CN111960719A - Lightweight aggregate concrete and preparation method thereof - Google Patents

Abstract

The invention relates to the field of concrete, and particularly discloses lightweight aggregate concrete and a preparation method thereof. The lightweight aggregate concrete is prepared from the following raw materials in parts by weight: 255 portions and 340 portions of cement; 370 and 450 parts of lightweight aggregate; sand 430 and 510 portions; 30-45 parts of aluminosilicate ore powder; 0.25-0.5 part of mesoporous silica-water-soluble thickener microspheres; 160 portions of fly ash and 200 portions of fly ash; 6-9 parts of a water reducing agent; 160 portions of water and 180 portions of water. The preparation method comprises the following steps: taking water accounting for 30-50% of the total amount of water as soaking water, taking the rest water as mixing water, adding a water reducing agent into the soaking water, immersing the lightweight aggregate in the soaking water, taking out the lightweight aggregate after the lightweight aggregate is saturated with water, and draining to obtain pre-wet lightweight aggregate; mixing and pre-stirring the pre-wetted lightweight aggregate and the rest solid materials to obtain a first mixture; and adding mixing water and the rest soaking water into the first mixture, and stirring to obtain the lightweight aggregate concrete. The lightweight aggregate concrete has the advantage of good homogeneity; in addition, the lightweight aggregate concrete prepared by the preparation method has the advantages of good homogeneity and high strength.

Description

Lightweight aggregate concrete and preparation method thereof

Technical Field

The invention relates to the technical field of concrete, in particular to lightweight aggregate concrete and a preparation method thereof.

Background

The light aggregate concrete is prepared by using natural porous light aggregate or artificial ceramsite as coarse aggregate, natural sand or light sand as fine aggregate, portland cement, water and additive in certain proportion and has dry apparent density not greater than 1950kg/m³The concrete of (2). The apparent density of the lightweight aggregate concrete is smaller than that of common concrete, so that the size of a infrastructure structure can be reduced, the using area of a building is increased, the cost of foundation engineering and material transportation is reduced, the foundation load is reduced, the functions of the building are improved, and the like.

The lightweight aggregate concrete has the advantages that the lightweight aggregate is adopted to replace stones, and the strength of the lightweight aggregate is lower than that of the stones, so that the strength of the lightweight aggregate concrete is lower; meanwhile, the lightweight aggregate has low apparent density, so the lightweight aggregate is easy to float upwards during concrete pouring, and the uniformity of the concrete is poor. Chinese patent application No. 201710240657.9 discloses lightweight aggregate concrete and a method for preparing the same, which improves the strength of the concrete by adding carbon fibers, but does not solve the problem of poor homogeneity of lightweight aggregate concrete.

Therefore, there is a need for a lightweight aggregate concrete having good homogeneity.

Disclosure of Invention

In view of the problem of poor homogeneity of lightweight aggregate concrete in the prior art, a first object of the present invention is to provide lightweight aggregate concrete having the advantage of good homogeneity.

The second purpose of the invention is to provide a preparation method of lightweight aggregate concrete, and the lightweight aggregate concrete prepared by the preparation method has the advantages of good homogeneity and high strength.

In order to achieve the first object, the invention provides the following technical scheme: the lightweight aggregate concrete is prepared from the following raw materials in parts by weight:

255 portions and 340 portions of cement;

370 and 450 parts of lightweight aggregate;

sand 430 and 510 portions;

30-45 parts of aluminosilicate ore powder;

0.25-0.5 part of mesoporous silica-water-soluble thickener microspheres;

160 portions of fly ash and 200 portions of fly ash;

6-9 parts of a water reducing agent;

160 portions of water and 180 portions of water.

By adopting the technical scheme, the viscosity of the concrete system is increased by adopting the mesoporous silica-water-soluble thickener beads, the floating difficulty of the lightweight aggregate is increased, the mesoporous silica is used as a water-soluble thickener carrier, and the water-soluble thickener is carried by utilizing the pore structure of the mesoporous silica, so that the water-soluble thickener can be slowly released in the concrete and gradually acts on the concrete system, the loss of the slump of the concrete over time is reduced, the influence of the water-soluble thickener on the slump of the concrete is reduced, and the homogeneity and the workability of the concrete are improved. Meanwhile, the characteristic of good dispersibility of the mesoporous silica is utilized, so that the water-soluble thickening agent can be fully dispersed in the concrete mixing process, the water-soluble thickening agent can be ensured to uniformly increase the system viscosity, the homogeneity of the concrete is further ensured, in addition, the mesoporous silica has excellent strength performance, the structural strength of the concrete can be improved when the mesoporous silica is added into the concrete as a carrier, the connection between the set cement and the silica interface is enhanced due to the pore structure of the mesoporous silica, namely, the strength of the set cement and the silica interface region can be ensured, and the overall structural strength of the concrete is improved.

Because the aluminosilicate ore powder is used for replacing part of cement, hydrous silicon oxide and hydrous aluminum oxide contained in the aluminosilicate ore powder can react with calcium hydroxide precipitated during hydration of the cement to generate hydrous calcium silicate gel and hydrous calcium aluminate gel, on one hand, the system viscosity is improved, the floating difficulty of the lightweight aggregate is increased, and the concrete homogeneity is improved; on the other hand, the hydration degree of cement is improved, the porosity of the set cement is reduced, the structure of the set cement is more compact, and various physical and mechanical properties of the concrete are correspondingly improved.

Further, the preparation method of the mesoporous silica-water-soluble thickener bead comprises the following steps:

the method comprises the following steps: weighing 0.1-0.2 part of water-soluble thickening agent, dissolving in water, adding 0.15-0.3 part of vacuum-dried mesoporous silica, and stirring at 50-55 ℃ for 2-2.5h to obtain a mixed suspension;

step two: heating the mixed suspension obtained in the step one at 80-100 ℃ until no steam escapes from the mixed suspension, and obtaining a primary dried crystal block;

step three: vacuum drying the primary dried crystal blocks obtained in the step two for 5-6h at the drying temperature of 120-;

step four: and (4) grinding and screening the finally dried crystal blocks obtained in the third step to obtain the mesoporous silica-water-soluble thickener microspheres.

By adopting the technical scheme, one part of the water-soluble thickening agent is coated outside the mesoporous silica-water-soluble thickening agent microbeads, the other part of the water-soluble thickening agent is remained in the inner holes of the mesoporous silica microbeads, and the water-soluble thickening agent coated outside the mesoporous silica-water-soluble thickening agent microbeads is dissolved in the concrete mixing and transporting process, so that the viscosity of a concrete system is increased, the pressure of the concrete system on lightweight aggregate is improved, the possibility of the lightweight aggregate floating up during pouring is reduced, and the stable quality of the concrete before pouring is ensured; along with the pouring of the concrete, the water-soluble thickening agent in the mesoporous silica-water-soluble thickening agent microspheres is gradually dissolved, the viscosity of a concrete system is continuously increased, the floating difficulty of the lightweight aggregate is further increased, and the floating possibility of the lightweight aggregate after the pouring of the concrete is reduced. The mesoporous silica-water-soluble thickener microspheres prepared by the method can reduce the influence of the addition of the water-soluble thickener on the fluidity of concrete and ensure the workability and the workability of lightweight aggregate concrete while ensuring that the upward floating of the lightweight aggregate is fully limited by the addition of the water-soluble thickener.

Further, the water-soluble thickener is an acrylate-methacrylate copolymer emulsion thickener.

By adopting the technical scheme, the acrylic ester-methacrylic ester copolymer emulsion thickener has a good thickening effect at the pH of 8-9, is close to the pH of concrete in the concrete transportation and pouring periods, namely can just show a good thickening effect in the concrete mixing and pouring periods, and can inhibit the lightweight aggregate from floating; and the calcium hydroxide generated by cement hydration can cause the pH of a concrete system to gradually rise, and finally the pH can reach more than 12 after the self-curing of the concrete is finished, namely, the thickening effect of the thickening agent is reduced along with the progress of the hydration reaction, and the concrete system is gradually cured to interfere the floating of the lightweight aggregate, so that the influence of the thickening agent on the fluidity of the concrete is reduced, the concrete slump loss in the later period of pouring is reduced, and the uniformity and the workability of the concrete are improved.

Further, the aluminosilicate ore powder is one of zeolite, kaolin, montmorillonite or bentonite.

By adopting the technical scheme, the zeolite, kaolin, montmorillonite or bentonite adopted also comprises active silicon dioxide and active aluminum oxide which can react with calcium hydroxide generated by cement hydration to generate water-containing calcium silicate gel and water-containing calcium aluminate gel, so that the homogeneity and the physical and mechanical properties of the concrete are further improved.

Further, the zeolite is an activated zeolite.

By adopting the technical scheme, due to the porous structure of the zeolite, the zeolite has huge internal and external specific surface areas, the reaction is more favorably carried out, the bleeding quantity of concrete can be effectively reduced, the structural viscosity of the concrete is improved, the slurry wrapping quantity of the lightweight aggregate is improved, so that the interface relation between the lightweight aggregate and the cement is improved, the mechanical property of the concrete is improved, meanwhile, in the self-hardening process of the concrete, the vacuum-like state is formed inside the zeolite powder, so that the zeolite powder particles and the cement gel are more tightly connected into a whole through the chemical action and the physical action, and the compression resistance and the tensile resistance of the concrete are further improved. The specific surface area of the activated zeolite is further increased after the activated zeolite is adopted, so that the reaction is favorably carried out.

Further, the activated zeolite is obtained by calcining natural zeolite at the temperature of 350-400 ℃ for 3-4 h.

By adopting the technical scheme, the zeolite is activated by adopting a high-temperature calcination method, the activation method is simple and easy for industrial operation, and the crystal water and organic matters in the activated zeolite obtained by treatment are fully removed, so that the internal porosity of the zeolite is increased, the diameter of the holes is increased, the zeolite structure is looser, the specific surface area is increased, the reaction is facilitated, and the strength of the concrete is further improved.

Further, the water reducing agent is at least one of lignin sulfonate water reducing agents or molasses water reducing agents.

By adopting the technical scheme, the lignosulfonate water reducing agent and/or the molasses water reducing agent are/is adopted as the water reducing agent, and both the lignosulfonate water reducing agent and the molasses water reducing agent contain a certain amount of reducing sugar, so that the water reducing agent has a certain retardation effect on concrete, can effectively inhibit the concrete slump loss with time, can meet the performance requirement of high-grade concrete when the lignosulfonate water reducing agent and the molasses water reducing agent are used in a composite manner, and is suitable for the preparation of light aggregate concrete with different strength types.

In order to achieve the second object, the invention provides the following technical scheme: a preparation method of lightweight aggregate concrete comprises the following steps:

s1: pre-wetting treatment of the lightweight aggregate: taking water accounting for 30-50% of the total amount of water as soaking water, taking the rest water as mixing water, adding a water reducing agent into the soaking water, uniformly stirring, immersing the weighed lightweight aggregate into the soaking water added with the water reducing agent until the lightweight aggregate is saturated with water, and then taking out and draining the saturated lightweight aggregate to obtain pre-wet lightweight aggregate;

s2: mixing and pre-stirring the pre-wetted lightweight aggregate, cement, fly ash, sand, aluminosilicate ore powder and mesoporous silica-water-soluble thickener microbeads for 25-35s to obtain a first mixture;

s3: adding mixing water and the rest soaking water into the first mixture, and stirring for 140-160s to obtain the lightweight aggregate concrete.

By adopting the technical scheme, as the lightweight aggregate is subjected to pre-wetting treatment, enough water is pre-stored in the inner gap of the lightweight aggregate, on one hand, the density of the lightweight aggregate is increased, the possibility of the lightweight aggregate floating is reduced, and meanwhile, the lightweight aggregate is prevented from absorbing a large amount of mixing water in the concrete stirring process, so that the fluidity of the concrete is ensured, and the loss of the slump of the concrete over time is effectively reduced; on the other hand, the cement near the lightweight aggregate is fully hydrated by the moisture in the lightweight aggregate, the contact surface state of the lightweight aggregate and the cement stone is improved, the compactness of a cement hydration product is increased, and the strength of the concrete is improved.

The water reducing agent is added into the soaking water and absorbed by the lightweight aggregate together, so that the water reducing agent gradually seeps out of the lightweight aggregate after the concrete is mixed, namely the water reducing agent is slowly released, the loss of the slump of the concrete over time can be effectively reduced, the defects of low flowability of the fresh concrete caused by firstly doping the water reducing agent and the defect of easy bleeding of the concrete caused by later doping the water reducing agent are overcome, and the quality of the fresh concrete is ensured.

Further, the surface drying is carried out on the waterlogged lightweight aggregate after draining in the step S1 until no water stain exists on the surface of the waterlogged lightweight aggregate, and the pre-wet lightweight aggregate is obtained.

By adopting the technical scheme, as the saturated lightweight aggregate is subjected to surface drying, a local water-less state is formed near the contact surface of the lightweight aggregate and the set cement, the possibility that the cement is hydrated on the surface of the lightweight aggregate to generate a calcium hydroxide crystal layer during mixing is reduced, namely, the influence of the calcium hydroxide crystal layer with a looser structure on the contact surface structure of the lightweight aggregate and the set cement is reduced, and the strength of the concrete is ensured.

In conclusion, the invention has the following beneficial effects:

1. according to the invention, the mesoporous silica-water-soluble thickener microspheres and aluminosilicate ore are used as raw materials, so that the floating difficulty of the lightweight aggregate is increased by improving the viscosity of a concrete system, the homogeneity of the lightweight aggregate concrete is improved, and the integral structural strength of the concrete is further improved;

2. the acrylate-methacrylate copolymer emulsion thickener is preferably adopted, and the acrylate-methacrylate copolymer emulsion thickener has a good thickening effect at the pH of 8-9, is close to the pH of concrete in the concrete transportation and pouring periods, namely, the thickener just can show a good thickening effect in the concrete mixing and pouring periods, so that the lightweight aggregate is inhibited from floating upwards, the thickening effect of the thickener is reduced along with the proceeding of a hydration reaction, the concrete slump loss in the later pouring period is reduced, and the uniformity and the workability of concrete are improved;

3. according to the method, the lightweight aggregate is subjected to pre-wetting treatment by adding the water reducing agent into the soaking water, so that the lightweight aggregate is prevented from absorbing a large amount of mixing water in the concrete stirring process, and the water reducing agent obtains a slow release effect, so that the concrete slump loss is reduced, the workability and the workability of the concrete are improved, and the quality of fresh concrete is ensured.

Drawings

FIG. 1 is a flow chart of a method for preparing lightweight aggregate concrete according to the present invention.

Detailed Description

The present invention will be described in further detail with reference to the following drawings and examples.

The raw material information mentioned in the following is shown in Table 1

Table 1 raw material information table

Preparation example of mesoporous silica-Water-soluble thickener Microbeads

Preparation example 1

The method comprises the following steps: weighing 3kg of acrylate-methacrylate copolymer emulsion thickener, dissolving in water, adding 5kg of vacuum dried mesoporous silica, and stirring at 55 ℃ for 2h to obtain a mixed suspension;

step two: heating the mixed suspension at 90 ℃ until no steam escapes from the mixed suspension, and obtaining a primary dried crystal block;

step three: vacuum drying the primary dried crystal block for 5.5h at the drying temperature of 125 ℃ to obtain a final dried crystal block;

step four: and grinding and screening the finally dried crystal blocks to obtain the mesoporous silica-water-soluble thickener microspheres with the particle size of less than 0.5 mm.

Preparation example 2

The method comprises the following steps: weighing 3kg of cellulose thickening agent, dissolving in water, adding 5kg of vacuum-dried mesoporous silica, and stirring for 2 hours at 55 ℃ to obtain a mixed suspension;

step two: heating the mixed suspension at 90 ℃ until no steam escapes from the mixed suspension, and obtaining a primary dried crystal block;

step three: vacuum drying the primary dried crystal block for 5.5h at the drying temperature of 125 ℃ to obtain a final dried crystal block;

step four: and grinding and screening the finally dried crystal blocks to obtain the mesoporous silica-water-soluble thickener microspheres with the particle size of less than 0.5 mm.

Examples

Example 1

The lightweight aggregate concrete is prepared by the following steps of raw materials with the components and the weight shown in Table 2 and by the method shown in figure 1:

s1: pre-wetting treatment of the lightweight aggregate: taking water accounting for 40% of the total amount of water as soaking water, taking the rest water as mixing water, adding a water reducing agent into the soaking water, uniformly stirring, immersing the weighed lightweight aggregate into the soaking water added with the water reducing agent until the lightweight aggregate is saturated with water, and then taking out the saturated lightweight aggregate and draining to obtain pre-wet lightweight aggregate;

s2: mixing and pre-stirring the pre-wetted lightweight aggregate, cement, fly ash, sand, aluminosilicate ore powder and mesoporous silica-water-soluble thickener microbeads for 30s to obtain a first mixture;

s3: adding mixing water and the rest soaking water into the first mixture, and stirring for 150s to obtain the lightweight aggregate concrete.

In this example, the mesoporous silica-water soluble thickener beads were prepared by the method described in preparation example 1, zeolite powder was used as the aluminosilicate ore powder, and a polycarboxylic acid water reducing agent was used as the water reducing agent.

Example 2

A lightweight aggregate concrete, which is different from example 1 in that: the mesoporous silica-water-soluble thickener beads used were prepared by the method described in preparation example 2.

Example 3

A lightweight aggregate concrete, which is different from example 1 in that: the adding amount of the mesoporous silica-water-soluble thickener micro-beads is 0.25 kg.

Example 4

A lightweight aggregate concrete, which is different from example 1 in that: the adding amount of the mesoporous silica-water-soluble thickener micro-beads is 0.5 kg.

Example 5

A lightweight aggregate concrete, which is different from example 1 in that: the aluminosilicate ore powder is kaolin.

Example 6

A lightweight aggregate concrete, which is different from example 1 in that: the aluminosilicate ore powder is montmorillonite.

Example 7

A lightweight aggregate concrete, which is different from example 1 in that: the aluminosilicate ore powder is bentonite.

Example 8

A lightweight aggregate concrete, which is different from example 1 in that: the zeolite is calcined and activated before use, the calcination temperature is 380 ℃, and the calcination time is 4 h.

Example 9

A lightweight aggregate concrete, which is different from example 1 in that: the amount of zeolite powder added was 30 kg.

Example 10

A lightweight aggregate concrete, which is different from example 1 in that: the amount of zeolite powder added was 45 kg.

Example 11

A lightweight aggregate concrete, which is different from example 1 in that: the water reducing agent is lignin sulfonate water reducing agent.

Example 12

A lightweight aggregate concrete, which is different from example 1 in that: the water reducing agent is a sugar dense water reducing agent.

Example 13

A lightweight aggregate concrete, which is different from example 1 in that: the water reducing agent comprises 4kg of lignosulfonate water reducing agent and 4kg of sugar dense water reducing agent.

Example 14

A lightweight aggregate concrete, which is different from example 1 in that: and in S1, performing surface drying on the drained water-saturated lightweight aggregate until no water stain exists on the surface of the water-saturated lightweight aggregate, thereby obtaining the pre-wet lightweight aggregate.

TABLE 2 materials and weights (kg) thereof in examples 1-7 and examples 9-13

Comparative example

Comparative example 1

A lightweight aggregate concrete, which is different from example 1 in that: the raw materials are not added with aluminosilicate ore powder and mesoporous silica-water-soluble thickener micro-beads.

Comparative example 2

A lightweight aggregate concrete, which is different from example 1 in that: the raw materials are not added with aluminosilicate ore powder.

Comparative example 3

A lightweight aggregate concrete, which is different from example 1 in that: the raw materials are not added with the mesoporous silica-water soluble thickener micro-beads.

Comparative example 4

A lightweight aggregate concrete, which is different from example 1 in that: the raw materials are not added with mesoporous silica-water soluble thickener microbeads, and 0.15kg of acrylate-methacrylate copolymer emulsion thickener is directly added. Wherein the acrylate-methacrylate copolymer emulsion thickener is added in S3 along with the blending water.

Comparative example 5

A lightweight aggregate concrete, which is different from example 1 in that: the addition amount of the mesoporous silica-water soluble thickener micro-beads is 0.1 kg.

Comparative example 6

A lightweight aggregate concrete, which is different from example 1 in that: the addition amount of the mesoporous silica-water soluble thickener micro-beads is 0.6 kg.

Comparative example 7

A lightweight aggregate concrete, which is different from example 1 in that: the amount of aluminosilicate ore powder added was 20 kg.

Comparative example 8

A lightweight aggregate concrete, which is different from example 1 in that: the amount of aluminosilicate ore powder added was 50 kg.

Comparative example 9

A lightweight aggregate concrete, which is different from example 1 in that: the water reducing agent is added in S3 together with the mixing water.

TABLE 3 comparative examples 1-8 materials and their weights (kg)

Performance test

The lightweight aggregate concretes prepared in examples 1 to 14 and comparative examples 1 to 9 were subjected to the following property tests:

according to the standard of the ordinary concrete mechanical property test method (GB/T50081-2002), a concrete standard cubic test piece is manufactured according to the requirements of a compression test and a bending test, the test piece is maintained in a standard maintenance room, and a related performance test is carried out after the test piece reaches a specified age.

Test-mechanical Property test

The 28d compressive strength (MPa) of the lightweight aggregate concrete was measured according to the cubic compressive strength test described in section 6.0.4 of Standard test methods for mechanical Properties of ordinary concrete (GB/T50081-2002), and the 28d flexural strength (MPa) of the lightweight aggregate concrete was measured according to the flexural strength test described in section 10.0.4.

And (3) test results: the test results of the test pieces obtained in examples 1 to 14 and comparative examples 1 to 9 are shown in Table 4.

Test second slump and change with time test

Slump measurement was carried out according to the slump and slump spread method described in section 3.1 of Standard methods for testing the Properties of ordinary concrete mixtures (GB/T50080-2002).

The amount of change with time in slump was measured according to the method for measuring the amount of change with time in slump of 1h described in section 6.5.1.2 of concrete admixtures (GB 8076-2008).

And (3) test results: the results of the tests on the lightweight aggregate concrete obtained in examples 1 to 14 and comparative examples 1 to 9 are shown in Table 4.

Test three-dry apparent Density measurement

The dry apparent density of lightweight aggregate concrete was measured by the baking method for crushed test pieces described in section 7.3 of the technical Specification for lightweight aggregate concrete (JGJ 51-2002).

And (3) test results: the test results of the test pieces obtained in examples 1 to 14 and comparative examples 1 to 9 are shown in Table 4.

TABLE 4 EXAMPLES 1-14 AND COMPARATIVE EXAMPLES 1-9 test results

And (3) analyzing test results:

table 4 shows that, when comparing example 1 with comparative examples 1 to 3, the compression strength and the flexural strength of example 1 are both greater than those of comparative examples 1 to 3, and the compression strength and the flexural strength of example 1 are close to those of comparative example 3, the compression strength and the flexural strength of comparative example 1 are slightly greater than those of comparative example 2, the compression strength and the flexural strength of comparative examples 1 and 2 are both much less than those of example 1, and the initial slump is as follows from large to small: comparative example 1, comparative example 3, example 1 and comparative example 2, and the slump loss with time of 1h was as small as large as example 1, comparative example 2, comparative example 3 and comparative example 1 in this order.

After the mesoporous silica-water-soluble thickening agent is added, the water-soluble thickening agent is dissolved, so that the viscosity of a concrete system is improved, the lightweight aggregate is effectively prevented from floating upwards, the uniformity of the lightweight aggregate concrete is improved, and the mechanical strength of the lightweight aggregate concrete is further improved. Meanwhile, the viscosity of the system is improved, so that the initial fluidity of the concrete is reduced, namely the initial slump is reduced, and the viscosity of the system is increased, so that gaps among the aggregates are filled, the loss of the concrete over time of the slump over time is reduced, namely the fluidity of the concrete during pouring is ensured, and the workability of the light aggregate concrete is ensured. The added aluminosilicate ore powder reacts with calcium hydroxide generated by cement hydration to generate hydrous calcium silicate gel and hydrous calcium aluminate gel, so that on one hand, the viscosity of a concrete system can be improved to a small extent, the light aggregate is inhibited from floating upwards, and the effect of improving the homogeneity of the light aggregate concrete is achieved; on the other hand, the cement hydration degree can be improved, the cement stone porosity is reduced, various physical and mechanical properties of the concrete are improved, and the strength of the lightweight aggregate concrete is enhanced.

As can be seen from table 4, when comparing example 1 with example 2, the lightweight aggregate concrete prepared from the mesoporous silica-water-soluble thickener prepared in preparation example 1 has a large initial slump, that is, when the water-soluble thickener is an acrylate-methacrylate copolymer emulsion thickener, the influence on the concrete fluidity is small, which indicates that the acrylate-methacrylate copolymer emulsion thickener does not show a good thickening effect at the initial stage of concrete mixing, that is, when the pH of the concrete system is low, so that the influence on the concrete fluidity is small, and as the concrete mixing time increases, the pH of the concrete system increases, the thickening effect of the acrylate-methacrylate copolymer emulsion thickener gradually increases, the floating of the lightweight aggregate is sufficiently inhibited, and the homogeneity of the lightweight aggregate concrete is improved.

As can be seen from table 4, when comparing examples 1, 3 and 4 with comparative examples 5 to 6, the compressive strength and the flexural strength of the lightweight aggregate concrete gradually increase and the initial slump gradually decreases as the addition amount of the mesoporous silica-water-soluble thickener beads increases, but when the addition amount of the mesoporous silica-water-soluble thickener beads is less than 0.25kg, the compressive strength and the flexural strength of the lightweight aggregate concrete are improved less, i.e., the inhibition effect on the floating of the lightweight aggregate is smaller, the homogeneity of the lightweight aggregate concrete is improved less, but the fluidity of the lightweight aggregate concrete is reduced more obviously and the practicability is lower; when the adding amount of the mesoporous silica-water-soluble thickener beads is more than 0.5kg, the flowability of the lightweight aggregate concrete continues to be reduced along with the increase of the adding amount of the mesoporous silica-water-soluble thickener beads, but the compressive strength and the flexural strength of the lightweight aggregate concrete are not obviously improved, which shows that after the adding amount of the mesoporous silica-water-soluble thickener beads reaches 0.5kg, the floating of the lightweight aggregate is fully inhibited, the lightweight aggregate is fully dispersed in a concrete system, and the physical and mechanical properties of the lightweight aggregate concrete cannot be improved by continuously increasing the adding amount of the mesoporous silica-water-soluble thickener beads, so that the flowability of the lightweight aggregate concrete is reduced, the workability is reduced, the actual construction is not facilitated, the cost is additionally increased, the economic benefit is poorer, and the actual use is not facilitated.

As can be seen from table 4, comparing example 1 with examples 5 to 7, the compressive strength, flexural strength, initial slump and slump loss of lightweight aggregate concrete are relatively close, which indicates that kaolin, montmorillonite, bentonite and zeolite can be added as aluminosilicate mineral powder, and the lightweight aggregate concrete can show better quality after being added, wherein when zeolite is added as aluminosilicate mineral powder into lightweight aggregate concrete, the lightweight aggregate concrete shows the best quality, and zeolite is the better choice of aluminosilicate mineral powder.

As can be seen from table 4, comparing example 1 with example 8, the lightweight aggregate concrete prepared from the calcined and activated zeolite has better performances, which indicates that the reaction efficiency of the zeolite is improved after calcination and activation, because the crystallized water and organic matters in the calcined and activated zeolite are sufficiently removed, the internal porosity of the zeolite is increased, the pore diameter is increased, the zeolite structure is looser, the specific surface area is increased, the reaction is facilitated, the strength of the concrete is further improved, and the quality of the lightweight aggregate concrete is improved.

As can be seen from Table 4, when comparing examples 1, 9 and 10 with comparative examples 7 to 8, the compressive strength and the flexural strength of the lightweight aggregate concrete are gradually improved and the initial slump is gradually reduced as the addition amount of the aluminosilicate ore powder, i.e., zeolite, is gradually increased, and when the addition amount of the zeolite is less than 30kg, the improvement of the physical and mechanical properties of the lightweight aggregate concrete is small, and when the addition amount of the zeolite is more than 50kg, the improvement of the physical and mechanical properties of the lightweight aggregate concrete is slowed down, and the economic benefit of continuously increasing the addition amount is low.

As is clear from Table 4, when the polycarboxylic acid water reducing agents were used in comparison with examples 11 to 13, the slump loss with time was large, and it was found that the lignosulfonate water reducing agents or the molasses water reducing agents were effective for suppressing the slump loss with time, and the concrete was retarded mainly by containing a certain amount of reducing sugars in both the lignosulfonate water reducing agents and the molasses water reducing agents. When the lignosulfonate water reducing agent and the molasses water reducing agent are used in a compounding mode, the compression resistance and the bending resistance of the lightweight aggregate concrete are obviously improved, and the fact that the lignosulfonate water reducing agent and the molasses water reducing agent are used in a compounding mode can effectively improve the compactness of cement stones in the lightweight aggregate concrete, so that the quality of the lightweight aggregate concrete is improved, the performance requirements of high-grade concrete can be met, and the preparation method is suitable for preparing lightweight aggregate concrete with different strength types.

As can be seen from table 4, comparing example 1 with example 14, the compressive and flexural properties of the concrete obtained by adding the surface-dried lightweight aggregate and mixing them are further improved, which indicates that the surface-dried pre-wetted lightweight aggregate is beneficial to the physical and mechanical properties of the concrete, because a local water-deficient state is formed near the contact surface between the surface-dried pre-wetted lightweight aggregate and the set cement, the possibility that the cement hydrates on the surface of the lightweight aggregate to form a calcium hydroxide crystal layer during mixing is reduced, that is, the influence of the calcium hydroxide crystal layer with a looser structure on the contact surface structure of the lightweight aggregate and the set cement is reduced, so that the strength of the concrete is ensured.

As can be seen from Table 4, when the same amount of the acrylate-methacrylate copolymer emulsion thickener as an additive was added directly during the concrete mixing process, the compression strength, the flexural strength and the initial slump of the lightweight aggregate concrete were reduced, comparing example 1 with comparative example 4. The reduction of the initial slump shows that the mesoporous silica micro-beads have a certain slow release effect on the acrylate-methacrylate copolymer emulsion thickener, so that the initial viscosity of a concrete system is greatly increased, and the flowability of the lightweight aggregate concrete is greatly influenced. The reduction of the compressive strength and the flexural strength shows that the dispersibility of the acrylate-methacrylate copolymer emulsion thickener directly added into a concrete system is weaker than that of the mesoporous silica-water-soluble thickener microspheres, so that the inhibition effect on the floating of the lightweight aggregate is not uniform enough, the lightweight aggregate in the lightweight aggregate concrete is not uniform enough, namely the lightweight aggregate concrete is poor in homogeneity, and the quality of the lightweight aggregate concrete is lower.

As can be seen from table 4, when the water reducing agent is added to the soaking water to soak the lightweight aggregate, the lightweight aggregate can absorb part of the water reducing agent and gradually release the absorbed water reducing agent in the subsequent mixing process, so that the fluidity and workability of the lightweight aggregate concrete are effectively improved.

The present embodiment is only for explaining the present invention, and it is not limited to the present invention, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present invention.

Claims (9)

1. The lightweight aggregate concrete is characterized by being prepared from the following raw materials in parts by weight:

255 portions and 340 portions of cement;

370 and 450 parts of lightweight aggregate;

sand 430 and 510 portions;

30-45 parts of aluminosilicate ore powder;

0.25-0.5 part of mesoporous silica-water-soluble thickener microspheres;

160 portions of fly ash and 200 portions of fly ash;

6-9 parts of a water reducing agent;

160 portions of water and 180 portions of water.

2. The lightweight aggregate concrete according to claim 1, wherein the preparation method of the mesoporous silica-water soluble thickener beads comprises the following steps:

the method comprises the following steps: weighing 0.1-0.2 part of water-soluble thickening agent, dissolving in water, adding 0.15-0.3 part of vacuum-dried mesoporous silica, and stirring at 50-55 ℃ for 2-2.5h to obtain a mixed suspension;

step two: heating the mixed suspension at 80-100 ℃ until no steam escapes from the mixed suspension, and obtaining a primary dried crystal block;

step three: carrying out vacuum drying on the primary dried crystal block for 5-6h at the drying temperature of 120-;

step four: and grinding and screening the finally dried crystal blocks to obtain the mesoporous silica-water-soluble thickener beads.

3. The lightweight aggregate concrete according to claim 1 or 2, wherein the water-soluble thickener is an acrylate-methacrylate copolymer emulsion thickener.

4. The lightweight aggregate concrete according to claim 1, wherein the aluminosilicate ore powder is one of zeolite, kaolin, montmorillonite or bentonite.

5. The lightweight aggregate concrete according to claim 4, wherein the zeolite is an activated zeolite.

6. The lightweight aggregate concrete as recited in claim 5, wherein said activated zeolite is obtained by calcining natural zeolite at 350-400 ℃ for 3-4 h.

7. The lightweight aggregate concrete according to claim 1, wherein the water reducing agent is at least one of a lignosulfonate water reducing agent or a molasses water reducing agent.

8. The method for preparing a lightweight aggregate concrete according to any one of claims 1 to 7, characterized by comprising the steps of:

s1: pre-wetting treatment of the lightweight aggregate: taking water accounting for 30-50% of the total amount of water as soaking water, taking the rest water as mixing water, adding a water reducing agent into the soaking water, uniformly stirring, immersing the weighed lightweight aggregate into the soaking water added with the water reducing agent until the lightweight aggregate is saturated with water, and then taking out and draining the saturated lightweight aggregate to obtain pre-wet lightweight aggregate;

s2: mixing and pre-stirring the pre-wetted lightweight aggregate, cement, fly ash, sand, aluminosilicate ore powder and mesoporous silica-water-soluble thickener microbeads for 25-35s to obtain a first mixture;

s3: adding mixing water and the rest soaking water into the first mixture, and stirring for 140-160s to obtain the lightweight aggregate concrete.

9. The method for producing a lightweight aggregate concrete according to claim 8, wherein the water-saturated lightweight aggregate drained in S1 is subjected to surface drying until no water stain is present on the surface of the water-saturated lightweight aggregate, thereby obtaining a pre-wetted lightweight aggregate.

Images