CN116063096A - A kind of high-solid carbon-free autoclaved aerated concrete and its preparation method - Google Patents

Abstract

The invention provides a high-solid carbon-free autoclaved aerated concrete and a preparation method thereof, which belong to the technical field of building materials. The high-solid carbon-free autoclaved aerated concrete includes the following components in parts by mass: 15-50 parts of cement, steel slag 20-55 parts, 10-30 parts of slag, 5-15 parts of lime, 0-5 parts of gypsum, 20-60 parts of water, 0.1-0.4 parts of foaming agent, 0-0.5 parts of water reducing agent, 1-4 parts of activator part, 0.02-0.5 part of foam stabilizer. The invention uses bulk solid waste steel slag and slag as the main raw materials, which is beneficial to the resource utilization of industrial waste residue, reduces the amount of cement in autoclaved aerated concrete, effectively reduces the production cost of autoclaved aerated concrete, and adopts pressure swing curing The process is conducive to deep mineralization reaction, can directly absorb a large amount of CO ₂ , and the amount of carbon fixation is greater than 15% of its own mass. It is an effective way to utilize carbon and greatly shortens the production cycle of autoclaved aerated concrete. It can be used in Aerated concrete products with qualified strength can be produced in a short period of time.

Description

A kind of high-solid carbon-free autoclaved aerated concrete and its preparation method

technical field

The invention relates to the technical field of building materials, in particular to a high-solid carbon-free autoclaved aerated concrete and a preparation method thereof.

Background technique

Air-entrained concrete is a kind of lightweight porous concrete. Based on its light weight (the apparent density is generally 300-800kg/m3) and porosity, air-entrained concrete has excellent properties such as heat preservation, shock resistance, sound absorption, fire resistance, and easy processing. . Under the background of vigorously promoting green buildings and energy-saving building materials in the country, it has been widely used in the engineering field as a new type of building material. The raw materials for traditional air-entrained concrete preparation include cementitious materials, admixtures or aggregates, and special admixtures. Adding chemical air-generating agents to the mixed slurry produces air bubbles, and the volume of the slurry expands. As the hydration reaction of the slurry proceeds , air bubbles are retained in the hardened slurry, and the green body forms a porous structure. According to the curing method, it can be divided into autoclaved curing and autoclaved curing. At present, the most widely used curing method is autoclaved curing. Autoclaved curing is generally performed in a cement autoclave at 180°C-200°C for 8-15h. The aerated concrete blocks produced by this curing method have a faster strength development speed. The curing temperature of non-autoclaved curing is lower than 100°C, and the curing time is generally longer. Compared with high-energy-consuming autoclaved curing, non-autoclaved curing is safe, low in cost, and has a good application prospect.

Invention patent (CN 111807807A) discloses a non-autoclaved light-weight thermal insulation granular aerated concrete block and its preparation method. Lightweight particle aerated concrete is made by compounding cement, fly ash, slag powder, lightweight particles, foaming agent, coagulant, foam stabilizer, water reducing agent, water repellent, fiber and water. After the foaming of the slurry is completed, the surface of the sample is covered with a thin plastic film to prevent water evaporation, and it is cured for 24 hours at a temperature of 18-22°C, the mold is removed, and it is placed in a standard curing box for 26-30 days. The aerated concrete block with light weight, good thermal insulation performance, strong durability, good waterproof performance, simple process and easy preparation has been obtained.

Common disadvantages in the existing autoclaved-free aerated concrete preparation methods include: 1. The long curing period limits its wide application. Unlike the rapid formation of a large amount of calcium silicate hydrate gel and minerals with high crystallinity such as tobermullite and hydrogarnet during the autoclaving process, the autoclaved air-entrained concrete often requires longer curing time (3- 28 days) to form enough hydration products to provide strength. In actual production, the cost problem caused by the long production cycle limits its wide application. 2. The amount of cement is high, and industrial solid waste cannot be used as raw materials in large quantities, and the production cost is relatively high. 3. The carbon emission in the production process is large, and it does not have a high carbon sequestration function. The firing process of cement, the main raw material of concrete, produces a large amount of CO2 emissions.

Contents of the invention

The purpose of the present invention is to provide a high-carbon-fixed autoclaved aerated concrete and its preparation method to solve the technical problems in the background technology. High-solid carbon-free autoclaved aerated concrete can absorb a large amount of carbon dioxide during production and use, and absorb a large amount of solid waste such as steel slag; at the same time, through the synergistic effect of "front-end hydration-carbonation curing-subsequent hydration" to prepare lightweight and high-strength concrete Autoclaved aerated concrete shortens its production cycle and reduces production costs. High carbon-fixed non-autoclaved aerated concrete has the advantages of efficiently absorbing CO2 in cement kiln tail gas, eliminating solid waste, short production cycle, low cost, light weight and high strength.

The mineralization of steel slag can improve the early strength of steel slag, solve the problem of volume expansion of building materials prepared by hydration of steel slag, greatly improve the utilization rate of steel slag, and shorten the maintenance cycle. At the same time, absorbing carbon dioxide in industrial waste gas can also be used in To a certain extent, it alleviates the greenhouse effect and has certain economic, environmental and social benefits. The oxides of calcium, magnesium and ferrous iron in solid waste such as steel slag can participate in the carbonization reaction, and the content of calcium oxide accounts for 35%-55%. On the one hand, substances containing calcium, magnesium and divalent iron react with carbon dioxide to form microcrystalline calcite (calcium carbonate), dolomite, iron dolomite and siderite, etc., and on the other hand, they can easily react with water to form C-S-H condensation. Hydration products such as glue and ettringite. Both effects can promote the growth of the strength of the prepared product.

In order to achieve the above object, the technical scheme adopted in the present invention is as follows:

A high-carbon-fixed autoclaved aerated concrete, comprising the following components in parts by mass: 15-50 parts of cement, 20-55 parts of steel slag, 10-30 parts of slag, 5-15 parts of lime, and 0-5 parts of gypsum , 20-60 parts of water, 0.1-0.4 parts of foaming agent, 0-0.5 parts of water reducing agent, 1-4 parts of stimulating agent, and 0.02-0.5 parts of foam stabilizer.

Further, the cement is Portland cement with a strength not lower than 42.5 grade, the steel slag is steel slag powder with a specific surface area not lower than 350m2/kg, and the slag is slag powder with a specific surface area not lower than 350m2/kg.

Further, the lime is quicklime, the gypsum is desulfurized gypsum, and the water reducer is one or more of polycarboxylate high-efficiency water-reducers, naphthalene-based high-efficiency water-reducers, and sulfamate water-reducers.

Further, the foaming agent is aluminum powder paste, and the activator is water glass with a modulus of 1-2.

Further, the foam stabilizer is one or more of soluble oil, cellulose ether, and polyvinyl alcohol.

A preparation method of high carbon-fixed autoclaved aerated concrete, said method comprising the steps of:

Step 1: Brush the mold with release oil;

Step 2: Weigh cement, steel slag, slag, lime, gypsum and other powders in proportion, mix them evenly, then add water reducer, activator and water and stir at low speed for 5 minutes;

Step 3: Add the remaining water and foam stabilizer to the weighed foaming agent, and pour the foaming agent suspension into the stirring pot and stir quickly for 30-60s;

Step 4: Pour the slurry into the mold, stop in a steam curing box at 40-60°C for 4-8 hours, then cut off the bread head and remove the mold;

Step 5: Pressure swing mineralization maintenance: Send the cut green body to a carbonization curing kettle filled with a CO2 volume concentration of 25-99%, the first 0-2h, the pressure is 0.001-0.05MPa, the second-4h, the pressure is 0.1- 0.3 MPa;

Step 6: Post-curing: after the carbonization curing of the green body, move it to a standard curing room, and maintain it for 1-3 days at a temperature of 20°C and a relative humidity above 90%.

The hydration products after block pre-curing are mainly C-S-H gel and ettringite, and the amount of ettringite and C-S-H gel in the hydration product increases significantly after being stimulated by the admixture. With the pre-curing temperature, more Hydration products are the key to the early strength of blocks. CO2 mineralization maintenance requires a certain degree of plasticity in the cell wall of foam concrete, so the early strength should not be too high. Steel slag and slag itself have hydraulic and gelling properties, which can enhance the strength of blocks. Calcium hydroxide is formed by quicklime during the digestion process to release heat, which is beneficial to the gasification of aluminum powder, and at the same time supplements a certain amount of calcium material, which is beneficial to the subsequent carbonization reaction. The activator can destroy the vitreous structure in the steel slag and improve its hydration activity. The foam stabilizer can maintain the stability of the air bubbles in the slurry, making the cell walls tough and more uniform in shape.

The present invention has the following beneficial effects due to the adoption of the above technical solution:

The invention uses bulk solid waste steel slag and slag as main raw materials, which is beneficial to the resource utilization of industrial waste residue, reduces the amount of cement in autoclaved aerated concrete, effectively reduces the production cost of autoclaved aerated concrete, and adopts pressure swing curing technology, which is conducive to deep mineralization reaction, can directly absorb a large amount of CO ₂ , and the amount of carbon fixation is greater than 15% of its own mass. It is an effective way to utilize carbon and greatly shortens the production cycle of autoclaved aerated concrete. Aerated concrete products with qualified strength can be produced in a short period of time.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, preferred embodiments are given below to further describe the present invention in detail. However, it should be noted that many of the details listed in the specification are only for readers to have a thorough understanding of one or more aspects of the present invention, and these aspects of the present invention can be implemented even without these specific details.

Comparative Example 1: A method for preparing an autoclaved carbon-fixing aerated concrete based on the hydration-mineralization synergistic effect, including the following components in parts by mass: 15 parts of cement, 55 parts of steel slag, 15 parts of slag, and 10 parts of quicklime 5 parts of gypsum, 20 parts of water, 0.4 part of aluminum powder paste, 0.5 part of polycarboxylate superplasticizer, 1 part of water glass with a modulus of 1, and 0.1 part of polyvinyl alcohol foam stabilizer.

1) The preparation method comprises the steps:

2) Brush the mold with release oil;

3) Weigh cement, steel slag, slag, lime, gypsum and other powder materials in proportion, mix them evenly, then add water reducer, activator and water and stir at low speed for 5 minutes;

4) Add the remaining water and foam stabilizer to the weighed foaming agent, and pour the foaming agent suspension into the stirring pot and stir rapidly for 60 seconds;

5) Pour the slurry into the mold, stop in a steam curing box at 55°C for 4 hours, then cut off the bread head and remove the mold;

6) Curing at room temperature: the body is placed in a natural curing room, and cured for 3 days at a temperature of 20°C and a relative humidity of 90% or more.

The measured bulk density of the block is 599kg/m3, the compressive strength is 2.9MPa, and the carbon fixation capacity is 2.57%.

Comparative Example 2: A method for preparing an autoclaved carbon-fixing aerated concrete based on the hydration-mineralization synergistic effect, including the following components in parts by mass: 40 parts of cement, 20 parts of steel slag, 30 parts of slag, and 7.5 parts of quicklime 2.5 parts of gypsum, 40 parts of water, 0.15 parts of aluminum powder paste, 0.25 parts of water reducer, 2 parts of water glass with a modulus of 1.5, and 0.02 parts of soluble oil foam stabilizer.

1) The preparation method comprises the steps:

2) Brush the mold with release oil;

3) Weigh cement, steel slag, slag, lime, gypsum and other powder materials in proportion, mix them evenly, then add water reducer, activator and water and stir at low speed for 5 minutes;

4) Add the remaining water and foam stabilizer to the weighed foaming agent, and pour the foaming agent suspension into the stirring pot and stir rapidly for 60 seconds;

5) Pour the slurry into the mold, stop in a steam curing box at 55°C for 4 hours, then cut off the bread head and remove the mold;

6) Pressure swing carbonization curing: Send the cut body to a carbonization curing kettle with a CO2 volume concentration of 25%, the pressure is 0.02MPa for the 0-2h, and 0.2MPa for the 2-4h.

The measured bulk density of the block is 730kg/m3, the compressive strength is 4.1MPa, and the carbon fixation capacity is 15.9%.

Comparative example 3: A method for preparing an autoclaved carbon fixation type aerated concrete based on the synergistic effect of hydration-mineralization, including the following components in parts by mass: 50 parts of cement, 30 parts of steel slag, 5 parts of slag, and 15 parts of quicklime 60 parts of water, 0.1 part of water reducing agent, 0.4 part of aluminum powder paste, 1.4 parts of water glass with a modulus of 2, and 0.5 part of cellulose ether foam stabilizer.

7) The preparation method comprises the steps of:

8) Brush the mold with release oil;

9) Weigh cement, steel slag, slag, lime, gypsum and other powder materials in proportion, mix them evenly, then add water reducer, activator and water and stir at low speed for 5 minutes;

10) Add the remaining water and foam stabilizer to the weighed foaming agent, and pour the foaming agent suspension into the stirring pot and stir rapidly for 30s;

11) Pour the slurry into the mold, stop for 8 hours in a steam curing box at 55°C, and then cut off the bread head and remove the mold;

12) Ordinary carbonization curing: Send the cut body to a carbonization curing kettle with a CO2 volume concentration of 99%, and carbonize it at a pressure of 0.2 MPa for 2 hours.

13) Post-curing: the green body is moved to a natural curing room, and cured for 3 days at a temperature of 20°C and a relative humidity of more than 90%.

The measured bulk density of the block is 690kg/m3, the compressive strength is 3.2MPa, and the carbon fixation capacity is 10.2%.

Example 1: A method for preparing an autoclave-free carbon fixation type aerated concrete based on the hydration-mineralization synergistic effect, including the following components in parts by mass: 15 parts of cement, 55 parts of steel slag, 15 parts of slag, and 10 parts of quicklime 5 parts of gypsum, 20 parts of water, 0.4 part of aluminum powder paste, 0.5 part of water reducer, 1 part of water glass with a modulus of 1, and 0.1 part of polyvinyl alcohol foam stabilizer.

1) The preparation method comprises the steps:

2) Brush the mold with release oil;

3) Weigh cement, steel slag, slag, lime, gypsum and other powder materials in proportion, mix them evenly, then add water reducer, activator and water and stir at low speed for 5 minutes;

4) Add the remaining water and foam stabilizer to the weighed foaming agent, and pour the foaming agent suspension into the stirring pot and stir rapidly for 60 seconds;

5) Pour the slurry into the mold, stop in a steam curing box at 55°C for 4 hours, then cut off the bread head and remove the mold;

6) Pressure swing carbonization curing: Send the cut body to a carbonization curing kettle with a CO2 volume concentration of 25%. The pressure is 0.01 MPa for the first 0-2 hours, and the pressure is 0.1 MPa for the first 2-4 hours.

7) Post-curing: After the carbonization and curing of the green body, the green body is moved to a natural curing room, and cured for 3 days at a temperature of 20°C and a relative humidity of 90% or more.

The measured bulk density of the block is 648kg/m3, the compressive strength is 3.9MPa, and the carbon fixation capacity is 15.1%.

Example 2: A method for preparing a non-autoclaved carbon fixation type aerated concrete based on the hydration-mineralization synergistic effect, including the following components in parts by mass: 40 parts of cement, 20 parts of steel slag, 30 parts of slag, and 7.5 parts of quicklime 2.5 parts of gypsum, 40 parts of water, 0.15 parts of aluminum powder paste, 0.25 parts of water reducer, 2 parts of water glass with a modulus of 1.5, and 0.02 parts of soluble oil foam stabilizer.

The preparation method comprises the following steps:

1) Brush the mold with release oil;

2) Weigh cement, steel slag, slag, lime, gypsum and other powder materials in proportion, mix them evenly, then add water reducer, activator and water and stir at low speed for 5 minutes;

3) Add the remaining water and foam stabilizer to the weighed foaming agent, and pour the foaming agent suspension into the stirring pot and stir rapidly for 30s;

4) Pour the slurry into the mold, stop in a steam curing box at 40°C for 4 hours, then cut off the bread head and remove the mold;

5) Pressure swing carbonization curing: Send the cut body to a carbonization curing kettle with a CO2 volume concentration of 75%. The pressure is 0.05 MPa for the first 0-2 hours, and the pressure is 0.3 MPa for the first 2-4 hours.

8) Post-curing: After the carbonization and curing of the green body, it is moved to a natural curing room and cured for 1 day under the conditions of a temperature of 20°C and a relative humidity of more than 90%.

The measured bulk density of the block is 735kg/m3, the compressive strength is 5.0MPa, and the carbon fixation capacity is 16.2%.

Example 3: A method for preparing an autoclave-free carbon fixation aerated concrete based on the hydration-mineralization synergistic effect, including the following components in parts by mass: 50 parts of cement, 30 parts of steel slag, 5 parts of slag, and 15 parts of quicklime 60 parts of water, 0.1 part of water reducing agent, 0.4 part of aluminum powder paste, 1.4 parts of water glass with a modulus of 2, and 0.5 part of cellulose ether foam stabilizer.

The preparation method comprises the following steps:

1) Brush the mold with release oil;

2) Weigh cement, steel slag, slag, lime, gypsum and other powder materials in proportion, mix them evenly, then add water reducer, activator and water and stir at low speed for 5 minutes;

3) Add the remaining water and foam stabilizer to the weighed foaming agent, and pour the foaming agent suspension into the stirring pot and stir rapidly for 30s;

4) Pour the slurry into the mold, stop in a steam curing box at 55°C for 8 hours, then cut off the bread head and remove the mold;

5) Pressure swing carbonization curing: Send the cut body to a carbonization curing kettle with a CO2 volume concentration of 99%. The pressure is 0.02 MPa for the first 0-2 hours, and the pressure is 0.2 MPa for the first 2-4 hours.

6) Post-curing: After the carbonization curing of the green body, the green body is moved to a natural curing room and cured for 3 days at a temperature of 20°C and a relative humidity of 90% or more.

The measured bulk density of the block is 650kg/m3, the compressive strength is 4.0MPa, and the carbon fixation capacity is 15.6%.

From Comparative Example 1 and Example 1, it can be seen that there is no _CO2 intervention in the curing process, only hydration provides strength, and the strength of air-entrained concrete is lower than 3.5MPa, and there is no carbon fixation effect. Mineralization maintenance is necessary to improve strength and carbon sequestration.

It can be seen from Comparative Example 2 and Example 2 that the synergistic effect of mineralization curing and post-curing is beneficial to increase the strength of air-entrained concrete.

From Comparative Example 3 and Example 3, it can be known that pressure swing mineralization curing is beneficial to improve the strength and carbon fixation of aerated concrete.

In summary, the method for preparing autoclaved carbon-fixation-free aerated concrete based on the hydration-mineralization synergistic effect described in this invention can be used to produce high-carbon-fixed non-autoclaved aerated concrete, which has the ability to efficiently absorb cement kiln tailings The CO2 in the flue gas, the absorption of solid waste, the advantages of short production cycle, low cost, light weight and high strength.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications should also be It is regarded as the protection scope of the present invention.

Claims (6)

1. A high-carbon-fixed autoclaved aerated concrete, characterized in that: it comprises the following components by mass: 15-50 parts of cement, 20-55 parts of steel slag, 10-30 parts of slag, and 5-15 parts of lime , 0-5 parts of gypsum, 20-60 parts of water, 0.1-0.4 parts of foaming agent, 0-0.5 parts of water reducing agent, 1-4 parts of activator, and 0.02-0.5 parts of foam stabilizer. 2. A kind of high-carbon-fixed autoclaved aerated concrete according to claim 1, characterized in that: the cement is Portland cement with a strength not lower than 42.5 grades, and the steel slag has a specific surface area not lower than 350m2/kg Steel slag powder, slag is slag powder with a specific surface area not less than 350m2/kg. 3. A kind of high carbon-fixed autoclaved aerated concrete according to claim 1, characterized in that: the lime is quicklime, the gypsum is desulfurized gypsum, and the water reducer is polycarboxylic acid high-efficiency water reducer, naphthalene series high-efficiency water reducer One or more of water agent and sulfamate superplasticizer. 4. A kind of high-carbon-solid-free autoclaved aerated concrete according to claim 1, characterized in that: the foaming agent is aluminum powder paste, and the activator is water glass with a modulus of 1-2. 5. A kind of high-carbon-free autoclaved aerated concrete according to claim 1, characterized in that: the foam stabilizer is one or more of soluble oil, cellulose ether, and polyvinyl alcohol. 6. According to any one of claims 1-5, a method for preparing high-carbon-free autoclaved aerated concrete, characterized in that: said method comprises the steps of: Step 1: Brush the mold with release oil; Step 2: Weigh cement, steel slag, slag, lime, gypsum and other powders in proportion, mix them evenly, then add water reducer, activator and water and stir at low speed for 5 minutes; Step 3: Add the remaining water and foam stabilizer to the weighed foaming agent, and pour the foaming agent suspension into the stirring pot and stir quickly for 30-60s; Step 4: Pour the slurry into the mold, stop in a steam curing box at 40-60°C for 4-8 hours, then cut off the bread head and remove the mold; Step 5: Pressure swing mineralization maintenance: Send the cut green body to a carbonization curing kettle filled with a CO2 volume concentration of 25-99%, the first 0-2h, the pressure is 0.001-0.05MPa, the second-4h, the pressure is 0.1- 0.3 MPa; Step 6: Post-curing: after the carbonization curing of the green body, move it to a standard curing room, and maintain it for 1-3 days at a temperature of 20°C and a relative humidity above 90%.