Geopolymer road base material based on desulfurized gypsum and preparation method of geopolymer road base material

Abstract

The invention provides a geopolymer road base material based on desulfurized gypsum and a preparation method of the geopolymer road base material, and relates to the field of materials. Comprising water and a solid material, and the solid material comprises the following raw materials in percentage by mass: 80%-90% of desulfurized gypsum, 5%-15% of ordinary Portland cement, 0.15%-2% of nano silicon dioxide, 0.1%-0.3% of calcium formate, 0.01%-0.03% of lithium carbonate and 1%-3% of magnesium oxide. Nano SiO2 is compounded with lithium carbonate and magnesium oxide, double blocking of an AFt generation path is achieved, and after curing forming, the compressive strength is larger than or equal to 5 MPa in 7 days and larger than or equal to 8 MPa in 28 days.

Description

Technical Field

[0001] The present invention relates to the field of materials, and in particular to a desulfurized gypsum-based geopolymer road base material and a preparation method thereof. Background Art

[0002] Traditional road base materials (such as cement-stabilized crushed stone) pose challenges such as high carbon emissions and resource consumption. Desulfurized gypsum, a byproduct of coal-fired power plants, generates over 100 million tons of wastewater annually, yet its utilization rate is less than 30%. This is primarily due to its high impurities and low hydration activity, which can lead to expansion and cracking later in the process. Patent CN119019103A, which combines calcined desulfurized gypsum with finely divided steel slag, suffers from insufficient early strength and fails to address the AFt expansion issue.

[0003] Patent CN118930313A discloses a method for preparing a water-fertilizer storage and slow-release material using desulfurized gypsum. The method uses desulfurized gypsum for a water-fertilizer slow-release material, but does not involve its application in road engineering.

[0004] Therefore, there is an urgent need to develop a desulfurized gypsum-based road material with both high strength and low expansion properties. Summary of the Invention

[0005] The purpose of the present invention is to provide a geopolymer road base material based on desulfurized gypsum, which compounds nano-SiO2 with lithium carbonate and magnesium oxide to achieve double blocking of the AFt generation path. After curing and molding, the compressive strength is ≥5MPa after 7 days and ≥8MPa after 28 days.

[0006] Another object of the present invention is to provide a method for preparing a geopolymer road base material based on desulfurized gypsum, which first calcines the desulfurized gypsum to increase the reactivity of the desulfurized gypsum and thereby increase the strength after molding.

[0007] The present invention solves the technical problem by adopting the following technical solutions.

[0008] In one aspect, an embodiment of the present invention provides a desulfurized gypsum-based geopolymer road base material, comprising water and solid material, wherein the solid material comprises the following raw materials by mass percentage:

[0009] Desulfurized gypsum 80%-90%, ordinary Portland cement 5%-15%, nano silicon dioxide 0.15%-2%, calcium formate 0.1%-0.3%, lithium carbonate 0.01%-0.03%, magnesium oxide 1%-3%.

[0010] In some embodiments of the present invention, the solid materials are composed of the following raw materials in terms of mass percentage:

[0011] Desulfurized gypsum 90%, ordinary Portland cement 7%, nano silicon dioxide 0.3%, calcium formate 0.3%, lithium carbonate 0.03%, magnesium oxide 2.07%.

[0012] In some embodiments of the present invention, the solid material is composed of the following raw materials by mass percentage:

[0013] Desulfurized gypsum 85%, ordinary Portland cement 13%, nano silicon dioxide 0.15%, calcium formate 0.15%, lithium carbonate 0.03%, magnesium oxide 1.52%.

[0014] In some embodiments of the present invention, the water content of the road base material is 10-15%.

[0015] In some embodiments of the present invention, the water content of the road base material is 14%.

[0016] On the other hand, an embodiment of the present invention provides a method for preparing a geopolymer road base material based on desulfurized gypsum, comprising the following steps:

[0017] S1, crushing the desulfurized gypsum and then calcining it;

[0018] S2, dry-mixing the calcined desulfurized gypsum, cement, nano-SiO2, calcium formate, lithium carbonate and magnesium oxide according to the proportion;

[0019] S3, adding water to perform wet mixing, with the mixing time being ≥5 minutes, to obtain the road base material.

[0020] In some embodiments of the present invention, in step S1, the particle size of the crushed desulfurized gypsum is ≤2 mm.

[0021] In some embodiments of the present invention, in step S1, the calcination temperature is 200-300° C., and the calcination time is 1-2 hours.

[0022] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects:

[0023] The road base material provided by the present invention uses desulfurized gypsum as the main raw material and is mixed with nano-silicon dioxide, calcium formate, lithium carbonate and silicate cement. It can not only consume a large amount of desulfurized gypsum, reduce pollution and realize the secondary utilization of resources, but also, as a road base material, its 7-day compressive strength is ≥5MPa and 28-day ≥25MPa.

[0024] Among them, silicate cement is the main cementitious material and can provide basic strength.

[0025] Nanosilica significantly enhances the material's early strength and density by filling micropores and promoting hydration reactions. It also improves the material's impermeability and chemical resistance, extending the road's service life. The filling effect of nanosilica also reduces water consumption and improves the material's workability.

[0026] Calcium formate acts as an early strength agent to accelerate cement hydration and shorten the time it takes for roads to be open to traffic. It also improves the fluidity and plasticity of base materials, facilitating construction operations.

[0027] Lithium carbonate may modulate the hydration reaction rate, further optimizing strength development.

[0028] Desulfurized gypsum improves the material's resistance to sulfate attack and reduces environmental damage to roads. Furthermore, the desulfurized gypsum content in the present invention is greater than 80%, allowing for large-scale consumption of desulfurized gypsum, reducing solid waste emissions and aligning with the concept of sustainable development. Desulfurized gypsum is inexpensive, and its large-scale use effectively reduces material costs.

[0029] Magnesium oxide acts as an expansion agent, compensating for material shrinkage, reducing the risk of cracking and enhancing crack resistance. The expansion effect of magnesium oxide adapts to temperature changes and can reduce deformation caused by thermal expansion and contraction.

[0030] The preparation method provided by the present invention first crushes and calcines the desulfurized gypsum, which can improve the surface activity of the desulfurized gypsum, thereby improving the bonding strength between the desulfurized gypsum and other raw materials, and improving the overall strength and performance of the base material. DETAILED DESCRIPTION

[0031] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0032] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to specific embodiments.

[0033] In one aspect, an embodiment of the present invention provides a desulfurized gypsum-based geopolymer road base material, comprising water and solid material, wherein the solid material comprises the following raw materials by mass percentage:

[0034] Desulfurized gypsum 80%-90%, ordinary Portland cement 5%-15%, nano silicon dioxide 0.15%-2%, calcium formate 0.1%-0.3%, lithium carbonate 0.01%-0.03%, magnesium oxide 1%-3%.

[0035] Preferably, the solid material comprises the following raw materials by mass percentage:

[0036] Desulfurized gypsum 90%, ordinary Portland cement 7%, nano silicon dioxide 0.3%, calcium formate 0.3%, lithium carbonate 0.03%, magnesium oxide 2.07%.

[0037] Preferably, the solid material comprises the following raw materials by mass percentage: 85% desulfurized gypsum, 13% ordinary Portland cement, 0.15% nano-silicon dioxide, 0.15% calcium formate, 0.03% lithium carbonate, and 1.52% magnesium oxide.

[0038] Desulfurized gypsum, primarily composed of calcium sulfate dihydrate (CaSO4·2H2O), has a content of ≥93%, and contains small amounts of impurities such as silicon dioxide, sodium oxide, calcium carbonate, and calcium sulfite. It is a renewable resource with a small particle size, high purity, low content of harmful impurities, and stable hydration properties. In this invention, desulfurized gypsum is the primary raw material, providing calcium to promote cement hydration, regulate the material's setting time, and improve workability.

[0039] Ordinary Portland cement is made by grinding Portland cement clinker, 5%-20% mixed materials (such as slag and fly ash), and an appropriate amount of gypsum. It mainly contains tricalcium silicate and dicalcium silicate. It has high strength, high heat of hydration, good frost resistance, low shrinkage, and good wear resistance. As the main cementitious material, it provides basic strength and forms a hardened body through hydration, which imparts early and late strength to the material.

[0040] Nanosilica, amorphous silicon dioxide (SiO2), nanoscale particles (1-100nm). It has a high specific surface area, excellent optical properties, and can improve the material's aging resistance, strength, and chemical resistance. In the present invention, it can fill micropores, promote hydration reactions, and enhance material density. It improves the strength, wear resistance, and impermeability of road base materials, reduces water consumption, and improves the workability of base materials.

[0041] Calcium formate has the molecular formula C2H2O4Ca. It is a white crystalline powder that dissolves in water and exhibits early strength and coagulant properties. In the present invention, it acts as an early strength agent to accelerate cement hydration, shorten setting time, and increase early strength, particularly at low temperatures. It also improves the workability and construction properties of the material, promotes cement hydration, and enhances its density.

[0042] Lithium carbonate, chemical formula Li2CO3. Colorless monoclinic crystals, slightly soluble in water. In the present invention, it plays a role in regulating the hydration reaction rate, optimizing strength development, adjusting the material's setting time and hardening process, and improving the material's stability and adaptability.

[0043] Magnesium oxide is a white solid, highly refractory, alkaline oxide with expansive properties. In this invention, it acts as an expansion agent to compensate for material shrinkage, reduce the risk of cracking, improve crack resistance, and enhance the adaptability of the base material to temperature changes, reducing deformation caused by thermal expansion and contraction, thereby enhancing the durability and stability of the material.

[0044] The water content of the road base material is 10-15%, preferably 14%.

[0045] The method for preparing the above-mentioned road base material comprises the following steps:

[0046] S1, crushing the desulfurized gypsum to a particle size of ≤2 mm, and then calcining at 200-300°C for 1-2 hours;

[0047] S2, dry-mixing the calcined desulfurized gypsum, cement, nano-SiO2, calcium formate, lithium carbonate and magnesium oxide according to the proportion;

[0048] S3, adding water to perform wet mixing, with the mixing time being ≥5 minutes, to obtain the road base material.

[0049] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0050] Example 1

[0051] Prepare the raw materials according to the following ratio:

[0052] Desulfurized gypsum 90%, ordinary Portland cement 7%, nano silicon dioxide 0.3%, calcium formate 0.3%, lithium carbonate 0.03%, magnesium oxide 2.07%.

[0053] Prepare the base material as follows:

[0054] S1, crushing the desulfurized gypsum to a particle size of ≤2 mm, and then calcining it at 250°C for 1.5 h;

[0055] S2, dry-mixing the calcined desulfurized gypsum, cement, nano-SiO2, calcium formate, lithium carbonate and magnesium oxide according to the proportion;

[0056] S3, adding water to carry out wet mixing for ≥5 minutes to obtain the road base material with a water content of 14%.

[0057] Example 2

[0058] Prepare the raw materials according to the following ratio:

[0059] Desulfurized gypsum 85%, ordinary Portland cement 13%, nano silicon dioxide 0.15%, calcium formate 0.15%, lithium carbonate 0.03%, magnesium oxide 1.52%.

[0060] Prepare the base material as follows:

[0061] S1, crushing the desulfurized gypsum to a particle size of ≤2 mm, and then calcining at 200 ° C for 2 h;

[0062] S2, dry-mixing the calcined desulfurized gypsum, cement, nano-SiO2, calcium formate, lithium carbonate and magnesium oxide according to the proportion;

[0063] S3, adding water to carry out wet mixing for ≥5 minutes to obtain the road base material with a water content of 14%.

[0064] Example 3

[0065] Prepare the raw materials according to the following ratio:

[0066] Desulfurized gypsum 80%, ordinary Portland cement 15%, nano silicon dioxide 1.67%, calcium formate 0.3%, lithium carbonate 0.03%, magnesium oxide 3%.

[0067] Prepare the base material as follows:

[0068] S1, crushing the desulfurized gypsum to a particle size of ≤2 mm, and then calcining at 300 °C for 1 h;

[0069] S2, dry-mixing the calcined desulfurized gypsum, cement, nano-SiO2, calcium formate, lithium carbonate and magnesium oxide according to the proportion;

[0070] S3, adding water to carry out wet mixing for ≥5 minutes to obtain the road base material with a water content of 10%.

[0071] Example 4

[0072] Prepare the raw materials according to the following ratio:

[0073] Desulfurized gypsum 85%, ordinary Portland cement 10%, nano silicon dioxide 2%, calcium formate 0.3%, lithium carbonate 0.03%, magnesium oxide 2.67%.

[0074] Prepare the base material as follows:

[0075] S1, crushing the desulfurized gypsum to a particle size of ≤2 mm, and then calcining at 300 °C for 1 h;

[0076] S2, dry-mixing the calcined desulfurized gypsum, cement, nano-SiO2, calcium formate, lithium carbonate and magnesium oxide according to the proportion;

[0077] S3, adding water to carry out wet mixing for ≥5 minutes to obtain the road base material with a water content of 15%.

[0078] Experimental example

[0079] The base material of Example 1 was used as raw material, transferred into a mold, vibrated and compacted to produce samples. The compressive strength and expansion rate of the samples were tested on the 7th, 28th and 90th days, respectively. The results are shown in Table 1.

[0080] Table 1

[0081] Age Compressive strength Expansion rate 7 days 6.5MPa 0.02％ 28 days 28.3MPa 0.05％ 90 days 32.0MPa 0.07％

[0082] It can be seen from Table 1 that the road base material of Example 1 has high compressive strength, with a 7-day compressive strength of ≥5 MPa and a 28-day compressive strength of ≥8 MPa; and a small expansion rate, with a 7-day expansion rate of 0.02% and a 90-day expansion rate of less than 0.1%.

[0083] In summary, the road base material provided by the embodiment of the present invention uses desulfurized gypsum as the main raw material, and is combined with nano-silicon dioxide, calcium formate, lithium carbonate and silicate cement. It can not only consume a large amount of desulfurized gypsum, reduce pollution, and realize the secondary utilization of resources, but also has excellent mechanical properties as a road base material.

[0084] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

Claims

1. A geopolymer road base material based on desulfurized gypsum, characterized in that: It includes water and solid materials, and the solid materials include the following raw materials by mass percentage: Desulfurized gypsum 80%-90%, ordinary Portland cement 5%-15%, nano silicon dioxide 0.15%-2%, calcium formate 0.1%-0.3%, lithium carbonate 0.01%-0.03%, magnesium oxide 1%-3%.

2. The desulfurized gypsum-based geopolymer road base material according to claim 1, characterized in that: The solid materials are calculated by mass percentage and are as follows: Desulfurized gypsum 90%, ordinary Portland cement 7%, nano silicon dioxide 0.3%, calcium formate 0.3%, lithium carbonate 0.03%, magnesium oxide 2.07%.

3. The desulfurized gypsum-based geopolymer road base material according to claim 1, characterized in that: The solid materials are calculated by mass percentage and are as follows: Desulfurized gypsum 85%, ordinary Portland cement 13%, nano silicon dioxide 0.15%, calcium formate 0.15%, lithium carbonate 0.03%, magnesium oxide 1.52%.

4. The desulfurized gypsum-based geopolymer road base material according to claim 1, characterized in that: The water content of the road base material is 10-15%.

5. The desulfurized gypsum-based geopolymer road base material according to claim 1, characterized in that: The water content of the road base material is 14%.

6. A method for preparing a geopolymer road base material based on desulfurized gypsum according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, crushing the desulfurized gypsum and then calcining it; S2, dry-mixing the calcined desulfurized gypsum, cement, nano-SiO2, calcium formate, lithium carbonate and magnesium oxide according to the proportion; S3, adding water to perform wet mixing, with the mixing time being ≥5 minutes, to obtain the road base material.

7. The method for preparing a geopolymer road base material based on desulfurized gypsum according to claim 6, characterized in that: In the step S1, the particle size of the crushed desulfurized gypsum is ≤2 mm.

8. The method for preparing a geopolymer road base material based on desulfurized gypsum according to claim 6, characterized in that: In the step S1, the calcination temperature is 200-300° C., and the calcination time is 1-2 hours.