, mud content 3%, crushing index 19%) was completely immersed in KH550 compound coupling agent and allowed to stand for 48 hours. After being taken out, it was placed in a vacuum constant temperature drying oven and dried at 40-60°C until the moisture content was less than 0.3% to obtain modified basalt sand.

[0041] (3) Pour cement and water reducer (the amount of water reducer is 1% of the cement mass, the active ingredient of the water reducer is greater than 90%, the residual water is less than 3%, the bulk density is 500-700 g / L, and the mortar water reduction rate is greater than 23%) into a concrete mortar mixer and stir at a speed of 15 r / min for 5 minutes. After thorough mixing, add mixing water and continue stirring at a speed of 15 r / min until a noticeable adhesive state appears. Then add river sand and modified basalt sand (the amount of modified basalt sand is 75% of the total mass of river sand and modified basalt sand) to mix and prepare mortar. Add thickener to the mortar and adjust the mortar consistency to a truncated cone expansion method fluidity of less than 17 cm. Then, add modified rubber basalt fibers with lengths of 6 mm, 9 mm, 12 mm, and 18 mm in equal proportions to the mortar. Stir at a speed of 15 r / min for 10 minutes and then at a speed of 40 r / min and stirred for 20 min to prepare a concrete slurry. In the concrete slurry, the mass fraction of the modified rubber basalt fiber was 0.3%, the adhesive ratio was 0.15, and the sand-adhesive ratio was 0.3.

[0042] (4) Use lubricating oil to evenly apply the part of the mold that contacts the concrete slurry, inject the concrete slurry into the mold, start the vibrating table to continuously vibrate until the concrete surface comes out of the slurry, and then perform surface treatment. Then cover the surface of the block with a layer of plastic wrap and let it stand for 24 hours before removing the mold and placing it in the curing room for curing. The curing temperature is 20℃, the humidity is 95%, and the curing time is 28 days.

[0043] Examples 2 to 18

[0044] A high-toughness, frost-resistant concrete block for high-altitude infrastructure projects has a composition and preparation method that are basically the same as those in Example 1. The difference lies in the amount of modified rubber basalt fiber, water-binder ratio, and sand-binder ratio in the concrete slurry, as shown in Table 2.

[0045] The concrete blocks prepared in Examples 1 to 18 were subjected to flexural strength tests and flexural toughness index tests. The test data are shown in Table 2.

[0046]

[0047] According to the test results in Table 2, the effects of the three factors of modified rubber basalt fiber dosage, water-binder ratio, and sand-binder ratio in concrete slurry on the 28d flexural strength of ECC were analyzed. Through the analysis of the average value and range of the 28d flexural strength at different levels of the above three factors, it can be concluded that the range of the modified rubber basalt fiber factor is 2.83 MPa, among which the optimal mass fraction of the modified rubber basalt fiber is 1.2%; the range of the water-binder ratio factor is 3.35 MPa, and the optimal water-binder ratio is 0.15; the range of the sand-binder ratio factor is 0.96 MPa, and the optimal sand-binder ratio is 0.35; the order of influence of the amount of modified rubber basalt fiber, water-binder ratio, and sand-binder ratio on the 28d flexural strength of ECC is water-binder ratio > modified rubber basalt fiber > sand-binder ratio, that is, among the three factors, the change in water-binder ratio has the greatest impact on the 28d flexural strength of hybrid fiber ECC. The effect of changing the amount of modified rubber basalt fiber is slightly lower than that of water-binder ratio on the 28d flexural strength of ECC, but higher than that of changing sand-binder ratio. The sand-binder ratio has the least impact on the flexural strength.

[0048] According to the results of range analysis, when the mass fraction of modified rubber basalt fiber in concrete slurry is 1.2%, the water-binder ratio is 0.16, and the sand-binder ratio is 0.38, the 28d flexural strength of the hybrid fiber ECC specimen is the highest, which is 21.94 MPa.

[0049] Similarly, in the concrete slurry, when the mass fraction of modified rubber basalt fiber is 1.2%, the water-binder ratio is 0.17, and the sand-binder ratio is 0.36, the flexural toughness index of the hybrid fiber ECC specimen is the highest, which is 6.92.

[0050] In order to explore the optimal dosage of modified basalt sand, the percentage of modified basalt sand in the total sand mass was adjusted, and the frost resistance and impermeability of concrete blocks prepared with different modified basalt sand dosages were tested.

[0051] Example 19

[0052] A high-toughness, frost-resistant concrete block for high-altitude infrastructure projects, whose composition and preparation method are basically the same as those in Example 1, except that in the concrete slurry, the mass fraction of modified rubber basalt fiber is 0.3%, the water-binder ratio is 0.15, and the sand-binder ratio is 0.3; the amount of modified basalt sand used is 25% of the total mass of river sand and modified basalt sand.

[0053] Examples 20 to 23

[0054] A high-toughness frost-resistant concrete block for high-altitude infrastructure projects has a composition and preparation method that are basically the same as those in Example 19, except that the amount of modified basalt sand used is different, as shown in Table 3.

[0055] The concrete blocks prepared in Examples 19 to 23 were tested for frost resistance and permeability. The test data are shown in Table 3. The frost resistance of concrete is measured by the number of freeze-thaw cycles that the concrete can withstand without experiencing a loss in compressive strength and mass less than the values ​​specified in the standard. The permeability of concrete is measured by the maximum water pressure that the concrete can withstand without experiencing water seepage.

[0056]

[0057] According to the test results in Table 3, the frost resistance and impermeability of the concrete blocks prepared in Examples 19 to 22 are greater than those of the concrete blocks prepared in Example 23, indicating that the use of modified basalt sand can effectively improve the frost resistance and impermeability of concrete blocks. Among them, when the amount of modified basalt sand is 75%, the prepared concrete blocks have the best frost resistance and impermeability, which can meet the requirements of high-altitude infrastructure projects for the frost resistance of concrete blocks to the greatest extent.

[0058] The above describes a preferred embodiment of the present invention, but it should be understood that the invention is not limited to the contents disclosed herein. As long as non-substantial improvements are made using the method concepts and technical solutions of the present invention, or the method concepts and technical solutions of the present invention are applied to other occasions, they are all within the scope of protection of the present invention.

Claims

1. A method for preparing high-toughness frost-resistant concrete blocks for high-altitude infrastructure projects, characterized in that: The following steps are involved: (1) Crushing and grinding basalt and heating it in an incinerator until it melts, drawing it into continuous fibers using a platinum-rhodium alloy drawing plate, passing the continuous fibers through a softened rubber pool to cover the surface with a rubber layer, and after the surface of the basalt fibers is covered with the rubber layer, cutting them into basalt fiber fragments, subjecting the basalt fiber fragments to plasma modification, and then soaking, rinsing, drying, placing them in a coupling agent and letting them stand, taking them out and drying them to obtain modified rubber basalt fibers; (2) Place basalt sand in a coupling agent and let it stand, then take it out and dry it to obtain modified basalt sand; (3) After cement and water reducer are fully mixed, mixing water is added and continuously mixed until a noticeable adhesive state is achieved. Then, river sand and modified basalt sand are added and mixed to prepare mortar. A thickener is added to the mortar to adjust the consistency of the mortar. Then, modified rubber basalt fiber is added to the mortar and mixed evenly to prepare concrete slurry. The modified rubber basalt fiber is a mixture of modified rubber basalt fibers with lengths of 6 mm, 9 mm, 12 mm, and 18 mm in equal proportions. (4) forming the concrete slurry to obtain high-toughness frost-resistant concrete blocks for high-altitude infrastructure projects; The coupling agent in step (1) and step (2) is KH550 coupling agent, and the coupling time is 48 to 72 hours.

2. The method for preparing high-toughness frost-resistant concrete blocks for high-altitude infrastructure projects according to claim 1, characterized in that: The plasma modification method in step (1) is as follows: under the conditions of an air flow rate of 25 to 35 mL / min, a voltage of 60 to 75 V, and a current of 2 to 3 A, the basalt fiber fragments are treated at a distance of 1 to 2 cm from the plasma flame for 5 to 15 seconds.

3. The method for preparing high-toughness frost-resistant concrete blocks for high-altitude infrastructure projects according to claim 1, characterized in that: The drying in step (1) and step (2) is performed until the moisture content is less than 0.3%, and the drying temperature is 40 to 60°C.

4. The method for preparing high-toughness frost-resistant concrete blocks for high-altitude infrastructure projects according to claim 1, characterized in that: The amount of the water reducer in step (3) is 1% to 1.5% of the mass of the cement, and the amount of the modified basalt sand is 25% to 100% of the total mass of the river sand and the modified basalt sand; in the concrete slurry, the mass fraction of the modified rubber basalt fiber is 0.3% to 1.5%, the water-binder ratio is 0.15 to 0.25, and the sand-binder ratio is 0.3 to 0.

4.

5. The method for preparing high-toughness frost-resistant concrete blocks for high-altitude infrastructure projects according to claim 4, characterized in that: The active ingredient of the water reducer is greater than 90%, the residual moisture is less than 3%, the bulk density is 500-700 g / L, the mortar water reduction rate is greater than 23%, the mass fraction of the modified rubber basalt fiber is 1.2%, the water-binder ratio is 0.16, and the sand-binder ratio is 0.

38.

6. The method for preparing high-toughness frost-resistant concrete blocks for high-altitude infrastructure projects according to claim 1, characterized in that: The consistency of the mortar in step (3) is a truncated cone expansion method fluidity of less than 17 cm, the mass fraction of the modified rubber basalt fiber is 1.2%, the water-binder ratio is 0.17, and the sand-binder ratio is 0.

36.

7. The method for preparing high-toughness frost-resistant concrete blocks for high-altitude infrastructure projects according to claim 1, characterized in that: The modified basalt sand is used in an amount of 75%.

8. A high-toughness frost-resistant concrete block for high-altitude infrastructure projects, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 7.

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