Red mud-based salt-excited cementing material based on acidification-thermal activation as well as preparation method and application of red mud-based salt-excited cementing material

Abstract

The invention discloses a red mud-based salt excited cementing material based on acidification-thermal activation as well as a preparation method and application thereof, and belongs to the technical field of solid waste-based cementing materials. The red mud-based salt excited cementing material provided by the invention is prepared from the following components in percentage by mass: 98 to 99 percent of red mud-solid waste gypsum complex, 0.2 to 0.5 percent of water reducing agent and 0.5 to 1.8 percent of early strength agent, the red mud-solid waste gypsum complex is prepared by thermally activating acidified red mud and solid waste gypsum in a mass ratio of (8-10): 1, and the acidified red mud is obtained by neutralizing a composite dealkalizing agent and Bayer red mud; the composite dealkalizing agent comprises 60 to 70 percent of carboxylic acid components and 30 to 40 percent of sulfonic acid components. The utilization rate of the Bayer red mud reaches up to 85% or above, and the problem that the utilization rate of the Bayer red mud is low in the prior art is solved; meanwhile, the obtained cementing material has good early strength and later strength, and the performance of the cementing material is equivalent to or even better than that of existing cement mortar.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste-based cementitious materials, and in particular to a red mud-based salt-activated cementitious material based on acidification-heat activation, and a preparation method and application thereof. Background Art

[0002] The information disclosed in the background of the invention is only intended to enhance the understanding of the overall background of the invention and should not be necessarily regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Red mud is a kind of alkaline solid waste with high water content discharged when the aluminum industry extracts alumina. Its stockpile is large, and its comprehensive utilization rate is less than 10%. A large amount of red mud discharged is stored in open-air yards, occupying a large amount of land resources, easily generating a large amount of dust, seriously polluting groundwater, causing land alkalinization, affecting land cultivation, agricultural and forestry irrigation, and drinking water for humans and livestock, posing a threat to food safety and health. Therefore, the resource utilization of red mud is imminent. According to the different alumina production processes, red mud is divided into three categories: Bayer red mud (Bayer red mud), sintering red mud and combined red mud. Among them, Bayer red mud is usually obtained by processing low-silicon bauxite, mainly composed of iron oxide, aluminum oxide and alkali, with a high pH value and poor activity, so it is more challenging in terms of resource utilization.

[0004] At present, the prior art reports a technical solution for preparing alkali-activated / geopolymer-based cementitious materials using Bayer red mud waste. However, due to the high content of alkali components in Bayer red mud, the end product is seriously alkali-prone, resulting in decreased performance and potential pollution risks to the ecological environment. In addition, the red mud utilization is low, making it difficult to achieve high-value-added utilization of large quantities of Bayer red mud. Therefore, it is urgent to provide a new red mud dealkalization method and achieve high-value green large-scale utilization of red mud. Summary of the invention

[0005] In view of this, the present invention provides a red mud-based salt-activated cementitious material based on acidification-heat activation, and a preparation method and application thereof, which solves the problems of alkali efflux and alkaline pollution of red mud-based alkali-activated / geopolymer-based cementitious materials, and the utilization rate of Bayer red mud is high. The prepared red mud-based salt-activated cementitious material has the advantages of low cost, high mechanical strength, and green environmental protection.

[0006] In a first aspect, the present invention provides a red mud-based salt-activated cementitious material based on acidification and heat activation, which comprises, by mass fraction, 98-99% of a red mud-solid waste gypsum composite, 0.2-0.5% of a water reducer, and 0.5-1.8% of an early strength agent;

[0007] The red mud-solid waste gypsum complex is prepared by thermal activation of acidified red mud and solid waste gypsum in a mass ratio of (8-10):1, and the acidified red mud is obtained by neutralizing a composite dealkalizer with Bayer red mud; the composite dealkalizer includes 60-70% of carboxylic acid components and 30-40% of sulfonic acid components by mass fraction.

[0008] Preferably, the early strength agent is selected from silicate cement or sulphoaluminate cement.

[0009] Preferably, the water reducer is selected from polycarboxylic acid water reducer or naphthalene water reducer.

[0010] Preferably, the solid waste gypsum is selected from one or more of phosphogypsum, desulfurized gypsum, titanium gypsum, fluorinated gypsum, citric acid gypsum, mirabilite gypsum or salt gypsum.

[0011] Preferably, the molar ratio of the composite dealkalizing agent to the alkali component in Bayer red mud is (1-1.1):1.

[0012] Preferably, the carboxylic acid component is selected from one or more of acetic acid, citric acid, oxalic acid, propionic acid or tartaric acid; the sulfonic acid component is selected from one or more of aminoethanesulfonic acid, aromatic sulfonic acid, naphthalenesulfonic acid or methanesulfonic acid.

[0013] In a second aspect, the present invention provides a method for preparing the above-mentioned red mud-based salt-activated gelling material based on acidification-heat activation, comprising the following steps:

[0014] The Bayer red mud is added with water to prepare a red mud slurry, a composite dealkalizing agent is added to the red mud slurry, and the mixture is stirred to obtain an acidified red mud slurry;

[0015] Adding solid waste gypsum to the acidified red mud slurry and mixing, drying and thermally activating the mixture to obtain a red mud-solid waste gypsum complex;

[0016] The red mud-solid waste gypsum composite, the water reducing agent and the early strength agent are uniformly mixed to obtain the product.

[0017] Preferably, the water-cement ratio of the red mud slurry is 0.4-0.6.

[0018] Preferably, in the steps of filtering and washing with water after stirring, the stirring time is 20 to 50 minutes.

[0019] Preferably, the thermal activation step is specifically as follows: heating to 200-300° C. at a heating rate of 5-15° C. / min, keeping the temperature for activation for 2-4 hours, and cooling.

[0020] In a third aspect, the present invention provides the use of the above-mentioned red mud-based salt-activated cementitious material based on acidification and heat activation or the red mud-based salt-activated cementitious material based on acidification and heat activation prepared by the above-mentioned preparation method in the field of construction engineering.

[0021] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0022] (1) The present invention uses a composite dealkalizing agent composed of carboxylic acid (R-COOH) and sulfonic acid (R-SO3H) to neutralize red mud. The neutralization process generates an organic sodium salt, which can achieve efficient solidification of sodium ions and has a high stimulating effect on the red mud synergistic solid waste system, thereby avoiding the problem of alkali-producing in the final prepared red mud-based salt-stimulated cementitious material, which can not only avoid adverse effects on the environment, but also ensure the performance stability of the cementitious material.

[0023] (2) The red mud-based salt-activated cementitious material of the present invention has a utilization rate of more than 85% for Bayer red mud, which solves the problem of low utilization rate of Bayer red mud in the prior art, and the total solid waste utilization rate is as high as more than 95%; at the same time, the obtained red mud-based salt-activated cementitious material has good early strength and late strength, and its performance is equivalent to or even better than that of existing cement mortar, and it has good application prospects in the field of construction engineering (such as road engineering, bridge engineering, tunnel engineering, mining engineering, etc.), realizing the high-value utilization of solid waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute an improper limitation of the present invention. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 This is the mineral phase composition analysis of the acidified red mud and the original Bayer red mud in Example 1 of the present invention. DETAILED DESCRIPTION

[0026] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0027] The present invention provides a red mud-based salt-activated cementitious material based on acidification and heat activation, which comprises, by mass fraction, 98-99% of a red mud-solid waste gypsum complex, 0.2-0.5% of a water reducer, and 0.5-1.8% of an early strength agent;

[0028] The red mud-solid waste gypsum complex is prepared by thermal activation of acidified red mud and solid waste gypsum in a mass ratio of (8-10):1, and the acidified red mud is obtained by neutralizing a composite dealkalizer with Bayer red mud; the composite dealkalizer includes 60-70% of carboxylic acid components and 30-40% of sulfonic acid components by mass fraction.

[0029] The present invention is based on the excitation mechanism of salt components on silicon-aluminum-calcium components, and rationally utilizes the alkaline components in red mud. Under the action of the acidic composite dealkalizer composed of carboxylic acid components and sulfonic acid components, the alkaline components in the red mud undergo an acid-base neutralization reaction to generate organic sodium salts, thereby avoiding the adverse effects of the red mud alkaline components. The organic sodium salt generated by the neutralization reaction achieves efficient solidification of sodium ions, and has a high excitation effect on the red mud synergistic solid waste system, thereby greatly reducing the amount of alkaline excitation components added in the red mud-based salt-excited cementitious materials, which can improve the utilization rate of red mud on the one hand, and avoid the occurrence of alkali efflux on the other hand.

[0030] The solid waste gypsum added in the present invention contains CaSO4. Under the action of thermal activation, the calcium components in the solid waste gypsum can undergo a synergistic activation reaction with the silicon and aluminum components in the red mud, thereby improving the physical and mechanical properties of the terminal product; at the same time, the thermal activation method can enable the silicon, aluminum and calcium components in the red mud-solid waste gypsum to be fully mixed with the salt components generated by acidification, thereby generating a red mud-based salt-activated cementitious material in one step, thereby avoiding the secondary addition of salt activators; in addition, the sulfate ions in the solid waste gypsum also have a salt-activated effect, thereby further improving the activation effect of the salt activator on the silicon, aluminum and calcium components in the red mud-solid waste gypsum system.

[0031] The water reducing agent and early strength agent added in the present invention can further improve the slurry performance and mechanical strength of the red mud-based cementitious material. The early strength agent of the present invention is selected from silicate cement or sulphoaluminate cement, which can improve the early strength of the red mud-based cementitious material; the water reducing agent is selected from any one of a polycarboxylate water reducing agent or a naphthalene water reducing agent.

[0032] In the present invention, the solid waste gypsum is selected from one or more of phosphogypsum, desulfurized gypsum, titanium gypsum, fluorinated gypsum, citric acid gypsum, mirabilite gypsum or salt gypsum. The above solid waste gypsums all have CaSO4 as the main component.

[0033] In the present invention, the molar ratio of the composite dealkalizing agent to the alkali component in the Bayer red mud is (1-1.1):1, and more preferably (1.02-1.08):1. A slight excess of the composite dealkalizing agent can ensure that the alkali component in the Bayer red mud is completely neutralized. The alkali component in the Bayer red mud described in the present invention refers to sodium carbonate, sodium bicarbonate, cancrystal, etc. The present invention does not impose any special restrictions on the method for determining the content of the alkali component in the Bayer red mud. The present invention preferably uses an X-ray fluorescence spectrometer to test the chemical composition of the red mud, and calculates the alkali content based on the Na2O content.

[0034] In the present invention, the carboxylic acid component is selected from one or more of acetic acid, citric acid, oxalic acid, propionic acid or tartaric acid; the sulfonic acid component is selected from one or more of aminoethanesulfonic acid, aromatic sulfonic acid, naphthalenesulfonic acid or methanesulfonic acid. The present invention finds that the composite dealkalizer composed of carboxylic acid components and sulfonic acid components has a better dealkalization effect, and the subsequently generated organic salt has a higher solidification effect on sodium ions, and the generated organic salt has a strong enhancement effect on the gelling activity of the red mud synergistic multi-source solid waste system.

[0035] The present invention also provides a method for preparing the above-mentioned red mud-based salt-activated gelling material based on acidification-heat activation, comprising the following steps:

[0036] The Bayer red mud is added with water to prepare a red mud slurry, a composite dealkalizing agent is added to the red mud slurry, and an acidified red mud slurry is obtained after stirring;

[0037] Adding solid waste gypsum to the acidified red mud slurry and mixing, drying and thermally activating the mixture to obtain a red mud-solid waste gypsum complex;

[0038] The red mud-solid waste gypsum composite, water reducing agent and early strength agent are uniformly mixed to obtain the product.

[0039] In the present invention, the water-cement ratio of the red mud slurry is 0.4 to 0.6. Adding too much water will lead to waste, while adding too little water will make the red mud slurry have poor fluidity, which is not conducive to the neutralization reaction.

[0040] In the steps of filtering and washing after stirring in the present invention, the stirring time is 20 to 50 minutes. The stirring can be carried out at room temperature. During the stirring process, the alkali components in the red mud react with the composite dealkalizing agent to undergo a neutralization reaction.

[0041] The present invention does not impose any special restrictions on the steps of stirring, mixing, drying and mixing, and the common operation methods used by those skilled in the art can be adopted.

[0042] In the present invention, the thermal activation step is specifically as follows: heating to 200-300°C at a heating rate of 5-15°C / min, keeping the temperature for activation for 2-4h, and cooling. The present invention does not impose any special restrictions on the cooling method, such as natural cooling or air cooling. The activation temperature of the present invention is below 300°C, which can avoid the decomposition of the generated organic salt. At the same time, in order to improve the activation effect, the heat preservation activation temperature of the present invention is further preferably 280-300°C.

[0043] The present invention also provides the use of the above-mentioned red mud-based salt-activated cementitious material based on acidification-heat activation or the red mud-based salt-activated cementitious material based on acidification-heat activation prepared by the above-mentioned preparation method in the field of construction engineering.

[0044] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0045] In the following examples, the early strength agent is silicate cement and the water reducer is polycarboxylate water reducer. The chemical composition of red mud was tested by X-ray fluorescence spectrometer, and the alkali content was calculated by the Na2O content.

[0046] Example 1

[0047] This embodiment provides a method for preparing a red mud-based salt-activated gelling material based on acidification-heat activation, comprising the following steps:

[0048] (1) Calculating the total amount of alkali components in Bayer red mud, and preparing the red mud into a Bayer red mud slurry with a water-cement ratio of 0.5;

[0049] (2) 60 parts of acetic acid and 40 parts of aminoethanesulfonic acid are fully mixed to prepare a composite dealkalizing agent for standby use;

[0050] (3) adding the composite dealkalizer to the Bayer red mud slurry at a molar ratio of 1.05:1 to the total amount of the Bayer red mud alkali component, stirring for 30 minutes at room temperature (25±3°C) to obtain acidified red mud;

[0051] (4) adding desulfurized gypsum powder to the acidified red mud slurry at a mass ratio of 8:1 between the acidified red mud and the desulfurized gypsum, stirring the mixture thoroughly and setting aside;

[0052] (5) The red mud-desulfurized gypsum composite slurry is heat-treated in a drying device, wherein the heating rate is 10°C / min, the activation temperature is 300°C, the activation time is 3h, and then air-cooled to room temperature to obtain a heat-activated red mud-desulfurized gypsum composite.

[0053] (6) 98 parts of red mud-desulfurized gypsum composite, 0.2 parts of water reducing agent, and 1.8 parts of early strength agent are fully mixed to obtain a red mud-based salt-activated cementitious material.

[0054] The acidified red mud obtained in step (3) and the original Bayer red mud were subjected to X-ray diffraction (XRD) test. Figure 1 As shown, it can be seen that after the red mud is acidified, the diffraction peaks of the mineral phases such as cancrystal, gibbsite, and hematite in the system disappear, indicating that the alkaline component minerals in the red mud participate in the neutralization reaction and generate salt components with the acidic composite dealkalizing agent. The salt components can participate in the later hydration reaction of red mud-based salt-activated cementitious materials, thereby preventing the occurrence of problems such as alkali efflorescence and alkali pollution in traditional red mud-based cementitious materials.

[0055] Example 2

[0056] The difference between this embodiment and embodiment 1 is that the composite dealkalizing agent in this embodiment is 70 parts of acetic acid and 30 parts of aminoethanesulfonic acid.

[0057] Example 3

[0058] The difference between this embodiment and embodiment 1 is that phosphogypsum is used to replace desulfurized gypsum in this embodiment.

[0059] Example 4

[0060] The difference between this embodiment and embodiment 1 is that the mass ratio of red mud to desulfurized gypsum in this embodiment is 10:1.

[0061] Example 5

[0062] The difference between this embodiment and embodiment 1 is that the thermal activation temperature of the red mud-desulfurized gypsum composite in this embodiment is 200°C.

[0063] Example 6

[0064] The difference between this embodiment and embodiment 1 is that, in this embodiment, the red mud-desulfurized gypsum composite is 99 parts, the water reducing agent is 0.5 parts, and the early strength agent is 0.5 parts.

[0065] Comparative Example 1

[0066] This comparative example is a standard mortar prepared with 42.5# ordinary Portland cement. The specific preparation method refers to GBT17671-2021 cement mortar strength test method.

[0067] Comparative Example 2

[0068] The difference between this comparative example and Example 1 is that the dealkalizing agent in this comparative example is acetic acid and does not contain aminoethanesulfonic acid.

[0069] Comparative Example 3

[0070] The difference between this comparative example and Example 1 is that the dealkalizing agent in this comparative example is aminoethanesulfonic acid, and does not contain acetic acid.

[0071] Comparative Example 4

[0072] The difference between this comparative example and Example 1 is that the dealkalizing agent in this comparative example is hydrochloric acid.

[0073] Test example

[0074] The properties of the cementitious materials of Examples 1 to 6 and Comparative Examples 1 to 4 were tested with reference to "Test Methods for Basic Properties of Building Mortar" (JGJ / T 70-2009). The results are shown in Table 1.

[0075] Table 1 Test results of cementitious materials performance

[0076]

[0077] It can be seen from Table 1 that the sodium acetate and sodium sulfonate generated after acid-base neutralization have a synergistic stimulating effect on the gelling activity of the red mud-desulfurized gypsum system. From Comparative Example 4, it can be seen that sodium chloride is generated after hydrochloric acid reacts with the alkaline components in the red mud. The stimulating effect of chloride on the red mud-desulfurized gypsum system is relatively weak, so the performance of the end product is poor.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A red mud-based salt-activated gelling material based on acidification and heat activation, characterized in that: Calculated by mass fraction, it includes 98-99% of red mud-solid waste gypsum composite, 0.2-0.5% of water reducing agent and 0.5-1.8% of early strength agent; The red mud-solid waste gypsum complex is prepared by thermal activation of acidified red mud and solid waste gypsum in a mass ratio of (8-10):1, and the acidified red mud is obtained by neutralizing a composite dealkalizer with Bayer red mud; the composite dealkalizer includes 60-70% of carboxylic acid components and 30-40% of sulfonic acid components by mass fraction.

2. The acid-heat activated red mud-based salt-activated gelling material according to claim 1, characterized in that: The early strength agent is selected from silicate cement or sulphoaluminate cement; the water reducer is selected from polycarboxylic acid water reducer or naphthalene water reducer.

3. The acid-heat activated red mud-based salt-activated gelling material according to claim 1, characterized in that: The solid waste gypsum is selected from one or more of phosphogypsum, desulfurized gypsum, titanium gypsum, fluorinated gypsum, citric acid gypsum, mirabilite gypsum or salt gypsum.

4. The acid-heat activated red mud-based salt-activated gelling material according to claim 1, characterized in that: The molar ratio of the composite dealkalizing agent to the alkali component in the Bayer red mud is (1-1.1):

1.

5. The acid-heat activated red mud-based salt-activated gelling material according to claim 1, characterized in that: The carboxylic acid component is selected from one or more of acetic acid, citric acid, oxalic acid, propionic acid or tartaric acid; the sulfonic acid component is selected from one or more of aminoethanesulfonic acid, aromatic sulfonic acid, naphthalenesulfonic acid or methanesulfonic acid.

6. The method for preparing a red mud-based salt-activated gelling material based on acidification and heat activation according to any one of claims 1 to 5, characterized in that: The steps include: The Bayer red mud is added with water to prepare a red mud slurry, a composite dealkalizing agent is added to the red mud slurry, and an acidified red mud slurry is obtained after stirring; Adding solid waste gypsum to the acidified red mud slurry and mixing, drying and thermally activating the mixture to obtain a red mud-solid waste gypsum complex; The red mud-solid waste gypsum composite, water reducing agent and early strength agent are uniformly mixed to obtain the product.

7. The preparation method according to claim 6, characterized in that: The water-cement ratio of the red mud slurry is 0.4-0.

6.

8. The preparation method according to claim 6, characterized in that: In the steps of filtering and washing with water after stirring, the stirring time is 20 to 50 minutes.

9. The preparation method according to claim 6, characterized in that: The thermal activation step specifically comprises: heating to 200-300° C. at a heating rate of 5-15° C. / min, keeping the temperature for activation for 2-4 hours, and cooling.

10. Use of the acid-heat-activated red mud-based salt-activated cementitious material according to any one of claims 1 to 5 or the acid-heat-activated red mud-based salt-activated cementitious material prepared by the preparation method according to any one of claims 6 to 9 in the field of construction engineering.

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