A method for the production of low cost foamed concrete for roofs

Abstract

The application discloses a preparation method of low-cost foamed concrete for a roof, and comprises the following steps: recycling waste concrete and drying the waste concrete at normal temperature; repeatedly crushing the dried waste concrete and collecting the waste concrete by gradient; uniformly mixing silicate cement, recycled concrete particles, a composite foaming agent, a polycarboxylic acid water reducing agent and a heat preservation reinforcing agent according to proportions to obtain dry mixture; uniformly mixing sodium chloride and water according to proportions to obtain wet mixture; pouring the wet mixture into the dry mixture, stirring at high speed to prepare foamed concrete slurry, pouring the slurry into a mold, demolding after 24h of standing, and placing the foamed concrete into a curing chamber for curing, and the low-cost foamed concrete is prepared. Since a large amount of recycled concrete particles are adopted, the cost is significantly reduced, and the amino-grafted graphene oxide and the silicate cement are used for common foaming, so that better heat insulation effect can be achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of foamed concrete, in particular to a preparation method of low-cost foamed concrete for roof. BACKGROUND

[0002] Foamed concrete is a new type of lightweight containing a large number of closed pores, which is formed by fully foaming the foaming agent by the foaming system of the foaming machine, uniformly mixing the foam with the cement slurry, and then being cast in situ or molded by the pumping system of the foaming machine, and being naturally cured.

[0003] Foamed concrete belongs to bubble-like thermal insulation material, and its outstanding feature is to form closed foam pores in the concrete, so as to make the concrete lightweight and heat-insulating. Meanwhile, it is a special variety of aerated concrete, and its pore structure and material performance are close to those of aerated concrete. The difference between them is only the difference between the pore shape and the foaming means. Four generations of physical foaming agents have been developed, which are rosin resin foaming agent, surfactant foaming agent, animal and plant protein foaming agent, and composite foaming agent. The currently used chemical foaming agents are hydrogen peroxide, calcium carbide, ammonium salt, and aluminum powder.

[0004] The Chinese invention patent CN111233408A discloses a coal gangue chemical foamed concrete and a preparation method thereof. The concrete comprises the following raw materials: fast-hardening sulphoaluminate cement or ordinary portland cement, a mixture of coal gangue and quicklime, foamed cement waterproof stabilizing agent, foamed cement early strength enhancer, naphthalene-based water reducing agent, manganese dioxide, water, and potassium chlorate solution. The coal gangue chemical foamed concrete prepared by the present application has the characteristics of small slurry water-cement ratio, high late strength of foamed concrete, and slow foaming speed. Moreover, the requirement for environmental temperature is not strict, and the production cycle is extended, and the production conditions are reduced. The coal gangue chemical foamed concrete has the advantages of light material, high strength, good heat preservation effect, low construction cost, and high safety factor. It can be used for building external wall insulation, roof insulation, settlement type toilet backfilling, and mine goaf filling, effectively reducing the environmental pollution caused by coal gangue, and turning waste into treasure.

[0005] With the continuous development of the building industry, the waste concrete produced by the abandoned buildings is also increasing, which causes great burden to the environment. However, there is no low-cost foamed concrete with waste concrete as the main raw material on the market at present, so it is necessary to study a preparation method of low-cost foamed concrete for roof with waste concrete as the main raw material. SUMMARY

[0006] Based on the technical problems existing in the background art, the present application provides a preparation method of low-cost foamed concrete for roof.

[0007] The technical scheme of the present application is as follows:

[0008] A preparation method of low-cost foamed concrete for a roof comprises the following steps:

[0009] A waste concrete is recycled and dried at room temperature;

[0010] B The dried waste concrete is repeatedly crushed and collected by gradient to obtain recycled concrete particles with a particle size of 10-50 microns, 50-200 microns and 200-500 microns, respectively;

[0011] C Silicate cement, recycled concrete particles, a composite foaming agent, a polycarboxylic acid water reducer and a thermal insulation enhancer are uniformly mixed in proportion to obtain dry mixture;

[0012] D Sodium chloride and water are uniformly mixed in proportion to obtain wet mixture;

[0013] E The wet mixture is poured into the dry mixture, and foamed concrete slurry is prepared by high-speed stirring for 3-5 minutes. The slurry is poured into a mold, and after 24 hours of standing, the mold is removed and placed in a curing room for curing.

[0014] Preferably, in step A, the humidity of the dried concrete is less than 5%.

[0015] Preferably, in step C, the weight ratio of each raw material in the dry mixture is as follows: silicate cement 30-35 parts, recycled concrete particles 38-55 parts, composite foaming agent 5-8 parts, polycarboxylic acid water reducer 1-2 parts and thermal insulation enhancer 0.3-0.5 parts.

[0016] Preferably, in step C, the composite foaming agent is a mixture of solid foaming agent fatty acid methanol amide and potassium bicarbonate in a mass ratio of 1:(18-25).

[0017] Preferably, in step C, the thermal insulation enhancer is modified graphene oxide.

[0018] Further preferably, the modified graphene oxide is amino-grafted graphene oxide.

[0019] Preferably, in step D, the mass ratio of sodium chloride to water is 100:(2-6).

[0020] Preferably, in step E, the mass ratio of dry mixture to wet mixture is (5-8):1.

[0021] The application has the advantages that the preparation method of the low-cost foamed concrete for roof comprises the following steps: recycling waste concrete and drying at room temperature; repeatedly crushing the dried waste concrete and collecting by gradient; uniformly mixing silicate cement, recycled concrete particles, composite foaming agent, polycarboxylic acid water reducer and heat preservation enhancer to obtain dry mixture; uniformly mixing sodium chloride and water to obtain wet mixture; pouring the wet mixture into the dry mixture, stirring at high speed to prepare foamed concrete slurry, pouring the slurry into a mold, demolding after 24h, and placing in a curing room for curing. DETAILED DESCRIPTION

[0022] Embodiment 1

[0023] A preparation method of low-cost foamed concrete for roof comprises the following steps:

[0024] A recycling waste concrete and drying at room temperature;

[0025] B repeatedly crushing the dried waste concrete and collecting by gradient to obtain recycled concrete particles with a particle size of 10-50μm, 50-200μm and 200-500μm respectively;

[0026] C uniformly mixing silicate cement, recycled concrete particles, composite foaming agent, polycarboxylic acid water reducer and heat preservation enhancer to obtain dry mixture;

[0027] D uniformly mixing sodium chloride and water to obtain wet mixture;

[0028] E pouring the wet mixture into the dry mixture, stirring at high speed to prepare foamed concrete slurry, pouring the slurry into a mold, demolding after 24h, and placing in a curing room for curing.

[0029] In step A, the humidity of the dried concrete is less than 5%.

[0030] In step C, the weight ratio of each raw material in the dry mixture is as follows: 32 parts of 42.5R silicate cement, 39 parts of recycled concrete particles, 7 parts of composite foaming agent, 1.4 parts of polycarboxylic acid water reducer and 0.4 parts of heat preservation enhancer.

[0031] The composite foaming agent in step C is a mixture of solid foaming agent fatty acid methanol amide and potassium bicarbonate in a mass ratio of 1:22.

[0032] The thermal insulation enhancer in step C is modified graphene oxide.

[0033] The modified graphene oxide is amino-grafted graphene oxide. The preparation method of the amino-grafted graphene oxide refers to the method disclosed in Example 1 of Chinese Invention Patent CN113233448A.

[0034] In step D, the mass ratio of sodium chloride to water is 100:5.

[0035] In step E, the mass ratio of dry mixture to wet mixture is 7:1.

[0036] Example 2

[0037] A method for preparing low-cost foamed concrete for roofs comprises the following steps:

[0038] A waste concrete is recycled and dried at room temperature;

[0039] B The dried waste concrete is repeatedly crushed and collected by gradient to obtain recycled concrete particles with a particle size of 10 μm≤ particle size≤ 50 μm, recycled concrete particles with a particle size of 50 μm≤ particle size≤ 200 μm, and recycled concrete particles with a particle size of 200 μm≤ particle size≤ 500 μm, respectively;

[0040] C Silicate cement, recycled concrete particles, composite foaming agent, polycarboxylate superplasticizer and thermal insulation enhancer are uniformly mixed in proportion to obtain dry mixture;

[0041] D Sodium chloride and water are uniformly mixed in proportion to obtain wet mixture;

[0042] E Pour the wet mixture into the dry mixture, stir at high speed to prepare foamed concrete slurry, the stirring time is 5 min, pour the slurry into the mold, stand for 24 h, then demold and put into the curing room for curing.

[0043] In step A, the humidity of the dried concrete is less than 5%.

[0044] In step C, the weight ratio of each raw material in the dry mixture is as follows: 42.5R silicate cement 30 parts, recycled concrete particles 55 parts, composite foaming agent 5 parts, polycarboxylate superplasticizer 2 parts and thermal insulation enhancer 0.3 parts.

[0045] The composite foaming agent in step C is a mixture of solid foaming agent fatty acid methanol amide and potassium bicarbonate in a mass ratio of 1:25.

[0046] The heat preservation enhancer in step C is modified graphene oxide.

[0047] The modified graphene oxide is amino-grafted graphene oxide. The preparation method of the amino-grafted graphene oxide refers to the method disclosed in Example 1 of Chinese Invention Patent CN113233448A.

[0048] In step D, the mass ratio of sodium chloride to water is 100:2.

[0049] In step E, the mass ratio of dry mixture to wet mixture is 8:1.

[0050] Example 3

[0051] A method for preparing low-cost foamed concrete for roofs, comprising the following steps:

[0052] A waste concrete is recycled and dried at room temperature;

[0053] B The dried waste concrete is repeatedly crushed and collected by gradient to obtain recycled concrete particles with a particle size of 10 μm≤50 μm, recycled concrete particles with a particle size of 50 μm≤200 μm, and recycled concrete particles with a particle size of 200 μm≤500 μm.

[0054] C Silicate cement, recycled concrete particles, composite foaming agent, polycarboxylic acid water reducer, and heat preservation enhancer are uniformly mixed in proportion to obtain dry mixture;

[0055] D Sodium chloride and water are uniformly mixed in proportion to obtain wet mixture;

[0056] E Pour the wet mixture into the dry mixture, stir at high speed to make foamed concrete slurry, the stirring time is 3 min, pour the slurry into the mold, stand for 24 h, then demold, put into the curing room for curing.

[0057] In step A, the humidity of the dried concrete is less than 5%.

[0058] In step C, the weight ratio of each raw material in the dry mixture is as follows: 42.5R silicate cement 35 parts, recycled concrete particles 38 parts, composite foaming agent 8 parts, polycarboxylic acid water reducer 1 part, and heat preservation enhancer 0.5 part.

[0059] In step C, the composite foaming agent is a mixture of solid foaming agent fatty acid methanol amide and potassium bicarbonate in a mass ratio of 1:18.

[0060] In step C, the heat preservation enhancer is modified graphene oxide.

[0061] The modified graphene oxide is amino-grafted graphene oxide. The preparation method of the amino-grafted graphene oxide refers to the method disclosed in Example 1 of Chinese Invention Patent CN113233448A.

[0062] In step D, the mass ratio of sodium chloride to water is 100:6.

[0063] In step E, the mass ratio of dry mixture to wet mixture is 5:1.

[0064] Example 4

[0065] A preparation method of low-cost foamed concrete for a roof, comprising the following steps:

[0066] A waste concrete is recycled and dried at room temperature;

[0067] B The dried waste concrete is repeatedly crushed and collected by gradient to obtain recycled concrete particles with a particle size of 10 μm≤particle size≤50 μm, recycled concrete particles with a particle size of 50 μm≤particle size≤200 μm, and recycled concrete particles with a particle size of 200 μm≤particle size≤500 μm, respectively;

[0068] C Silicate cement, recycled concrete particles, composite foaming agent, polycarboxylate superplasticizer and thermal enhancement agent are uniformly mixed in proportion to obtain dry mixture;

[0069] D Sodium chloride and water are uniformly mixed in proportion to obtain wet mixture;

[0070] E Pour the wet mixture into the dry mixture, stir at high speed to prepare foamed concrete slurry, the stirring time is 4 min, pour the slurry into a mold, stand for 24 h, then demold, put into a curing room for curing.

[0071] In step A, the humidity of the dried concrete is less than 5%.

[0072] In step C, the weight ratio of each raw material in the dry mixture is as follows: 32 parts of 42.5R silicate cement, 39 parts of recycled concrete particles, 7 parts of composite foaming agent, 1.4 parts of polycarboxylate superplasticizer, and 0.4 parts of thermal enhancement agent.

[0073] In step C, the composite foaming agent is a mixture of solid foaming agent fatty acid methanol amide and potassium bicarbonate in a mass ratio of 1:22.

[0074] In step C, the thermal enhancement agent is unmodified graphene oxide.

[0075] The mass ratio of sodium chloride and water in step D is 100:5.

[0076] The mass ratio of dry mixture and wet mixture in step E is 7:1.

[0077] Embodiment 5

[0078] A method for preparing low-cost foamed concrete for roofs, comprising the following steps:

[0079] A waste concrete is recycled and dried at room temperature;

[0080] B The dried waste concrete is repeatedly crushed and collected by gradient to obtain recycled concrete particles with a particle size of 10 μm≤50 μm, recycled concrete particles with a particle size of 50 μm≤200 μm, and recycled concrete particles with a particle size of 200 μm≤500 μm, respectively.

[0081] C Silicate cement, recycled concrete particles, composite foaming agent, polycarboxylic acid water reducer, and thermal enhancement agent are uniformly mixed in proportion to obtain a dry mixture;

[0082] D Sodium chloride and water are uniformly mixed in proportion to obtain a wet mixture;

[0083] E Pour the wet mixture into the dry mixture, stir at high speed to prepare a foamed concrete slurry, the stirring time is 4 min, pour the slurry into a mold, and let it stand for 24 h before demolding, then put it into a curing room for curing.

[0084] The humidity of the concrete after drying in step A is less than 5%.

[0085] In step C, the weight ratio of each raw material in the dry mixture is as follows: 32 parts of 42.5R silicate cement, 39 parts of recycled concrete particles, 7 parts of composite foaming agent, 1.4 parts of polycarboxylic acid water reducer, and 0.4 parts of thermal enhancement agent.

[0086] In step C, the composite foaming agent is a mixture of solid foaming agent fatty acid methanol amide and potassium bicarbonate in a mass ratio of 1:22.

[0087] In step C, the thermal enhancement agent is modified graphene oxide.

[0088] The modified graphene oxide is an organosilane oligomer grafted modified graphene oxide. The preparation method of the amino grafted graphene oxide refers to the method disclosed in Example 1 of Chinese invention patent CN108002377A.

[0089] The mass ratio of sodium chloride and water in step D is 100:5.

[0090] The mass ratio of the dry mixture and the wet mixture in step E is 7:1.

[0091] Comparative Example

[0092] The thermal insulation enhancer in Example 1 is removed, and the rest of the formulation and the preparation method remain unchanged.

[0093] The low-cost foamed concrete for roof prepared in Examples 1-6 is detected, and the following detection results are obtained:

[0094] Density kg / m 3 ]] Thermal conductivity W / m.K Example 1 210 0.035 Example 2 206 0.038 Example 3 213 0.034 Example 4 207 0.052 Example 5 205 0.047 Comparative Example 205 0.057

[0095] Note: The test method for the thermal conductivity is GB / T10295-2008 Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials - Heat Flow Meter Method.

[0096] From the above detection data, it can be seen that the low-cost foamed concrete for roof has very good thermal insulation performance.

[0097] The above description is only the preferred specific implementation of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art, according to the technical solution and the inventive concept of the present application, makes equivalent replacement or change within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A method for the production of low cost foamed concrete for roofs, characterized in that, The method comprises the following steps: A. recycling waste concrete and drying at room temperature; B. repeatedly crushing the dried waste concrete and collecting by gradient to obtain recycled concrete particles with a particle size of 10 μm C. mixing silicate cement, recycled concrete particles, composite foaming agent, polycarboxylic acid water reducer and thermal enhancement agent in proportion to obtain dry mixture; D. mixing sodium chloride and water in proportion to obtain wet mixture; E. pouring the wet mixture into the dry mixture, stirring at high speed to prepare foamed concrete slurry, the stirring time being 3-5 min, pouring the slurry into a mold, standing for 24 h and then demolding, and placing in a curing room for curing; In step C, the thermal enhancement agent is modified graphene oxide; and the modified graphene oxide is amino-grafted graphene oxide.

2. A process for the production of low cost foamed concrete for roofs as claimed in claim 1, wherein, In step A, the humidity of the dried concrete is less than 5%.

3. A process for the production of low cost foamed concrete for roofs as claimed in claim 1, wherein, In step C, the weight ratio of each raw material in the dry mixture is as follows: silicate cement 30-35 parts, recycled concrete particles 38-55 parts, composite foaming agent 5-8 parts, polycarboxylic acid water reducer 1-2 parts and thermal enhancement agent 0.3-0.5 parts.

4. A process for the production of low cost foamed concrete for roofs as claimed in claim 1, wherein, In step C, the composite foaming agent is a mixture of solid foaming agent fatty acid methanol amide and potassium bicarbonate in a mass ratio of 1: (18-25).

5. A process for the production of low cost foamed concrete for roofs as claimed in claim 1, wherein, In step D, the mass ratio of sodium chloride to water is 100: (2-6).

6. A process for the production of low cost foamed concrete for roofs as claimed in claim 1 wherein, In step E, the mass ratio of the dry mixture to the wet mixture is (5-8): 1.