A method for preparing a red mud-based foam concrete

Abstract

The application relates to the technical field of building materials, and discloses a preparation method of a red mud-based foam concrete, which comprises the following steps: adjusting the water content of red mud; adding sawdust and stirring; then adding lime powder and stirring; then introducing industrial waste gas; then immersing ceramic sand particles in the mixture; mixing water and cement uniformly, adding a foaming agent to foam, and obtaining a foaming liquid; adding cement clinker, limestone powder, gypsum whiskers and auxiliary cementing materials into the mixture liquid in which the ceramic sand particles are immersed, and stirring uniformly; then adding the foaming liquid into the mixture liquid, and continuing to stir, so that the red mud-based foam concrete is obtained. In the application, the red mud is used in a wet state, the water in the red mud is fully utilized, and the red mud is prevented from being dried; lime powder is added into the red mud, and industrial waste gas containing a large amount of CO2, SO2, NO X , etc. is introduced, so that calcium carbonate, calcium sulfate, calcium nitrate and other nano particles are formed on the surface of red mud particles, and the activity of the red mud is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, in particular to a preparation method of red mud-based foam concrete. BACKGROUND

[0002] Red mud is a waste produced in the process of extracting alumina from bauxite, and is named because of its reddish-brown mud-like appearance. About 0.5-2.5 tons of red mud are produced for every ton of alumina produced, and each ton of red mud is accompanied by 3-4 cubic meters of alkaline waste liquid. With the continuous development of bauxite industry, the annual discharge of red mud in China is more than 15 million tons. Red mud can be divided into sintering method, Bayer method and combined method red mud according to different alumina production methods. Due to the different abundance of bauxite content, different methods are adopted for alumina production at home and abroad. The yield of Bayer method accounts for more than 90% of the world's total yield.

[0003] The red mud produced by the Bayer method is rich in Fe(OH)3gel and Al(OH)3gel, which makes the red mud have strong water retention and is not easy to dry, and the dehydration energy consumption is large. In addition, the red mud has high alkalinity, and the pH value of the red mud filtrate is usually 12-14, far exceeding the national discharge standard, which brings great harm to the environment. The high content of alkaline leachate in red mud and the low activity of red mud as a mineral admixture make it difficult to utilize red mud as a building material.

[0004] At present, the application of red mud in concrete is mainly as a mineral admixture, and the activity is improved mainly by means of acidification, thermal activation, physical activation, alkali activation and other means, but the energy consumption is high, and the high alkaline leachate in red mud is mainly used to activate the activity of other mineral admixtures. The preparation of foam concrete from red mud is one of the methods for utilizing red mud.

[0005] Patent 201710279623.0 discloses a geopolymer foam concrete and a preparation method thereof, which is composed of steel slag powder, modified red mud, modified metakaolin, fly ash, ground slag powder, red mud filtrate and foaming agent. The red mud is a red mud after pressure filtration, and the red mud filtrate is used as an activator.

[0006] Patent 201810642800.1 discloses a red mud foam concrete block and a preparation method thereof, which comprises cement, red mud, manganese dioxide, hydrogen peroxide, polycarboxylate high-performance water reducing agent, foam stabilizer, water, wherein the foam stabilizer comprises calcium stearate and peanut oil, and the red mud is dried at 100℃ and sieved through a 100 mesh sieve.

[0007] Patent 202110477218.6 discloses a red mud modified foam light soil and its preparation method and application, the weight ratio of each raw material is: red mud 25-50 parts, admixture 15-50 parts, fiber 0.3-2.5 parts, activator 1-30 parts, surfactant 0.3-1.0 parts, foaming agent 0.5-20 parts, water reducing agent 0.5-1.8 parts; the red mud has been activated at 500-900℃ high temperature.

[0008] 202210825851.4 discloses a preparation method of geopolymer foam concrete for filling cold-bent thin-walled steel, comprising the following steps: S1 preparing slurry: taking dry materials by weight parts, taking fly ash 18-22 parts, phosphoric acid based silico-aluminate powder 32-36 parts, sintered red mud 8-12 parts, slaked lime 6-9 parts and water glass 13-15 parts, the water-cement weight ratio of water to dry materials is 0.4-0.45, S2 preparing foam; S3 preparing geopolymer slurry; S4 casting; S5 curing.

[0009] Patent 202310328789.2 discloses an alkali-red mud activated foam concrete, its preparation method and application, which utilizes the alkaline leachate in red mud and cement, chemical activator, etc. to activate slag powder, red mud, fly ash and cement, and then utilizes foaming agent to prepare foamed concrete.

[0010] However, the above patents all perform dehydration treatment on red mud, which involves drying, high temperature activation and other links, and the energy consumption is high. The present application provides a preparation method of red mud-based foam concrete, which simultaneously utilizes the leachate in red mud and red mud, avoids the dehydration link during the use of red mud, reduces the energy consumption during the dehydration of red mud, improves the activity of red mud and improves the utilization rate of red mud. SUMMARY

[0011] The present application provides a preparation method of red mud-based foam concrete to solve the problems of high dehydration energy consumption and low activity of red mud during utilization.

[0012] Technical scheme: The present application provides a preparation method of red mud-based foam concrete, comprising the following steps:

[0013] S1. Adjusting the water content of red mud: mixing red mud with water to prepare a red mud solution with a certain water-solid ratio;

[0014] S2. Sawdust treatment: adding sawdust to the red mud solution and stirring;

[0015] S3. Introducing industrial waste gas: adding lime powder to the product obtained in S2 and stirring uniformly; then introducing industrial waste gas into it;

[0016] S4. Soaking ceramic sand particles: ceramic sand particles with a particle size less than 2 mm are selected and soaked in the product obtained in S3;

[0017] S5. Foaming: cement is added to water and stirred uniformly, and then a foaming agent is added to the mixture to foam;

[0018] S6. Preparing foam concrete: cement clinker, limestone powder, gypsum whiskers, and auxiliary cementitious materials are added to the product obtained in S4 and stirred uniformly; then the product obtained in S5 is added to the mixture and stirred uniformly, obtaining the red mud-based foam concrete.

[0019] Further, in S1, the water-solid ratio is 5:1 to 10:1.

[0020] Further, in S2, the mass of the sawdust is 5 to 15% of the mass of the red mud; the sawdust is powder-like wood that falls during wood processing.

[0021] Further, in S3, the mass of the lime powder is 1 to 10% of the mass of the red mud; the lime powder is one of slaked lime powder or quicklime powder.

[0022] Further, in S3, the industrial waste gas is one of coal, steel, and cement industrial waste gas.

[0023] Further, in S4, the mass of the ceramic sand is 0.5 to 0.8 times the mass of the red mud.

[0024] Further, in S4, the soaking time is 10 to 30 minutes.

[0025] Further, in S5, the mass ratio of the cement to water is 1 to 10:100; and the ratio of the foaming agent to water is 1:30 to 50.

[0026] Beneficial effects: Compared with the prior art, the beneficial effects of the present application are:

[0027] 1) According to the preparation method disclosed in the present application, when red mud is used to prepare cementitious materials, on the one hand, the water in the red mud is fully utilized by using the red mud in a wet state, and the drying of the red mud and the adsorption of Fe(OH)3 gel and Al(OH)3 gel in the red mud after drying are avoided, thereby avoiding the problem of difficulty in uniform dispersion due to the high viscosity of the red mud; on the other hand, by adding lime powder to the red mud and introducing industrial waste gas containing a large amount of CO2, SO2, NO XThe coal power, steel, and cement industry waste gas can be reacted with lime powder in the alkaline solution to generate calcium carbonate, calcium sulfate, and calcium nitrate, thereby solving the problem of industrial waste gas emission and reducing the alkalinity in the red mud slurry, and forming calcium carbonate, calcium sulfate, calcium nitrate, and other nanoparticles and whiskers on the surface of red mud particles, thereby improving the activity of the red mud.

[0028] 2) The Fe(OH)3 gel and Al(OH)3 gel contained in the red mud can improve the stability of the foam in the foam concrete.

[0029] 3) The powdered sawdust and sawdust generated in wood processing are stirred in the red mud leachate, the sawdust can adsorb the alkali liquor in the red mud leachate, and after the concrete hardens due to lack of water, the sawdust can release part of the alkali liquor to supplement the water for the concrete and stimulate the unreacted cement particles and mineral admixtures, thereby inhibiting the red mud from causing realkalization in the concrete; in addition, the sawdust is stirred in the alkaline leachate, and cellulose in the wood can be released, which can improve the slurry consistency and the stability of the foam concrete.

[0030] 4) The cement is dispersed and hydrated in water with a large water-cement ratio, and under the stirring action, the cement can be rapidly hydrated and form calcium silicate hydrate C-S-H, calcium hydroxide, ettringite, and other nanoparticles, and under this condition, the foam can be foamed, the foam can be nucleated and foamed at the above-mentioned nanoparticle sites, which is helpful to the dispersion and stability of the foam and reduces the damage rate of the foam.

[0031] 5) The ceramic sand is placed in the red mud leachate, the ceramic sand can adsorb part of the leachate, and after the concrete hardens due to lack of water, the ceramic sand can release part of the alkali liquor to supplement the water for the concrete and stimulate the unreacted cement particles and mineral admixtures, thereby inhibiting the red mud from causing realkalization in the concrete. DETAILED DESCRIPTION

[0032] The application will be described in detail below in conjunction with the embodiments.

[0033] Embodiment 1

[0034] A preparation method of red mud-based foam concrete, comprising the following steps:

[0035] S1. Adjusting the water content of the red mud: measuring the water content of the red mud to be 10%, and adjusting the water-solid ratio in the red mud solution to be 10:1;

[0036] S2. Sawdust treatment: adding 5 parts of sawdust to the solution obtained in S1 and stirring for 10 min; the above-mentioned sawdust is powdered wood generated in wood processing;

[0037] S3. Passing industrial waste gas: adding lime powder (1 part) with 1% of the mass of the red mud to the solution obtained in S2 and stirring uniformly; then passing industrial waste gas into it; the above industrial waste gas is coal power; the above lime powder is slaked lime powder;

[0038] S4. Soaking ceramic sand particles: selecting ceramic sand particles with a particle size of less than 2 mm and soaking them in the mixed solution obtained in S3 for 10 min, the mass of the ceramic sand being 0.5 times the mass of the red mud, 50 parts;

[0039] S5. Foaming: adding cement into water to make the mass ratio of cement to water 1:100 and stirring uniformly, then adding 10 parts of foaming agent to foam 30 times, wherein the cement and water are 3 parts and 300 parts respectively;

[0040] S6. Preparing foam concrete: adding 1000 parts of ordinary cement clinker, 160 parts of limestone powder, 54 parts of gypsum whisker and 345 parts of mineral powder into the mixed solution obtained in S4 and stirring uniformly, then adding the foam obtained in S5 and stirring uniformly.

[0041] Embodiment 2:

[0042] A method for preparing red mud-based foam concrete, comprising the following steps:

[0043] S1. Adjusting the water content of red mud: measuring the water content of red mud as 20%, and taking 200 parts of red mud (dry material) and adjusting the water-solid ratio in the red mud solution to 5:1;

[0044] S2. Sawdust treatment: adding 30 parts of sawdust into the solution obtained in S1 and stirring for 60 min; the above sawdust is powder-shaped wood falling during wood processing;

[0045] S3. Passing industrial waste gas: adding lime powder (20 parts) with 10% of the mass of the red mud into the solution obtained in S2 and stirring uniformly; then passing industrial waste gas into it; the above industrial waste gas is steel; the above lime powder is quicklime powder;

[0046] S4. Soaking ceramic sand particles: selecting ceramic sand particles with a particle size of less than 2 mm and soaking them in the mixed solution obtained in S3 for 30 min, the mass of the ceramic sand being 0.8 times the mass of the red mud, 160 parts;

[0047] S5. Foaming: adding cement into water to make the mass ratio of cement to water 10:100 and stirring uniformly, then adding 10 parts of foaming agent to foam 50 times, wherein the cement and water are 50 parts and 500 parts respectively;

[0048] S6. Preparation of foam concrete: add 1000 parts of ordinary cement clinker, 200 parts of limestone powder, 50 parts of gypsum whisker, 500 parts of fly ash to the mixed solution obtained in S4, stir uniformly, then add the foam obtained in S5, stir uniformly.

[0049] Embodiment 3:

[0050] A method for preparing a red mud-based foam concrete, comprising the following steps:

[0051] S1. Adjust the water content of red mud: measure the water content of red mud as 15%, take 100 parts of red mud (dry material) and adjust the water-solid ratio in the red mud solution to 5:1;

[0052] S2. Sawdust treatment: add 10 parts of sawdust to the solution obtained in S1 and stir for 30 minutes; the above-mentioned sawdust is powder-like wood falling during wood processing;

[0053] S3. Introduce industrial waste gas: add 5% of lime powder (5 parts) of the mass of red mud to the solution obtained in S2 and stir uniformly; then introduce industrial waste gas; the above-mentioned industrial waste gas is cement industrial waste gas; the above-mentioned lime powder is slaked lime powder;

[0054] S4. Immerse ceramic sand particles: select ceramic sand particles with a particle size less than 2 mm and immerse them in the mixed solution obtained in S3 for 10 minutes; the mass of ceramic sand is 0.6 times the mass of red mud, which is 60 parts;

[0055] S5. Foaming: add cement to water so that the mass ratio of cement to water is 1:100 and stir uniformly, then add 5 parts of foaming agent to foam 40 times; the cement and water are 2 parts and 200 parts;

[0056] 6) Preparation of foam concrete: add 600 parts of ordinary cement clinker, 100 parts of limestone powder, 45 parts of gypsum whisker, 400 parts of fly ash to the mixed solution obtained in S4, stir uniformly, then add the foam obtained in S5; stir uniformly.

[0057] Embodiment 4:

[0058] A method for preparing a red mud-based foam concrete, comprising the following steps:

[0059] S1. Adjust the water content of red mud: measure the water content of red mud as 15%, take 100 parts of red mud (dry material) and adjust the water-solid ratio in the red mud solution to 5:1;

[0060] S2. Sawdust treatment: add 10 parts of sawdust to the solution obtained in S1 and stir for 30 minutes; the above-mentioned sawdust is powder-like wood falling during wood processing;

[0061] S3. Industrial waste gas is introduced into the solution obtained in S2: 5% lime powder (6 parts) of the mass of the red mud is added to the solution obtained in S2 and stirred uniformly; then industrial waste gas is introduced into the solution; the industrial waste gas is cement industrial waste gas; the lime powder is quicklime powder;

[0062] S4. Immersing the ceramic sand particles: ceramic sand particles with a particle size of less than 2 mm are selected and immersed in the mixed solution obtained in S3 for 20 min; the mass of the ceramic sand is 0.6 times the mass of the red mud, which is 72 parts;

[0063] S5. Foaming: cement is added to water to make the mass ratio of the cement to the water 3:100, and stirred uniformly; then 10 parts of a foaming agent is added to foam 40 times; the cement and the water are 12 parts and 400 parts, respectively;

[0064] S6. Preparing the foam concrete: 700 parts of ordinary cement clinker, 200 parts of limestone powder, 54 parts of gypsum whiskers, and 360 parts of mineral powder are added to the mixed solution obtained in S4 and stirred uniformly; then the foam obtained in S5 is added and stirred uniformly.

[0065] The specific mixing ratio of each component of the red mud-based foam concrete in Embodiments 1-4 is shown in Table 1.

[0066]

[0067] Performance detection

[0068] Table 2 is the 28d strength activity index of the red mud dried after being treated by the treatment method of the present application (treated according to S1 and S3 in Embodiments 1-4 in turn), which is measured according to the standard “Fly Ash for Use in Cement and Concrete” GB / T1596-2017; the comparative red mud is red mud without any treatment.

[0069]

[0070] It can be seen that the activity of the red mud treated by the technology of the present application is significantly improved.

[0071] Table 3 is the performance evaluation index of the present application, and the performance evaluation index of the foam concrete is executed according to “Foam Concrete” (JGJ266-2011), “Foam Concrete Application Technical Specification” (JGJ / T 341-2014), etc.; the mixing ratio of the comparative example is 600 parts of 52.5 cement, 200 parts of red mud, 200 parts of fly ash, 400 parts of water, and 10 parts of animal protein foaming agent (foamed 40 times).

[0072] As can be seen from Table 3, the foam concrete prepared by the present application has better performance in terms of each age strength, 28d settlement rate (related to the damage rate of the foam), 90d dry shrinkage, etc.

[0073]

[0074] As shown in Table 3, the mechanical properties, the sedimentation rate and the shrinkage deformation value of the embodiment of the application are superior to those of the comparative examples under the same density grade and the lower density grade ratio.

[0075] The above embodiments are only for illustrating the technical concept and characteristics of the application, and the purpose is to enable those skilled in the art to understand the content of the application and implement it, and cannot limit the protection scope of the application. Any equivalent transformation or modification according to the spirit and essence of the application shall be covered within the protection scope of the application.

Claims

1. A method of producing a red mud based foamed concrete, characterised in that, The method comprises the following steps: S1. Adjusting the water content of red mud: red mud and water are mixed to prepare a red mud solution with a certain water-solid ratio; S2. Sawdust treatment: sawdust is added to the red mud solution and stirred; S3. Introducing industrial waste gas: lime powder is added to the product of S2 and stirred evenly; then industrial waste gas is introduced into it; S4. Immersing ceramic sand particles: ceramic sand particles with a particle size less than 2 mm are selected and immersed in the product of S3; S5. Foaming: cement is added to water and stirred evenly, then a foaming agent is added to foam; S6. Preparing foam concrete: cement clinker, limestone powder, gypsum whiskers, and auxiliary cementitious materials are added to the product of S4 and stirred evenly; then the product of S5 is added and stirred evenly to obtain red mud-based foam concrete.

2. The method of producing red mud based foamed concrete according to claim 1, characterized in that: In S1, the water-solid ratio is 5:1 to 10:

1.

3. The method of producing red mud based foamed concrete according to claim 1, characterized in that: In S2, the mass of sawdust is 5-15% of the mass of red mud; the sawdust is powder-shaped wood falling during wood processing.

4. The method of producing red mud based foamed concrete according to claim 1, characterized in that: In S3, the mass of lime powder is 1-10% of the mass of red mud; the lime powder is one of slaked lime powder or quicklime powder.

5. The method of producing red mud based foamed concrete according to claim 1, characterized in that: In S3, the industrial waste gas is one of coal, steel, and cement industrial waste gas.

6. The method of producing red mud based foamed concrete according to claim 1, characterized in that: In S4, the mass of ceramic sand is 0.5-0.8 times the mass of red mud.

7. The method of producing red mud based foamed concrete according to claim 1, characterized in that: In S4, the immersion time is 10-30 min.

8. The method of producing red mud based foamed concrete according to claim 1, characterized by: In S5, the mass ratio of cement to water is 1-10:100; the ratio of foaming agent to water is 1:30-50.

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