A high-ductility cement-based composite material and preparation method thereof

Abstract

The present invention provides a high-ductility cement-based composite material, which comprises, by weight, 20-30 parts of Portland cement, 25-45 parts of fly ash, 10-20 parts of mineral powder, 1-2 parts of PP fiber, 0.5-1 part of a polycarboxylic acid high-performance water reducer, 1-10 parts of 40-70 mesh quartz sand, 5-10 parts of 70-100 mesh quartz sand, 0.1-0.5 parts of polyacrylamide, and 15-20 parts of water. The modified PP fiber is PP fiber modified by nano-calcium carbonate, nano-silicon dioxide, and a coupling agent. The preparation method comprises the following steps: respectively weighing Portland cement, fly ash, mineral powder, quartz sand, and polyacrylamide, dry-mixing them in proportion to obtain a dry mix; then adding the polycarboxylic acid high-performance water reducer and water to the dry mix in at least two portions and stirring them; and finally adding the modified PP fiber and continuing to stir to obtain the cement-based composite material. The cement-based composite material has excellent mechanical properties, can improve the strength and durability of the structure, and has high ductility and high strength.

Description

Technical Field

[0001] The present invention relates to the technical field of cement-based materials, and in particular to a high-ductility cement-based composite material and a preparation method thereof. Background Art

[0002] High-ductility cementitious composites are fiber-reinforced composites, engineered through a mix design of matrix, fiber, and interface based on micromechanics and fracture mechanics. Their properties and engineering applications have been extensively researched by international and domestic researchers. High-ductility cementitious composites possess exceptional tensile deformation capacity, with an ultimate tensile strain exceeding 3% under uniaxial tension. Furthermore, they exhibit strain hardening behavior similar to that of metallic materials under tension.

[0003] At present, most domestic and foreign manufacturers use Japanese PVA fibers to prepare high-ductility cement-based composite materials. Due to the high price of this fiber, the fiber cost accounts for nearly 80% of the total material cost. The current market price of high-ductility cement-based composite materials is 8,000 to 12,000 yuan / m 3 However, the high cost has greatly limited its promotion and application in engineering.

[0004] In order to meet the strength requirements during use, the existing technology includes the addition of domestic synthetic fibers (PP fiber, PAN fiber, PVA fiber, POM fiber, etc.). The addition of synthetic fibers can improve the ductility and bending toughness, but at the same time it will also lead to a significant reduction in its working performance. In addition, the above-mentioned synthetic fibers are expensive, which limits their promotion and application.

[0005] Therefore, how to obtain low-cost, high-ductility cement-based composite materials has become an important issue that needs to be solved urgently. Summary of the Invention

[0006] The object of the present invention is to provide a high-ductility cement-based composite material and a preparation method thereof, which not only has excellent mechanical properties and can improve the strength and durability of the structure, but also has high ductility and high strength.

[0007] The embodiments of the present invention are achieved through the following technical solutions:

[0008] A high-ductility cement-based composite material comprises, by weight, 20-30 parts of ordinary Portland cement, 25-45 parts of fly ash, 10-20 parts of mineral powder, 1-2 parts of PP fiber, 0.5-1 part of polycarboxylic acid high-performance water reducer, 1-10 parts of 40-70 mesh quartz sand, 5-10 parts of 70-100 mesh quartz sand, 0.1-0.5 parts of polyacrylamide, and 15-20 parts of water; the modified PP fiber is PP fiber modified by nano-calcium carbonate, nano-silica, and a coupling agent.

[0009] Through the synergistic effect of the above-mentioned components and proportions, the material obtained by the present invention not only has excellent mechanical properties, which can improve the mechanical properties and durability of the structure, but also has high ductility and high strength, excellent performance and good durability, can meet the requirements of various construction processes such as casting, molding, and spraying, effectively reinforce masonry structures and ordinary reinforced concrete structures, and improve the seismic resistance of buildings. In addition, the selection of raw material components and the production cost of the preparation method are only 1 / 4 to 1 / 2 of that of traditional super-ductile composite materials, which has excellent economic benefits; in particular, the added modified PP fiber has an increased surface roughness and a reduced fiber contact angle, which makes the cement-based composite material better in the construction process and has a higher density, which can better meet the filling requirements, and active functional groups such as carbon-oxygen double bonds and carbon-carbon bonds are introduced into the surface of the modified PP fiber, which improves the interface adhesion between the PP fiber and the cement matrix, improves the salt corrosion resistance of the cement mortar, and has a significant compressive performance effect.

[0010] Furthermore, the preparation method of the modified PP fiber is:

[0011] (1) Plasma treatment of PP fibers using argon plasma for 1-5 minutes to obtain first PP fibers; the present invention pre-plasma treatment of PP fibers using plasma to convert the hydrophobic surface of the PP fibers into a hydrophilic surface, thereby increasing the physical adhesion between the PP fibers and the matrix and enhancing the modulus of rupture and toughness of the PP fibers to cement;

[0012] (2) Soaking the first PP fiber in an alcohol solvent (such as ethanol) for 10-15 hours, washing and drying; then adding a mixed solution of deionized water, alcohol solvent and silane coupling agent (KH-550, concentration 30-50%), ultrasonically soaking at 50-70°C for 6-8 hours, washing and drying, and cooling to obtain a second PP fiber; the mass ratio of deionized water, alcohol solvent and silane coupling agent in the mixed solution is 1:6-12:5-10; the liquid-solid ratio of the mixed solution to the first PP fiber is 10-20:1;

[0013] (3) Deionized water, sodium polyacrylate, nano-calcium carbonate, and nano-silicon dioxide (mass ratio of 400:1-3:5-12:5-15) are mixed and ultrasonically stirred at 70-110°C for 1 hour to obtain a nanoparticle dispersion. The second PP fiber is placed in the nanoparticle dispersion and reacted at 70-110°C for 2 hours. The fiber is then washed with anhydrous ethanol, filtered, and dried to obtain a modified PP fiber. The liquid-to-solid ratio of the nanoparticle dispersion to the second PP fiber is 10-20:1.

[0014] The method for preparing the above-mentioned high-ductility cement-based composite material includes the following steps: weighing silicate cement, fly ash, mineral powder, quartz sand and polyacrylamide respectively and dry-mixing them in proportion to obtain a dry mix; then adding a polycarboxylic acid high-performance water reducer and water to the dry mix at least twice and stirring them, each stirring time being at least 8 minutes; finally, adding modified PP fiber and continuing to stir to obtain the cement-based composite material.

[0015] The technical solutions of the embodiments of the present invention have at least the following advantages and beneficial effects:

[0016] Through the synergistic effect of the various components and proportions of the present invention, the obtained material not only has excellent mechanical properties and can improve the strength and durability of the structure, but also has high ductility and high strength, excellent performance and good durability, can meet the requirements of various construction processes such as casting, molding, and spraying, effectively reinforce brick structures, and improve the seismic performance of buildings; in particular, the added modified PP fiber has an increased surface roughness and a reduced fiber contact angle, so that the cement-based composite material has better fluidity and higher density during the construction process, which can better meet the filling requirements, and active functional groups such as carbon-oxygen double bonds and carbon-carbon bonds are introduced into the surface of the modified PP fiber, which improves the interfacial adhesion between the PP fiber and the cement matrix, improves the salt corrosion resistance of the cement mortar, and has a significant effect on the compressive performance. DETAILED DESCRIPTION

[0017] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0018] Example 1

[0019] A high-ductility cement-based composite material, comprising, by weight, 25 parts of Portland cement, 30 parts of fly ash, 15 parts of mineral powder, 1.5 parts of modified PP fiber, 0.8 parts of polycarboxylic acid high-performance water reducer, 5 parts of 40-70 mesh quartz sand, 7 parts of 70-100 mesh quartz sand, 0.3 parts of polyacrylamide, and 18 parts of water;

[0020] The modified PP fiber is a PP fiber modified by nano-calcium carbonate, nano-silicon dioxide and a coupling agent, and its preparation method is as follows:

[0021] (1) first treating the PP fiber with argon plasma for 3 minutes to obtain a first PP fiber;

[0022] (2) Soaking the first PP fiber in anhydrous ethanol for 12 h, washing and drying;

[0023] Deionized water, alcohol solvent and 40% silane coupling agent KH-550 were mixed in a mass ratio of 1:9:10 and ultrasonically immersed for 7 hours to obtain a mixed solution;

[0024] The first PP fiber was placed in a mixed solution (liquid-to-solid ratio of 15:1) and ultrasonically mixed and immersed at 60°C for 7 hours. The fiber was taken out, washed with deionized water, filtered, and dried in a vacuum oven at 60°C for 8 hours. The fiber was cooled to room temperature to obtain a second PP fiber.

[0025] (3) Deionized water, sodium polyacrylate, nano-calcium carbonate, and nano-silicon dioxide were mixed in a mass ratio of 400:1.5:7:10, and stirred at 80°C for 1 hour to obtain a nanoparticle dispersion. The second PP fiber was placed in the nanoparticle dispersion (liquid-solid ratio of 15:1), reacted at 80°C for 2 hours, and then washed with anhydrous ethanol, filtered, and dried to obtain the modified PP fiber.

[0026] The preparation method of the above-mentioned high-ductility cement-based composite material includes the following steps: weighing silicate cement, fly ash, mineral powder, quartz sand and polyacrylamide respectively and dry-mixing them in proportion to obtain a dry mix; then adding a polycarboxylic acid high-performance water reducer and water to the dry mix in three times and stirring them, each stirring time is 4 minutes; finally, adding modified PP fiber and continuing stirring for 5 minutes to obtain the cement-based composite material.

[0027] Example 2

[0028] The difference between this embodiment and Example 1 is that: a high-ductility cement-based composite material, calculated by weight, includes 22 parts of Portland cement, 28 parts of fly ash, 13 parts of mineral powder, 1.2 parts of modified PP fiber, 0.6 parts of polycarboxylic acid high-performance water reducer, 3 parts of 40-70 mesh quartz sand, 7 parts of 70-100 mesh quartz sand, 0.2 parts of polyacrylamide, and 17 parts of water.

[0029] Example 3

[0030] The difference between this embodiment and Example 1 is that: a high-ductility cement-based composite material, calculated by weight, includes 28 parts of Portland cement, 40 parts of fly ash, 18 parts of mineral powder, 1.8 parts of modified PP fiber, 0.9 part of polycarboxylic acid high-performance water reducer, 8 parts of 40-70 mesh quartz sand, 9 parts of 70-100 mesh quartz sand, 0.5 part of polyacrylamide, and 19 parts of water.

[0031] Comparative Example 1

[0032] The difference between this comparative example and Example 1 is that: a high-ductility cement-based composite material, calculated by weight, includes 15 parts of Portland cement, 50 parts of fly ash, 5 parts of mineral powder, 0.5 parts of modified PP fiber, 0.1 parts of polycarboxylic acid high-performance water reducer, 0.5 parts of 40-70 mesh quartz sand, 1 part of 70-100 mesh quartz sand, 2 parts of polyacrylamide, and 10 parts of water.

[0033] Comparative Example 2

[0034] The difference between this comparative example and Example 1 is that the PP fiber is not modified.

[0035] Experimental Example 1

[0036] Test Example 3: Compression Test and Tensile Test

[0037] Compression Test: After forming the specimen (cube), uniaxial compression tests were performed using an electro-hydraulic servo universal testing machine under standard curing conditions for 7 and 28 days. A force sensor simultaneously monitored the pressure of the specimen in real time. The loading rate was 0.6 MPa / s, and the test was terminated when the compressive load dropped to 85% of the maximum value.

[0038] Tensile testing: A 330 x 60 x 13" dogbone tensile test block was used, with a tensile test area measuring 30 mm x 13 mm. The tensile test was conducted on a 100 kN electronic universal testing machine. The tensile fixture consisted of a tensile force sensor, a universal joint, an LVDT, and a fixture. The tensile test loading method was displacement-controlled, with a loading rate of 0.1 mm / min. Displacement and force values ​​were collected using an LVDT and a 10 kN force sensor, using a Donghua D3818Y strain gauge. The results of the compressive strength, tensile strength, and tensile deformation capacity tests are shown in Table 1.

[0039] Table 1

[0040]

[0041] As can be seen from the data in Table 1, the material prepared in the embodiment of the present invention exhibits high compressive strength, tensile strength and elongation; and its density is high and the interfacial adhesion is good, which improves the sulfate corrosion resistance of the cement mortar and is able to effectively prevent the diffusion of chloride ions; however, the components in Comparative Example 1 are not within the scope of the embodiment of the present invention, and the PP fiber in Comparative Example 2 is not modified. The performance indicators of its products are all poor, especially the PP fiber in Comparative Example 2 is not modified, which makes the cement-based composite material have poor fluidity and poor density during construction, resulting in poor interfacial adhesion between the PP fiber and the cement matrix, unable to exert good and lasting salt corrosion resistance, and poor compressive performance and elongation effects; this is sufficient to illustrate that the compounding of the various component ratios provided by the embodiment of the present invention can produce a specific correlation, which cannot be replaced by other component ratios, indicating that the samples of the embodiment of the present invention can better improve the strength and impermeability of concrete, thereby delaying the penetration of chloride salts and extending the service life of concrete.

[0042] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A high ductility cement-based composite material, characterized in that: By weight, it includes 20-30 parts of Portland cement, 25-45 parts of fly ash, 10-20 parts of mineral powder, 1-2 parts of modified PP fiber, 0.5-1 part of polycarboxylic acid high-performance water reducer, 6-20 parts of quartz sand, 0.1-0.5 parts of polyacrylamide, and 15-20 parts of water; Preparation method of the modified PP fiber: (1) First, the PP fiber is plasma treated with argon plasma for 1-5 minutes to obtain the first PP fiber; (2) Soaking the first PP fiber in an alcohol solvent for a period of time, washing and drying; then adding a mixed solution of deionized water, alcohol solvent and silane coupling agent, ultrasonically soaking for a period of time at a certain temperature, washing and drying, and cooling to obtain a second PP fiber; (3) After deionized water, sodium polyacrylate, nano-calcium carbonate and nano-silicon dioxide are mixed and stirred for a period of time to obtain a nanoparticle dispersion. The second PP fiber is placed in the nanoparticle dispersion and ultrasonically reacted at a certain temperature for a period of time, and then washed and dried to obtain the modified PP fiber.

2. The high ductility cement-based composite material according to claim 1, characterized in that: In step (2), the mass ratio of deionized water, alcohol solvent and silane coupling agent in the mixed solution is 1:6-12:5-10.

3. The high ductility cement-based composite material according to claim 1, characterized in that: In step (2), the liquid-to-solid ratio of the mixed solution to the first PP fiber is 10-20:

1.

4. The high ductility cement-based composite material according to claim 1, characterized in that: In step (3), the mass ratio of deionized water, sodium polyacrylate, nano-calcium carbonate and nano-silicon dioxide is 400:1-3:5-12:5-15.

5. The high ductility cement-based composite material according to claim 1, characterized in that: In step (3), the liquid-to-solid ratio of the nanoparticle dispersion to the second PP fiber is 10-20:

1.

6. The high ductility cement-based composite material according to claim 1, characterized in that: The quartz sand includes 40-70 mesh quartz sand and 70-100 mesh quartz sand in a mass ratio of 1:1-5.

7. A method for preparing a high-ductility cement-based composite material according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: respectively weighing silicate cement, fly ash, mineral powder, quartz sand and polyacrylamide and dry-mixing them in proportion to obtain a dry mix; then adding a polycarboxylic acid high-performance water reducer and water into the dry mix at least twice and stirring them; finally adding modified PP fiber and continuing stirring to obtain a cement-based composite material.

8. The method for preparing a high-ductility cement-based composite material according to claim 7, characterized in that: Each stirring time should be at least 8 minutes.

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