An ultra-stable CO2 foam concrete, a preparation method and application thereof

Abstract

The application discloses a kind of super-stable CO2 foam concrete, its preparation method and application, belong to building material technical field.The preparation method of the CO2 foam concrete is as follows: foaming agent is mixed with nano foam stabilizer, then the mixture is dissolved in calcium hydroxide solution to prepare foaming liquid;Red mud, lime and deionized water are mixed and stirred uniformly, then slag powder, cement and fly ash are sequentially added, stirred uniformly to obtain red mud mixture;Foam is prepared using foaming liquid, then the foam is introduced into the red mud mixture to obtain CO2 foam concrete.In the present application, the reaction product of calcium hydroxide solution and CO2 bubbles can significantly improve the stability of CO2 foam, and red mud and lime can adjust the setting and hardening rate of the matrix, so that the stability reduction of CO2 foam and the solidification enhancement of the cementitious material matrix finally reach a dynamic balance, significantly improving the stability, strength and thermal insulation performance of CO2 foam concrete.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to an ultra-stable CO2 foam concrete, its preparation method and application. Background Technology

[0002] In recent years, under the strategic goal of "dual carbon" (carbon reduction and emission reduction), developing green and low-carbon concrete materials has become an inevitable choice for developing a low-carbon economy. Foamed concrete not only possesses advantages such as lightweight, high strength, waterproofing, fire resistance, low cost, and material saving, but also has enormous CO2 absorption potential, promising to achieve "carbon-negative" concrete production and is widely used for filling goaf areas in mines. Furthermore, compared to air, foamed concrete prepared using CO2 as the foaming gas exhibits superior thermal insulation properties, capable of blocking heat transfer from rock masses as an insulation layer, showing broad development and application prospects in the control of heat hazards in high-temperature mines. However, the high solubility of CO2 and the acidity of its aqueous solution lead to poor stability of CO2 foamed concrete, causing rapid defoaming before the cementitious material sets and hardens. Therefore, improving the stability, strength, and thermal insulation properties of CO2 foamed concrete is of great significance for promoting its application. Summary of the Invention

[0003] In view of the shortcomings of the existing technology, the purpose of this invention is to solve the problem of poor stability of CO2 foamed concrete, and at the same time endow foamed concrete with excellent strength and thermal insulation properties.

[0004] The technical solution of the present invention is as follows:

[0005] This invention provides a method for preparing CO2 foamed concrete, comprising the following steps:

[0006] A foaming agent and a nano foam stabilizer are mixed, and then the mixture is dissolved in a calcium hydroxide solution to prepare a foaming liquid. Red mud, lime and deionized water are mixed and stirred evenly, and then slag powder, cement and fly ash are added in sequence and stirred evenly to obtain a red mud mixture. Foam is prepared using the foaming liquid, and then the foam is introduced into the red mud mixture to obtain CO2 foamed concrete.

[0007] In the above method for preparing CO2 foamed concrete, the mass fractions of each component are as follows:

[0008] 400-500 parts slag powder, 50-100 parts fly ash, 50-100 parts cement, 100-300 parts red mud, 60-100 parts lime, 2-4 parts foaming agent, 0.1-0.2 parts nano foam stabilizer, 600-1200 parts calcium hydroxide solution, and 330-550 parts deionized water.

[0009] In the above method for preparing CO2 foamed concrete, the red mud is selected from Bayer process red mud, and its pH value is 12-13.

[0010] In the above-mentioned method for preparing CO2 foamed concrete, the foaming agent is selected from one or more of the following: synthetic surfactants with carboxyl groups as hydrophilic groups and hydroxyl groups as hydrophobic groups, rosin soap, and sulfonic acid surfactants.

[0011] In the above-mentioned method for preparing CO2 foamed concrete, the nano-foam stabilizer is selected from one or more of nano-alumina, nano-silica, and nano-zinc oxide.

[0012] In the above method for preparing CO2 foamed concrete, the pH of the calcium hydroxide solution is selected from 9 to 11.

[0013] In the above-mentioned method for preparing CO2 foamed concrete, the foam preparation method is as follows: connecting a CO2 foaming gas cylinder to a foaming machine, and placing the foaming liquid in the foaming machine to prepare foam; wherein, the volume fraction of CO2 in the CO2 foaming gas is selected from 40% to 100%; preferably 40%, 60%, 80% or 100%.

[0014] The present invention provides CO2 foamed concrete prepared by the above method.

[0015] This invention provides the application of the above-mentioned CO2 foamed concrete in filling goaf areas in mines and controlling heat hazards in high-temperature mines.

[0016] The beneficial effects of this invention are as follows:

[0017] The high solubility of CO2 and its acidic nature when dissolved in water result in poor stability of CO2 foamed concrete, leading to rapid defoaming before the cementitious materials harden. The fundamental reason for this poor stability lies in the rapid decrease in surface tension of CO2 bubbles, while the cementitious materials solidify slowly, resulting in a slow increase in bubble confinement force and subsequent defoaming. This invention uses calcium hydroxide solution instead of water as the foaming agent to prepare CO2 foam. The reaction products (CaCO3 particles) between the calcium hydroxide solution and CO2 bubbles can be adsorbed onto the foam walls, significantly improving the stability of the CO2 foam. Furthermore, this invention uses red mud and lime to activate the cementitious matrix, including slag powder, fly ash, and cement, to regulate the setting and hardening rate of the matrix. Ultimately, this achieves a dynamic balance between the decrease in CO2 foam stability and the strengthening of the cementitious matrix, significantly improving the stability, strength, and thermal insulation performance of the CO2 foamed concrete. Detailed Implementation

[0018] The materials used in this invention are as follows:

[0019] The red mud used is Bayer process red mud with a pH value of 12-13, sourced from Chinalco Shanxi Branch.

[0020] The foaming agent can be selected from one or more combinations of synthetic surfactants with carboxyl groups as hydrophilic groups and hydroxyl groups as hydrophobic groups, rosin soap, and sulfonic acid surfactants; in the following embodiments of the present invention, the foaming agent was purchased from Zhenjiang Yifa New Material Technology Co., Ltd.

[0021] The slag powder conforms to grade S95 as specified in GB / T18046-2017 "Granulated Blast Furnace Slag Powder for Cement, Mortar and Concrete".

[0022] The fly ash conforms to the Class I fly ash specified in GB / T1596-2017 "Fly Ash for Cement and Concrete".

[0023] The cement is PO 42.5 cement.

[0024] Other materials used in this invention, unless otherwise stated, are commercially available. Other terms used in this invention, unless otherwise specified, generally have the meanings commonly understood by those skilled in the art. The invention is further described in detail below with reference to specific embodiments and data. The following embodiments are merely illustrative and not intended to limit the scope of the invention in any way.

[0025] Example 1

[0026] Preparation of CO2 foamed concrete:

[0027] The formula components are as follows:

[0028] 500 parts slag powder, 50 parts fly ash, 50 parts cement, 100 parts red mud, 100 parts lime, 2 parts foaming agent, 0.1 parts nano alumina, 600 parts calcium hydroxide solution (pH 12), and 400 parts deionized water.

[0029] The preparation method is as follows:

[0030] A foaming agent is mixed with nano-alumina, and then the mixture is dissolved in a calcium hydroxide solution to prepare a foaming liquid. Red mud, lime and deionized water are mixed and stirred evenly, and then slag powder, cement and fly ash are added in sequence and stirred evenly. A carbon dioxide gas cylinder is connected to a foaming machine (the volume fraction of carbon dioxide foaming gas is 100%), and the foaming liquid is placed in the foaming machine to prepare foam. Then the foam is introduced into the above red mud mixture to obtain CO2 foamed concrete.

[0031] Example 2

[0032] Preparation of CO2 foamed concrete:

[0033] The formula components are as follows:

[0034] 500 parts slag powder, 50 parts fly ash, 50 parts cement, 100 parts red mud, 100 parts lime, 2 parts foaming agent, 0.1 parts nano alumina, 600 parts calcium hydroxide solution (pH 10), and 400 parts deionized water.

[0035] The preparation method is as follows:

[0036] A foaming agent is mixed with nano-alumina, and then the mixture is dissolved in a calcium hydroxide solution to prepare a foaming liquid. Red mud, lime and deionized water are mixed and stirred evenly, and then slag powder, cement and fly ash are added in sequence and stirred evenly. A carbon dioxide gas cylinder is connected to a foaming machine (the volume fraction of carbon dioxide foaming gas is 100%), and the foaming liquid is placed in the foaming machine to prepare foam. Then the foam is introduced into the above red mud mixture to obtain CO2 foamed concrete.

[0037] Example 3

[0038] Preparation of CO2 foamed concrete:

[0039] The formula components are as follows:

[0040] 500 parts slag powder, 50 parts fly ash, 50 parts cement, 200 parts red mud, 100 parts lime, 2 parts foaming agent, 0.1 parts nano alumina, 600 parts calcium hydroxide solution (pH 10), and 400 parts deionized water.

[0041] The preparation method is as follows:

[0042] A foaming agent is mixed with nano-alumina, and then the mixture is dissolved in a calcium hydroxide solution to prepare a foaming liquid. Red mud, lime and deionized water are mixed and stirred evenly, and then slag powder, cement and fly ash are added in sequence and stirred evenly. A carbon dioxide gas cylinder is connected to a foaming machine (the volume fraction of carbon dioxide foaming gas is 100%), and the foaming liquid is placed in the foaming machine to prepare foam. Then the foam is introduced into the above red mud mixture to obtain CO2 foamed concrete.

[0043] Comparative Example 1

[0044] Preparation of CO2 foamed concrete:

[0045] The formula components are as follows:

[0046] 500 parts slag powder, 50 parts fly ash, 50 parts cement, 100 parts red mud, 2 parts foaming agent, 0.1 parts nano alumina, and 600+350 parts deionized water.

[0047] The preparation method is as follows:

[0048] The foaming agent is mixed with nano-alumina, and then the mixture is dissolved in deionized water (600 parts) to prepare the foaming liquid; red mud is mixed with deionized water (350 parts) and stirred evenly, and then slag powder, cement and fly ash are added in sequence and stirred evenly; a carbon dioxide gas cylinder is connected to a foaming machine (the volume fraction of carbon dioxide foaming gas is 100%), the foaming liquid is placed in the foaming machine to prepare foam, and then the foam is introduced into the above red mud mixture to obtain CO2 foamed concrete.

[0049] Comparative Example 2

[0050] Preparation of CO2 foamed concrete:

[0051] The formula components are as follows:

[0052] 500 parts slag powder, 50 parts fly ash, 50 parts cement, 100 parts red mud, 100 parts lime, 2 parts foaming agent, 0.1 parts nano alumina, and 600+400 parts deionized water.

[0053] The preparation method is as follows:

[0054] The foaming agent is mixed with nano-alumina, and then the mixture is dissolved in deionized water (600 parts) to prepare the foaming liquid; red mud, lime and deionized water (400 parts) are mixed and stirred evenly, and then slag powder, cement and fly ash are added in sequence and stirred evenly; a carbon dioxide cylinder is connected to a foaming machine (the volume fraction of carbon dioxide foaming gas is 100%), the foaming liquid is placed in the foaming machine to prepare foam, and then the foam is introduced into the above red mud mixture to obtain CO2 foamed concrete.

[0055] I. Performance Testing

[0056] The performance of CO2 foamed concrete in the above implementation cases was determined. The test items included the oven-dry density, settlement value, compressive strength, and thermal conductivity of CO2 foamed concrete. Among them, the test methods for oven-dry density and 28-day compressive strength are as described in JG / T266-2011 "Foamed Concrete"; the determination of thermal conductivity is as described in GB / T10294 "Determination of Steady-State Thermal Resistance and Related Properties of Insulation Materials - Protective Hot Plate Method"; the settlement value can reflect the stability of foamed concrete, and its test method is as described in the literature [Cementand Concrete Research, 138(2020)106233.]. The test results are shown in Table 1:

[0057] Table 1

[0058] Testing items Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 <![CDATA[Absolute dry density / kg / m 3 > 614 618 624 607 613 Settlement value / mm 2.03 1.25 1.03 2.67 2.54 Compressive strength / MPa 2.24 2.87 3.12 1.98 2.03 Thermal conductivity / W / (m·K) 0.0623 0.0545 0.0513 0.0652 0.0642

[0059] As shown in Table 1, the settlement of the foamed concrete in Example 2 was significantly lower than that in Comparative Example 1, Comparative Example 2, and Example 1, indicating that the stability of the foamed concrete was significantly improved when using a calcium hydroxide solution with a pH of 10 as the foaming liquid. The settlement of the foamed concrete in Example 3 was further reduced compared to Example 2, indicating that using red mud to adjust the setting and hardening rate of the matrix could further improve the foam stability. The foamed concrete prepared in Examples 2 and 3 exhibited excellent stability, strength, and thermal insulation properties. Comparative Example 1, without the addition of lime and calcium hydroxide solution, produced foamed concrete with poor stability, low strength, and high thermal conductivity. The addition of lime to Comparative Example 2 improved the stability, strength, and thermal conductivity of the foamed concrete to some extent. Example 1, based on Comparative Example 2, added a calcium hydroxide solution with a pH of 12 as a foaming liquid, but the improvement in the stability, strength, and thermal conductivity of the foamed concrete was not significant. However, Example 2, based on Example 1, added a calcium hydroxide solution with a pH of 10 as a foaming liquid, and the stability, strength, and thermal conductivity of the foamed concrete were significantly improved. This shows that the pH of the foaming liquid significantly affects the various properties of the foamed concrete.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method of making a CO2 foam concrete, characterized in that, The steps are as follows: 2 parts of foaming agent are mixed with 0.1 part of nano-stable foaming agent, and then the mixture is dissolved in 600 parts of calcium hydroxide solution with pH of 10 to prepare a foaming liquid; 200 parts of red mud, 100 parts of lime and 400 parts of deionized water are mixed and stirred uniformly, and then 500 parts of slag powder, 50 parts of cement and 50 parts of fly ash are added in sequence and stirred uniformly to obtain a red mud mixture; a foam is prepared by using the foaming liquid, and then the foam is introduced into the red mud mixture to obtain CO2 foam concrete; The preparation method of the foam is as follows: a CO2 foaming gas cylinder is connected to a foaming machine, and the foaming liquid is placed in the foaming machine to prepare the foam; the volume fraction of CO2 in the CO2 foaming gas is 100%.

2. The production method according to claim 1, characterized by, The red mud is selected from Bayer process red mud, and the pH value is 12-13.

3. The preparation method according to claim 1, characterized in that, The foaming agent is selected from one or more of a synthetic surfactant with carboxyl as a hydrophilic group and hydroxyl as a hydrophobic group, rosin soap and a sulfonic acid-based surfactant.

4. The production method according to claim 1, characterized by, The nano-stable foaming agent is selected from one or more of nano-alumina, nano-silicon oxide and nano-zinc oxide.

5. CO2 foam concrete prepared by the method of any one of claims 1-4.

6. Application of the CO2 foam concrete of claim 5 in mine goaf filling and high-temperature mine heat hazard treatment.