A solidified agent based on a bidirectional excitation slag full solid waste system and a preparation method thereof

Abstract

This invention relates to the field of curing agent technology, and more particularly to a curing agent based on a bidirectional activated slag solid waste system and its preparation method. The aforementioned curing agent based on a bidirectional activated slag solid waste system comprises, by weight, the following components: 60-80% cementitious component, 10-30% alkali-activated component, 5-15% sulfate-activated component, and 0-0.5% composite additive component. This invention scientifically proportions the various raw materials, organically combines the effective components, fully utilizes the characteristics and synergistic effects of each component, and rationally adjusts the process parameters. The curing agent of this invention exhibits good curing effect, excellent stability, and high compressive strength, significantly improving the high moisture content and low strength properties of waste excavated geological materials from both physical and chemical perspectives.

Description

Technical Field

[0001] This invention relates to the field of curing agent technology, and in particular to a curing agent based on a bidirectional activated slag solid waste system and its preparation method. Background Technology

[0002] Every year, my country generates a large amount of waste excavated geological materials during urban underground space construction, dredging projects, and island and reef engineering development. These waste excavated geological materials are stored in stockpiles and urgently need to be disposed of. Transforming these materials into engineering materials through chemical modification can effectively solve the land use and pollution problems associated with these stockpiles, offering significant economic and environmental benefits.

[0003] Currently, a common method for the resource recovery of waste excavated geological materials is to chemically modify cement-based materials to improve their mechanical properties. However, cement is a high-carbon material. According to statistics, my country's cement production in 2020 was 2.377 billion tons, and the CO2 emissions from cement production were approximately 1.39 billion tons. Using cement-based materials to treat waste excavated geological materials is inconsistent with environmental protection principles.

[0004] Meanwhile, my country's industrial activities generate large quantities of solid waste such as blast furnace slag and industrial by-product gypsum, which are not being effectively utilized. According to incomplete statistics, my country produces 200 million tons of blast furnace slag and 150 million tons of industrial by-product gypsum annually. Currently, the comprehensive utilization rate of these materials is not high, and their large-scale accumulation will cause environmental pollution and resource waste.

[0005] Because slag itself possesses inherent hydraulic properties, it exhibits good activity after chemical activation such as alkali activation and sulfate activation. The sulfates abundant in industrial by-product gypsum have a good activation effect in an alkaline environment. Adding alkaline substances and industrial by-product gypsum to slag can achieve bidirectional activation through both alkali and sulfate activation. The sources of slag activity are CaO and Al2O3. After chemical activation, the hydraulic cementitious properties of slag are better expressed. Simultaneously, the sulfates abundant in sulfate activation have a better activation effect in the alkaline environment provided by alkali-activated materials. This indicates that the combined application of alkali and sulfate activation yields a better activation effect. The hydration of CaO and Al2O3 in slag can form hydrated calcium silicate, hydrated calcium aluminate, and aluminosilicates, similar to cement hydration products. Furthermore, the active silicon, aluminum, and calcium components in slag can react with sulfate materials such as gypsum to form hydraulic minerals such as ettringite and hydrated calcium silicate. Due to the physical and chemical differences between slag cementitious materials and cement, slag has a better curing effect than cement, which gives it the potential to replace cement and other high-carbon emission curing materials.

[0006] However, in the existing technology, the activation and utilization of slag mainly focuses on unidirectional activation, while research and utilization of bidirectional activation are relatively scarce. Therefore, there is an urgent need to further study a non-cement-based curing agent based on bidirectional activation of slag. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by proposing a solidifying agent based on a bidirectional induced slag solid waste system and its preparation method.

[0008] A solidifying agent based on a bidirectional activating slag solid waste system comprises the following raw materials by mass: 60-80% gelling component, 10-30% alkali activating component, 5-15% sulfate activating component, and 0-0.5% composite additive component.

[0009] Preferably, the composite admixture component is at least one of the following: accelerator, early strength agent, retarder, and antifreeze agent.

[0010] Preferably, the sulfate activating component is phosphogypsum or desulfurized gypsum.

[0011] More preferably, the average particle size of the sulfate-activated component is ≤0.08 mm.

[0012] Preferably, the gelling component is granulated blast furnace slag powder.

[0013] More preferably, the specific surface area of ​​the gelling component is 400–800 m². 2 / kg and alkalinity greater than or equal to 1.0.

[0014] Preferably, the alkaline activating component is sodium hydroxide, magnesium oxide, calcium oxide, or a composite calcium oxide.

[0015] More preferably, the composite calcium oxide is prepared by the following steps: bamboo charcoal powder is added to hydrochloric acid solution and ultrasonically stirred for 10-30 min, filtered and washed, vacuum dried, and passed through a 100-mesh sieve; the product is added to water, calcium hydrogen phosphate is added and stirred for 10-20 h, freeze-dried, calcined at 300-400℃ for 10-30 min under nitrogen protection, cooled to room temperature, pulverized and passed through a 60-mesh sieve, added to anhydrous ethanol, calcium oxide and amino-terminated polyamide amine are added and shaken for 20-40 min, and then freeze-dried.

[0016] Specifically, the mass ratio of bamboo charcoal powder, dicalcium phosphate, calcium oxide, and amino-terminated polyamide amine is 10-20:1-3:1-3:1-2.

[0017] Specifically, the concentration of the hydrochloric acid solution is 1-3 mol / L.

[0018] This invention combines dicalcium phosphate with bamboo charcoal powder to form calcium-rich biochar, which is then compounded with calcium oxide. With the help of terminal amino polyamide amine, the composite calcium oxide forms a porous structure and introduces surface modification groups, which significantly improves the dispersibility of calcium oxide and creates a long-lasting alkaline environment. This avoids the problems of rapid alkalinity increase and excessive alkali consumption caused by the rapid hydration of traditional calcium oxide.

[0019] More preferably, the particle size of the alkali-activated component is ≤0.08 mm.

[0020] The above-mentioned preparation method of solidifying agent based on bidirectional activation slag solid waste system includes the following steps: drying and grinding the gelling component, alkali activation component, and sulfate activation component; and then mixing each component evenly.

[0021] Compared with existing technologies, the present invention has the following advantages: (1) The present invention scientifically proportions each raw material and organically combines the effective components, giving full play to the characteristics and synergistic effects of each component and rationally adjusting the process parameters; the curing agent of the present invention has good curing effect, good stability, and high compressive strength, and significantly improves the properties of waste excavated geological materials such as high moisture content and low strength from a physical and chemical perspective.

[0022] (2) The materials in the cementitious components used in this invention have inherent hydraulic properties. After alkali activation and sulfate activation, they exhibit good activity. Furthermore, the sulfate-rich sulfate in the sulfate-activating component has a better activation effect in the alkaline environment created by the alkali-activating component. The silicon and calcium elements in the cementitious components, after activation by the alkali and sulfate-activating components, undergo hydration reactions with these components to generate hydraulic minerals such as ettringite and hydrated calcium silicate, which contribute to strength generation.

[0023] The composite calcium oxide used in this invention can effectively regulate the alkaline release rate and, in synergy with the bidirectional activation of slag and sulfate activation components, can fully activate the activity of slag and improve the long-term strength and durability of the solidified body.

[0024] (3) The preparation method of the present invention is simple and convenient. By reasonably adjusting the process parameters and selecting the optimal range of process parameters, the raw materials are more firmly bonded, so that the curing agent achieves the best effect. By adjusting the selection and ratio of material components, it can be adapted to various engineering application scenarios, including but not limited to: roadbed base, various backfill materials, soil improvement, surface cover, etc. At the same time, suitable composite admixture components are added to meet the needs of various practical projects.

[0025] (4) This invention can realize the utilization of slag and industrial by-product gypsum, while greatly digesting the waste excavated geological materials. It can effectively solve the land and environmental problems caused by the stockpiling of large quantities of solid waste and waste excavated geological materials.

[0026] (5) This invention utilizes a complete solid waste system to treat waste excavated geological materials, achieving the comprehensive utilization goal of "treating waste with waste", which is in line with the economic concept of low-carbon, green and environmentally friendly development, and realizes the green, efficient, high-quality, high-value, large-scale and comprehensive utilization of my country's "large-scale solid waste".

[0027] (6) This invention can effectively replace cement, a high-energy-consuming and high-carbon-emission material, for the treatment of waste excavation geological materials, and can avoid greenhouse gas emissions generated by cement. This is in line with the concept of environmental protection and responds to the call of the national dual-carbon strategy. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0029] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available. The amino-terminated polyamide amine (PAMAM, G3.0) used in the following examples was purchased from Hangzhou Xinqiao Biotechnology Co., Ltd.

[0030] The composition of each embodiment is shown in Table 1.

[0031] Table 1. Material dosing design schemes for each embodiment (dry mass ratio, dimensionless)

[0032] Note: The composite additives mentioned in Table 1 can be added as needed according to engineering requirements. In each embodiment of the present invention, they are water-retaining agents (specifically anionic polyacrylamide with a molecular weight of 12-13 million and a water absorption rate of ≥300 times).

[0033] The composite calcium oxide used in Example 5 was prepared using the following steps: 12g of bamboo charcoal powder was added to 90g of 1.5mol / L hydrochloric acid solution and ultrasonically stirred for 25min. The mixture was then filtered and washed with deionized water, vacuum dried, and passed through a 100-mesh sieve. The product was added to 70g of deionized water, and 2.5g of dicalcium phosphate was added. The mixture was stirred at 250r / min for 18h and then freeze-dried. The mixture was then placed in a muffle furnace and calcined at 320℃ for 25min under nitrogen protection. After cooling to room temperature, the mixture was pulverized and passed through a 60-mesh sieve. The mixture was added to 70g of anhydrous ethanol, and 2.5g of calcium oxide and 1.2g of terminal amino polyamide amine were added. The mixture was shaken on a shaker for 35min at a vibration speed of 220r / min and then freeze-dried.

[0034] The composite calcium oxide used in Example 6 was prepared by the following steps: 15g of bamboo charcoal powder was added to 80g of 2mol / L hydrochloric acid solution and ultrasonically stirred for 20min. The mixture was then filtered and washed with deionized water, vacuum dried, and passed through a 100-mesh sieve. The product was added to 80g of deionized water, and 2g of dicalcium phosphate was added. The mixture was stirred at 300r / min for 15h and then freeze-dried. The mixture was then placed in a muffle furnace and calcined at 350℃ for 20min under nitrogen protection. After cooling to room temperature, the mixture was pulverized and passed through a 60-mesh sieve. The mixture was added to 80g of anhydrous ethanol, and 2g of calcium oxide and 1.5g of amino-terminated polyamide amine were added. The mixture was shaken on a shaker for 30min at a vibration speed of 250r / min and then freeze-dried.

[0035] control group Ordinary silicate cement was used as a control, with the material name being C; specifically, it was cement material with a grade of 42.5, purchased from a cement plant in Nanjing, Jiangsu Province.

[0036] The abandoned excavated geological material was set as high liquid limit clay. Various high liquid limit clays were selected (as shown in Table 2) to simulate abandoned excavated geological materials in different regions and test the corresponding experimental results.

[0037] Table 2 Physical properties of abandoned excavated geological materials

[0038] The only difference in physical properties between the abandoned excavated geological materials S1 to S3 is their moisture content, while the only difference between S4 and S6 is their moisture content.

[0039] The curing agent obtained in Examples 1-6, the ordinary silicate cement material used in the control group, and the waste excavated geological material were used in a mass ratio of 1:9.

[0040] In practical engineering, unconfined compressive strength is one of the most important mechanical performance indicators, serving as a key factor in determining whether a material can effectively serve in real-world applications. Unconfined compressive strength specifically refers to the maximum axial stress a material can withstand under unconstrained lateral conditions. It allows for rapid and accurate testing of a material's mechanical properties, as shown in Table 3.

[0041] Table 3 Unconfined compressive strength of cured specimens

[0042] Taking GMP-S1 as an example, it is formed by mixing the curing agent (GMP) obtained in Example 1 with the waste excavated geological material S1 at a mass ratio of 1:9.

[0043] Table 3 shows that, under the same abandoned excavated geological materials and curing age, the unconfined compressive strength results obtained by using the curing agent obtained in this invention are all better than the results obtained by curing with traditional cement materials.

[0044] The strength index of the curing agent obtained by this invention is superior to that of ordinary silicate cement materials. This is because the slag itself in the bidirectional activated slag system has potential hydraulic properties and contains a large amount of active silicon and calcium elements to be activated. After being activated by relatively alkaline sodium hydroxide, magnesium oxide, calcium oxide or composite calcium oxide, a pozzolanic reaction occurs, filling the pores and providing strength. In addition, phosphogypsum and desulfurized gypsum provide a large number of sulfate ions, promoting the formation of ettringite with high early strength, thereby promoting the hydration reaction and providing higher strength. At the same time, sulfate has a better activation effect in an alkaline environment. The combined application of alkaline activation and sulfate activation promotes each other and complements each other.

[0045] The unconfined compressive strength of the curing agent (GFD) obtained in Example 6 is the highest value under various ages and abandoned excavated geological materials. Therefore, for projects with high strength requirements, the GFD can be used as a reference for designing the mix proportion.

[0046] To further clarify the superior performance of the curing agent obtained in this invention, a wet-dry cycle test was conducted to evaluate the self-healing ability of the cured material after being subjected to changes in the external environment. At the same time, the wet-dry cycle test can effectively simulate the alternating wet and dry environment of the cured material during its service life, and can effectively evaluate the engineering performance of the cured material in the face of changes in the external environment. It is also a relatively accelerated test that can quickly and effectively evaluate the service performance of the cured material in the most extreme environment.

[0047] Following the American Society for Testing and Materials (ASTM) D4843-1988 Standard test method for wetting and drying test of solid wastes, the material was cured for 28 days before its mass was tested. Subsequently, the material was immersed in distilled water maintained at 20°C for 24 hours. After immersion, it was placed in an oven at 30°C for 48 hours. This process constitutes one cycle. This experimental example will test the changes after 5 cycles and 7 cycles. The formula for calculating the mass loss rate is as follows: .

[0048] Table 4 Dry and Wet Cycles of Curing Materials

[0049] Table 4 shows that the cured material obtained by the curing agent of this invention can effectively resist 7 wet-dry cycles. The reason for this is that the curing agent obtained by this invention has better resistance to wet-dry cycles than ordinary silicate cement materials. This is because the slag itself in the bidirectional activated slag system has potential hydraulic properties and contains a large amount of active silicon and calcium elements to be activated. After being activated by relatively alkaline sodium hydroxide, magnesium oxide, calcium oxide or composite calcium oxide, a pozzolanic reaction occurs, filling the pores and providing strength. In addition, phosphogypsum and desulfurized gypsum provide a large number of sulfate ions, promoting the formation of ettringite with high early strength, which in turn promotes the hydration reaction, further filling the pores and resisting wet-dry cycles. At the same time, sulfate has a better activation effect in an alkaline environment. The combined application of alkaline activation and sulfate activation promotes each other and complements each other.

[0050] To further elucidate the superior performance of the curing agent obtained in this invention, the efficiency of the curing agent in curing high-moisture-content waste excavated geological materials was evaluated by testing the moisture content after curing. Referencing GB / T 50123-2019 "Standard for Geotechnical Testing Methods," this experimental example will test the moisture content changes after 3 days and 7 days.

[0051] Table 5 Moisture content of cured materials

[0052] In summary, this invention discloses a solidifying agent based on a bidirectional induced slag solid waste system and its preparation method. It is suitable for various engineering applications, including but not limited to: roadbed base courses, various backfill materials, soil improvement, and surface cover. Furthermore, by adding suitable composite admixtures, it can meet the needs of various practical engineering projects.

[0053] This invention possesses the following superior characteristics: It scientifically proportions various raw materials, organically combines effective components, fully leverages the characteristics and synergistic effects of each component, and rationally adjusts process parameters to meet the needs of multiple application scenarios; the curing agent of this invention exhibits excellent curing effect, superior stability, and high compressive strength, significantly improving the high moisture content and low strength properties of waste excavated geological materials from a physical and chemical perspective; utilizing a complete solid waste system to treat waste excavated geological materials enables the utilization of slag and industrial by-product gypsum while maximizing the digestion of waste excavated geological materials, effectively solving land and environmental problems caused by the stockpiling of large quantities of solid waste and waste excavated geological materials, achieving the comprehensive utilization goal of "treating waste with waste." Simultaneously, it can effectively replace cement, a high-energy-consuming and high-carbon-emission material, in the treatment of waste excavated geological materials, avoiding greenhouse gas emissions from cement and aligning with the economic concept of low-carbon, green, and environmentally friendly development. The preparation method of this invention is simple, convenient, economical, and environmentally friendly, suitable for various engineering implementation scenarios.

[0054] The present invention has been described in detail above. Those skilled in the art will recognize that the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. While specific embodiments have been provided, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein.

Claims

1. A solidifying agent based on a bidirectional activating slag solid waste system, characterized in that, Its raw materials, by weight, include: 60-80% gelling component, 10-30% alkali activating component, 5-15% sulfate activating component, and 0-0.5% composite additive component.

2. The solidifying agent based on the bidirectional activating slag solid waste system according to claim 1, characterized in that, The composite admixture consists of at least one of the following: quick-setting agent, early-strength agent, retarder, and antifreeze agent.

3. The solidifying agent based on the bidirectional activating slag solid waste system according to claim 1, characterized in that, The sulfate activating component is phosphogypsum or desulfurized gypsum.

4. The solidifying agent based on the bidirectional activating slag solid waste system according to claim 3, characterized in that, The average particle size of the sulfate-activated component is ≤0.08 mm.

5. The solidifying agent based on a bidirectional activating slag solid waste system according to claim 1, characterized in that, The cementing component is granulated blast furnace slag powder.

6. The solidifying agent based on the bidirectional activating slag solid waste system according to claim 5, characterized in that, The specific surface area of ​​the gelling component is 400–800 m². 2 / kg and alkalinity greater than or equal to 1.

0.

7. The solidifying agent based on a bidirectional activating slag solid waste system according to claim 1, characterized in that, The alkaline activating components are sodium hydroxide, magnesium oxide, calcium oxide, or a combination of calcium oxide.

8. The solidifying agent based on the bidirectional activating slag solid waste system according to claim 7, characterized in that, The composite calcium oxide is prepared by the following steps: bamboo charcoal powder is added to hydrochloric acid solution and ultrasonically stirred for 10-30 min, filtered and washed, vacuum dried, and passed through a 100-mesh sieve; the product is added to water, calcium phosphate is added and stirred for 10-20 h, freeze-dried, calcined at 300-400℃ for 10-30 min under nitrogen protection, cooled to room temperature, pulverized and passed through a 60-mesh sieve, added to anhydrous ethanol, calcium oxide and amino-terminated polyamide amine are added and shaken for 20-40 min, and then freeze-dried.

9. The solidifying agent based on the bidirectional activating slag solid waste system according to claim 7, characterized in that, The particle size of the alkali-activated component is ≤0.08mm.

10. A method for preparing a solidifying agent based on a bidirectional induced slag solid waste system as described in any one of claims 1-9, characterized in that, Includes the following steps: The gelling component, alkali-activated component, and sulfate-activated component are dried and ground; then the components are mixed evenly.

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