Low-shrinkage high-toughness concrete material as well as preparation method and application thereof

Abstract

The invention provides a low-shrinkage high-toughness concrete material as well as a preparation method and application thereof, and belongs to the technical field of concrete materials. The low-shrinkage high-toughness concrete material provided by the invention comprises the following components in parts by weight: 300-500 parts of cement; 600 to 800 parts of fly ash; 30 to 50 parts of silica fume; 200 to 400 parts of quartz sand; 10-50 parts of an anti-dry shrinkage functional material; 200 to 400 parts of water; 10 to 50 parts of a water reducing agent; 5 to 20 parts of a thickening agent; 10 to 50 parts of PVA fiber; wherein the anti-dry shrinkage functional material is generated after carbonization of recycled concrete micro powder. The carbonized recycled concrete fine powder is used for preparing the aragonite whiskers, the aragonite whiskers and the PVA fibers are staggered to form a net shape, shrinkage of concrete is limited, and the aragonite whiskers can be well applied to pavement materials of assembly type pavements. And moreover, the recycled concrete is used, so that the recycling of building (structure) wastes is realized, and the requirements of energy conservation and environmental protection are met.

Description

Technical Field

[0001] The present invention belongs to the technical field of concrete materials, and particularly relates to a high-toughness concrete material with low shrinkage, and a preparation method and application thereof. Background Art

[0002] As a kind of rapid pavement, precast cement concrete pavement is widely used in scenarios such as temporary road construction and rapid repair of old pavements. In related technologies, ECC (Engineered Cementitious Composites) is usually used to make precast cement concrete pavement. ECC is composed of materials such as portland cement, fine silica sand, water and fine synthetic fibers, and has characteristics such as good flexural toughness and excellent crack resistance. However, generally only quartz sand is used as aggregate in ECC, lacking coarse aggregate, which leads to higher shrinkage strain during its service process and is prone to large dry shrinkage in case of water loss, reducing the performance of precast cement concrete pavement.

[0003] Construction waste generally contains a large amount of waste concrete, mortar, stones and bricks and tiles. These components can be considered as aggregates in newly made concrete. However, in the prior art, these components are usually directly discarded without effective application, not meeting the development requirements of energy conservation and environmental protection.

[0004] Therefore, it is really necessary to provide a high-toughness concrete material with low shrinkage, and a preparation method and application thereof to solve the above problems. Summary of the Invention

[0005] The present invention provides a high-toughness concrete material with low shrinkage, and a preparation method and application thereof. Vaterite whiskers are prepared using carbonized recycled concrete fine powder, which intersects with PVA fibers to form a three-dimensional network structure, restricting the dry shrinkage of concrete. Moreover, the use of recycled concrete realizes the reuse of construction (structure) waste, meeting the requirements of energy conservation and environmental protection, and can effectively solve at least one technical problem involved in the background art.

[0006] In order to solve the above technical problems, the present invention is realized as follows: A high-toughness concrete material with low shrinkage includes the following components in parts by weight: 300 - 500 parts of cement; 600 - 800 parts of fly ash; 30 - 50 parts of silica fume; 200 - 400 parts of quartz sand; 10 - 50 parts of anti-dry-shrinkage functional material; 200 - 400 parts of water; 10 - 50 parts of water reducer; 5 - 20 parts of thickener; 10 - 50 parts of PVA fiber; wherein, the anti-dry-shrinkage functional material is formed by carbonizing recycled concrete fine powder. The anti-dry-shrinkage functional material is prepared by the following method: Dissolve diethylenetriamine in water to obtain a solution with a concentration of 1 - 3 mol / L. Add recycled concrete powder into the solution to make the solid-liquid ratio 50 - 100 g / L, forming a mixed solution. Continuously introduce carbon dioxide into the mixed solution, heat the mixed solution and maintain it at a temperature of 40 - 80 °C, so that the recycled concrete powder undergoes carbonization under the action of carbon dioxide to generate calcium carbonate, and the generated calcium carbonate generates aragonite whiskers under the influence of diethylenetriamine. After the reaction lasts for 1 - 4 h, centrifuge and dry the slurry to obtain the anti-drying shrinkage functional material.

[0007] As a preferred improvement, the water reducing agent is a polycarboxylate water reducing agent with a water reducing efficiency greater than 20%.

[0008] As a preferred improvement, the thickening agent is hydroxypropyl methylcellulose.

[0009] As a preferred improvement, the particle size range of the quartz sand is 10 - 600 μm, and the average particle size is 100 - 140 μm.

[0010] As a preferred improvement, the length of the PVA fiber is 9 - 15 mm, the diameter is 30 - 40 μm, and the density is 1.2 - 1.4 g / cm 3 。

[0011] As a preferred improvement, the particle size of the recycled concrete powder is less than 600 μm.

[0012] As a preferred improvement, the calcium content of the fly ash is less than 10%; the silica content of the silica fume is above 90%.

[0013] A preparation method of the above-mentioned low-shrinkage and high-toughness concrete material includes the following steps: Take 300 - 500 parts of cement, 600 - 800 parts of fly ash, 30 - 50 parts of silica fume, 200 - 400 parts of quartz sand, 10 - 50 parts of anti-drying shrinkage functional material, 200 - 400 parts of water, 10 - 50 parts of water reducing agent, 5 - 20 parts of thickening agent, and 10 - 50 parts of PVA fiber by mass; mix the cement, fly ash, and silica fume, continue to mix after adding water and the water reducing agent, then add the quartz sand and mix, then add 2 / 3 of the anti-drying shrinkage functional material and the PVA fiber and mix, and finally add the remaining 1 / 3 of the anti-drying shrinkage functional material and the PVA fiber and mix to obtain the low-shrinkage and high-toughness concrete material.

[0014] An application of the above-mentioned low-shrinkage and high-toughness concrete material is used as the pavement material for assembled pavements.

[0015] The beneficial effects of the present invention are as follows: (1) Use carbonized recycled concrete fine powder to prepare aragonite whiskers, which intersect with PVA fibers to form a three-dimensional network structure, restricting the shrinkage of concrete; (2) During the carbonization process of recycled concrete fine powder, DETA is added. By changing the crystal orientation of calcium carbonate, the carbonization product of recycled concrete fine powder with DETA, the formation of aragonite whiskers can be controlled, and aragonite whiskers with a large aspect ratio can be obtained. (3) Using recycled concrete fine powder to replace part of the PVA fiber material and reduce the proportion of PVA in concrete. The cost of recycled concrete fine powder is much lower than that of PVA fiber material, which can achieve the purpose of cost reduction and improve the practicability of high-toughness concrete materials with low shrinkage. (4) The use of recycled concrete realizes the reuse of construction (structure) waste. During the carbonization process of recycled fine aggregate, the gas carbon dioxide is absorbed as a solid precipitate, reducing the carbon dioxide content in the atmosphere, stabilizing carbon in solid materials, reducing carbon emissions, and meeting the development needs of energy conservation and emission reduction. Description of the Drawings

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts, where: Figure 1 SEM image showing aragonite crystals. Specific Embodiments

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0018] This embodiment provides a high-toughness concrete material with low shrinkage, including the following components in parts by weight: 300 - 500 parts of cement; 600 - 800 parts of fly ash; 30 - 50 parts of silica fume; 200 - 400 parts of quartz sand; 10 - 50 parts of anti-dry shrinkage functional material; 200 - 400 parts of water; 10 - 50 parts of water reducer; 5 - 20 parts of thickener; 10 - 50 parts of PVA fiber; among them, the anti-dry shrinkage functional material is generated after the carbonization of recycled concrete fine powder.

[0019] Specifically, the water reducer is a polycarboxylate-based water reducer with a water reduction efficiency greater than 20%; the thickener is hydroxypropyl methylcellulose; the particle size range of the quartz sand is 10 - 600 μm, and the average particle size is 100 - 140 μm; the length of the PVA fiber is 9 - 15 mm, the diameter is 30 - 40 μm, and the density is 1.2 - 1.4 g / cm3 ; The particle size of recycled concrete powder is less than 600μm; the calcium content of fly ash is less than 10%; the silicon dioxide content of silica ash is above 90%.

[0020] Recycled concrete powder is processed from concrete, mortar, stone, bricks and tiles in construction waste, which realizes the reuse of construction waste and can achieve the purpose of resource recycling. It should be noted that in this embodiment, there is no clear requirement for the proportion of concrete, mortar, stone, bricks and tiles in the recycled concrete powder, and it can be made by conventional techniques in this field. The reason is that the recycled concrete powder is to achieve the reuse of waste, and although the content of related components in the waste is relatively random, once the related content is limited, it will limit the application of recycled concrete powder, which goes against the original intention of recycling.

[0021] After carbonization, recycled concrete powder generates aragonite whiskers, which have a large aspect ratio and are interlaced with PVA fibers to form a three-dimensional mesh structure, so that the concrete material can obtain a lower density and higher porosity, which can significantly reduce the weight while maintaining high strength, and reduce the risk of damage during transportation and hoisting. The shrinkage of concrete materials is mainly caused by the volume shrinkage due to internal water loss, and the three-dimensional mesh structure has good self-supporting stability. In the case of a large amount of water loss, the mutual support of the mesh fibers can resist the negative pressure generated by the water loss, which can greatly inhibit the shrinkage of concrete. After being prepared into an assembled cement concrete pavement, the service life of the pavement can be extended.

[0022] In addition, the aspect ratios and moduli of PVA fibers and aragonite whiskers are different, and they can play a complementary role in the system. Aragonite whiskers are inorganic fibers with a larger modulus than PVA fibers, a smaller aspect ratio than PVA fibers, and a shorter length than PVA fibers. Under dry conditions, concrete loses moisture and is prone to shrinkage, causing cracks. Aragonite whiskers have greater rigidity, which can improve the strength of concrete and resist concrete shrinkage. PVA fibers have less rigidity and higher toughness, which can play a bridging role when cracks occur in concrete, inhibiting the further development of cracks. At the same time, aragonite whiskers are smaller in size, which can inhibit the development of micro cracks, and PVA fibers are longer in length, which can inhibit the development of macro cracks. The two fibers are distributed in a three-dimensional disordered manner, inhibiting the development of cracks from different scales and aspects, thereby improving the anti-shrinkage performance of concrete.

[0023] Recycled concrete powder can replace PVA fiber after carbonization treatment, which can reduce the amount of PVA fiber used, greatly reduce the preparation cost, greatly expand the application scope of high-toughness concrete, and can be more widely used in engineering construction.

[0024] The anti-shrinkage functional material is prepared by the following method: Dissolve diethylenetriamine in water to obtain a solution with a concentration of 1 - 3 mol / L; Add recycled concrete powder to the solution to make the solid-liquid ratio 50 - 100 g / L, forming a mixture. Continuously introduce carbon dioxide into the mixture, heat the mixture and maintain it at a temperature of 40 - 80 °C, so that the recycled concrete powder undergoes carbonation under the action of carbon dioxide to generate calcium carbonate, and the generated calcium carbonate generates aragonite whiskers under the influence of diethylenetriamine. After the reaction lasts for 1 - 4 h, centrifuge and dry the slurry to obtain an anti-drying shrinkage functional material.

[0025] A preparation method of the above-mentioned low-shrinkage and high-toughness concrete material includes the following steps: Take 300 - 500 parts of cement, 600 - 800 parts of fly ash, 30 - 50 parts of silica fume, 200 - 400 parts of quartz sand, 10 - 50 parts of anti-drying shrinkage functional material, 200 - 400 parts of water, 10 - 50 parts of water reducer, 5 - 20 parts of thickener, and 10 - 50 parts of PVA fiber by mass; mix the cement, fly ash, and silica fume, add water and water reducer and continue to mix, then add quartz sand and mix, then add 2 / 3 of the anti-drying shrinkage functional material and PVA fiber and mix, and finally add the remaining 1 / 3 of the anti-drying shrinkage functional material and PVA fiber and mix to obtain a low-shrinkage and high-toughness concrete material.

[0026] The anti-drying shrinkage functional material and PVA fiber are added slowly in two times to promote the uniform dispersion of the fiber and avoid the generation of agglomeration phenomena that affect the performance of the concrete.

[0027] An application of the above-mentioned low-shrinkage and high-toughness concrete material is used as a pavement material for assembled pavements.

[0028] Example 1 Mix 396 parts of cement, 683 parts of fly ash, and 30 parts of silica fume by mass for two minutes, add 285 parts of water and 20 parts of water reducer and mix for two minutes, then add 270 parts of quartz sand and mix for two minutes, add 16 parts of PVA fiber, mix for five minutes, and finally add the remaining 8 parts of PVA fiber and mix for five minutes to obtain low-shrinkage and high-toughness concrete. Pour the concrete slurry into a mold, use manual vibration to remove internal bubbles, make the surface flat, cover it with plastic wrap and cure for 24 h, then demold, and then place it in a standard curing room (temperature is 20 ± 2 °C, relative humidity is about 95%) and cure for 28 d to obtain a sample.

[0029] Example 2 Dissolve diethylenetriamine (DETA) in water at a concentration of 1 mol / L. Add recycled concrete powder to the solution to make the solid-liquid ratio 50 g / L, forming a mixed solution. Continuously introduce carbon dioxide into the mixed solution at a flow rate of 0.2 L / min / 100 ml. Heat the mixed solution and maintain it at 60 °C. After the reaction lasts for 2 h, centrifuge and dry the slurry to obtain the anti-dry shrinkage functional material.

[0030] Mix 396 parts of cement, 683 parts of fly ash, and 30 parts of silica fume by mass for two minutes. Add 285 parts of water and 20 parts of water reducer, and mix for two minutes. Then add 270 parts of quartz sand and mix for two minutes. Add 12 parts of PVA fiber and 4 parts of anti-dry shrinkage functional material, and mix for five minutes. Finally, add the remaining 6 parts of PVA fiber and 2 parts of anti-dry shrinkage functional material, and mix for five minutes to obtain low-shrinkage high-toughness concrete. Pour the low-shrinkage high-toughness concrete slurry into a mold, use manual vibration to remove internal air bubbles, make the surface flat, cover it with plastic wrap and cure for 24 h, then demold, and then place it in a standard curing room (temperature is 20 ± 2 °C, relative humidity is about 95%) and cure for 28 d to obtain the sample.

[0031] Example 3 The difference between this example and Example 2 is that the concentration of diethylenetriamine is 2 mol / L, and the other conditions are exactly the same as those in Example 2.

[0032] Example 4 The difference between this example and Example 2 is that the concentration of diethylenetriamine is 3 mol / L, and the other conditions are exactly the same as those in Example 2.

[0033] Example 5 The difference between this example and Example 3 is that the temperature during the carbonization process is maintained at 40 °C, and the other conditions are exactly the same as those in Example 3.

[0034] Example 6 The difference between this example and Example 3 is that the temperature during the carbonization process is maintained at 80 °C, and the other conditions are exactly the same as those in Example 3.

[0035] Example 7 The preparation process of the anti-dry shrinkage functional material in this example is exactly the same as that in Example 6. The difference lies in that the concrete preparation process is slightly different: Mix 396 parts of cement, 683 parts of fly ash, and 30 parts of silica fume by mass for two minutes, add 285 parts of water and 20 parts of water reducer, mix for two minutes, then add 270 parts of quartz sand and mix for two minutes, add 8 parts of PVA fiber and 8 parts of dry shrinkage-resistant functional material, mix for five minutes, and finally add the remaining 4 parts of PVA fiber and 4 parts of dry shrinkage-resistant functional material, mix for five minutes to obtain low-shrinkage and high-toughness concrete. Pour the concrete slurry into a mold, use manual vibration to remove internal air bubbles, make the surface flat, cover it with plastic wrap and cure for 24 hours, then demold it, and then place it in a standard curing room (temperature is 20 ± 2 °C, relative humidity is about 95%) and cure for 28 days to obtain a sample.

[0036] Example 8 The preparation process of the dry shrinkage-resistant functional material in this example is exactly the same as that in Example 6, the difference is that the concrete preparation process is slightly different: Mix 396 parts of cement, 683 parts of fly ash, and 30 parts of silica fume by mass for two minutes, add 285 parts of water and 20 parts of water reducer, mix for two minutes, then add 270 parts of quartz sand and mix for two minutes, add 4 parts of PVA fiber and 12 parts of dry shrinkage-resistant functional material, mix for five minutes, and finally add the remaining 2 parts of PVA fiber and 6 parts of dry shrinkage-resistant functional material, mix for five minutes to obtain low-shrinkage and high-toughness concrete. Pour the concrete slurry into a mold, use manual vibration to remove internal air bubbles, make the surface flat, cover it with plastic wrap and cure for 24 hours, then demold it, and then place it in a standard curing room (temperature is 20 ± 2 °C, relative humidity is about 95%) and cure for 28 days to obtain a sample.

[0037] Test the aspect ratio, axial tensile strength, axial tensile ultimate strain, and dry shrinkage value of the samples prepared in Examples 1-8. The test results are shown in Table 1.

[0038] Table 1 Performance test table of samples in Examples 1-8

[0039] Comparing the test results of Example 1 and other examples, it can be seen that after adding the dry shrinkage-resistant functional material, the dry shrinkage value of the sample at 28 days decreased significantly, and the maximum decrease was more than 50%. It shows that the present invention can effectively inhibit the dry shrinkage phenomenon of concrete.

[0040] Comparing the test results of Comparative Examples 2, 3, and 4, it can be seen that the concentration of diethylenetriamine has a significant effect on the aspect ratio of the anti-dry shrinkage functional material. When the concentration is 2 mol / L, the aspect ratio is the highest, which is most conducive to forming a three-dimensional network structure with PVA fibers. Therefore, both the tensile strength and tensile strain are relatively high, and at the same time, the dry shrinkage value is the lowest. The reason is that after carbon dioxide is introduced into the recycled concrete micropowder slurry, amorphous calcium carbonate is first formed, and then it is transformed into calcium carbonate crystals. When no diethylenetriamine is added, stable calcite is preferentially generated. After adding diethylenetriamine, the organic amine ions in diethylenetriamine will adsorb on the surface of amorphous calcium carbonate. As the crystals gradually form, the organic amine ions adsorbed on the (0 1 1) crystal plane will hinder the growth of calcium carbonate in the direction perpendicular to the c-axis, and preferentially grow in the c-axis direction, forming needle-shaped aragonite crystals. Aragonite whiskers belong to the orthorhombic crystal system, and the crystal grows along the c-axis direction during crystal growth, so the shape is fibrous with a relatively high aspect ratio. Its crystal structure is as Figure 1 shown. With the increase in the concentration of diethylenetriamine, the aspect ratio of aragonite whiskers increases. However, when the concentration of diethylenetriamine is too high, the improvement effect on the aspect ratio of aragonite whiskers is not obvious. Therefore, in the present invention, when its concentration is 2 mol / L, a relatively high aspect ratio can be achieved.

[0041] Comparing the test results of Comparative Examples 3, 5, and 6, it can be seen that the higher the temperature, the larger the aspect ratio of the generated anti-dry shrinkage functional material. The aspect ratio generated at 80 °C is the highest, the axial tensile strength and axial tensile strain are the highest, and the dry shrinkage value is the smallest. The reason is that the higher the aspect ratio of the anti-dry shrinkage functional material, the higher the axial tensile strength and axial tensile strain of the concrete. When cracks occur due to dry shrinkage of the concrete, the concrete has a stronger restricting effect on the crack propagation, so the dry shrinkage value is smaller.

[0042] Comparing the test results of Comparative Examples 6, 7, and 8, it can be known that the higher the percentage of the anti-dry shrinkage functional material replacing PVA fibers, the lower the axial tensile strength and axial tensile strain. When the replacement percentage is 50%, the dry shrinkage value is the smallest, which is 408 µm / m, and the axial tensile strength and axial tensile strain are also relatively high. The reason is that the anti-dry shrinkage material contains aragonite whiskers, and the modulus of aragonite whiskers is larger than that of PVA fibers, which is not conducive to the development of cracks during axial tension. Therefore, the axial tensile strength and axial tensile strain decrease with the increase in the dosage of the anti-dry shrinkage material. However, the stiffness of aragonite whiskers is large, which can improve the concrete strength and limit the shrinkage of the concrete under dry conditions. Therefore, appropriately increasing the dosage of the anti-dry shrinkage material can reduce the dry shrinkage. But when the dosage is too high, the toughness of the concrete decreases significantly, so the restricting effect on shrinkage under dry conditions weakens, and the dry shrinkage increases. Therefore, the optimal dosage is 50%.

[0043] Taking all factors into consideration, the component ratio and preparation process conditions adopted in Example 7 are the most optimal. Example 7 can be selected as the theoretical basis for practical engineering applications to guide the preparation of high-toughness concrete with low shrinkage in actual engineering application scenarios.

[0044] The embodiments of the present invention have been described above. However, the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative rather than restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many forms without departing from the purpose of the present invention and the scope protected by the claims, and all of them fall within the protection scope of the present invention.

Claims

1. A low shrinkage, high toughness concrete material, characterized in that: The composition comprises the following components in parts by weight: 300-500 parts of cement; 600-800 parts of fly ash; 30-50 parts of silica fume; 200-400 parts of quartz sand; 10-50 parts of anti-shrinkage functional material; 200-400 parts of water; 10-50 parts of water reducing agent; 5-20 parts of thickener; 10-50 parts of PVA fiber; wherein the anti-shrinkage functional material is generated by carbonizing recycled concrete powder; The anti-shrinkage functional material is prepared by the following method: Dissolve diethylenetriamine in water to obtain a solution with a concentration of 1-3 mol / L; Recycled concrete powder is added into the solution to make the solid-liquid ratio be 50-100g / L to form a mixed solution, carbon dioxide is continuously introduced into the mixed solution, and the mixed solution is heated and maintained at a temperature of 40-80°C, so that the recycled concrete powder is carbonized to generate calcium carbonate under the action of carbon dioxide, and the generated calcium carbonate generates aragonite whiskers under the influence of diethylenetriamine. After the reaction is continued for 1-4 hours, the slurry is centrifuged and dried to obtain an anti-shrinkage functional material.

2. The low shrinkage and high toughness concrete material according to claim 1, characterized in that: The water reducing agent is a polycarboxylic acid-based water reducing agent with a water reducing efficiency greater than 20%.

3. The low shrinkage and high toughness concrete material according to claim 1, characterized in that: The thickener is hydroxypropyl methylcellulose.

4. The low shrinkage and high toughness concrete material according to claim 1, characterized in that: The particle size range of quartz sand is 10-600μm, and the average particle size is 100-140μm.

5. The low shrinkage and high toughness concrete material according to claim 1, characterized in that: PVA fiber length 9-15mm, diameter 30-40μm, density 1.2-1.4g / cm 3 .

6. The low shrinkage and high toughness concrete material according to claim 1, characterized in that: The particle size of recycled concrete powder is less than 600μm.

7. The low shrinkage and high toughness concrete material according to claim 1, characterized in that: The calcium content of fly ash is less than 10%; the silicon dioxide content of silica ash is above 90%.

8. A method for preparing a low shrinkage, high-toughness concrete material as claimed in any one of claims 1 to 7, characterized in that: The steps include: Take 300-500 parts of cement, 600-800 parts of fly ash, 30-50 parts of silica fume, 200-400 parts of quartz sand, 10-50 parts of anti-shrinkage functional material, 200-400 parts of water, 10-50 parts of water reducer, 5-20 parts of thickener, and 10-50 parts of PVA fiber according to mass proportion; mix the cement, fly ash and silica fume, add water and water reducer and continue to mix, then add quartz sand and mix, then add 2 / 3 of anti-shrinkage functional material and PVA fiber and mix, finally add the remaining 1 / 3 of anti-shrinkage functional material and PVA fiber and mix, so as to obtain a low-shrinkage and high-toughness concrete material.

9. An application of the low shrinkage and high toughness concrete material according to any one of claims 1 to 7, characterized in that: Used as pavement material for prefabricated pavements.

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