Preparation method and application of composite solid waste-based cementing material

Abstract

The invention relates to the technical field of mixed gels, in particular to a preparation method and application of a composite solid waste-based cementing material, and the preparation method comprises the following steps: grinding dried granulated blast-furnace slag, steel slag, fly ash, iron tailings, phosphogypsum and Portland cement, mixing to obtain a pretreated powder raw material, adding a modified activator into the pretreated powder raw material, and uniformly mixing to obtain the composite solid waste-based cementing material. And stirring to obtain the composite solid waste-based cementing material. The synergistic effect of the alkaline activator and the sulfate activator is matched with the nucleation induction effect of the mineral modified admixture, so that hydration process synchronization of multiple solid waste components is realized, sulfate, Ca < 2 + > and an aluminum phase quickly generate ettringite, the mineral admixture is used as a crystal nucleus for growth of a hydration product, the hydration induction period is greatly shortened, and the hydration efficiency is improved. The early strength development rate of the material is increased, the later strength is continuously increased without shrinkage, and the engineering pain point of insufficient early strength or later strength stagnation of a traditional solid waste-based material is solved.

Description

Technical Field

[0001] This invention relates to the field of mixed gel technology, specifically to a method for preparing a composite solid waste-based gelling material and its application. Background Technology

[0002] Silicate cement is the most widely used cementitious material in the world, but its production process has significant shortcomings. For every ton of cement clinker produced, about 1 ton of CO2 is emitted due to limestone decomposition and fossil fuel combustion. my country has been the world's largest cement producer for 35 consecutive years, with an annual production capacity of over 2.2 billion tons. It is the core source of carbon emissions in the building materials industry. At the same time, cement production consumes a large amount of non-renewable minerals such as limestone and clay, resulting in a high degree of resource dependence and creating a prominent contradiction with the dual carbon goals and the construction of ecological civilization.

[0003] Existing technologies mostly employ single physical grinding or simple alkali activation methods to enhance the activity of solid waste, lacking synergistic regulation of multiple components. Simply refining particles through grinding cannot chemically activate the silicon-aluminum-oxygen bonds of low-activity solid waste (such as iron tailings and fly ash). While single alkali activation can dissociate the activity of slag, its activation effect on steel slag and fly ash is limited, and it easily leads to excessive alkalinity of the slurry, causing subsequent volume expansion. In addition, the hydration rates of different solid wastes vary greatly, and existing solutions cannot achieve synchronous hydration processes, resulting in low early strength and slow strength growth in the later stages of the material, which is difficult to meet the requirements of modern engineering for rapid hardening and early strength. Therefore, in response to the problems mentioned above, this invention proposes a method for preparing composite solid waste-based cementitious materials and their applications. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing composite solid waste-based cementitious materials and their applications, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a composite solid waste-based cementitious material includes the following steps: S1. Dry 40-50 parts granulated blast furnace slag, 10-15 parts steel slag, 10-15 parts fly ash, and 8-12 parts iron tailings. Add 6-10 parts phosphogypsum to lime, stir evenly, and neutralize to pH 6-8. Let stand and then dry. S2. Grind the dried granulated blast furnace slag, steel slag, fly ash, iron tailings, phosphogypsum, and 10-15 parts of silicate cement to a specific surface area of ​​300-500 m². 2 / kg, after mixing, pretreated powder raw materials are obtained; S3. Add 5-10 parts of modified activator to the pretreated powder raw material, and stir to obtain composite solid waste-based cementitious material; The modified activator in step S3 is prepared through the following steps: S31. Add alkaline activator and sulfate activator to deionized water to prepare basic synergistic activator. Add modified mineral admixture to deionized water, stir evenly, and then let stand at a constant temperature for pre-activation treatment. S32. Add the pre-activated modified mineral admixture to the basic synergistic activator, stir and cool to room temperature to obtain the activator slurry, add the dispersant and stir to adjust the viscosity to 500-800 mPa·s, and mature at 20-25℃ to obtain the matured activator. S33. The aging activator is vacuum dried and then ground to obtain modified activator powder.

[0006] Furthermore, the modified mineral admixture in step S31 is prepared through the following steps: S311. Mix slag powder with sodium sulfate evenly, add an appropriate amount of deionized water, stir to form a paste, let stand at room temperature, calcine the paste slag powder at a constant temperature, then cool to room temperature, grind and sieve to obtain modified slag powder. S312. Add silica fume to hydrogen peroxide solution, add nitric acid, stir at room temperature, add polycarboxylic acid dispersant, heat to 50-55℃ and continue stirring, filter the solution to obtain precipitate, wash the precipitate with deionized water, vacuum dry the washed precipitate, grind it and sieve it to obtain modified silica fume. S313. Modified slag powder and modified silica fume are mixed, deionized water is added and stirred to form a suspension, and after standing, modified silane coupling agent is added and stirred. After drying, grinding and sieving, modified mineral admixture is obtained.

[0007] Furthermore, the modified silane coupling agent in step S313 is prepared through the following steps: γ-aminopropyltriethoxysilane was added to deionized water and stirred. Epichlorohydrin was then added, along with triethylamine catalyst. The mixture was heated to 50-60°C and stirred for 40-50 minutes. Hydroxysilicone oil was then added, and stirring was continued for 30-40 minutes. The modified silane coupling agent was obtained after vacuum drying.

[0008] Furthermore, in step S31, the mass ratio of alkaline activator to sulfate activator is 100:(40-60), the mass ratio of basic synergistic activator to modified mineral admixture is 100:(112-160), the mass ratio of basic synergistic activator to deionized water is (42-80):100, and the mass ratio of modified mineral admixture to deionized water is (40-60):100.

[0009] Furthermore, in step S32, the mass ratio of the activator slurry to the dispersant is 100:(0.5-2).

[0010] Furthermore, in step S311, the mass ratio of slag powder, sodium sulfate and deionized water is 100:(5-10):(60-80).

[0011] Furthermore, in step S312, the mass ratio of silica fume, hydrogen peroxide solution, nitric acid, and polycarboxylic acid dispersant is 100:(200-300):(5-10):(0.74-3.6).

[0012] Furthermore, in step S313, the mass ratio of modified slag powder to modified silica fume, deionized water, and modified silane coupling agent is 100:(150-200):(3-8), wherein the mass ratio of modified slag powder to modified silica fume is 100:(40-60).

[0013] Furthermore, in the preparation of the modified silane coupling agent, the mass ratio of γ-aminopropyltriethoxysilane, deionized water, epichlorohydrin, triethylamine catalyst, and hydroxyl silicone oil is 100:(50-80):(80-100):(1-3):(20-40).

[0014] Furthermore, the composite solid waste-based cementitious material prepared according to any one of the preparation methods can be used in concrete preparation.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention achieves the synchronization of the hydration process of multiple solid waste components through the synergistic effect of alkaline activators and sulfate activators, combined with the nucleation-inducing effect of mineral-modified admixtures. Sulfate and Ca... 2+ The aluminum phase rapidly generates ettringite, while the mineral admixtures serve as nuclei for the growth of hydration products, significantly shortening the hydration induction period. This enables the material to achieve an increased early strength development rate and continuous strength growth without shrinkage in the later stages, solving the engineering pain points of insufficient early strength or stagnant strength in the later stages of traditional solid waste-based materials. 2. By adjusting the dosage of activator and the ratio of mineral admixtures, this invention can flexibly adjust the initial and final setting times to adapt to different construction environments. At the same time, the uniform gel network formed by the hydration products significantly improves the fluidity and water retention of the slurry, making it less prone to segregation and bleeding, and suitable for complex conditions such as pumping construction and thin-layer casting. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the preparation process of the composite solid waste-based cementitious material in this invention; Figure 2 This is a schematic diagram of the preparation process of the modified activator in this invention; Figure 3 This is a schematic diagram of the preparation process of the modified mineral admixture in this invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] Please see Figures 1-3 The present invention provides a technical solution: Example 1: A method for preparing a composite solid waste-based cementitious material includes the following steps: I. Preparation of modified silane coupling agents: Weigh out 50g of γ-aminopropyltriethoxysilane, 25g of deionized water, 40g of epichlorohydrin, 0.5g of triethylamine catalyst, and 10g of hydroxyl silicone oil. Add water to the silane and stir for 30min. Add epichlorohydrin and catalyst, heat to 50℃ and stir for 40min. Add hydroxyl silicone oil and continue stirring for 30min. After vacuum drying at 60℃, the modified silane coupling agent is obtained.

[0019] II. Preparation of Modified Mineral Admixtures: S311. Weigh 150g of slag powder, 7.5g of sodium sulfate, and 90g of deionized water, mix and stir into a paste, let stand at room temperature for 12 hours, calcine at 300℃ for 2 hours, cool to room temperature, and grind through a 200-mesh sieve to obtain modified slag powder. S312. Weigh 74g silica fume, 148g hydrogen peroxide solution, 3.7g nitric acid, and 0.74g polycarboxylic acid dispersant. Add silica fume to the mixture and stir at room temperature for 1 hour. After adding the dispersant, heat to 50℃ and stir for 2 hours. Filter to obtain precipitate, wash three times with deionized water, vacuum dry at 60℃ to constant weight, grind and pass through a 200-mesh sieve to obtain modified silica fume. S313. Weigh 224g (160g modified slag powder + 64g modified silica fume), 336g deionized water, and 6.72g modified silane coupling agent, mix them to form a suspension, let it stand at room temperature for 6 hours, add the coupling agent and stir for 1 hour, dry at 80℃ to constant weight, grind and pass through a 200-mesh sieve to obtain modified mineral admixture.

[0020] III. Preparation of Modified Activators: S31. Weigh 200g of alkaline activator and 80g of sulfate activator, add 84g of deionized water, stir until completely dissolved to obtain the basic synergistic activator. Weigh 224g of modified mineral admixture, add 89.6g of deionized water, stir evenly, and place in a 25℃ constant temperature oven for 12h to complete the pre-activation treatment and prepare the modified mineral admixture. S32. Add the pre-activated modified mineral admixture to the basic synergistic activator, stir at high speed for 2 minutes, and cool to room temperature to obtain the activator slurry. Add 0.5g of dispersant to every 100g of activator slurry, and stir to adjust the viscosity to 500mPa. The curing activator was obtained by sealing and curing at 20°C for 24 hours. S33. Place the aging activator in a vacuum drying oven at 60℃ and dry it to constant weight. Grind it through a 200-mesh sieve to obtain modified activator powder.

[0021] IV. Preparation of Composite Solid Waste-Based Cementitious Materials: S1. Place 400g of granulated blast furnace slag, 100g of steel slag, 100g of fly ash, and 80g of iron tailings in an oven at 105℃ and dry to constant weight (moisture content <2%). Add 60g of phosphogypsum to lime and stir evenly. Neutralize to pH=6, let stand for 24h, and then dry in an oven at 105℃ to constant weight. S2. Mix the dried granulated blast furnace slag, steel slag, fly ash, iron tailings, and phosphogypsum with 100g of silicate cement, and grind them in a ball mill until the specific surface area is 300m². 2 / kg, mix evenly to obtain pretreated powder raw material; S3. Add 45g of modified activator to 840g of pretreated powder raw material, stir at high speed for 3min until uniform, and obtain composite solid waste-based cementitious material.

[0022] Example 2: A method for preparing a composite solid waste-based cementitious material includes the following steps: I. Preparation of modified silane coupling agents: Weigh 50g of γ-aminopropyltriethoxysilane, 30g of deionized water, 45g of epichlorohydrin, 1g of triethylamine catalyst, and 15g of hydroxyl silicone oil. Add water to the silane and stir for 32min. Add epichlorohydrin and catalyst, heat to 52℃ and stir for 42min. Add hydroxyl silicone oil and continue stirring for 32min. After vacuum drying at 62℃, the modified silane coupling agent is obtained.

[0023] II. Preparation of Modified Mineral Admixtures: S311. Weigh 160g of slag powder, 11.2g of sodium sulfate, and 112g of deionized water, mix and stir into a paste, let stand at room temperature for 13 hours, then calcine at 320℃ for 2.2 hours, cool to room temperature, and grind through a 250-mesh sieve to obtain modified slag powder. S312. Weigh 90g silica fume, 225g hydrogen peroxide solution, 6.3g nitric acid, and 1.8g polycarboxylic acid dispersant. Add silica fume to the mixture and stir at room temperature for 1.2h. After adding the dispersant, heat to 52℃ and stir for 2.2h. Filter to obtain precipitate, wash three times with deionized water, vacuum dry at 64℃ to constant weight, grind and pass through a 250-mesh sieve to obtain modified silica fume. S313. Weigh 250g (170g modified slag powder + 80g modified silica fume), 425g deionized water, and 12.5g modified silane coupling agent, mix them to form a suspension, let it stand at room temperature for 6.4h, add coupling agent and stir for 1.2h, dry at 84℃ to constant weight, grind through a 250-mesh sieve to obtain modified mineral admixture.

[0024] III. Preparation of Modified Activators: S31. Weigh 200g of alkaline activator and 100g of sulfate activator, add 120g of deionized water, stir until completely dissolved to obtain basic synergistic activator. Weigh 250g of modified mineral admixture, add 125g of deionized water, stir evenly, and place in a 30℃ constant temperature oven for 13h to complete the pre-activation treatment. S32. Add the pre-activated modified mineral admixture to the basic synergistic activator, stir at high speed for 4 minutes, and cool to room temperature to obtain the activator slurry. Add 1g of dispersant to every 100g of activator slurry and stir to adjust the viscosity to 550mPa. The curing activator was obtained by sealing and curing at 22°C for 25 hours. S33. Place the aging activator in a vacuum drying oven at 64℃ and dry it to constant weight. Grind it through a 250-mesh sieve to obtain modified activator powder.

[0025] IV. Preparation of Composite Solid Waste-Based Cementitious Materials: S1. Place 430g of granulated blast furnace slag, 120g of steel slag, 120g of fly ash, and 90g of iron tailings in an oven at 105℃ and dry to constant weight (moisture content <2%). Add 70g of phosphogypsum to lime and stir evenly. Neutralize to pH=6.4. Let stand for 25h and then dry in an oven at 110℃ to constant weight. S2. Mix the dried granulated blast furnace slag, steel slag, fly ash, iron tailings, and phosphogypsum with 120g of silicate cement, and grind in a ball mill until the specific surface area is 380m². 2 / kg, mix evenly to obtain pretreated powder raw material; S3. Add 60g of modified activator to 850g of pretreated powder raw material, stir at high speed for 4min until uniform, and obtain composite solid waste-based cementitious material.

[0026] Example 3: A method for preparing a composite solid waste-based cementitious material includes the following steps: I. Preparation of modified silane coupling agents: Weigh out 50g of γ-aminopropyltriethoxysilane, 35g of deionized water, 47.5g of epichlorohydrin, 1.25g of triethylamine catalyst, and 17.5g of hydroxyl silicone oil. Add water to the silane and stir for 34min. Add epichlorohydrin and catalyst, heat to 54℃ and stir for 44min. Add hydroxyl silicone oil and continue stirring for 34min. After vacuum drying at 64℃, the modified silane coupling agent is obtained.

[0027] II. Preparation of Modified Mineral Admixtures: S311. Weigh 180g of slag powder, 14.4g of sodium sulfate, and 135g of deionized water, mix and stir into a paste, let stand at room temperature for 13 hours, then calcine at 340℃ for 2.4 hours, cool to room temperature, and grind through a 300-mesh sieve to obtain modified slag powder. S312. Weigh 100g silica fume, 280g hydrogen peroxide solution, 8g nitric acid, and 2.5g polycarboxylic acid dispersant. Add silica fume to the mixture and stir at room temperature for 1.4h. After adding the dispersant, heat to 54℃ and stir for 2.4h. Filter to obtain precipitate, wash 4 times with deionized water, vacuum dry at 68℃ to constant weight, grind and pass through a 300-mesh sieve to obtain modified silica fume. S313. Weigh 280g (181g modified slag powder + 99g modified silica fume), 504g deionized water, and 18.2g modified silane coupling agent, mix them to form a suspension, let it stand at room temperature for 6.8h, add coupling agent and stir for 1.4h, dry at 88℃ to constant weight, grind through a 300-mesh sieve to obtain modified mineral admixture.

[0028] III. Preparation of Modified Activators: S31. Weigh 200g of alkaline activator and 110g of sulfate activator, add 139.5g of deionized water, stir until completely dissolved to obtain the basic synergistic activator. Weigh 280g of modified mineral admixture, add 154g of deionized water, stir evenly, and place in a 35℃ constant temperature oven for 13h to complete the pre-activation treatment and prepare the modified mineral admixture. S32. Add the pre-activated modified mineral admixture to the basic synergistic activator, stir at high speed for 6 minutes, and cool to room temperature to obtain the activator slurry. Add 1.5g of dispersant to every 100g of activator slurry, and stir to adjust the viscosity to 600mPa. The curing activator was obtained by sealing and curing at 24℃ for 26 hours. S33. Place the aging activator in a vacuum drying oven at 68℃ and dry it to constant weight. Grind it through a 300-mesh sieve to obtain modified activator powder.

[0029] IV. Preparation of Composite Solid Waste-Based Cementitious Materials: S1. Place 470g of granulated blast furnace slag, 130g of steel slag, 130g of fly ash, and 110g of iron tailings in an oven at 105℃ and dry to constant weight (moisture content <2%). Add 90g of phosphogypsum to lime and stir evenly. Neutralize to pH=7.2, let stand for 26h, and then dry in an oven at 115℃ to constant weight. S2. Mix the dried granulated blast furnace slag, steel slag, fly ash, iron tailings, and phosphogypsum with 140g of silicate cement, and grind in a ball mill until the specific surface area reaches 460m². 2 / kg, mix evenly to obtain pretreated powder raw material; S3. Add 75g of modifier to 860g of pretreated powder raw material, stir at high speed for 5min until uniform, and obtain composite solid waste-based cementitious material.

[0030] Example 4: A method for preparing a composite solid waste-based cementitious material includes the following steps: I. Preparation of modified silane coupling agents: Weigh out 50g of γ-aminopropyltriethoxysilane, 40g of deionized water, 50g of epichlorohydrin, 1.5g of triethylamine catalyst, and 20g of hydroxyl silicone oil. Add water to the silane and stir for 36min. Add epichlorohydrin and catalyst, heat to 56℃ and stir for 46min. Add hydroxyl silicone oil and continue stirring for 36min. After vacuum drying at 66℃, the modified silane coupling agent is obtained.

[0031] II. Preparation of Modified Mineral Admixtures: S311. Weigh 200g of slag powder, 20g of sodium sulfate, and 160g of deionized water, mix and stir into a paste, let stand at room temperature for 15 hours, then calcine at 360℃ for 2.6 hours, cool to room temperature, and grind through a 350-mesh sieve to obtain modified slag powder. S312. Weigh 120g silica fume, 360g hydrogen peroxide solution, 12g nitric acid, and 3.6g polycarboxylate dispersant. Add silica fume to the mixture and stir at room temperature for 1.6h. After adding the dispersant, heat to 56℃ and stir for 2.6h. Filter to obtain precipitate, wash 4 times with deionized water, vacuum dry at 72℃ to constant weight, grind and pass through a 350-mesh sieve to obtain modified silica fume. S313. Weigh 320g (200g modified slag powder + 120g modified silica fume), 640g deionized water, and 25.6g modified silane coupling agent, mix them to form a suspension, let it stand at room temperature for 7.2h, add coupling agent and stir for 1.6h, dry at 92℃ to constant weight, grind through a 350-mesh sieve to obtain modified mineral admixture.

[0032] III. Preparation of Modified Activators: S31. Weigh 200g of alkaline activator and 120g of sulfate activator, add 160g of deionized water, stir until completely dissolved to obtain the basic synergistic activator. Weigh 320g of modified mineral admixture, add 192g of deionized water, stir evenly, and place in a 40℃ constant temperature oven for 15h to complete the pre-activation treatment and prepare the modified mineral admixture. S32. Add the pre-activated modified mineral admixture to the basic synergistic activator, stir at high speed for 8 minutes, and cool to room temperature to obtain the activator slurry. Add 2g of dispersant to every 100g of activator slurry and stir to adjust the viscosity to 650mPa. The curing activator was obtained by sealing and curing at 25°C for 27 hours. S33. Place the aging activator in a vacuum drying oven at 72℃ and dry it to constant weight. Grind it through a 350-mesh sieve to obtain modified activator powder.

[0033] IV. Preparation of Composite Solid Waste-Based Cementitious Materials: S1. Place 500g of granulated blast furnace slag, 150g of steel slag, 150g of fly ash, and 120g of iron tailings in an oven at 105℃ and dry them to constant weight (moisture content <2%). Add 100g of phosphogypsum to lime and stir evenly. Neutralize to pH=8, let stand for 27h, and then dry in an oven at 120℃ to constant weight. S2. Mix the dried granulated blast furnace slag, steel slag, fly ash, iron tailings, and phosphogypsum with 150g of silicate cement, and grind in a ball mill until the specific surface area is 500m². 2 / kg, mix evenly to obtain pretreated powder raw material; S3. Add 90g of modifier to 870g of pretreated powder raw material and stir at high speed for 6min until uniform to obtain composite solid waste-based cementitious material.

[0034] Comparative Example 1 Comparative Example 1 differs from Example 1 in that the modified silane coupling agent is replaced with a silane coupling agent, and the remaining steps are exactly the same as in Example 1.

[0035] Comparative Example 2 Comparative Example 2 differs from Example 1 in that the modified mineral admixture is replaced with slag powder, while the remaining steps are exactly the same as in Example 1.

[0036] Comparative Example 3 Comparative Example 3 differs from Example 1 in that the modified activator is replaced with a basic and sulfate composite activator, while the remaining steps are exactly the same as in Example 1.

[0037] Referring to the current standards GB50010-2010 "Code for Design of Concrete Structures" and GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete", basic mechanical properties tests were conducted on composite cementitious concrete prepared with composite solid waste-based cementitious materials. When the replacement rate of composite solid waste-based cementitious materials is 30%, 50%, and 80%, the cubic compressive strength and cubic splitting tensile strength of the composite cementitious concrete are tested at 3d, 7d, 28d, and 56d, respectively. 1. Test the compressive strength of concrete cubes made of composite cementitious materials in accordance with GB / T50081-2019, ASTM C109 (compressive strength), and CECS13-2009 (stress-strain curve). 150mm×150mm×150mm composite cementitious concrete cube specimens were poured according to different substitution rates and cured to the corresponding age. The upper and lower surfaces of the specimens and the bearing plate of the testing machine were cleaned, ensuring that the center of the specimen was aligned with the center of the bearing plate. The loading rate was controlled at 0.8MPa / s, and the load was continuously and uniformly applied until the specimen failed. The failure load (kN) was recorded, and the compressive strength (MPa) of the specimen was calculated according to the formula. in, For compressive strength, To break the load, The test block is the area under pressure. The specific test results are shown in Table 1 below. Table 1 As shown in Table 1, curing age has a significant effect on improving compressive strength. Strength development shows a trend of rapid increase in the early stages and slower increase in the later stages. In all groups, the compressive strength of concrete continuously increases with the increase in curing age. The strength growth rate is faster at 3d, 7d, and 28d, while the growth rate slows down at 28d and 56d but still shows an increase. Within the same group and at the same age, the compressive strength gradually decreases with increasing replacement rate. However, the composite solid waste-based cementitious material prepared in this invention, even with a high replacement rate of 80%, still maintains a 56-day compressive strength ≥30.9MPa (Example 1), which is higher than C3. The concrete design strength of 0 (30MPa) indicates that the cementitious activity of solid waste was effectively activated, and the compressive strength can still be guaranteed even with a high substitution rate. The performance of the examples is significantly better than that of the comparative examples, which verifies the core advantages of the modification process of the present invention. Under the same substitution rate and the same age, the compressive strength of all examples is significantly higher than that of the comparative examples, and the performance of comparative example 3 is the worst. The reason is that the modified silane coupling agent, modified mineral admixture and modified activator of the present invention form a synergistic effect, which effectively improves the hydration degree of solid waste cementitious materials, optimizes the microstructure of concrete, and makes the interface between solid waste and silicate cement more tightly bonded.

[0038] 2. Calculate the splitting tensile strength of composite cementitious concrete cubes according to formula (9.0.5) in GB / T50081-2019. A 150mm×150mm×150mm cubic specimen was prepared in the same manner as the compressive strength specimen. A center line was drawn in the middle of the top / bottom surface to determine the splitting surface. A circular arc-shaped pad and a pad strip were placed between the specimen and the bearing plate, aligned with the center line and perpendicular to the top surface of the specimen. The loading rate was controlled at 0.08MPa / s, and the loading was continuously applied until the specimen failed. The failure load (kN) was recorded, and the splitting tensile strength (MPa) was calculated according to formula (9.0.5). The specific test results are shown in Table 2 below. Table 2 As can be seen from the data in Table 2, the core principles of concrete tensile performance testing using the splitting method are highly consistent with those of compressive performance, while also demonstrating the unique characteristics of tensile performance. The variation of tensile strength with age and replacement rate is completely consistent with that of compressive strength. The tensile performance of the example is significantly better than that of the comparative example, and the modification process has a more prominent effect on improving tensile performance. Concrete tensile performance is more sensitive to microstructural defects and interfacial bonding states. The modification process of this invention has a more significant increase in tensile strength. For example, with a 30% replacement rate and 28 days, the tensile strength of Example 3 is 3.74 MPa, while that of Comparative Example 3 is only 2.61 MPa, an increase of 43%. This is because the modified silane coupling agent optimizes the interfacial transition zone between aggregate and cementitious paste, the modified mineral admixture refines the hydration product grains, and the modified activator... It promotes the uniform distribution of hydration products, reduces the generation and propagation of microcracks, and significantly improves tensile strength. Examples 2 and 3 are the groups with the best tensile strength. The parameter adaptability determines the upper limit of tensile strength, indicating that the appropriate grinding specific surface area, modified activator viscosity and phosphogypsum neutralization pH can not only improve compressive strength, but also optimize the micro-homogeneity of concrete, thereby improving the weak tensile strength. The decrease in tensile strength of the comparative example is greater than that of compressive strength, reflecting the micro-structural defects of ordinary processes. The splitting tensile failure load of all groups is completely matched with the calculated tensile strength (according to GB / T50081-2019 formula 9.0.5), and the test data under the same conditions have no significant fluctuations, indicating that the specimen preparation, loading operation and data calculation all meet the requirements of the specifications, and the test results are true and valid.

[0039] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a composite solid waste-based cementitious material, characterized in that, Includes the following steps: S1. Dry 40-50 parts granulated blast furnace slag, 10-15 parts steel slag, 10-15 parts fly ash, and 8-12 parts iron tailings. Add 6-10 parts phosphogypsum to lime, stir evenly, and neutralize to pH 6-8. Let stand and then dry. S2. Grind the dried granulated blast furnace slag, steel slag, fly ash, iron tailings, phosphogypsum, and 10-15 parts of silicate cement to a specific surface area of ​​300-500 m². 2 / kg, after mixing, pretreated powder raw materials are obtained; S3. Add 5-10 parts of modified activator to the pretreated powder raw material, and stir to obtain composite solid waste-based cementitious material; The modified activator in step S3 is prepared through the following steps: S31. Add alkaline activator and sulfate activator to deionized water to prepare basic synergistic activator. Add modified mineral admixture to deionized water, stir evenly, and then let stand at a constant temperature for pre-activation treatment. S32. Add the pre-activated modified mineral admixture to the basic synergistic activator, stir and cool to room temperature to obtain the activator slurry, add the dispersant and stir to adjust the viscosity to 500-800 mPa·s, and mature at 20-25℃ to obtain the matured activator. S33. The aging activator is vacuum dried and then ground to obtain modified activator powder.

2. The method for preparing a composite solid waste-based cementitious material according to claim 1, characterized in that, The modified mineral admixture in step S31 is prepared through the following steps: S311. Mix slag powder with sodium sulfate evenly, add an appropriate amount of deionized water, stir to form a paste, let stand at room temperature, calcine the paste slag powder at a constant temperature, then cool to room temperature, grind and sieve to obtain modified slag powder. S312. Add silica fume to hydrogen peroxide solution, add nitric acid, stir at room temperature, add polycarboxylic acid dispersant, heat to 50-55℃ and continue stirring, filter the solution to obtain precipitate, wash the precipitate with deionized water, vacuum dry the washed precipitate, grind it and sieve it to obtain modified silica fume. S313. Modified slag powder and modified silica fume are mixed, deionized water is added and stirred to form a suspension. After standing, modified silane coupling agent is added and stirred. After drying, grinding and sieving, modified mineral admixture is obtained.

3. The preparation method of a composite solid waste-based cementitious material according to claim 2, characterized in that, The modified silane coupling agent in step S313 is prepared through the following steps: γ-aminopropyltriethoxysilane was added to deionized water and stirred. Epichlorohydrin was then added, along with triethylamine catalyst. The mixture was heated to 50-60°C and stirred for 40-50 minutes. Hydroxysilicone oil was then added, and stirring was continued for 30-40 minutes. The modified silane coupling agent was obtained after vacuum drying.

4. The method for preparing a composite solid waste-based cementitious material according to claim 1, characterized in that, In step S31, the mass ratio of alkaline activator to sulfate activator is 100:(40-60), the mass ratio of basic synergistic activator to modified mineral admixture is 100:(112-160), the mass ratio of basic synergistic activator to deionized water is (42-80):100, and the mass ratio of modified mineral admixture to deionized water is (40-60):

100.

5. The method for preparing a composite solid waste-based cementitious material according to claim 1, characterized in that, In step S32, the mass ratio of activator slurry to dispersant is 100:(0.5-2).

6. The method for preparing a composite solid waste-based cementitious material according to claim 2, characterized in that, In step S311, the mass ratio of slag powder, sodium sulfate and deionized water is 100:(5-10):(60-80).

7. The method for preparing a composite solid waste-based cementitious material according to claim 2, characterized in that, In step S312, the mass ratio of silica fume, hydrogen peroxide solution, nitric acid, and polycarboxylic acid dispersant is 100:(200-300):(5-10):(0.74-3.6).

8. The method for preparing a composite solid waste-based cementitious material according to claim 2, characterized in that, In step S313, the mass ratio of modified slag powder to total modified silica fume, deionized water, and modified silane coupling agent is 100:(150-200):(3-8), wherein the mass ratio of modified slag powder to modified silica fume is 100:(40-60).

9. The method for preparing a composite solid waste-based cementitious material according to claim 3, characterized in that, In the preparation of the modified silane coupling agent, the mass ratio of γ-aminopropyltriethoxysilane, deionized water, epichlorohydrin, triethylamine catalyst, and hydroxyl silicone oil is 100:(50-80):(80-100):(1-3):(20-40).

10. The application of the composite solid waste-based cementitious material prepared by the preparation method according to any one of claims 1-9 in concrete preparation.

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