Novel water-stable material with high durability and preparation method thereof

Abstract

The invention provides a high-durability novel water-stable material and a preparation method thereof, and belongs to the field of cement materials. The novel water-stable material comprises the following materials in percentage by weight: 10-20% of red mud, 10-15% of coal gangue, 45-70% of aggregate, 8-12% of an alkaline activator and 2-8% of an additive. The red mud / coal gangue is used for replacing the traditional cement macadam base, so that the recycling of solid wastes is realized, and the environmental pollution is reduced. The red mud, the coal gangue and the aggregate are pretreated before the alkaline exciting agent is added, the method is simple, and the effect is obvious; and additives such as bentonite, diatomite, wormcast and the like are added, so that the compressive strength, durability, stability and impermeability of the red mud / coal gangue base are improved.

Description

Technical Field

[0001] The present invention relates to the field of cement materials, and particularly relates to a new type of water-stabilized material with high durability and a preparation method thereof. Background Art

[0002] Red mud is a solid residue discharged during the production of alumina, containing gel active components such as SiO2 and Al2O3. According to different production methods of alumina, it is divided into sintering method, Bayer method and combined sintering-Bayer method red mud. China discharges more than 10 million tons of red mud every year, and the cumulative stockpile of red mud is as high as tens of millions of tons, with a utilization rate of only 10%. The discharge of red mud is increasing, resulting in serious environmental pollution problems.

[0003] Coal gangue is a solid waste discharged during coal mining and coal washing. It is a black-gray rock with a lower carbon content and harder than coal, which is associated with coal seams during the coal formation process. Its main components are Al2O3 and SiO2. In addition, it also contains toxic heavy metal elements such as Pb, Sn, As, and Cr. The large accumulation of coal gangue waste not only occupies land and affects the environment, but also the leaching water of gangue will pollute the surrounding soil and groundwater. In addition, coal gangue contains a certain amount of combustible materials, which are prone to spontaneous combustion under suitable conditions, emitting harmful gases such as sulfur dioxide, nitrogen oxides, carbon oxides and soot to pollute the atmosphere and affecting the health of residents in mining areas.

[0004] Adhering to the pollution control concept of green development, it is crucial to recycle red mud and coal gangue solid wastes and turn waste into treasure. Chinese Patent CN113683332B discloses a preparation method of a red mud coal gangue accelerator, which prepares a red mud coal gangue solid waste into an accelerator for use in bulk building materials; Chinese Patent CN102557576A discloses a production process of red mud coal gangue sintered bricks, which prepares red mud and coal gangue solid wastes into sintered bricks for use in wall construction. However, there are few reports on using red mud and coal gangue solid wastes as water-stabilized materials. With the rapid economic development, the cost of using cement increases year by year, and it is urgent to find a completely replaceable resource.

[0005] In summary, the environmental pollution caused by the large-area stacking of red mud and coal gangue solid wastes and the high cost of the cement-based road water-stabilized layer have become the main problems. In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] To solve the problems existing in the prior art, the purpose of the present invention is to provide a new type of water-stable material with high durability and its preparation method. Red mud, coal gangue solid wastes, alkaline activators, additives, and aggregates such as slag and fly ash are mixed together in a certain proportion, stirred evenly, and prepared into a water-stable layer after fixed curing, which can effectively replace the costly cement-based road water-stable layer. The water-stable layer prepared by the method of the present application has the characteristics of high durability and excellent compressive strength, realizing resource utilization while protecting the environment.

[0007] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] On the one hand, the present invention provides a new type of water-stable material with high durability, and the new type of water-stable material includes the following materials by weight percentage: 10-20% of red mud, 10-15% of coal gangue, 45-70% of aggregate, 8-12% of alkaline activator, and 2-8% of additive.

[0009] Further, the aggregate is selected from one or more of slag, sand, crushed stone, fly ash, and washed sand.

[0010] The washed sand is the sand washed after the separation of engineering soil and mud and sand.

[0011] Red mud has a cemented pore-frame structure, mainly forming three structures: aggregates, granuloids, and agglomerates. Larger voids are formed between the structures. Adding an appropriate proportion of aggregate can improve the high durability, frost stability, dry shrinkage, and wet shrinkage of the water-stable material.

[0012] Further, the alkaline activator is selected from one or more of water glass, quicklime powder, gypsum dihydrate, sodium sulfate, and sodium silicate.

[0013] The alkaline activator can catalyze the hydration of raw materials and accelerate the reaction rate; the gel material formed by alkali activation has the advantages of early strength, rapid hardening, high strength, and corrosion resistance.

[0014] Further, the additive is selected from one or more of silica fume, bentonite, diatomite, and earthworm manure.

[0015] Adding a certain proportion of additive can improve the performance of the water-stable material.

[0016] The main chemical components of silica fume are SiO2, Al2O3, and NaO, and the minor components are Fe2O3, MgO, and CaO. The particles of silica fume are relatively fine, which can effectively improve the strength, compressive strength, and impermeability of the solidified red mud / coal gangue-based water-stable material.

[0017] The main chemical component of bentonite is montmorillonite, and it also contains SiO2 and Al2O3. It is a common decolorizer, binder, and catalyst. Adding bentonite improves the strength, waterproofness, impermeability, and flatness of the red mud / coal gangue-based water-stable material.

[0018] The main chemical component of diatomite is SiO2, and the minor components are Fe2O3, CaO, MgO, and Al2O3. Adding diatomite improves the strength, waterproofness, and flatness of the red mud / coal gangue-based water-stable material.

[0019] Vermicompost is weakly acidic, with a pH between 6.5 and 7.0. Appropriate addition can adjust the stability of the pH.

[0020] Furthermore, the red mud is Bayer red mud with a moisture content of 10-60%.

[0021] On the other hand, the present invention provides a method for preparing a novel water-stable material with high durability, including the following steps:

[0022] (1) Pretreatment of raw materials: Crushing and screening red mud, coal gangue, and aggregates respectively;

[0023] (2) Activation of raw materials: Roasting the screened red mud and leaching with water in four stages to remove alkali; Calcining coal gangue;

[0024] (3) Preparation of water-stable layer material: Adding each raw material according to the ratio to aggregates, activated red mud, coal gangue, alkaline activator, and additive, stirring and mixing evenly, and curing.

[0025] Furthermore, in step (2), the particle size of the red mud is 5-10 mm, preferably 5 mm, and the particle size of the aggregates is 1-10 mm. Furthermore, in step (2), the roasting temperature of the red mud is 680-700 °C and the roasting time is 30 min.

[0026] Furthermore, in step (2), the water leaching temperature of the red mud is 90-100 °C and the water leaching time is 60 min.

[0027] Furthermore, in step (2), the calcining temperature of the coal gangue is 400-450 °C.

[0028] After the red mud is roasted at 680-700 °C for 30 min and leached with water at 90-100 °C for 60 min, the bound alkali and free alkali can be effectively removed. Adding aggregates such as fly ash and slag can enhance the compressive strength of the water-stable material.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The novel water-stabilized material provided by the present invention uses red mud and coal gangue solid wastes as raw materials to replace traditional cement, effectively reducing the cement usage cost, achieving comprehensive utilization of solid wastes, and protecting the environment.

[0031] (2) Aggregates such as fly ash and slag are added to the novel water-stabilized material provided by the present invention, improving the strength, compressive resistance, and impermeability of the solidified red mud-coal gangue-based water-stabilized material. The additive bentonite enhances the waterproofness, flatness, and other physical properties of the water-stabilized material; earthworm manure neutralizes the alkalinity of red mud.

[0032] (3) In the preparation method of the novel water-stabilized material provided by the present invention, after the red mud is crushed and screened, it is roasted and subjected to water immersion and alkali removal treatment. It is roasted at a high temperature of 700 °C, and the combined alkali and free alkali in the red mud solid waste can be removed by four-stage water immersion. Brief Description of the Drawings

[0033] Figure 1 It is the process flow chart of the preparation method of a novel water-stabilized material with high durability described in the present invention. Detailed Embodiments

[0034] The present invention will be described in detail below with reference to the drawings and embodiments.

[0035] Embodiment 1

[0036] A novel water-stabilized material with high durability includes the following materials in weight percentages: 10% red mud, 10% coal gangue, 70% fly ash, 8% water glass, and 2% silica fume.

[0037] According to Figure 1 the process flow chart shown, the novel water-stabilized material is prepared:

[0038] (1) Pretreatment of raw materials: The red mud, coal gangue, and aggregates are respectively crushed and then screened. The obtained red mud has a particle size of 5 - 10 mm, and the aggregates have a particle size of 1 - 10 mm;

[0039] (2) Activation of raw materials: The screened red mud is roasted at 700 °C for 30 min and then subjected to alkali removal by four-stage water immersion at 90 °C for 60 min; the coal gangue is calcined at 400 - 450 °C;

[0040] (3) Preparation of water-stabilized layer material: Add each raw material according to the above ratio to fly ash, activated red mud, coal gangue, water glass, and silica fume, stir and mix evenly, and cure for more than 3 days.

[0041] Embodiment 2

[0042] A novel water-stabilized material with high durability includes the following materials in weight percentages: 20% red mud, 15% coal gangue, 45% fly ash, 12% water glass, and 8% silica fume.

[0043] According to Figure 1 the process flow chart shown below, prepare the new type of water-stable material:

[0044] (1) Pretreatment of raw materials: Crush and screen red mud, coal gangue and aggregate respectively. The obtained red mud has a particle size of 5 - 10 mm, and the aggregate has a particle size of 1 - 10 mm;

[0045] (2) Activation of raw materials: Roast the screened red mud at 700 °C for 30 min, soak it in water in four stages at 90 °C for 60 min and then remove alkali; Calcinate the coal gangue at 400 - 450 °C;

[0046] (3) Preparation of water-stable layer material: Add each raw material according to the above ratio to fly ash, activated red mud, coal gangue, water glass and silica fume, stir and mix evenly, and cure for more than 3 days.

[0047] Example 3

[0048] A new type of water-stable material with high durability, comprising the following materials by weight percentage: 15% red mud, 15% coal gangue, 50% fly ash, 10% water glass, 10% silica fume.

[0049] According to Figure 1 the process flow chart shown below, prepare the new type of water-stable material:

[0050] (1) Pretreatment of raw materials: Crush and screen red mud, coal gangue and aggregate respectively. The obtained red mud has a particle size of 5 - 10 mm, and the aggregate has a particle size of 1 - 10 mm;

[0051] (2) Activation of raw materials: Roast the screened red mud at 700 °C for 30 min, soak it in water in four stages at 90 °C for 60 min and then remove alkali; Calcinate the coal gangue at 400 - 450 °C;

[0052] (3) Preparation of water-stable layer material: Add each raw material according to the above ratio to fly ash, activated red mud, coal gangue, water glass and silica fume, stir and mix evenly, and cure for more than 3 days.

[0053] Performance test: Conduct a 7-day unconfined compressive strength test on the specimens obtained in Examples 1 - 3.

[0054] The experimental results are as follows (Table 1)

[0055] Table 1. Results of 7-day unconfined compressive strength test

[0056] Item 7d Unconfined Compressive Strength (MPa) Example 1 6.2 Example 2 6.7 Example 3 7.0

[0057] As can be seen from Table 1, the new water-stable material prepared by the preparation method of the present invention has good compressive strength, which meets the 7-day unconfined compressive strength standard for expressways and first-class highways under extremely heavy and especially heavy traffic load levels in the "Technical Rules for the Construction of Highway Pavement Bases" JIG / TF20-2015.

[0058] By using red mud and coal gangue to replace the traditional cement gravel base, the recycling of solid waste is realized, environmental pollution is reduced, and the use cost of cement is saved. The combined alkali and free alkali in the red mud are removed by roasting and water immersion methods; aggregate and alkaline activator are added to activate and form a gel material. The preparation method is simple, and the prepared new water-stable material has good compressive strength.

[0059] Finally, it should be noted that the above are only the preferred embodiments of the present invention, which are only used to illustrate the technical solutions of the present invention and are not intended to limit them; any modifications, equivalent replacements, improvements, etc. made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A new type of water-stable material with high durability, characterized in that, The novel water-stabilized material comprises the following materials by weight percentage: 10-20% of red mud, 10-15% of coal gangue, 45-70% of aggregate, 8-12% of alkaline activator, and 2-8% of additive.

2. The novel water-stable material according to claim 1, characterized in that, The aggregate is selected from one or more of slag, sand, crushed stone, fly ash, and washed sand.

3. The novel water-stable material according to claim 1, wherein The alkaline activator is selected from one or more of water glass, quicklime powder, gypsum dihydrate, sodium sulfate, and sodium silicate.

4. The novel water-stable material according to claim 1, characterized in that, The additive is selected from one or more of silica fume, bentonite, diatomite, and earthworm castings.

5. The novel water-stable material according to claim 1, wherein The red mud is Bayer red mud with a moisture content of 10-60%.

6. A preparation method of the novel water-stable material as described in claim 1, characterized in that, It includes the following steps: (1) Pretreatment of raw materials: Crushing and screening red mud, coal gangue, and aggregate respectively. (2) Activation of raw materials: Roasting the screened red mud and performing four-stage water leaching for alkali removal; calcining coal gangue. (3) Preparation of water-stabilized layer material: Adding each raw material according to the ratio to aggregate, activated red mud, coal gangue, alkaline activator, and additive, stirring and mixing evenly, and curing.

7. The preparation method according to claim 6, characterized in that, In step (1), the particle size of the red mud is 5-10 mm, and the particle size of the aggregate is 1-10 mm.

8. The preparation method according to claim 6, characterized in that, In step (2), the roasting temperature of the red mud is 680-700 °C, and the roasting time is 30 min.

9. The preparation method according to claim 6, characterized in that, In step (2), the water leaching temperature of the red mud is 90-100 °C, and the water leaching time is 60 min.

10. The preparation method according to claim 6, characterized in that, In step (2), the calcining temperature of the coal gangue is 400-450 °C.

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