Limestone powder-fly ash concrete and preparation method thereof

Abstract

The invention provides limestone powder-fly ash concrete and a preparation method thereof. The limestone powder-fly ash concrete is prepared by mixing the following components: 200-360 parts of Portland cement, 45-65 parts of limestone powder, 30-60 parts of fly ash, 2-8 parts of modified fly ash, 1500-1800 parts of aggregate and 0-2 parts of a water reducing agent. The preparation method comprises the following steps: uniformly mixing the Portland cement, the limestone and the aggregate to obtain a first mixture; uniformly mixing the fly ash and the modified fly ash to obtain a second mixture; and adding the second mixture into the first mixture, adding a proper amount of water, mixing, forming and curing to obtain the limestone powder-fly ash concrete. The low-price resource limestone and fly ash can be comprehensively utilized, the cost of the concrete is reduced, and meanwhile, the performance and quality of the concrete are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete, in particular to a limestone powder-fly ash concrete and a preparation method thereof. BACKGROUND

[0002] Concrete is usually prepared by mixing cement as a cementing material, sand and gravel as aggregate, water and admixture according to a certain proportion, and stirring, and is a very important building material and has a wide application in the field of civil engineering.

[0003] Some admixtures are added into concrete, which can reduce the amount of cement and production cost, and can also improve the workability of concrete, such as reducing the hydration heat and improving the durability. At present, widely used admixtures in concrete include limestone and fly ash. Limestone can improve the compactness of concrete, and the CaCO3 component can react with the hydration products of cement to improve the early strength of concrete. Fly ash can also improve the compactness of concrete to a certain extent, but the silicate activity is low, and the contribution to the early strength of concrete is small. If used reasonably, it can improve the later strength of concrete to a certain extent. How to fully utilize limestone and fly ash comprehensively, effectively utilize low-cost or waste materials, and improve the performance and quality of concrete as a whole is a problem to be solved. SUMMARY

[0004] The present application provides a limestone powder-fly ash concrete and a preparation method thereof, which can comprehensively utilize low-cost resources such as limestone and fly ash, reduce the cost of concrete, and improve the performance and quality of concrete.

[0005] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows: A limestone powder-fly ash concrete is composed of the following components: 200-360 parts of Portland cement, 45-65 parts of limestone powder, 30-60 parts of fly ash, 2-8 parts of modified fly ash, 1500-1800 parts of aggregate, and 0-2 parts of water reducing agent.

[0006] Preferably, the preparation method of the modified fly ash comprises the following steps: (1) Hydroxylation treatment: adding a sodium hydroxide solution with a mass concentration of 5-10% to the fly ash, stirring for 3-4 hours, after the reaction is completed, solid-liquid separation is performed, the solid is washed with distilled water, the solid is dried, a sulfuric acid solution with a mass concentration of 20%-25% is added, stirring is performed for 5-8 hours, after the reaction is completed, solid-liquid separation is performed, the solid is washed with water until neutral, and the solid is dried to obtain the hydroxylated fly ash; (2) dispersing the hydroxylated fly ash in water, the weight ratio of the hydroxylated fly ash to water being 1:3-4, and then adding 0.5-2% of polyvinyl alcohol by weight of the water, wet ball milling, solid-liquid separation after the ball milling, drying the solid, and sieving to obtain the primary modified fly ash; (3) dissolving a silane coupling agent in a solvent, adding the solution into an atomizing device, spraying the solution into the primary modified fly ash after atomization, uniformly mixing, and drying at high temperature to remove the solvent to obtain the modified fly ash.

[0007] Preferably, in step (2), the time for the wet ball milling is 3-5 h.

[0008] Preferably, in step (2), the sieving is performed using a 325-mesh sieve.

[0009] Preferably, in step (3), the silane coupling agent is KH550 and / or KH792, and the amount used is 1-8% by weight of the primary modified fly ash.

[0010] Preferably, in step (3), the solvent is ethanol.

[0011] Preferably, in step (3), the temperature for the high-temperature drying is 85-95℃.

[0012] Preferably, the limestone powder is composed of coarse limestone powder and fine limestone powder, wherein the particle size of the coarse limestone powder is controlled to be between 30-90 μm, the particle size of the fine limestone powder is less than 30 μm, and the weight ratio of the coarse limestone powder to the fine limestone powder is 0.1-0.3:1.

[0013] Preferably, the particle size of the fly ash is composed of coarse fly ash, medium fly ash, and fine fly ash, the particle size of the coarse fly ash is controlled to be between 45-90 μm, the particle size of the medium fly ash is controlled to be between 30-45 μm, the particle size of the fine fly ash is less than 30 μm, and the weight ratio of the coarse fly ash to the medium fly ash to the fine fly ash is 0.1-0.2:0.3-0.4:1.

[0014] The application further provides a preparation method of the limestone powder-fly ash concrete as described above, comprising the following steps: S1. uniformly mixing Portland cement, limestone, and aggregate to obtain a first mixture; S2. uniformly mixing fly ash and modified fly ash to obtain a second mixture; S3. adding the second mixture into the first mixture, adding an appropriate amount of water, mixing, shaping, curing, to obtain the limestone powder-fly ash concrete.

[0015] The limestone powder-fly ash concrete and the preparation method thereof as described above have the following advantages: (1) the limestone powder and fly ash are mixed in the concrete simultaneously, the limestone powder in a proper amount activates the early reaction system inside the concrete, the hydration reaction of the cement and fly ash is accelerated, so that the setting speed of the concrete is accelerated, the early strength of the concrete is improved, and the needs of the building engineering can be better met.

[0016] (2) the flowability of each raw material inside the concrete is improved by the fly ash in a proper amount, so that the compactness of the concrete is improved, the strength of the concrete is more uniform, and the durability of the concrete is better improved.

[0017] (3) the part of the fly ash used is modified further, the hydroxylated fly ash can occur polymerization reaction in the process of the hydration reaction through the action of the polyvinyl alcohol and the coupling agent, a network complex structure is formed, and the toughness and the bending strength of the concrete are further improved. DETAILED DESCRIPTION

[0018] To make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the present application will be described clearly and completely in combination with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by the person skilled in the art without creative labor belong to the protection scope of the present application.

[0019] The portland cement used in the embodiment is P·O42.5, and the fly ash used is detected, and the composition is as shown in Table 1: Table 1 fly ash chemical composition table Embodiment 1

[0020] A limestone powder-fly ash concrete is composed of the following components: 300 parts of portland cement, 55 parts of limestone powder, 45 parts of fly ash, 5 parts of modified fly ash, 1000 parts of crushed stone, 615 parts of sand, 0.8 parts of polycarboxylate water reducer, and 155 parts of water.

[0021] The preparation method of the modified fly ash comprises the following steps: (1) hydroxylated treatment: sodium hydroxide solution with a mass concentration of 8% is added to the fly ash, stirring reaction is carried out for 4 h, after the reaction is completed, solid-liquid separation is carried out, washing is carried out with distilled water, the solid is dried, sulfuric acid solution with a mass concentration of 25% is added, stirring reaction is carried out for 6 hours, after the reaction is completed, solid-liquid separation is carried out, the solid is washed to neutral with water, and drying is carried out, so that the fly ash treated by hydroxyl is obtained; (2) The hydroxylated fly ash is dispersed in water, the weight ratio of the hydroxylated fly ash to water is 1:3, 1.2% of polyvinyl alcohol by weight of water is added, wet ball milling is carried out for 4 h, solid-liquid separation is carried out after the ball milling is completed, the solid is dried, and then the primary modified fly ash is obtained by screening through a 325 mesh sieve; (3) 5% of silane coupling agent KH550 by weight of the primary modified fly ash is weighed, the silane coupling agent KH550 is dissolved in ethanol, the volume ratio of KH550 to ethanol is 2:8, the silane coupling agent KH550 is added to an atomization device, and then the silane coupling agent KH550 is sprayed into the primary modified fly ash after atomization, the primary modified fly ash is uniformly mixed, and then the modified fly ash is obtained by drying at 90°C to remove the solvent.

[0022] The preparation method comprises the following steps: S1. uniformly mixing portland cement, limestone and aggregate to obtain a first mixture; S2. uniformly mixing fly ash and modified fly ash to obtain a second mixture; S3. adding the second mixture to the first mixture, adding an appropriate amount of water, mixing, shaping, curing, and obtaining limestone fly ash concrete.

[0023] The limestone powder and the fly ash with different particle sizes are applied in the above embodiment 1, and specifically, the limestone powder and the fly ash with different particle sizes are as follows: Table 2 Composition of limestone powder and fly ash in embodiment 1

[0024] The particle size of the coarse limestone powder is controlled to be between 30-90 μm, the particle size of the fine limestone powder is less than 30 μm, the particle size of the coarse fly ash is controlled to be between 45-90 μm, the particle size of the medium fly ash is controlled to be between 30-45 μm, and the particle size of the fine fly ash is less than 30 μm.

[0025] The slump, impermeable grade and compressive strength of the above embodiments 1-1 to 1-6 are tested, and the results are shown in Table 3.

[0026] Table 3 Test results of concrete performance in embodiment 1 Embodiment 2

[0027] A limestone fly ash concrete is prepared by mixing the following components: 300 parts of portland cement, 45 parts of limestone powder, 55 parts of fly ash, 8 parts of modified fly ash, 1010 parts of gravel, 620 parts of sand, 0.7 parts of polycarboxylate superplasticizer, and 157 parts of water.

[0028] The preparation method of the modified fly ash comprises the following steps: (1) Hydroxylation treatment: add 5% sodium hydroxide solution to fly ash, stir and react for 4 h, separate the solid and liquid after the reaction is complete, wash with distilled water, dry the solid, then add 20% sulfuric acid solution, stir and react for 6 h, separate the solid and liquid after the reaction is complete, wash the solid with water until it is neutral, and dry to obtain hydroxylated fly ash; (2) Dispersing the hydroxylated fly ash in water at a weight ratio of 1:4, adding 2% polyvinyl alcohol by weight of water, and wet ball milling for 4 h. After ball milling, solid-liquid separation is performed, and the solid is dried and passed through a 325 mesh sieve to obtain primary modified fly ash; (3) Weigh 6% of the weight of the primary modified fly ash as silane coupling agent KH792, dissolve the silane coupling agent KH792 in ethanol, and add the silane coupling agent KH792 to ethanol in a volume ratio of 2:9. Add the silane coupling agent to the atomizing device, spray it into the primary modified fly ash after atomization, mix evenly, and dry it at 95°C to remove the solvent to obtain the modified fly ash.

[0029] The preparation method comprises the following steps: S1. uniformly mixing silicate cement, limestone and aggregate to obtain a first mixture; S2. The fly ash and modified fly ash are mixed to obtain a second mixture; S3. Add the second mixture to the first mixture, add an appropriate amount of water, mix, shape, and cure to obtain limestone powder-fly ash concrete.

[0030] Limestone powder and fly ash of different particle sizes are used in the above embodiment 1, specifically: Table 4 Composition of limestone powder and fly ash in Example 2

[0031] Among them, the particle size of coarse limestone powder is controlled between 30-90 μm, the particle size of fine limestone powder is less than 30 μm, the particle size of coarse fly ash is controlled between 45-90 μm, the particle size of medium fly ash is controlled between 30-45 μm, and the particle size of fine fly ash is less than 30 μm.

[0032] The slump, impermeability grade and compressive strength of Examples 2-1 to 2-6 were tested, and the results are shown in Table 3.

[0033] Table 5 Concrete performance test results of Example 2

[0034] Comparative Example 1 Comparative Example 1 is basically the same as Example 1-1, but modified fly ash is not used and is replaced by fly ash.

[0035] Comparative Example 2 Comparative Example 2 is substantially the same as Example 2-1, but the modified fly ash is not used, and is replaced by fly ash.

[0036] Comparative Example 3 A limestone powder-fly ash concrete is composed of the following components mixed together: Portland cement 300 parts, limestone powder 55 parts, fly ash 49.58 parts, crushed stone 1000 parts, sand 615 parts, polycarboxylate superplasticizer 0.8 parts, silane coupling agent KH550 0.24 parts, polyvinyl alcohol 0.18 parts, and water 155 parts.

[0037] The particle sizes of the limestone powder and fly ash are the same as in Example 1-1.

[0038] Comparative Example 4 A limestone powder-fly ash concrete is composed of the following components mixed together: Portland cement 300 parts, limestone powder 45 parts, fly ash 61.91 parts, crushed stone 1010 parts, sand 620 parts, polycarboxylate superplasticizer 0.7 parts, silane coupling agent KH792 0.45 parts, polyvinyl alcohol 0.64 parts, and water 157 parts.

[0039] The particle sizes of the limestone powder and fly ash are the same as in Example 2-1.

[0040] The slump, impermeability grade, and compressive strength of Comparative Examples 1-4 were tested, and the results are shown in Table 3.

[0041] Table 6. Results of concrete performance tests for comparative examples

Claims

1. A limestone powder-fly ash concrete, characterized in that: It is composed of a mixture of the following components: 200-360 parts of Portland cement, 45-65 parts of limestone powder, 30-60 parts of fly ash, 2-8 parts of modified fly ash, 1500-1800 parts of aggregate, and 0-2 parts of water reducer.

2. The limestone powder-fly ash concrete according to claim 1, characterized in that: The preparation method of the modified fly ash comprises the following steps: (1) Hydroxylation treatment: add a sodium hydroxide solution with a mass concentration of 5-10% to the fly ash, stir and react for 3-4 hours, separate the solid and liquid after the reaction is completed, wash with distilled water, dry the solid, then add a sulfuric acid solution with a mass concentration of 20%-25%, stir and react for 5-8 hours, separate the solid and liquid after the reaction is completed, wash the solid with water until it is neutral, and dry to obtain hydroxylated fly ash; (2) dispersing the hydroxylated fly ash in water at a weight ratio of 1:3-4, adding polyvinyl alcohol at a weight ratio of 0.5-2% by weight of water, and wet ball milling. After the ball milling is completed, solid-liquid separation is performed, and the solid is dried and sieved to obtain primary modified fly ash; (3) Dissolve the silane coupling agent in a solvent, add it to an atomizing device, spray it into the primary modified fly ash after atomization, mix it evenly, dry it at high temperature to remove the solvent, and obtain modified fly ash.

3. The limestone powder-fly ash concrete according to claim 2, characterized in that: In step (2), the wet process of spheroidal graphite is carried out for 3-5 h.

4. The limestone powder-fly ash concrete according to claim 2, characterized in that: In step (2), the sieving is performed using a 325-mesh sieve.

5. The limestone powder-fly ash concrete according to claim 2, characterized in that: In step (3), the silane coupling agent is KH550 and / or KH792, and the amount used is 1-8% by weight of the primary modified fly ash.

6. The limestone powder-fly ash concrete according to claim 2, characterized in that: In step (3), the solvent is ethanol.

7. The limestone powder-fly ash concrete according to claim 2, characterized in that: In step (3), the high temperature drying temperature is 85-95°C.

8. The limestone powder-fly ash concrete according to claim 1, characterized in that: The limestone powder consists of coarse limestone powder and fine limestone powder, wherein the particle size of the coarse limestone powder is controlled between 30-90 μm, the particle size of the fine limestone powder is less than 30 μm, and the weight ratio of the coarse limestone powder to the fine limestone powder is 0.1-0.3:

1.

9. The limestone powder-fly ash concrete according to claim 1, characterized in that: The particle size of the fly ash consists of coarse fly ash, medium fly ash and fine fly ash. The particle size of the coarse fly ash is controlled between 45-90 μm, the particle size of the medium fly ash is controlled between 30-45 μm, and the particle size of the fine fly ash is less than 30 μm. The weight ratio of the coarse fly ash, the medium fly ash and the fine fly ash is 0.1-0.2:0.3-0.4:

1.

10. The method for preparing limestone powder-fly ash concrete according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. The Portland cement, limestone and aggregate are mixed to obtain a first mixture; S2. The fly ash and modified fly ash are mixed to obtain a second mixture; S3. Add the second mixture to the first mixture, add an appropriate amount of water, mix, shape, and cure to obtain limestone powder-fly ash concrete.

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