CN117383884B - Anti-seismic anti-cracking aerated concrete block and preparation method thereof - Google Patents

Abstract

The invention discloses an earthquake-resistant and crack-proof aerated concrete building block and a preparation method thereof, which belong to the technical field of building materials. The invention comprises the following raw materials in parts by weight: 65-80 parts of cement; 310-330 parts of sand; 65-80 parts of quicklime; 12-16 parts of gypsum; 0.6-0.7 parts of aluminum powder; 0.5-0.7 parts of water reducer; 3.5-5.0 parts of organic admixture; 0.01-0.05 parts of auxiliary foaming agent; and 200-230 parts of water. The aerated concrete provided by the invention has low dry density, high compressive strength, strong mechanical properties, low expansion rate, can fully utilize existing equipment for experiments, and is economical and environmentally friendly.

Description

A kind of earthquake-resistant and crack-resistant aerated concrete block and preparation method thereof

Technical Field

The invention relates to the technical field of building materials, and in particular to an earthquake-resistant and crack-resistant aerated concrete building block and a preparation method thereof.

Background technique

Aerated concrete is a new type of building material that is lightweight, porous, thermally insulating and fireproof. It generally weighs 500-700 kg/cubic meter, which is only 1/4-1/3 of clay bricks and lime sand bricks, and 1/5 of ordinary concrete. It can be used as load-bearing walls for ground floor buildings and filling walls for high-rise buildings. Due to the reduced self-weight of the building and the small destructive power of the earthquake, the earthquake resistance of the building is greatly improved.

However, the existing aerated concrete blocks have low compressive strength, linear shrinkage of about 0.4-0.7 mm/m, large shrinkage rate, and are prone to cracking. There is currently no particularly effective method.

The application number is "202011074860.1", and the name of the invention is "A method for preparing aerated concrete using recycled concrete aggregate and aerated concrete", which discloses "A method for preparing aerated concrete using recycled concrete aggregate, comprising the following steps: S1 Recycled aggregate pretreatment: weigh the recycled raw materials, dry them, and obtain recycled aggregate; the recycled raw materials include: recycled concrete powder, nano-silica sol aqueous solution, hydroxypropyl distarch phosphate; S2 Slurry preparation: take water, add slurry raw materials, ball mill to obtain fine slurry, add recycled aggregate, quicklime powder and cement, add aluminum powder to obtain slurry;", wherein nano-silica sol nanoparticles are used. Although this will increase the concrete pressure, the larger specific surface area of the nanoparticles will increase the reaction activity, accelerate the reaction rate, thicken the slurry quickly, and have poor casting stability. The filling effect of the nanoparticles will cause the porosity of the blocks to decrease and the weight to increase. Therefore, based on a comprehensive judgment, it is not an aerated concrete block with better performance.

The application number is "202211499704.9", the invention name is "An environmentally friendly crack-resistant aerated concrete block and its preparation method", which discloses "4-6 parts of expansion fiber; 5.5-7.5 parts of anti-cracking fiber; mixed glue B 3-5 parts; fly ash 65-85 parts; lime 15-25 parts; cement 8-15 parts; aluminum powder 0.4-1 part; water reducer 1-2 parts; water 28-34 parts; wherein, the anti-cracking fiber is a fiber modified by mixed glue A; the mixed glue A consists of PAE, polyethylene glycol acrylate, MUF, and protein powder". However, in the preparation method, it discloses a technical scheme of "stirring and mixing the expanded fiber, fly ash, lime, cement, aluminum powder, water reducer and water, adding the mixed liquid, stirring and mixing to obtain a slurry, pouring the slurry into a mold, standing and hardening, demoulding, cutting, and obtaining a blank". However, aluminum powder is usually added last after all materials are evenly stirred, because aluminum powder will react with quicklime to generate hydrogen, and the speed is very fast. If it is stirred with other materials, the stirring time is long, which will cause hydrogen to overflow and affect the porosity and dry density.

Summary of the invention

In view of this, the present invention provides an earthquake-resistant and crack-resistant aerated concrete block and a preparation method thereof, the purpose of which is to prepare an aerated concrete block with low bulk density and high strength, that is, on the basis of taking into account light weight and other original properties, the cracking performance is mainly improved in three aspects: on the one hand, the shrinkage rate of the block is reduced, on the other hand, its mechanical strength is increased, and finally, the expansion and contraction effect caused by temperature difference is reduced, thereby increasing its earthquake-resistant and crack-resistant performance.

In order to achieve the above-mentioned invention object, the present invention provides the following technical solutions:

A seismic and crack-resistant aerated concrete block comprises the following raw materials in parts by weight: 65-80 parts of cement; 310-330 parts of sand; 65-80 parts of quicklime; 12-16 parts of gypsum; 0.6-0.7 parts of aluminum powder; 0.5-0.7 parts of water reducer; 3.5-5.0 parts of organic admixture; 0.01-0.05 parts of auxiliary foaming agent; and 200-230 parts of water.

The present invention also has the following additional technical features:

Preferably, the organic admixture is bisphenol A epoxy resin E44, a resin toughening agent and styrene-butadiene emulsion, in a mass ratio of 25:1:10.

Preferably, the auxiliary foaming agent is sodium bicarbonate.

Preferably, the following raw materials are included in parts by weight: 70 parts of cement; 320 parts of sand; 70 parts of quicklime; 14 parts of gypsum; 0.6 parts of aluminum powder; 4.2 parts of organic admixture; 0.02 parts of auxiliary foaming agent; 0.6 parts of water reducing agent; and 220 parts of water.

Preferably, the particle size of the sand is 50-150 mesh, and the sand is quartz sand, containing 30% by mass of 40-70 mesh and 70% by mass of 50-100 mesh. This is to take into account the fluidity and reactivity of the fine sand. However, if there is too much fine sand, the reaction will be too fast and cause suffocation. Therefore, coarse sand is used to regulate the gas generation.

Preferably, the water reducer is aminosulfonic acid high-efficiency water reducer.

The present invention also provides a method for preparing the above-mentioned earthquake-resistant and crack-resistant aerated concrete building block, comprising the following steps:

The first step is to weigh all the components, put sand, gypsum and part of the water into a mixer and mix them evenly, then add cement and the remaining water and mix them evenly, add quicklime and mix them evenly again, then add organic admixtures and mix them evenly, and finally add aluminum powder and auxiliary foaming agent and mix them evenly within one minute to obtain a mixture, all of which are operated at room temperature;

The second step is to pour the mixture into a mold and let it stand at 40-60°C for 2-4 hours to obtain a primary concrete block.

The third step is to transfer the primary concrete blocks into an autoclave and cure them for 2-4 hours at a temperature of 60-80°C and a pressure of 1.2-1.8MPa. After cutting into blocks, the temperature is increased at a rate of 5°C/min to a temperature of 90-150°C and a pressure of 1.2-3MPa and cured for 6-8 hours to obtain aerated concrete blocks.

The reaction principle of the present invention is as follows: quicklime and cement are stirred and hydrated to generate hydroxide. After aluminum powder is added, the aluminum powder reacts with the hydroxide during stirring to generate hydrogen and forms a pore structure during the slurry thickening process. During the curing and heating process, as the temperature rises, the volume of the gas increases and pores are formed. Since the addition of resin and styrene-butadiene emulsion blocks the gas generation of aluminum powder, the porosity is reduced and the dry density is increased, so sodium bicarbonate is added to assist in gas generation. The reaction of sodium bicarbonate with cement to generate carbon dioxide is a reversible reaction. During the steam curing process, as the temperature rises, the carbon dioxide gas expands and overflows, and the reaction balance is broken. At the same time, due to the increase in alkalinity of concrete, it is more conducive to the reaction of aluminum powder with alkali to generate hydrogen, thereby increasing the porosity and reducing the bulk density. Therefore, sodium bicarbonate as an auxiliary gas generating agent has the effect of killing two birds with one stone.

In addition, the porosity of aerated concrete is more than 50%. Improving the strength of the pore walls can significantly increase the mechanical properties of the blocks. Since bisphenol A epoxy resin E44 is a thermosetting resin, it can form a solidified and interconnected structure in the pore walls under the action of the resin toughening agent during steam curing. Styrene-butadiene emulsion can bond, fill cracks and reduce the shrinkage of concrete.

Compared with the prior art, the present invention has the following advantages:

The invention can fully utilize existing equipment to carry out experiments, which is economical and environmentally friendly; the aerated concrete of the invention has low dry density, high compressive strength, strong mechanical properties and low expansion rate.

Detailed ways

Some embodiments of the present invention are disclosed below, and those skilled in the art can appropriately improve the process parameters according to the content of this article. It is particularly important to point out that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included in the present invention. The methods and applications of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

The materials in the following examples are described as follows:

Cement was P.O42.5R ordinary Portland cement, purchased from Wuxi Jianghuai Building Materials Technology Co., Ltd.;

Sand: quartz sand, containing 30% by mass of 40-70 mesh and 70% by mass of 50-100 mesh, Lingshou County Rijin Mineral Products Processing Plant;

Quicklime: 200 mesh, purchased from Hebei Huihao Environmental Protection Technology Co., Ltd.;

Gypsum: Model P130, purchased from Lianyungang Pengwei Insulation Building Materials Co., Ltd.;

Aluminum powder: model GLS-65, purchased from Shandong Sanpin Aluminum Technology Co., Ltd.;

Resin toughening agent: Model SH-200-201, purchased from Guangzhou Xinxi Metallurgical Chemical Co., Ltd.;

Water reducer: aminosulfonate high-efficiency water reducer, purchased from Fenyangtang (Shanghai) Industrial Co., Ltd.;

Example Building blocks were prepared into cubic test blocks according to the specification of 100 mm×100 mm×100 mm, with three blocks in each group.

Example 1

Preparation of aerated concrete blocks 1

Take the following raw materials in parts by weight: 70 parts of cement; 360 parts of sand; 70 parts of quicklime; 14 parts of gypsum; 0.6 parts of aluminum powder; 4.2 parts of organic admixture; 0.02 parts of sodium bicarbonate; 0.6 parts of water reducer; 220 parts of water; among which the organic admixture is bisphenol A type epoxy resin E44, resin toughening agent and styrene-butadiene emulsion, in a mass ratio of 25:1:10.

Aerated concrete block 1 is prepared according to the following steps:

The first step is to weigh all the components, put sand, gypsum and half of the water into a mixer and stir for 2 minutes to mix evenly, then add cement and the remaining water to continue mixing evenly, wherein cement is added twice, water is also added twice, quicklime is added, and stirred for 1 minute to mix evenly, then organic admixtures are added and mixed evenly, and finally aluminum powder and auxiliary foaming agent are added and stirred evenly within 30 seconds to obtain a mixture, and the above operations are all performed at room temperature; i.e. 20-25°C;

In the second step, the mixture was poured into a mold and allowed to stand at 45°C for 160 min to obtain a primary concrete block;

In the third step, the primary concrete block is transferred into an autoclave and cured for 3 hours at a temperature of 65°C and a pressure of 1.2 MPa. After being cut into blocks, the temperature is increased at a rate of 5°C/min to 110°C and a pressure of 1.4 MPa and cured for 8 hours to obtain an aerated concrete block 1.

Example 2

Preparation of aerated concrete blocks 2

Take the following raw materials in parts by weight: 75 parts of cement; 350 parts of sand; 70 parts of quicklime; 15 parts of gypsum; 0.6 parts of aluminum powder; 4.0 parts of organic admixture; 0.03 parts of sodium bicarbonate; 0.5 parts of water reducer; 230 parts of water; among which the organic admixture is bisphenol A type epoxy resin E44, resin toughening agent and styrene-butadiene emulsion, in a mass ratio of 25:1:10.

Aerated concrete block 2 is prepared according to the following steps:

The first step is to weigh all the components, put sand, gypsum and half of the water into a concrete mixer and stir for 2 minutes to mix evenly, then add cement and the remaining water and stir for 2 minutes to mix evenly, add quicklime and stir for 1 minute to mix evenly, then add organic admixture and mix evenly, finally add aluminum powder and auxiliary foaming agent and stir evenly within 40 seconds to obtain a mixture, all of which are operated at room temperature;

In the second step, the mixture is poured into a mold and left to stand at 60°C for 2 hours to allow the aluminum powder to foam and obtain a primary concrete block.

In the third step, the primary concrete blocks are transferred into an autoclave and cured for 4 hours at a temperature of 70°C and a pressure of 1.5 MPa. After being cut into blocks, the temperature is increased at a rate of 5°C/min to 100°C and a pressure of 2.0 MPa and cured for 6 hours to obtain aerated concrete blocks 2.

Example 3

Preparation of aerated concrete blocks 3

Take the following raw materials in parts by weight: 65 parts of cement; 360 parts of sand; 66 parts of quicklime; 12 parts of gypsum; 0.7 parts of aluminum powder; 4.6 parts of organic admixture; 0.04 parts of sodium bicarbonate; 0.7 parts of water reducer; 210 parts of water; among which the organic admixture is bisphenol A type epoxy resin E44, resin toughening agent and styrene-butadiene emulsion, in a mass ratio of 25:1:10.

Aerated concrete blocks 3 are prepared according to the following steps:

The first step is to weigh all the components, put sand, gypsum and half of the water into a mixer and stir for 2 minutes to mix evenly, then add cement and the remaining water and continue to stir for 2 minutes to mix evenly, add quicklime, stir again for 1 minute to mix evenly, then add organic admixtures and mix evenly, finally add aluminum powder and auxiliary foaming agent and stir evenly within one minute to obtain a mixture, all of which are operated at room temperature;

In the second step, the mixture is poured into a mold and allowed to stand at 40°C for 4 hours to obtain a primary concrete block;

In the third step, the primary concrete blocks are transferred into an autoclave and cured for 3 hours at a temperature of 65°C and a pressure of 1.3 MPa. After being cut into blocks, the temperature is increased at a rate of 5°C/min to 100°C and a pressure of 1.9 MPa and cured for 8 hours to obtain aerated concrete blocks 3.

In order to clarify the advantages of this experimental method,

Comparative Example 1: Aerated concrete was prepared by conventional method, that is, no organic admixture, sodium bicarbonate and water reducing agent were added, and the rest was the same as Example 1.

Comparative Example 2: No bisphenol A epoxy resin E44 and resin toughening agent were added, and the rest was the same as Example 1.

Comparative Example 3: Sodium bicarbonate was not added, and the rest was the same as Example 1.

Comparative Example 4: No styrene-butadiene emulsion was added, and the rest was the same as Example 1.

Example 4

Performance Testing

The test was carried out according to the following test method, and the test results are shown in Table 1:

(1) Dry density: Tested in accordance with the method of GB/T11969-2008 "Test method for properties of autoclaved aerated concrete", unit: kg/m3.

(2) Drying shrinkage value: Tested in accordance with the method of GB/T 11972-1997 "Test method for drying shrinkage of aerated concrete", unit: mm/m.

(3) Split tensile strength: The test is conducted in accordance with the standard GB/T 11971-1997 “Test methods for mechanical properties of aerated concrete” to detect the splitting tensile strength of the block at 28 days, in MPa.

(4) Compressive strength: The compressive strength of the block at 28 days is measured in MPa according to the standard GB/T 11971-1997 “Test methods for mechanical properties of aerated concrete”.

Table 1 Performance test results of aerated concrete products in various embodiments

Comparative Example 1 is an existing method for preparing aerated concrete blocks. Comparative Example 2 does not add bisphenol A epoxy resin E44 and resin toughening agent. The compressive strength is lower than that of Example 1 and Comparative Example 1. It can be seen that epoxy resin E44 can greatly affect the mechanical properties of the blocks. This is because after adding bisphenol A epoxy resin E44 and resin toughening agent to concrete, the resin cross-linking and curing will be carried out in the steam pressurization stage, which will enhance the mechanical strength of the wall between the blocks, thereby increasing the compressive strength and splitting tensile strength of the blocks. Compared with the compressive strength of Comparative Example 1, it is also lower because its dry density is also lower, indicating that sodium carbonate Hydrogen can assist in foaming. During steam curing at high temperature, the carbon dioxide generated by sodium bicarbonate overflows the concrete and no longer reacts to generate calcium carbonate to form bubbles. Ammonium bicarbonate is selected as an auxiliary foaming agent, which will not form bubbles with too large pores compared to other foaming agents such as surfactant foaming agents, nor will it hinder the foaming process of aluminum powder. In Example 3, sodium bicarbonate is not added, and the dry density of the block is significantly increased, while the compressive strength and splitting tensile strength are increased, indicating that sodium bicarbonate can play an auxiliary role in foaming. In specific use, the relationship between dry density and mechanical properties can be balanced as needed. In Example 4, styrene-butadiene emulsion is not added, and it can be found that the dry density is slightly reduced, the compressive strength is slightly reduced, but the dry expansion value is significantly increased, indicating that styrene-butadiene emulsion can reduce the shrinkage rate of the block, making the block not easy to crack, and at the same time, it is shown that bisphenol A epoxy resin E44 and resin toughening agent also have the effect of reducing the shrinkage rate of the block. In combination with Example 2 and Example 4, it can be seen that the effect of styrene-butadiene emulsion on the compressive properties of the block is almost unchanged, but it can significantly affect the dry shrinkage performance and splitting strength of the block. The combined effect of epoxy resin and styrene-butadiene emulsion can significantly improve the splitting tensile strength of the block. This is because epoxy resin is brittle in nature, while styrene-butadiene emulsion can improve the impact resistance and make up for the defects of epoxy resin.

The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims (2)

1. The anti-seismic anti-cracking aerated concrete block is characterized by comprising the following raw materials in parts by weight: 70 parts of cement; 320 parts of sand; 70 parts of quicklime; 14 parts of gypsum; 0.6 parts of aluminum powder; 4.2 parts of organic additive; 0.02 parts of auxiliary foaming agent; 0.6 parts of water reducer; 220 parts of water;

The organic additive is bisphenol A epoxy resin E44, a resin toughening agent and styrene-butadiene emulsion, and the mass ratio is 25:1:10; the auxiliary foaming agent is sodium bicarbonate; the water reducer is sulfamic acid high-efficiency water reducer;

The preparation method of the anti-seismic anti-cracking aerated concrete block comprises the following steps:

Firstly, weighing each component, putting sand, gypsum and part of water into a stirrer to be uniformly mixed, adding cement and the rest of water to be uniformly mixed, adding quicklime to be uniformly mixed again, adding an organic additive to be uniformly mixed, finally adding aluminum powder and an auxiliary foaming agent to be uniformly stirred within one minute to obtain a mixture, and operating at room temperature;

Secondly, pouring the mixture into a mould, and standing for 2-4 hours at 40-60 ℃ to obtain a primary concrete block;

and thirdly, transferring the primary concrete block into an autoclave, curing for 2-4 hours under the conditions of the temperature of 60-80 ℃ and the pressure of 1.2-1.8MPa, cutting the block, heating to the temperature of 90-150 ℃ at 5 ℃/min, and curing for 6-8 hours under the conditions of the pressure of 1.2-3MPa, thus obtaining the aerated concrete block.

2. The earthquake-resistant and crack-resistant aerated concrete block of claim 1, wherein the sand has a particle size of 50-150 mesh.