A diatomite modified red mud-based cementitious material, and a preparation method and application thereof
By constructing a ternary composite system of red mud, cement, and blast furnace slag and modifying it with diatomaceous earth, the problems of low utilization rate of red mud and high risk of heavy metal leaching were solved, and the material achieved high strength and high adsorption performance, meeting the requirements of building and road engineering.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GUANGXI BEITOU HIGHWAY CONSTR & INVESTMENT GRP CO LTD
- Filing Date
- 2026-04-01
- Publication Date
- 2026-06-19
AI Technical Summary
The existing red mud has a low utilization rate, and it is difficult to balance mechanical properties and environmental safety. High adsorbent content leads to strength deterioration and high risk of heavy metal leaching.
A ternary composite system of red mud-cement-blast furnace slag was constructed by using diatomaceous earth-modified red mud-based cementitious materials. Calcium chloride activator was introduced, and the active silicon source of diatomaceous earth was used to activate the hydration reaction to generate CSH gel. Heavy metals were solidified through chemical precipitation and physical encapsulation, combining the dual barriers of chemical locking and physical adsorption.
It achieves high utilization rate of red mud, synergistic improvement of material mechanical properties and adsorption properties, 28-day compressive strength of 60.3 MPa, flexural strength of 10.3 MPa, and heavy metal leaching concentration below the standard, meeting the requirements of building and road engineering.
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Abstract
Description
Technical Field
[0001] This invention relates to the fields of solid waste resource utilization and building materials technology, and particularly to a diatomaceous earth modified red mud-based cementitious material, its preparation method, and its application. Background Technology
[0002] Red mud is a major solid waste generated by the alumina industry, with 1 to 2 tons of red mud being discharged for every ton of alumina produced. The long-term accumulation of large amounts of red mud not only occupies valuable land resources, but its rich alkali metals and heavy metals (such as As, Cr, Cd, etc.) can also easily leach into the soil and water bodies through rainwater, causing ecological and environmental risks and becoming a bottleneck restricting the sustainable development of the aluminum industry.
[0003] The resource utilization of red mud has become an important research topic. Currently, by introducing cementing components such as calcium hydroxide, the active phases in red mud (such as hydroxysappanite and sodium octahedrite) undergo a pozzolanic reaction to generate C-(A)-SH gel and semi-aluminate, enabling the application of red mud in building materials. However, the utilization rate of red mud is currently low (usually below 40%), requiring high dosages of cementing components. Simultaneously, to reduce the leaching of heavy metals from red mud and ensure environmental safety, adsorbents need to be added to red mud materials, such as bentonite or activated carbon. Increasing the adsorbent dosage helps reduce heavy metal leaching, but high adsorbent dosages can lead to strength degradation and deterioration of the material's mechanical properties. Summary of the Invention
[0004] In view of this, the purpose of this invention is to provide a diatomaceous earth-modified red mud-based cementitious material, its preparation method, and its application. The diatomaceous earth-modified red mud-based cementitious material provided by this invention achieves high utilization of red mud and synergistic improvement in both the material's mechanical properties and adsorption properties, solving the technical challenge of balancing material mechanical properties with environmental safety.
[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a diatomaceous earth-modified red mud-based cementitious material, comprising the following components in parts by weight: The composition consists of 100 parts cementitious components, 2-3 parts calcium chloride, 10-15 parts diatomaceous earth, 0.2-0.3 parts water-reducing agent, and 35-50 parts water. The cementitious component includes the following components by mass percentage: 40-50% red mud, 20-40% ordinary silicate cement, and 20-30% granulated blast furnace slag powder.
[0006] Preferably, the red mud is Bayer process red mud.
[0007] Preferably, the ordinary silicate cement is graded P·O 42.5R.
[0008] Preferably, the granulated blast furnace slag powder is grade S95.
[0009] Preferably, the diatomaceous earth is obtained by pretreatment of raw diatomaceous earth, the pretreatment including: acid washing, water washing, drying and grinding of the raw diatomaceous earth in sequence.
[0010] Preferably, the particle size of the diatomaceous earth is 300-800 mesh.
[0011] Preferably, the acid used for pickling is dilute sulfuric acid with a mass fraction of 30%, and the pickling time is 24-36 hours.
[0012] Preferably, the water-reducing agent is a polycarboxylate water-reducing agent.
[0013] This invention provides a method for preparing the diatomaceous earth-modified red mud-based cementitious material described in the above technical solution, comprising the following steps: The gelling components, diatomaceous earth, and calcium chloride are mixed to obtain a mixture; The mixture is combined with a water-reducing agent and water to obtain the diatomaceous earth-modified red mud-based cementitious material.
[0014] This invention provides the application of the diatomaceous earth modified red mud-based cementitious material described in the above technical solutions or the diatomaceous earth modified red mud-based cementitious material prepared by the preparation method described in the above technical solutions in building materials.
[0015] This invention provides a diatomaceous earth-modified red mud-based cementitious material, comprising the following components in parts by weight: 100 parts cementitious component, 2-3 parts calcium chloride, 10-15 parts diatomaceous earth, 0.2-0.3 parts water-reducing agent, and 35-50 parts water; wherein the cementitious component comprises the following components in weight percentage: 40-50% red mud, 20-40% ordinary silicate cement, and 20-30% granulated blast furnace slag powder. Compared with the prior art, this invention has the following beneficial effects: This invention constructs a ternary composite system of red mud, cement, and blast furnace slag. Calcium chloride is used as an activator to effectively stimulate the potential activity of red mud and blast furnace slag, promoting a complementary and mutually beneficial hydration reaction among the three components. The synergistic effect of multiple solid wastes allows for the achievement of required mechanical strength even with high red mud content (up to 50%) and relatively low cement content. Furthermore, diatomaceous earth, as a silicon-rich material, provides a certain amount of active silicon source for the system, participating in the hydration reaction and generating gel, further ensuring the strength of the material. This invention introduces diatomaceous earth to construct a dual coupling mechanism of "gelation solidification-pore adsorption": the gelation system solidifies heavy metals through chemical precipitation, ion exchange, and physical encapsulation, while the porous structure of diatomaceous earth facilitates secondary adsorption of residual ions; furthermore, the active silicon source of diatomaceous earth triggers a hydration reaction to generate CSH gel, which improves matrix density while overcoming the compatibility problem of strength reduction caused by the addition of conventional adsorbents. This invention, by combining the dual barriers of chemical solidification and physical adsorption, solves the technical bottleneck of existing red mud-based materials where it is difficult to simultaneously balance mechanical properties and the risk of heavy metal leaching.
[0016] Therefore, the diatomaceous earth-modified red mud-based cementitious material provided by this invention not only achieves high utilization of red mud, but also achieves synergistic improvement in the material's mechanical properties and adsorption properties (i.e., environmental safety).
[0017] The results of the examples show that the diatomaceous earth modified red mud-based cementitious material provided by the present invention has a 28-day compressive strength of 60.3 MPa and a flexural strength of 10.3 MPa, which meets the strength requirements of building and road engineering. The leaching concentrations of heavy metals such as As, Cr, and Pb are all lower than the limits in GB / T 30760-2024. Detailed Implementation
[0018] This invention provides a diatomaceous earth-modified red mud-based cementitious material, comprising the following components in parts by weight: The composition consists of 100 parts cementitious components, 2-3 parts calcium chloride, 10-15 parts diatomaceous earth, 0.2-0.3 parts water-reducing agent, and 35-50 parts water. The cementitious component includes the following components by mass percentage: 40-50% red mud, 20-40% ordinary silicate cement, and 20-30% granulated blast furnace slag powder.
[0019] Unless otherwise specified, all raw materials involved in this invention are commercially available products well known in the art.
[0020] The diatomaceous earth-modified red mud-based cementitious material provided by this invention comprises 100 parts by weight of cementitious components. In this invention, the cementitious components include the following components by weight percentage: 40-50% red mud (which can be 40%, 42%, 45%, 47%, or 50%), 20-40% ordinary Portland cement (which can be 20%, 25%, 30%, or 35%), and 20-30% granulated blast furnace slag powder (which can be 20%, 25%, or 30%). In this invention, the red mud is the core raw material, preferably Bayer process red mud. This invention achieves a red mud utilization rate of up to 50% by using a certain proportion of red mud, ordinary Portland cement, and granulated blast furnace slag powder, significantly reducing the amount of cementitious material used and resulting in better cost performance. In this invention, the preferred grade of the ordinary Portland cement is P·O 42.5R, which provides the basic cementitious properties. In this invention, the grade of the granulated blast furnace slag powder is preferably S95, and the granulated blast furnace slag powder participates in the hydration reaction to improve its strength.
[0021] Based on the mass fraction of the gelling components, the diatomaceous earth-modified red mud-based gelling material provided by this invention includes 2-3 parts of calcium chloride, which can be 2, 2.5, or 3 parts. In this invention, the calcium chloride acts as an activator to promote the hydration process of the gelling system.
[0022] Based on the mass fraction of the gelling components, the diatomaceous earth-modified red mud-based gelling material provided by the present invention comprises 10-15 parts of diatomaceous earth, which can be 10, 11, 12, 13, 14, or 15 parts. In the present invention, the diatomaceous earth is preferably obtained from raw diatomaceous earth (i.e., untreated diatomaceous earth) through pretreatment. The pretreatment preferably includes: sequentially acid washing, water washing, drying, and grinding of the raw diatomaceous earth. In the present invention, the particle size of the raw diatomaceous earth is preferably 300-800 mesh; the acid reagent used for acid washing is preferably dilute sulfuric acid, and the mass fraction of the dilute sulfuric acid is preferably 30%. In the embodiments of the present invention, the ratio of the raw diatomaceous earth to dilute sulfuric acid is preferably 100g:250mL; the acid washing time is preferably 24-36h. The present invention preferably mixes the raw diatomaceous earth with the acid reagent and performs acid washing under stirring conditions. In this invention, the acid washing serves to remove impurities from the surface of the raw diatomaceous earth, resulting in larger pore sizes and better adsorption performance. After acid washing, the acid-washed diatomaceous earth is preferably separated by vacuum filtration. In this invention, the water washing is performed until the soil is neutral. In this invention, the grinding is performed until the soil is in powder form (dried diatomaceous earth tends to clump).
[0023] In this invention, diatomaceous earth serves as a functional adsorbent. This invention abandons the traditional approach of sacrificing mechanical strength for environmental performance, utilizing the active silicon source of diatomaceous earth to trigger a hydration reaction and generate CSH gel. This improves matrix density while overcoming the compatibility problem of conventional adsorbents reducing strength. Furthermore, through a dual coupling mechanism of "cementing material solidification - diatomaceous earth adsorption," it combines chemical locking and physical adsorption as dual barriers, achieving synergistic fixation of heavy metal ions, significantly reducing the risk of heavy metal leaching, ensuring environmental safety, and solving the technical bottleneck of existing red mud-based materials where mechanical properties and heavy metal leaching risks are difficult to balance. The results of the embodiments show that adding diatomaceous earth at a dosage of 10% relative to the cementing component not only does not degrade strength but also promotes CSH gel formation, achieving a synergistic improvement in both mechanical and adsorption properties.
[0024] Based on the mass fraction of the cementing components, the diatomaceous earth-modified red mud-based cementitious material provided by the present invention includes 0.2-0.3 parts of a water-reducing agent, which can be 0.25 parts. In the present invention, the water-reducing agent is preferably a polycarboxylate water-reducing agent; the water-reducing agent is used to improve the workability of the mixture.
[0025] Based on the mass fraction of the gelling components, the diatomaceous earth modified red mud-based gelling material provided by the present invention includes 35 to 50 parts of water, that is, the water-cement ratio is 0.35 to 0.50, and the mass fraction of water can be 35, 40, 45 or 50 parts.
[0026] This invention uses red mud as the core raw material, constructs a cementing system with composite cement and blast furnace slag, introduces diatomaceous earth as a functional adsorbent, and adds calcium chloride as an activator. The resulting diatomaceous earth-modified red mud-based cementitious material possesses both excellent mechanical properties and environmental safety, enabling the large-scale, efficient resource utilization of red mud. Furthermore, the raw materials used in this invention are widely available and low in cost.
[0027] This invention provides a method for preparing the diatomaceous earth-modified red mud-based cementitious material described in the above technical solution, comprising the following steps: The gelling components, diatomaceous earth, and calcium chloride are mixed to obtain a mixture; The mixture is combined with a water-reducing agent and water to obtain the diatomaceous earth-modified red mud-based cementitious material.
[0028] In this invention, the water-reducing agent and water are preferably added in the form of a mixture of water-reducing agent and water. Specifically, a mixture of water-reducing agent and water is added to the mixture and stirred evenly to obtain the diatomaceous earth modified red mud-based cementitious material.
[0029] This invention provides the application of diatomaceous earth-modified red mud-based cementitious materials, as described in the above technical solutions or prepared by the methods described in the above technical solutions, in building materials. This invention does not impose special requirements on the application methods; methods well-known to those skilled in the art can be used. The diatomaceous earth-modified red mud-based cementitious materials provided by this invention are compatible with existing building material production lines and suitable for large-scale green applications. The diatomaceous earth-modified red mud-based cementitious materials provided by this invention can be widely used in construction, road engineering, and other fields, providing technical support for the large-scale application of red mud and the sustainable development of the aluminum industry.
[0030] To further illustrate the present invention, the following detailed description, in conjunction with examples, of the diatomaceous earth-modified red mud-based cementitious material, its preparation method, and its application, should not be construed as limiting the scope of protection of the present invention.
[0031] Example 1 A diatomaceous earth-modified red mud-based cementitious material has the following formulation as shown in Table 1. The diatomaceous earth-modified red mud-based cementitious material of Example 1 is denoted as M2.
[0032] Table 1. Formulation composition of diatomaceous earth modified red mud-based cementitious material in Example 1
[0033] In Table 1, diatomaceous earth is obtained from raw diatomaceous earth through pretreatment. The pretreatment method is as follows: raw diatomaceous earth (800 mesh) is mixed with 30wt% dilute sulfuric acid (the ratio of raw diatomaceous earth to dilute sulfuric acid is 100g:250mL), magnetically stirred for 24h, filtered, washed with water until neutral, dried, and ground into powder. The water-cement ratio is the ratio of the mass of water to the total mass of Bayer red mud, ordinary silicate cement, and granulated blast furnace slag powder.
[0034] Comparative Example 1 The addition of diatomaceous earth is omitted (no need to adjust the water-cement ratio), and the rest is the same as in Example 1. The red mud-based cementitious material of Comparative Example 1 is denoted as M1.
[0035] Comparative Example 2 In Example 1, the diatomaceous earth was replaced with 20 parts by mass, and the water-cement ratio was adjusted to 0.5; otherwise, the process remained the same as in Example 1. The red mud-based cementitious material in Comparative Example 2 was designated as M3.
[0036] Comparative Example 3 The addition of diatomaceous earth was omitted, and the red mud was replaced with 40 parts by mass, the cement with 40 parts by mass, and the blast furnace slag with 20 parts by mass. The rest was the same as in Example 1. The red mud-based cementitious material of Comparative Example 3 was designated as M4.
[0037] Comparative Example 4 Replace diatomaceous earth with an equal amount of activated carbon, change red mud to 40 parts by mass, change cement to 40 parts by mass, change blast furnace slag to 20 parts by mass, and the rest is the same as in Example 1. The red mud-based cementitious material in Comparative Example 4 is denoted as M5.
[0038] Comparative Example 5 The addition of diatomaceous earth and blast furnace slag powder was omitted, and the cement was replaced with 50 parts by weight; otherwise, it remained the same as in Example 1. The red mud-based cementitious material of Comparative Example 5 was designated as M6.
[0039] Comparative Example 6 A red mud-based cementitious material has the following formulation as shown in Table 2. The red mud-based cementitious material of Comparative Example 6 is designated as M7.
[0040] Table 2 shows the formulation composition of the red mud-based cementitious material in Comparative Example 6.
[0041] Comparative Example 7 A red mud-based cementitious material has the following formulation as shown in Table 3. The red mud-based cementitious material of Comparative Example 7 is designated as M8.
[0042] Table 3 shows the formulation composition of the red mud-based cementitious material in Comparative Example 7.
[0043] The performance of the cementitious materials obtained in the examples and comparative examples was tested, as follows: (1) Preparation of mortar specimens (in accordance with GB / T 17671-2021 standard) Raw material weighing: Weigh the cementitious components (Bayer red mud, ordinary silicate cement, granulated blast furnace slag powder) according to the mixing ratio of the examples and comparative examples. Accurately weigh the CaCl2 activator, water-reducing agent, diatomaceous earth, and the corresponding amounts of water and standard sand (cement-sand ratio 1:3, standard sand conforming to GSB08 1337 standard).
[0044] Mixing: First, mix the cementitious components, diatomaceous earth, and CaCl2 activator evenly. Then, add the water-reducing agent and water mixture and stir until a uniform mixture is formed. Next, add standard sand and continue stirring until it meets the workability requirements.
[0045] Molding: Pour the mixture into a 40mm×40mm×160mm mold, vibrate to shape, remove air bubbles, and then smooth the surface.
[0046] Curing: After molding, cure under standard curing conditions (temperature 20±2℃, relative humidity ≥95%) until the specified age (3d, 7d, 28d).
[0047] (2) Preparation of paste specimens (for leaching test) The preparation process is basically the same as that of the mortar specimens, the only difference being that no standard sand is added, and a 40mm×40mm×40mm mold is used for molding, with the same curing conditions.
[0048] (3) Performance testing methods Mechanical property testing: The compressive strength and flexural strength at 3d, 7d and 28d were tested according to GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)" to evaluate the load-bearing capacity of the material.
[0049] Flowability test: Determine the flowability of the mortar mixture to ensure that it meets the workability requirements for construction (must comply with the scope of GB 175-2007).
[0050] The environmental safety tests are as follows: Dynamic leaching test: Referring to the modified NEN 7375 method, a volume of 64 cm³ was used. 3 28-day neat pulp specimens were placed in a 320cm sieve. 3 In pure water, with a liquid-to-solid volume ratio (L / S) of 5.0, the solution was continuously flushed with dynamic water flow for 48 hours. After filtration, the concentration of heavy metal ions in the leachate was measured (ICP-MS method, in accordance with HJ 781-2016).
[0051] Extreme leaching test: According to HJ 557-2010, 28-day clean pulp powder (cured for 28 days, particle size passing through 70 mesh sieve) ground through a 70 mesh sieve was added to a wide-mouth bottle with water at a liquid-solid ratio of 1L:10kg. After shaking for 8 hours, the mixture was allowed to stand for 16 hours and 160 hours (leaching time is the sum of shaking time and standing time), and the ion concentration of the leachate was measured.
[0052] (4) Performance test results The mechanical properties and flowability test results of the red mud-based cementitious materials in the examples and comparative examples are shown in Table 4, the dynamic leaching test results of heavy metal ions are shown in Table 5, and the extreme leaching test results are shown in Tables 6 and 7.
[0053] Table 4. Road performance test results of red mud-based cementitious materials in the examples and comparative examples.
[0054] In Table 4, the fluidity of M3 is higher than that of M1 and M2, mainly because the water-cement ratio of M3 is higher, and the introduction of more water increases the fluidity.
[0055] Table 5. Results of dynamic leaching tests of heavy metal ions in red mud-based cementitious materials of the examples and comparative examples.
[0056] Table 6. Results of 1-day extreme leaching test of heavy metal ions in red mud-based cementitious materials of the examples and comparative examples.
[0057] Table 7. Results of 7-day extreme leaching test of heavy metal ions in red mud-based cementitious materials of the examples and comparative examples.
[0058] As can be seen from the above embodiments, the diatomaceous earth modified red mud-based cementitious material of the present invention achieves 50% resource utilization of Bayer process red mud, with a 28-day compressive strength of 60.3 MPa and a flexural strength of 10.3 MPa, meeting the strength requirements of building and road engineering; the heavy metal leaching concentration is lower than the limit value of GB / T 30760-2024.
[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A diatomaceous earth-modified red mud-based cementitious material, characterized in that, The components include the following parts by mass: The composition consists of 100 parts cementitious components, 2-3 parts calcium chloride, 10-15 parts diatomaceous earth, 0.2-0.3 parts water-reducing agent, and 35-50 parts water. The cementitious component includes the following components by mass percentage: 40-50% red mud, 20-40% ordinary silicate cement, and 20-30% granulated blast furnace slag powder.
2. The diatomaceous earth-modified red mud-based cementitious material according to claim 1, characterized in that, The red mud mentioned is Bayer process red mud.
3. The diatomaceous earth-modified red mud-based cementitious material according to claim 1, characterized in that, The grade of the ordinary silicate cement is P·O 42.5R.
4. The diatomaceous earth-modified red mud-based cementitious material according to claim 1, characterized in that, The granulated blast furnace slag powder is grade S95.
5. The diatomaceous earth-modified red mud-based cementitious material according to claim 1, characterized in that, The diatomaceous earth is obtained by pretreatment of raw diatomaceous earth, which includes acid washing, water washing, drying and grinding of the raw diatomaceous earth in sequence.
6. The diatomaceous earth-modified red mud-based cementitious material according to claim 5, characterized in that, The particle size of the diatomaceous earth is 300-800 mesh.
7. The diatomaceous earth-modified red mud-based cementitious material according to claim 5, characterized in that, The acid used for pickling is dilute sulfuric acid with a mass fraction of 30%, and the pickling time is 24-36 hours.
8. The diatomaceous earth-modified red mud-based cementitious material according to claim 1, characterized in that, The water-reducing agent is a polycarboxylate water-reducing agent.
9. A method for preparing the diatomaceous earth-modified red mud-based cementitious material according to any one of claims 1 to 8, characterized in that, Includes the following steps: The gelling components, diatomaceous earth, and calcium chloride are mixed to obtain a mixture; The mixture is combined with a water-reducing agent and water to obtain the diatomaceous earth-modified red mud-based cementitious material.
10. The application of the diatomaceous earth modified red mud-based cementitious material according to any one of claims 1 to 8 or the diatomaceous earth modified red mud-based cementitious material prepared by the preparation method according to claim 9 in building materials.