Coal-fired power plant solid waste-based cementitious material and preparation method thereof

Abstract

The application discloses a kind of solid waste-based cementing material of coal-fired power plant and preparation method thereof, belong to building material technical field.The material is made of the following weight parts of raw materials: 50-70 parts of fly ash, 10-30 parts of mineral powder, 10-30 parts of desulfurization gypsum, 1-5 parts of activator, 1-5 parts of seed crystal.The key of its preparation method lies in by implanting pre-synthesized C-S-H seed crystal, as nucleation base point in the hydration process of cementing material, effectively stimulate the potential activity of solid waste, induce the formation of dense hydration product structure.Cementing material prepared by the application has the advantages of high strength, low cost, environmental protection, etc., realizes the high value-added resource utilization of solid waste of coal-fired power plant.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a cementitious material prepared from industrial solid waste and its preparation method, particularly a high-strength cementitious material prepared by using solid waste from coal-fired power plants as the main raw material and activating its activity through seed crystal implantation technology. Background Technology

[0002] The large amounts of solid waste generated by coal-fired power plants, such as fly ash, bottom ash, and desulfurization gypsum, not only occupy a significant amount of land but also pose a potential threat to the environment. Currently, the utilization of these solid wastes mainly focuses on their use as cement admixtures or concrete additives. However, due to their low activity, limited dosage, and difficulty in preparing high-strength cementitious materials, the resource utilization efficiency is not high.

[0003] In existing technologies, high-temperature calcination or mechanical grinding is commonly used to improve the activity of solid wastes such as fly ash. For example, patent CN119774899B discloses a low-carbon cementitious material and its preparation method, which involves calcining a mixture of industrial solid wastes at a high temperature of 300~1000℃ for 1~8 hours and then adding an alkaline activator to obtain a high-strength low-carbon cementitious material. However, high-temperature calcination or mechanical grinding is energy-intensive and economically inefficient. Therefore, developing an efficient, green, low-cost method for activating solid wastes and preparing cementitious materials that can produce high-strength materials has become an urgent problem to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a cementitious material based on solid waste from coal-fired power plants and its preparation method. This method effectively stimulates the potential activity of solid waste through a "seedling" technique, producing a high-strength cementitious material without relying on high-intensity mechanical grinding and high-temperature calcination, thus achieving high-value-added resource utilization of solid waste from coal-fired power plants.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A solid waste-based cementitious material for coal-fired power plants comprises the following components in parts by weight: 50-70 parts fly ash, 10-30 parts mineral powder, 10-30 parts desulfurization gypsum, 1-5 parts activator, and 1-5 parts seed crystals.

[0006] Furthermore, the fly ash is the original fly ash from a coal-fired power plant.

[0007] Furthermore, the mineral powder is granulated blast furnace slag powder.

[0008] Furthermore, the desulfurized gypsum is obtained by drying desulfurized gypsum discharged from power plants to obtain dry powder desulfurized gypsum.

[0009] Furthermore, the activator is one or more of calcium hydroxide, sodium hydroxide, calcium chloride, sodium aluminate, calcium oxide, cement clinker, and sodium silicate.

[0010] Furthermore, the seed crystals are highly reactive hydrated calcium silicate (CSH) gel microcrystals prepared in advance via a hydrothermal synthesis method. The preparation method is as follows: Calcium-based raw materials (such as CaO) and silica-based raw materials (such as quartz sand or microsilica powder) are mixed at a Ca / Si molar ratio of 0.8-1.5, and water is added at a water-to-solid mass ratio of 5:1-10:1. The mixture is then subjected to a hydrothermal reaction at 150-200℃ for 6-24 hours. Subsequently, the reaction product is washed, dried, and ground until the specific surface area is ≥500 m². 2 / kg, thus obtaining the seed crystal.

[0011] The preparation method of the solid waste-based cementitious material is as follows: S1: Place fly ash, mineral powder, desulfurized gypsum, activator, and seed crystals in a mixer according to the specified ratio, and dry mix for 1-3 minutes to ensure uniform mixing. Then, add the specified amount of water and wet mix for 3-5 minutes to form a uniform slurry.

[0012] S2: Inject the slurry into the mold, vibrate to compact, and then cure. The curing regime is as follows: first cure for 1-3 days under standard curing conditions of 20±2℃ and humidity ≥90%, then demold and transfer to a steam or hot water environment of 60-80℃ for 3-7 days, or seal and cure at room temperature for 28 days.

[0013] The compressive strength of the cementitious material can reach more than 40 MPa after 28 days, preferably 50-70 MPa.

[0014] This invention makes full use of solid waste from coal-fired power plants such as fly ash and desulfurization gypsum. By implanting seed crystals, it provides nucleation sites for the hydration reaction of solid waste from coal-fired power plants, significantly improving the activity of solid waste. It eliminates the need for high-temperature calcination or mechanical grinding, achieving efficient synergistic utilization of solid waste from multiple sources. It has low energy consumption, low cost, and is easy to industrialize.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) This invention utilizes pre-synthesized hydrated calcium silicate seed crystals. These seed crystals act as "nucleation sites" during the hydration process of the cementitious system, effectively inducing and accelerating the dissolution of solid waste particles and the precipitation and growth of subsequent hydration products. This significantly improves the reaction rate and extent, thereby fully stimulating the potential activity of the solid waste. Due to the inducing effect of the seed crystals, the generated hydration products are more dense and uniform, forming a more optimized microstructure, resulting in a cementitious material with higher mechanical strength. This invention reduces preparation costs by introducing seed crystals; while commonly used cement strength grades are 32.5 MPa, 42.5 MPa, and 52.5 MPa, the cementitious material of this invention has a strength exceeding 60 MPa, meeting usage requirements.

[0016] 2) This invention makes extensive use of solid waste from coal-fired power plants, such as fly ash and desulfurized gypsum, resulting in carbon emissions that are only 20-30% of those of traditional cement, thus meeting the national "dual-carbon" strategy requirements. Furthermore, it eliminates the need for energy-intensive deep grinding processes, simplifying the preparation process and offering significant economic benefits. Compared to existing technologies, this invention avoids energy-intensive processes such as high-temperature calcination, with the main processes conducted at ambient temperature and pressure, resulting in low energy consumption, low cost, and ease of industrial production.

[0017] 3) The technology of this invention can be widely applied to ready-mixed concrete, road engineering, backfilling engineering and other fields, realizing the high-value utilization of solid waste from coal-fired power plants, providing a new way for the resource utilization of solid waste from coal-fired power plants, and has significant economic, social and environmental benefits. Attached Figure Description

[0018] Figure 1 This is a scanning electron microscope (SEM) image of the cementitious material prepared in Example 1 of the present invention. Detailed Implementation

[0019] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to these embodiments.

[0020] Example 1: Preparation of solid waste-based cementitious materials from coal-fired power plants A solid waste-based cementitious material for coal-fired power plants, with the following raw material proportions (parts by weight): 60 parts fly ash, 20 parts mineral powder, 10 parts desulfurized gypsum, 5 parts seed crystals (CSH gel), 5 parts calcium hydroxide, and 30 parts water.

[0021] Seed crystal preparation: CaO and microsilica powder were mixed at a Ca / Si molar ratio of 1.2, and water was added at a water-to-solid mass ratio of 10:1 to form a slurry. The slurry was placed in a high-pressure reactor and reacted at 180°C for 12 hours. The product was filtered, washed, dried at 105°C, and then ground to a specific surface area of ​​approximately 600 m² / kg.

[0022] A method for preparing a solid waste-based cementitious material from a coal-fired power plant includes the following steps: S1: Dry mix fly ash, mineral powder, desulfurized gypsum, calcium hydroxide and the above seed crystals in a planetary mixer for 2 minutes according to the proportion.

[0023] S2: Add an appropriate amount of water and continue to wet mix for 4 minutes to obtain a uniform slurry.

[0024] S3: Pour the slurry into a 40mm×40mm×160mm mold and vibrate to form the mold.

[0025] S4: After curing in a standard curing chamber (20℃, 95% humidity) for 24 hours, demold and then place in an 80℃ steam curing chamber for 3 days. Performance testing: The compressive strength was tested according to GB / T17671 "Test Method for Strength of Cement Mortar (ISO Method)". The compressive strength after 3 days of curing was measured to be 28.2 MPa, and the compressive strength after 28 days of curing was 38.7 MPa.

[0026] The scanning electron microscope (SEM) image of the cementitious material prepared in Example 1 of this invention after 28 days of curing is shown below. Figure 1 As shown, in Figure 1 As can be seen, a large number of interwoven CSH gels were generated in the hydration products, with a dense structure.

[0027] Example 2: Preparation of solid waste-based cementitious materials from coal-fired power plants Raw material ratio (parts by weight): 50 parts fly ash, 30 parts mineral powder, 10 parts desulfurized gypsum, 5 parts seed crystal (CSH gel), 5 parts sodium silicate, and 30 parts water.

[0028] Preparation method: The steps are the same as in Example 1.

[0029] Performance testing: 3-day compressive strength is 32.6 MPa, and 28-day compressive strength is 61.2 MPa.

[0030] Comparative Example 1: Preparation of Solid Waste-Based Cementitious Materials from Coal-Fired Power Plants Except for the absence of seed crystals, the raw materials and steps are exactly the same as in Example 1.

[0031] Performance testing: 3-day compressive strength is 21.7 MPa, and 28-day compressive strength is 27.6 MPa.

[0032] Comparative Example 2: Preparation of Solid Waste-Based Cementitious Materials from Coal-Fired Power Plants Mechanical excitation was used instead of seed crystals. The raw materials in Example 1 were dry-mixed in a planetary mixer for 2 minutes and then ultra-finely ground to a specific surface area of ​​600 m² / kg. No seed crystals were added, and the rest was the same as in Example 1.

[0033] Performance testing: 3-day compressive strength is 24.3 MPa, and 28-day compressive strength is 32.1 MPa.

[0034] Comparative Example 3: Preparation of Solid Waste-Based Cementitious Materials from Coal-Fired Power Plants After mixing CaO and microsilica powder at a Ca / Si molar ratio of 1.2, the mixture was not subjected to a high-temperature hydrothermal reaction, but was directly mixed with the raw materials in Example 1. The rest of the process was the same as in Example 1.

[0035] Performance testing: 3-day compressive strength is 23.1 MPa, and 28-day compressive strength is 25.7 MPa.

[0036] As can be seen from the comparison between the examples and the comparative examples, the present invention significantly improves the mechanical strength of cementitious materials through seed implantation technology, which is superior to simple mechanical grinding and activation.

Claims

1. A solid waste-based cementitious material from a coal-fired power plant, characterized in that, The composition includes the following components by weight: 50-70 parts fly ash, 10-30 parts mineral powder, 10-30 parts desulfurized gypsum, 1-5 parts activator, and 1-5 parts seed crystals. The seed crystals are hydrated calcium silicate CSH gel microcrystals with high reactivity, which are pre-prepared by hydrothermal synthesis.

2. The solid waste-based cementitious material for coal-fired power plants according to claim 1, characterized in that, The fly ash is the original fly ash from a coal-fired power plant.

3. The solid waste-based cementitious material for coal-fired power plants according to claim 1, characterized in that, The mineral powder is granulated blast furnace slag powder.

4. The solid waste-based cementitious material for coal-fired power plants according to claim 1, characterized in that, The desulfurized gypsum is obtained by drying desulfurized gypsum discharged from power plants to obtain dry powder desulfurized gypsum.

5. The solid waste-based cementitious material for coal-fired power plants according to claim 1, characterized in that, The activator is one or more of calcium hydroxide, sodium hydroxide, calcium chloride, sodium aluminate, calcium oxide, cement clinker, and sodium silicate.

6. The solid waste-based cementitious material for coal-fired power plants according to claim 1, characterized in that, The method for preparing the seed crystal is as follows: calcium raw material and silicon raw material are mixed at a Ca / Si molar ratio of 0.8-1.5, water is added at a water-solid mass ratio of 5:1-10:1, and the mixture is subjected to hydrothermal reaction at 150-200℃ for 6-24 hours. The reaction product is then washed, dried, and ground until the specific surface area is ≥500m² / kg to obtain the seed crystal.

7. The solid waste-based cementitious material for coal-fired power plants according to claim 6, characterized in that, The calcareous raw material is calcium hydroxide or calcium oxide, and the siliceous raw material is quartz sand or microsilica powder.

8. The method for preparing a solid waste-based cementitious material from a coal-fired power plant according to claim 6, characterized in that, Includes the following steps: S1: Place fly ash, mineral powder, desulfurized gypsum, activator and seed crystals in a mixer according to the proportion, dry mix for 1-3 minutes to make it evenly mixed; then add water and wet mix for 3-5 minutes to form a uniform slurry; S2: The slurry is injected into the mold, vibrated to form the shape, and then cured.

Images