UHPC material and preparation method thereof

Abstract

The invention belongs to the technical field of building materials, and particularly relates to a UHPC material and a preparation method thereof. The UHPC material disclosed by the invention is prepared from the following components in parts by weight: 668 to 674 parts of cement, 167 to 169 parts of fly ash, 113 to 115 parts of silica fume, 78 to 137 parts of steel fiber, 180 to 182 parts of water, 24 parts of an efficient polycarboxylate superplasticizer and 1210 to 1220 parts of sand. The steel fibers are steel fibers in recycled waste tires. The steel fibers adopted in the invention are extracted and recovered from waste tires, and the cost of the steel fibers is less than 20% of that of industrial steel fibers; the cement, the fly ash, the silica fume, the steel fiber, the water, the efficient polycarboxylic acid water reducer and the sand are scientifically proportioned, so that the prepared UHPC is excellent in compressive strength, tensile strength, crack resistance, toughness and working performance, and the cost is only 60% of that of the current commercial UHPC; according to the preparation method of the UHPC material, resource recycling is achieved, good economic, social and environmental benefits are achieved, and wide application prospects are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and particularly relates to a UHPC material and a preparation method thereof. Background Art

[0002] Ultra-high performance concrete (UHPC) is a high-performance fiber-reinforced cement-based composite material with good durability, wear resistance and impact resistance. UHPC mostly uses industrial steel fiber as a toughening material, and industrial steel fiber is a slender fiber made of high-strength steel, usually made by wire cutting, thin steel plate cutting, milling, melting and rolling. Its high cost and high energy consumption seriously limit the promotion and application of UHPC materials. Relying on extracting and recycling steel fibers from waste tires can not only achieve resource regeneration, but also its cost is less than 20% of industrial steel fibers. The cost of recycled steel fiber ultra-high performance concrete prepared by the present invention is only 60% of the current commercial UHPC, and it has broad application prospects. However, if the recycled steel fibers extracted from waste tires are directly applied to the UHPC preparation method in the prior art, its compressive strength, tensile strength, crack resistance and toughness cannot be guaranteed. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a UHPC material and a preparation method thereof.

[0004] To achieve the above object, the technical solution adopted by the present invention is: A UHPC material comprises the following components by weight: 668-674 parts of cement, 167-169 parts of fly ash, 113-115 parts of silica fume, 78-137 parts of steel fiber, 180-182 parts of water, 24 parts of high-efficiency polycarboxylic acid water reducer, and 1210-1220 parts of sand; the steel fiber is steel fiber recycled from waste tires.

[0005] The cement used is ordinary Portland cement with model number P•O42.5.

[0006] The sand is composed of sands of different mesh sizes; among them, sands of mesh 325, mesh 70-120, mesh 40-70, mesh 20-40, and mesh 10-20 are mixed in 228-230 parts, 144-146 parts, 215-218 parts, 251-254 parts, and 371-375 parts by weight.

[0007] A method for preparing a UHPC material comprises the following steps: Step 1: Extract and recycle steel fibers from waste tires; Step 2: Add cement, fly ash and silica fume into the mixer in order by weight, and stir at a preset speed for 1-2 minutes to mix evenly; Step 3: Slowly add water by weight at a preset speed, stir at a low speed for 1-2 minutes, then add high-efficiency polycarboxylate water-reducing agent by weight, stir evenly into a slurry, then add fine sand, stir evenly at a low speed, and stir at a high speed at a preset speed for 4-6 minutes; Step 4: Stir at a low speed, and at the same time, add the steel fiber extracted in step 1 in portions by weight evenly in multiple times, stir at a high speed for 5-8 minutes at a preset speed, and prepare concrete after standard curing for a preset time.

[0008] The method for extracting and recycling steel fibers from waste tires in step 1 is to extract and recycle them from waste tires by cutting and thermal decomposition; the details are as follows: The first step: crush and sort the waste tires; Step 2: Clean the steel fiber obtained in the first step to remove oil stains and dirt impurities on the surface; Step 3: Dry the cleaned steel fiber; Step 4: Surface modification of the dried steel fiber.

[0009] The specific method of the surface modification treatment is to spray a silane coupling agent on the surface of the steel fiber.

[0010] The preset stirring speed in step 2 is 100 to 150 rpm.

[0011] The preset speed of the low-speed stirring in step 3 is 100-150 rpm, and the preset high-speed stirring speed is 200-300 rpm.

[0012] The preset speed of the low-speed stirring in the step 4 is 100-150 rpm, and the preset high-speed stirring speed is 200-300 rpm; the preset time of the standard curing in the step 4 is 28 days.

[0013] The dosage of the high-efficiency polycarboxylate water-reducing agent is 2.5% of the mixed weight of the cementitious material, namely cement, fly ash and silica fume, and the mass ratio of water to the cementitious material is 0.19. Beneficial Effects

[0014] (1) The present invention uses steel fibers extracted and recycled from waste tires to replace traditional industrial steel fibers. By scientifically and rationally adjusting the composition ratio, the prepared UHPC has good compressive strength, tensile strength, crack resistance, toughness and working performance.

[0015] (2) The UHPC prepared by the present invention uses traditional steel fibers, which has similar mechanical properties to traditional industrial steel fibers and has a lower cost.

[0016] (3) In the present invention, the fluidity of UHPC is improved by optimizing the ratio of cement, fly ash and silica fume.

[0017] (4) In the present invention, the sand is selected according to the gradation, so that the interior of the UHPC is more compact.

[0018] (5) The water reducing agent in the present invention adopts polycarboxylic acid high-efficiency water reducing agent, and the dosage is 2.5% of the mixed weight of cementitious materials, namely cement, fly ash and silica fume, and the ratio of water to cementitious materials is 0.19, which effectively controls the consistency of concrete, ensures the uniform distribution of steel fibers, and improves the density and strength of UHPC.

[0019] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail as follows. DETAILED DESCRIPTION

[0020] In order to clearly and completely illustrate the technical solution in the present invention, the following is described through specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Embodiment 1:

[0021] A UHPC material comprises the following components by weight: 668-674 parts of cement, 167-169 parts of fly ash, 113-115 parts of silica fume, 78-137 parts of steel fiber, 180-182 parts of water, 24 parts of high-efficiency polycarboxylic acid water reducer, and 1210-1220 parts of sand; the steel fiber is steel fiber recycled from waste tires.

[0022] The present invention utilizes steel fibers from recycled waste tires to prepare UHPC, replacing traditional industrial steel fibers. Through a scientific and reasonable composition ratio, a UHPC with good compressive strength, tensile strength, crack resistance, toughness and working performance is obtained. At the same time, compared with UHPC prepared by traditional steel fibers, the cost is lower and the mechanical properties are similar. Embodiment 2:

[0023] A UHPC material, which is different from the first embodiment in that the cement used is ordinary Portland cement with a model of P•O42.5.

[0024] In actual use, the cement used is P•O42.5 ordinary Portland cement, which can not only meet the strength required by UHPC but also save costs. Embodiment three:

[0025] A UHPC material, which is different from the first embodiment in that: the sand is composed of sands of different mesh sizes; wherein the sands of mesh 325, mesh 70-120, mesh 40-70, mesh 20-40, and mesh 10-20 are mixed in 228-230 parts, 144-146 parts, 215-218 parts, 251-254 parts, and 371-375 parts by weight.

[0026] In actual use, based on the close packing theory, the particle size distribution of the sand used can be calculated to make the interior of UHPC more compact.

[0027] In this embodiment, the preferred sand mesh size is: M sand 325: 228kg, M sand 70-120: 144kg, M sand 40-70: 216kg, M sand 20-40: 252kg, M sand 10-20: 371kg. Embodiment 4:

[0028] A method for preparing a UHPC material comprises the following steps: Step 1: Extract and recycle steel fibers from waste tires; Step 2: Add cement, fly ash and silica fume into the mixer in order by weight, and stir at a preset speed for 1-2 minutes to mix evenly; Step 3: Slowly add water by weight at a preset speed, stir at a low speed for 1-2 minutes, then add high-efficiency polycarboxylate water-reducing agent by weight, stir evenly into a slurry, then add fine sand, stir evenly at a low speed, and stir at a high speed at a preset speed for 4-6 minutes; Step 4: Stir at a low speed, and at the same time, add the steel fiber extracted in step 1 in portions by weight evenly in multiple times, stir at a high speed for 5-8 minutes at a preset speed, and prepare concrete after standard curing for a preset time.

[0029] Furthermore, the method for extracting and recycling steel fibers from waste tires in step 1 is to extract and recycle them from waste tires by cutting and thermal decomposition; the details are as follows: The first step: crush and sort the waste tires; Step 2: Clean the steel fiber obtained in the first step to remove oil stains and dirt impurities on the surface; Step 3: Dry the cleaned steel fiber; Step 4: Surface modification of the dried steel fiber.

[0030] Furthermore, the specific method of the surface modification treatment is to spray a silane coupling agent on the surface of the steel fiber.

[0031] Furthermore, the preset stirring speed in step 2 is 100 to 150 rpm.

[0032] Furthermore, in the step three, the preset speed of the low-speed stirring is 100-150 rpm, and the preset high-speed stirring speed is 200-300 rpm.

[0033] Furthermore, the preset speed of the low-speed stirring in step 4 is 100-150 rpm, and the preset high-speed stirring speed is 200-300 rpm; the preset time of standard curing in step 4 is 28 days.

[0034] Furthermore, the dosage of the high-efficiency polycarboxylate water-reducing agent is 2.5% of the mixed weight of the cementitious material, namely cement, fly ash and silica fume, and the mass ratio of water to the cementitious material is 0.19.

[0035] In actual use, the present invention uses steel fibers extracted and recycled from waste tires to replace traditional industrial steel fibers. By reasonably adjusting the ratio with other components, UHPC with excellent mechanical properties and durability is prepared. At the same time, compared with UHPC prepared with traditional steel fibers, its cost is lower and its mechanical properties are similar.

[0036] In actual use, in order to control the consistency of concrete, ensure the uniform distribution of steel fibers, and improve the density and strength of UHPC, the water reducer uses polycarboxylic acid high-efficiency water reducer, the dosage is 2.5% of the cementitious material, and the water-cement ratio is 0.19. Embodiment five:

[0037] The following material ratios were used: 674 parts of cement, 169 parts of fly ash, 115 parts of silica fume, 79 parts of recycled steel fiber, 182 parts of water, 24 parts of high-efficiency polycarboxylic acid water-reducing agent, 230 parts of sand with mesh size 325, 146 parts of mesh size 70-120, 218 parts of mesh size 40-70, 254 parts of mesh size 20-40, and 375 parts of mesh size 10-20. The UHPC material was prepared using the method of Example 5. Embodiment six:

[0038] The following material ratios were used: 672 parts of cement, 168 parts of fly ash, 114 parts of silica fume, 98 parts of recycled steel fiber, 181 parts of water, 24 parts of high-efficiency polycarboxylic acid water-reducing agent, 229 parts of sand with mesh size 325, 145 parts of mesh size 70-120, 217 parts of mesh size 40-70, 252 parts of mesh size 20-40, and 373 parts of mesh size 10-20. The UHPC material was prepared using the method of Example 5. Embodiment seven:

[0039] The following material ratios were used: 670 parts of cement, 168 parts of fly ash, 114 parts of silica fume, 118 parts of recycled steel fiber, 180 parts of water, 24 parts of high-efficiency polycarboxylic acid water-reducing agent, 229 parts of sand with mesh size 325, 144 parts of mesh size 70-120, 216 parts of mesh size 40-70, 252 parts of mesh size 20-40, and 372 parts of mesh size 10-20. The UHPC material was prepared using the method of Example 5. Embodiment eight:

[0040] The following material ratios were used: 668 parts of cement, 167 parts of fly ash, 113 parts of silica fume, 137 parts of recycled steel fiber, 181 parts of water, 24 parts of high-efficiency polycarboxylic acid water-reducing agent, 228 parts of sand with mesh size 325, 144 parts of mesh size 70-120, 215 parts of mesh size 40-70, 251 parts of mesh size 20-40, and 371 parts of mesh size 10-20. The UHPC material was prepared using the method of Example 5.

[0041] Example 5 - Example The performance parameters of the prepared UHPC materials are compared in the following table: Test items Embodiment 5 Embodiment 6 Embodiment 7 Embodiment 8 Compressive strength 28d / MPa 125.8 129.2 132.2 139.5 Tensile strength 28d / MPa 8.2 9.7 10.9 12.1 Bending strength 28d / MPa 18.5 21.3 23.6 25.2 It can be seen from the above table that the UHPC material prepared by the present invention meets the requirements in terms of compressive strength, tensile strength and flexural strength.

[0042] In summary, the present invention overcomes the weakness of poor toughness of recycled steel fiber. Through scientific proportioning, cement, fly ash, silica fume, steel fiber, water, high-efficiency polycarboxylic acid water-reducing agent and sand are mixed to obtain UHPC materials that meet the requirements in terms of compressive strength, tensile strength and flexural strength. Not only waste tires are recycled, but also the preparation cost of UHPC materials is saved.

[0043] In the absence of conflicts, technicians in this field can combine the relevant technical features in the above examples according to actual conditions to achieve corresponding technical effects. The specific combinations are not described here one by one.

[0044] It should be noted that the descriptions of "first", "second", etc. in the present invention are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0045] The above are only preferred embodiments of the present invention. The present invention will not be limited to the embodiments shown herein, but should conform to the widest scope consistent with the principles and novel features disclosed herein. Any simple modification, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A UHPC material, It is characterized in that The invention comprises the following components by weight: 668-674 parts of cement, 167-169 parts of fly ash, 113-115 parts of silica fume, 78-137 parts of steel fiber, 180-182 parts of water, 24 parts of high-efficiency polycarboxylic acid water-reducing agent and 1210-1220 parts of sand; the steel fiber is steel fiber recycled from waste tires.

2. A UHPC material as claimed in claim 1, It is characterized in that The cement used is ordinary Portland cement with model number P•O42.

5.

3. A UHPC material as claimed in claim 1, It is characterized in that The sand is composed of sands of different mesh sizes; among them, sands of mesh 325, mesh 70-120, mesh 40-70, mesh 20-40, and mesh 10-20 are mixed in 228-230 parts, 144-146 parts, 215-218 parts, 251-254 parts, and 371-375 parts by weight.

4. A method for preparing a UHPC material according to any one of claims 1 to 3, It is characterized in that The steps include: Step 1: Extract and recycle steel fibers from waste tires; Step 2: Add cement, fly ash and silica fume into the mixer in order by weight, and stir at a preset speed for 1-2 minutes to mix evenly; Step 3: Slowly add water by weight at a preset speed, stir at a low speed for 1-2 minutes, then add high-efficiency polycarboxylate water-reducing agent by weight, stir evenly into a slurry, then add fine sand, stir evenly at a low speed, and stir at a high speed at a preset speed for 4-6 minutes; Step 4: Stir at a low speed, and at the same time, add the steel fiber extracted in step 1 in portions by weight evenly in multiple times, stir at a high speed for 5-8 minutes at a preset speed, and prepare concrete after standard curing for a preset time.

5. A method for preparing a UHPC material according to claim 4, It is characterized in that The method for extracting and recycling steel fibers from waste tires in step 1 is to extract and recycle them from waste tires by cutting and thermal decomposition; the details are as follows: The first step: crush and sort the waste tires; Step 2: Clean the steel fiber obtained in the first step to remove oil stains and dirt impurities on the surface; Step 3: Dry the cleaned steel fiber; Step 4: Surface modification of the dried steel fiber.

6. A method for preparing a UHPC material according to claim 5, It is characterized in that The specific method of the surface modification treatment is to spray a silane coupling agent on the surface of the steel fiber.

7. A method for preparing a UHPC material according to claim 4, It is characterized in that The preset stirring speed in step 2 is 100 to 150 rpm.

8. A method for preparing a UHPC material according to claim 4, It is characterized in that The preset speed of the low-speed stirring in step 3 is 100-150 rpm, and the preset high-speed stirring speed is 200-300 rpm.

9. A method for preparing a UHPC material according to claim 4, It is characterized in that The preset speed of the low-speed stirring in the step 4 is 100-150 rpm, and the preset high-speed stirring speed is 200-300 rpm; the preset time of the standard curing in the step 4 is 28 days.

10. A method for preparing a UHPC material according to claim 4, It is characterized in that The dosage of the high-efficiency polycarboxylate water-reducing agent is 2.5% of the mixed weight of the cementitious material, namely cement, fly ash and silica fume, and the mass ratio of water to the cementitious material is 0.19.