Phosphogypsum-high titanium slag solid waste-based composite cementitious material and preparation and application thereof

Abstract

The application discloses a phosphogypsum-high-titanium slag solid waste-based composite cementing material and a preparation and application thereof, and the preparation method comprises the following steps: mixing an activator with high-titanium slag, and grinding to 450 m2 / kg to obtain modified high-titanium slag; mixing phosphogypsum with water, primary setting, final setting, calcining at 180 DEG C, natural cooling in a furnace, aging, and obtaining modified phosphogypsum; mixing the modified phosphogypsum and the modified high-titanium slag, adding water, primary setting, final setting, and obtaining the phosphogypsum-high-titanium slag solid waste-based composite cementing material. The application solves the problems of slow hydration reaction, great environmental influence and unstable performance in the utilization of the existing phosphogypsum and high-titanium slag, and uses the phosphogypsum and the high-titanium slag as raw materials to be activated and modified, so that the solid waste-based cementing material with excellent mechanical performance (28-day compressive strength > 25 MPa) and good durability (softening coefficient > 0.85) is prepared, and the cement clinker consumption can be reduced by more than 30%.

Description

Technical Field

[0001] This invention relates to a method for preparing a composite cementitious material, specifically to a phosphogypsum-high titanium slag solid waste-based composite cementitious material and its preparation and application. Background Technology

[0002] Phosphogypsum and high-titanium slag are common industrial solid wastes, and converting them into composite cementitious materials has significant environmental and economic value. Resource utilization of these two solid wastes can effectively reduce environmental pollution, decrease land occupation, and promote a circular economy and sustainable development. They can replace traditional building materials, providing green and low-carbon options that meet the current environmental and energy-saving needs of the construction industry and promote the development of a low-carbon economy. By improving the mechanical properties, durability, and corrosion resistance of composite cementitious materials, their market value and application scope can be significantly increased, while reducing dependence on natural resources and promoting efficient resource utilization. This provides important support for achieving resource recycling, environmental protection, and sustainable development goals.

[0003] Phosphogypsum (PG) contains 15%–25% free water. After drying, it yields a powder with approximately 90% DH phase. Its crystal morphology exhibits a characteristic lamellar structure (containing parallel plate-like monomers and dovetail twins), making it suitable as a cementing material. The soluble phosphorus in PG reacts with free calcium... 2+The reaction produces calcium phosphate (Ca3(PO4)2), which inhibits the hydration process, making phosphogypsum acidic and potentially corroding gypsum products and equipment. Existing literature 1 (Wang Feng, Song Yu, He Zhaoyi, et al. Study on mechanical properties and microstructure of phosphogypsum composite cementitious materials [J / OL]. Inorganic Salt Industry, 2024, (12)30: 1-9) prepared composite cementitious materials using phosphogypsum, slag, Ca(OH)2, and Na2SO4 to solve the problem of phosphogypsum stockpiling. The optimal ratio is 67% slag, 30% phosphogypsum, 3% Ca(OH)2, and 3% Na2SO4, with a compressive strength of 37.45 MPa. High-titanium slag is a molten slag formed after water cooling during the smelting of vanadium-titanium magnetite. It has low pozzolanic activity and certain strength and can be used as an auxiliary cementitious material. However, using high-titanium slag directly as an auxiliary cementitious material will reduce the hydration activity of cement mortar, and it is not easy to crush, thus limiting its application in building materials. Existing literature 2 (Qing Ting. Design and performance study of ultra-high performance concrete system based on high-titanium slag [D]. Southwest University of Science and Technology, 2023) prepared ultra-high performance concrete (UHPC) using high-titanium slag powder, sand and crushed stone as raw materials. Its mechanical properties, volume stability, carbonation resistance and freeze-thaw resistance are better than those of natural river sand concrete, and its 28-day compressive strength can reach 138.51 MPa. Literature 3 (Wang Shuai, Lü Shuzhen, Zhao Jie, et al. Study on mineral admixtures for concrete prepared from high-titanium slag [J]. Journal of Southwest University of Science and Technology, 2021, 36(01): 28-34) shows that high-titanium slag powder can improve the fluidity of cement mortar, and the fluidity increases with the increase of fineness. Although the early activity of high-titanium slag is low, the later activity increases with the increase of fineness. When naturally cooled high-titanium slag is ground to 45 μm and the residue on the sieve is <12%, the activity index after 28 days and 90 days can reach 78.7% and 74.5%, respectively.

[0004] In summary, phosphogypsum, as an industrial solid waste from wet phosphate chemical processes, generates enormous amounts of waste and causes environmental pollution, urgently requiring the search for harmless treatment and resource utilization methods. Although various methods for utilizing phosphogypsum and high-titanium slag have been developed, their integrated application faces challenges such as slow hydration reactions, significant environmental impact, and unstable performance. Summary of the Invention

[0005] The purpose of this invention is to provide a phosphogypsum-high titanium slag solid waste-based composite cementitious material and its preparation and application. This invention solves the problems of slow hydration reaction, significant environmental impact, and unstable performance in the utilization of existing phosphogypsum and high titanium slag. Using phosphogypsum and high titanium slag as raw materials, activation and modification are carried out to prepare a solid waste-based cementitious material with excellent mechanical properties (28-day compressive strength > 25 MPa) and good durability (softening coefficient > 0.85), which can reduce the amount of cement clinker used by more than 30%.

[0006] To achieve the above objectives, the present invention provides a method for preparing a phosphogypsum-high-titanium slag solid waste-based composite cementitious material, the method comprising: (1) The activator is mixed with high-titanium slag and ground to 450 m² / kg to obtain modified high-titanium slag; phosphogypsum is mixed with water, initially solidified, then finally solidified, calcined at 180 ℃, naturally cooled in the furnace, and aged to obtain modified phosphogypsum; the activator is any two or more of N2-methyl polyol grinding aid, NaOH, water glass, fly ash and slag; (2) Mix modified phosphogypsum and modified high-titanium slag, add water, allow initial solidification, and then allow final solidification to obtain phosphogypsum-high-titanium slag solid waste-based composite cementitious material.

[0007] Preferably, in step (1), the activator is an N2-methyl polyol grinding aid, NaOH, water glass, fly ash, and slag.

[0008] Preferably, the mass fractions of N2-methyl polyol grinding aid, NaOH, water glass, fly ash and slag are 0.2%, 1.5%, 0.5%, 17.8% and 80%, respectively.

[0009] Preferably, in step (1), the mass ratio of the activator to the high-titanium slag is (10~35):(65~90); the mass of the water is 0.5~0.65 of the mass of the phosphogypsum.

[0010] Preferably, the mass ratio of the activator to the high-titanium slag is 1:3; the mass of the water is 0.61 times the mass of the phosphogypsum; the calcination time is 2 hours; and the aging time is 1 hour.

[0011] Preferably, in step (2), the mass ratio of the modified phosphogypsum to the modified high-titanium slag is (1~9):(1~9).

[0012] Preferably, the mass ratio of the modified phosphogypsum to the modified high-titanium slag is 4:6.

[0013] Preferably, in step (2), the mass of the water is 0.44 of the total mass of the composite cementitious material.

[0014] This invention provides a phosphogypsum-high titanium slag solid waste-based composite cementitious material prepared by the method described above.

[0015] This invention provides an application of the phosphogypsum-high titanium slag solid waste-based composite cementitious material as described above as a building material.

[0016] This invention discloses a phosphogypsum-high-titanium slag solid waste-based composite cementitious material, its preparation and application, which solves the problems of slow hydration reaction, significant environmental impact and unstable performance in the utilization of existing phosphogypsum and high-titanium slag, and has the following advantages: 1. Chemical-mechanical composite activation significantly enhances the activity of high-titanium ore slag. The determined chemical activator consists of 0.2% N2-methyl polyol grinding aid, 1.5% NaOH, 0.5% water glass, 17.8% fly ash, and 80% ore slag. The activator and high-titanium ore slag are mixed and ground to a concentration of 450 μm. The mass ratio of activator to high-titanium ore slag is 1:3. 2 At a concentration of / kg, the mechanical properties of the hardened slurry reached their optimal state, with compressive strengths of 21.8 MPa and 34.2 MPa at 7 days and 28 days, respectively, and activity indices of 69.75 and 76.34, respectively, all meeting the requirements of S75 grade slag.

[0017] 2. Under conditions of calcination temperature of 180℃, calcination time of 2 h, furnace cooling method, and aging time not exceeding 1 h, the prepared building phosphogypsum meets the P2.0 standard in GB / T 9776-2022 for building gypsum. Grey relational analysis shows that the CaSO4·0.5H2O phase content has the greatest impact on the physical properties of phosphogypsum, followed by the CaSO4·0.5H2O phase, while the CaSO4 phase has the least impact. Calcination temperature significantly affects compressive strength and water-cement ratio, calcination time mainly affects initial setting time, while aging time has a relatively small impact.

[0018] 3. The composite cementitious material prepared with a weight ratio of 4:6 of thermally modified phosphogypsum and activated modified high-titanium slag exhibited the best performance. After 28 days of hydration, the compressive strength was 25.79 MPa, and the flexural strength was 4.69 MPa. The softening coefficient was 0.88, and the linear expansion rate was 1.25%. The composite cementitious material showed good mechanical properties in humid environments, meeting relevant standards for building exterior wall materials and demonstrating promising application prospects. Regarding water resistance, the compressive strength decreased to 21.24 MPa after 90 days with prolonged hydration time, showing a certain trend of strength degradation. Carbonization resistance tests showed a carbonization depth of 7.2 cm after 28 days, indicating a certain degree of carbonization resistance. Freeze-thaw cycle tests showed no significant performance decline after 80 freeze-thaw cycles, demonstrating good freeze-thaw resistance and suitable for application in cold regions or freeze-thaw environments.

[0019] 4. The main hydration product of the composite cementitious material is CaSO4·0.5H2O, and the diffraction peak intensity of CaSO4·0.5H2O significantly increases with the increase of the blending ratio of phosphogypsum and high-titanium slag. The diffraction peak of AFt is also quite obvious, indicating that an appropriate amount of phosphogypsum can promote the formation of AFt, further enhancing the structural stability of the material. In addition, the C6S2H3 and C6S6H type CSH generated by the high-titanium slag under the pozzolanic effect can significantly improve the compactness of the composite matrix. The synergistic hydration reaction between it and gypsum crystals helps to improve the mechanical properties and durability of the composite cementitious material. Attached Figure Description

[0020] Figure 1 This is a photograph of the raw materials used in this invention.

[0021] Figure 2 This is the XRD pattern of the raw materials used in this invention.

[0022] Figure 3 The images shown are SEM images of the composite cementitious materials prepared in Examples 1-2 of this invention.

[0023] Figure 4 The graph shows the effect of modified high-titanium slag in Examples 1-2 and Comparative Examples 1-2 of this invention on the mechanical properties of composite cementitious materials.

[0024] Figure 5 This is a graph showing the development of the compressive strength of the composite cementitious materials in water and air in Examples 1 and 2 of the present invention.

[0025] Figure 6 These are physical images showing the carbonization of the composite cementitious materials in Examples 1 and 2 of this invention.

[0026] Figure 7 The images show the physical changes in the morphology of the composite cementitious materials in Examples 1 and 2 under different wet-dry cycles according to the present invention.

[0027] Figure 8 This is a graph showing the effect of different wet-dry cycles on the quality of the composite cementitious materials in Examples 1 and 2.

[0028] Figure 9 The graph shows the effect of different wet-dry cycles on the compressive strength of the composite cementitious material in Examples 1 and 2.

[0029] Figure 10 These are physical images showing the damage morphology of the composite cementitious materials in Examples 1 and 2 of the present invention after freeze-thaw cycles.

[0030] Figure 11 This is a graph showing the effect of different freeze-thaw cycle levels on the compressive strength of the composite cementitious material in Examples 1 and 2.

[0031] Figure 12 This is a graph showing the effect of different freeze-thaw cycle levels on the compressive strength of the composite cementitious material in Examples 1 and 2. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] The specific information regarding the materials and equipment involved in the following embodiments is as follows: 1. Reagents Cement: P·O 42.5R ordinary Portland cement produced by Sichuan Shuangma Cement Manufacturing Co., Ltd., with a density of 3.12 kg / m³. 3 Specific surface area is 360 m² 2 / kg.

[0034] High-titanium slag: High-titanium slag provided by Panzhihua Iron and Steel Group Co., Ltd., with an apparent density of 2.98 kg / m³.

[0035] Phosphogypsum: Derived from industrial waste in Deyang City, Sichuan Province, with a density of 2.05 kg / m³ and a specific surface area of ​​460 m². 2 / kg. The specific chemical composition of cement, high-titanium slag and phosphogypsum is detailed in Table 1.

[0036] Table 1 Chemical composition of main raw materials NaOH: A white, non-uniform, flaky solid used as an activator and as an analytical reagent, sourced from Weifang Yaxing Chemical Co., Ltd.

[0037] Water glass (sodium silicate): a colorless and transparent solution made by reacting SiO2 and NaOH at high temperature. Its modulus is 3, which means that the mass ratio of Na2O to SiO2 in sodium silicate (Na2O·nSiO2) is 3. It comes from Sichuan Jinkaiwei Technology Development Co., Ltd.

[0038] Grinding aid: N2-methyl polyol grinding aid, viscous liquid, yellowish-brown, with a certain odor, from Chengdu Wangzhong Building Materials Co., Ltd.

[0039] 2. Equipment Information on the instruments and equipment used in this invention is detailed in Table 2.

[0040] Table 2. Instruments and equipment used . Example 1 A method for preparing a phosphogypsum-high titanium slag solid waste-based composite cementitious material, the method comprising: (1) An activator with a mass ratio of 1:3 was mixed with high-titanium slag and ground to 450 m² / kg to obtain modified high-titanium slag. The activator consisted of 0.2% N2-methyl polyol grinding aid, 1.5% NaOH, 0.5% water glass, 17.8% fly ash, and 80% slag. Phosphogypsum was mixed with water, initially solidified for 17.36 min, and finally solidified for 23.51 min. It was calcined at 180 ℃ for 2 h, naturally cooled in the furnace, and aged for 1 h to obtain modified phosphogypsum. The mass of water was 0.61 of the mass of phosphogypsum (i.e., the standard consistency water-binder ratio was 0.61).

[0041] like Figure 1 As shown, the actual pictures of the raw materials used in this invention are as follows: A is an actual picture of high-titanium slag; B is an actual picture of phosphogypsum; and C is an actual picture of slag.

[0042] like Figure 2 As shown, the XRD patterns of the raw materials used in this invention are as follows: A is the XRD pattern of high-titanium slag; B is the XRD pattern of phosphogypsum; and C is a physical image of the slag.

[0043] (2) Modified phosphogypsum and modified high-titanium slag with a mass ratio of 4:6 were mixed, water was added, and the initial solidification time was 17.49 min, and the final solidification time was 37.64 min, to obtain phosphogypsum-high-titanium slag solid waste-based composite cementitious material, denoted as F4. The mass of water was 0.44 of the total mass of the composite cementitious material (i.e., the standard consistency water-cement ratio was 0.44).

[0044] Comparative Example 1 The preparation method of a phosphogypsum-high titanium slag solid waste-based composite cementitious material is basically the same as that in Example 1, except that: In step (1), modified high-titanium slag is not prepared; In step (2), the initial setting time is 12.23 min, the final setting time is 27.41 min, and the mass of water is 0.55 of the total mass of the composite cementitious material. The cementitious material obtained by the same operation as in Example 1 is denoted as T4.

[0045] Example 2 The preparation method of a phosphogypsum-high titanium slag solid waste-based composite cementitious material is basically the same as that in Example 1, except that: In step (2), the mass ratio of modified phosphogypsum to modified high-titanium slag is 1:9, 2:8, 3:7, 5:5, 6:4, 7:3, 8:2, or 9:1, respectively; the mass of water is 0.61, 0.56, 0.50, 0.48, 0.56, 0.66, 0.75, or 0.81 of the total mass of the composite cementitious material, respectively; the initial setting time is 33.54 min, 25.38 min, 19.39 min, 14.29 min, 12.45 min, 10.52 min, 8.57 min, or 7.46 min, respectively; and the final setting time is 68.37 min, 55.89 min, 48.45 min, 28.32 min, 25.33 min, 22.42 min, 18.51 min, or 15.29 min, respectively. min; The composite cementitious materials obtained by the same operation as in Example 1 are sequentially denoted as F1, F2, F3, F5, F6, F7, F8 and F9.

[0046] Comparative Example 2 The preparation method of the phosphogypsum-high titanium slag solid waste-based composite cementitious material is basically the same as that in Example 2, except that: In step (1), modified high-titanium slag is not prepared; In step (2), the mass ratio of modified phosphogypsum and modified high-titanium slag is 5:5, the initial setting time is 12.40 min, the final setting time is 21.53 min, and the mass of water is 0.61 of the total mass of the composite cementitious material. The cementitious material obtained by the same operation as in Example 1 is denoted as T5.

[0047] Comparative Example 3 To investigate the calcination temperature, the preparation method of the modified phosphogypsum was basically the same as in Example 1, with the difference being: The aging time was 0 h, the calcination temperatures were 130℃, 140℃, 150℃, 160℃, 170℃, 190℃ and 200℃ respectively, the water content was 1.07%, 1.09%, 1.14%, 0.98%, 0.69%, 0.63% or 0.67% of the phosphogypsum mass respectively, the initial setting time was 7.68 min, 5.86 min, 5.25 min, 5.22 min, 15.61 min, 16.20 min or 14.38 min respectively, and the final setting time was 10.89 min, 8.96 min, 7.47 min, 6.75 min, 20.03 min, 21.89 min or 17.17 min respectively; the modified phosphogypsum was obtained by the same operation as in Example 1.

[0048] Comparative Example 4 To investigate the calcination time, the preparation method of the modified phosphogypsum was basically the same as in Example 1, with the difference being: The aging time was 0 h, the cooling method was natural cooling in air, and the calcination time was 1 h, 1.5 h, 2 h, 2.5 h or 3 h in sequence. The mass of water was 1.06%, 0.83%, 0.61%, 0.77% or 0.84% ​​of the mass of phosphogypsum in sequence. The initial setting time was 12.61 min, 14.40 min, 16.20, 18.02 min or 20.30 min in sequence, and the final setting time was 14.63 min, 18.14 min, 21.89, 25.46 min or 31.32 min in sequence. Modified phosphogypsum was obtained by the same operation as in Example 1.

[0049] Comparative Example 5 To investigate the aging time, the preparation method of the modified phosphogypsum was basically the same as that in Example 1, except that: The aging time was 0 h, 1 h, 3 h or 5 h, and the mass of water was 0.60%, 0.62%, 0.65% or 0.69% of the mass of phosphogypsum, respectively. The initial setting time was 15.11 min, 14.38 min, 16.46 min or 17.12 min, respectively, and the final setting time was 19.38 min, 17.29 min, 19.50 min or 20.14 min, respectively. The modified phosphogypsum was obtained by the same operation as in Example 1.

[0050] Comparative Example 6 To investigate the cooling method, the preparation method of the modified phosphogypsum was basically the same as that in Example 1, with the difference being: The aging time was 0 h, and the cooling method was natural cooling in air or natural cooling in the furnace. When the cooling method was natural cooling in air, the mass of water was 0.61% of the mass of phosphogypsum, the initial setting time was 16.2 min, and the final setting time was 21.89 min; when the cooling method was natural cooling in the furnace, the mass of water was 0.60% of the mass of phosphogypsum, the initial setting time was 15.11 min, and the final setting time was 19.38 min.

[0051] Comparative Example 7 To investigate the effect of the ratio of activator to high-titanium slag (the amount of activator incorporated) on the mechanical properties of cementitious materials, the preparation method of the modified high-titanium slag was basically the same as in Example 1, with the difference being: The mass ratio of activator to high-titanium slag is 10:90, 15:85, 20:80, 30:70 or 35:65.

[0052] Comparative Example 8 To investigate the effect of grinding aid dosage on the specific surface area of ​​high-titanium slag, 5 kg of high-titanium slag was mixed with N2-methyl polyol grinding aid, and the grinding time was controlled at 25 min. The mass of N2-methyl polyol grinding aid was 0.1%, 0.2%, 0.3%, 0.4%, or 0.5% of the mass of high-titanium slag. After grinding for the same time, the specific surface areas were 180 m² / kg, 200 m² / kg, 220 m² / kg, 240 m² / kg, or 300 m² / kg, respectively.

[0053] Therefore, when the grinding aid dosage is 0.1%-0.5%, the specific surface area of ​​high-titanium slag increases linearly, and when the dosage is 0.5%, the growth trend of the specific surface area of ​​high-titanium slag accelerates.

[0054] Comparative Example 9 To investigate the influence of other components of the activator on the specific surface area of ​​high-titanium slag, NaOH (0.4%-0.6%) and water glass (0.8%-1.2%) were selected as activators, synergistically combined with slag (79.4%-80.6%) and fly ash (18.2%-18.8%) as inorganic activating components to enhance the hydration activity of high-titanium ore. A four-factor orthogonal experiment was designed using Design-Expert software, and a linear model was established for regression analysis against compressive strength. The optimal ratio was determined to be: 1.5% NaOH, 0.5% water glass, 18.5% fly ash, and 80% slag.

[0055] Comparative Example 10 To investigate the effect of different specific surface areas on the specific surface area of ​​high-titanium slag, an experiment was designed to grind high-titanium slag powder to different specific surface areas. The method was basically the same as the preparation method of modified high-titanium slag in Example 1, except that the grinding was controlled to obtain specific surface areas of 380 m² / kg, 420 m² / kg, 450 m² / kg, 480 m² / kg and 500 m² / kg respectively.

[0056] Experiment Example 1: Effect of different mass ratios of modified phosphogypsum and modified high-titanium slag on the properties of composite cementitious materials 1. Flexural and compressive strength The flexural and compressive strengths of the composite cementitious materials with different mass ratios of modified phosphogypsum and modified high-titanium slag in Examples 1-2 and Comparative Examples 1-2 were determined according to the method of existing technology 1 (GB / T 1346-2011, Test methods for standard consistency water content, setting time and soundness of cement [S]. Beijing: China Standards Press, 2011). The influence of different mass ratios of modified phosphogypsum and modified high-titanium slag on the performance of the composite cementitious materials was further analyzed.

[0057] like Figure 4The diagram shows the effect of modified high-titanium slag on the mechanical properties of the composite cementitious materials in Examples 1-2 and Comparative Examples 1-2 of the present invention. A represents flexural strength; B represents compressive strength; F4 represents the composite cementitious material prepared in Example 1 with a mass ratio of modified phosphogypsum and modified high-titanium slag of 4:6; T4 represents the composite cementitious material prepared in Comparative Example 1 with a mass ratio of modified phosphogypsum and high-titanium slag of 4:6; F5 represents the composite cementitious material prepared in Example 2 with a mass ratio of modified phosphogypsum and modified high-titanium slag of 5:5; and T5 represents the composite cementitious material prepared in Comparative Example 2 with a mass ratio of modified phosphogypsum and high-titanium slag of 5:5. Figure 4 It can be seen that, under the same mix proportion, the composite cementitious material with modified high-titanium slag exhibits a significant improvement in mechanical properties compared to the unmodified high-titanium slag. Specifically, at 28 days, the flexural strength and compressive strength of the material increased by 0.41 MPa and 2.02 MPa, respectively. This indicates that the alkali activator in Examples 1-2 has a significant activating effect on the composite cementitious material, and that the modified high-titanium slag can effectively improve its mechanical properties.

[0058] A comprehensive analysis of the results from Examples 1-2 and Comparative Example 1 revealed that the setting time of the composite cementitious material significantly decreased with increasing amounts of thermally modified phosphogypsum, particularly in terms of initial and final setting times. For example, the initial setting time of group F1 was 33.54 min, and the final setting time was 68.37 min, while the initial setting time of group F9 decreased to 7.46 min, and the final setting time was 15.29 min. This indicates that phosphogypsum has a significant effect on accelerating setting. The standard consistency water requirement fluctuated under different dosage combinations. When the ratio of phosphogypsum to high-titanium slag was 1:9 (group F1), the water-cement ratio was 0.61, while when the ratio was 9:1 (group F9), the water-cement ratio increased back to 0.81.

[0059] The results of flexural and compressive strength tests showed that the mortar prepared under the F4 mix proportion in Example 1 exhibited the best mechanical properties, and the optimal blending ratio of thermally modified phosphogypsum to high-titanium slag was 4:6 (F4 group). Under this mix proportion, the composite cementitious material exhibited good mechanical properties in the early stages of hydration. After 7 days of curing, the compressive strength was 22.95 MPa and the flexural strength was 4.05 MPa; after 28 days of curing, the compressive strength increased to 25.79 MPa and the flexural strength increased to 4.69 MPa, indicating that the material has the potential for strength growth.

[0060] 2. Softening coefficient and linear expansion coefficient The softening coefficient and linear expansion coefficient of the material were determined according to the method of existing technology 1 (GB / T 1346-2011, Test method for standard consistency water content, setting time and soundness of cement [S]. Beijing: China Standards Press, 2011).

[0061] The results for softening coefficient and linear expansion coefficient show that as the modified phosphogypsum content increases, the softening coefficient of the matrix tends to stabilize and decreases slowly. This is mainly because the decrease in the water-to-solid ratio of the cementitious material reduces the micropores within the cementitious material, leading to an increase in the softening coefficient. On the other hand, when the modified phosphogypsum content is too low, it may lead to the formation of excessive agglomerates in the cementitious material, affecting the density and uniformity of the matrix, thereby reducing the softening coefficient. Regarding the linear expansion coefficient, the change is small when the modified high-titanium slag content is between 10% and 60%, while the linear expansion rate reaches its lowest value of 1.25% when the modified phosphogypsum content is 40%. Based on the above results, to improve the utilization rate of thermally modified phosphogypsum and modified high-titanium slag, as well as the overall performance of the composite material, a 4:6 ratio of thermally modified phosphogypsum to modified high-titanium slag is selected. Under this ratio, the composite cementitious material has a compressive strength of 25.79 MPa, a softening coefficient of 0.88, and a linear expansion rate of 1.25% after 28 days.

[0062] Experiment Example 2: Effects of different conditions on the properties of phosphogypsum and the prepared materials 1. Calcination temperature To investigate the effect of calcination temperature on the properties of modified phosphogypsum, analysis of the results from Example 1 and Comparative Example 3 revealed that when the calcination temperature is between 130℃ and 160℃, the initial setting time of the phosphogypsum is 6 minutes, at which point the water requirement for standard consistency is close to 100%. Phase analysis showed that the content of the CaSO4·2H2O phase is relatively high in this temperature range, which exhibits a strong accelerating effect during hydration, leading to rapid setting. Simultaneously, a larger amount of water is required to react with CaSO4·0.5H2O, ultimately achieving a flowability of 180 mm ± 5 mm. However, in the temperature range of 170℃ to 200℃, the initial setting time significantly extends to approximately 16 minutes. In this stage, the content of the CaSO4·2H2O phase in the phosphogypsum is lower, and the accelerating effect is weakened. As the CaSO4·0.5H2O content increases, the water required for the hydration reaction decreases, thereby reducing the water requirement for standard consistency.

[0063] Modified phosphogypsum powders from Examples 1 and 3, calcined at different temperatures, were used to prepare slurries, and their compressive strength was tested. The results showed that the compressive strength of the material first increased and then decreased with increasing calcination temperature. At 130℃, the compressive strength after 2 hours of curing was 1.23 MPa. At 180℃, the highest compressive strength, reaching 4.43 MPa, was achieved after 2 hours of curing. After calcination at 200℃, the compressive strength after 2 hours was 4.01 MPa. The optimal calcination temperature was 180℃, the calcination time was 2 hours, and the furnace cooling method and aging time were no more than 1 hour. The resulting building phosphogypsum met the P2.0 standard in GB / T9776-2022 for building gypsum. At this temperature, the CaSO4·0.5H2O content was highest, resulting in ideal initial setting time, standard consistency, and compressive strength, while ensuring efficient utilization and stable performance of the phosphogypsum. Grey relational analysis showed that the content of the CaSO4·0.5H2O phase had the greatest impact on the physical properties of phosphogypsum, followed by the CaSO4·0.5H2O phase, while the CaSO4 phase had the least impact. Calcination temperature significantly affected compressive strength and water-cement ratio, calcination time mainly affected initial setting time, while aging time had a relatively small impact.

[0064] 2. Calcination time To investigate the effect of calcination time on the properties of modified phosphogypsum, the results of Example 1 and Comparative Example 4 were analyzed, and their compressive strength was tested. It was found that when the calcination time was 1 h, the compressive strength after curing for 2 h was 2.51 MPa (<3.00 MPa). When the calcination time was 1.5 h, the compressive strength after curing for 2 h was 3.50 MPa. When the calcination time was 2–3 h, the compressive strengths were 4.48 MPa, 4.21 MPa, and 4.00 MPa, respectively. When the calcination time was 3 h, the final setting time of the phosphogypsum was greater than 30 min. After comprehensive analysis, it was determined that a calcination time of 2 h resulted in the optimal physical and mechanical properties of the phosphogypsum.

[0065] 3. Aging time To investigate the effect of aging time on the properties of modified phosphogypsum, the compressive strength of the modified phosphogypsum under different aging times in Example 1 and Comparative Example 5 was measured. The results showed that the 2-hour compressive strength of the paste material first increased and then decreased with increasing aging time. Under short aging (1 hour), the 2-hour compressive strength of the phosphogypsum reached 5.97 MPa. However, after 5 hours of aging, the 2-hour compressive strength of the phosphogypsum decreased to 4.28 MPa. This indicates that appropriately extending the aging time helps improve the strength of phosphogypsum, but when the aging time exceeds 1 hour, the compressive strength of the phosphogypsum decreases. Therefore, reasonable control of the aging time is crucial for the mechanical properties of phosphogypsum; excessively long aging times may negatively affect its strength, while maintaining an aging time of around 1 hour significantly improves the material's performance.

[0066] 4. Cooling method To investigate the effect of cooling method on the properties of modified phosphogypsum, the results of Example 1 and Comparative Example 6 were analyzed. It was found that the phosphogypsum cooled by furnace had a shorter setting time, with an initial setting time of 15.11 min and a final setting time of 19.38 min. In contrast, the phosphogypsum cooled by air had an initial setting time of 16.2 min and a final setting time of 21.89 min, showing a longer setting time. This is because during furnace cooling, the CaSO4·2H2O in the phosphogypsum is relatively stable, and the slurry has a setting-promoting effect. Furthermore, with furnace cooling, the increased CaSO4·0.5H2O content results in a lower requirement for achieving the standard consistency, leading to a 0.1% increase in the standard consistency water requirement. In addition, by testing the compressive strength of phosphogypsum under different cooling methods, the compressive strength of the hardened slurry obtained by furnace cooling was 0.1 MPa higher after 2 hours than that obtained by air cooling.

[0067] Experiment Example 3: Effects of different conditions on the modification of high-titanium slag and the properties of the prepared materials 1. Ratio of activator to high-titanium slag To investigate the effect of the ratio of activator to high-titanium slag (the amount of activator incorporated) on the modification of high-titanium slag and the mechanical properties of the prepared cementitious material, the compressive strength of high-titanium slag with different amounts of activator incorporated in Example 1 and Comparative Example 7 was measured.

[0068] Test results show that the amount of activator incorporated has a positive effect on the mechanical properties of the material. The activator consists of 0.2% N2-methyl polyol grinding aid, 1.5% NaOH, 0.5% water glass, 18.5% fly ash, and 80% slag. When the mass ratio of activator to high-titanium slag is 1:3, the mixture is ground to 450 μm. 2At a concentration of / kg, the mechanical properties of the hardened slurry reached their optimal state, with 7-day and 28-day compressive strengths of 21.8 MPa and 34.2 MPa, respectively, both meeting the requirements of S75 grade slag. Both compressive and flexural strengths reached their peak values, with 28-day flexural and compressive strengths of 6.29 MPa and 34.20 MPa, respectively. As the activator dosage decreased, the compressive strength gradually decreased.

[0069] The activity index of the material was determined according to the method of existing technology 1 (GB / T 1346-2011, Test method for standard consistency water content, setting time and soundness of cement [S]. Beijing: China Standards Press, 2011).

[0070] Test results show that, comparing the 7-day and 28-day activity indices, the highest 7-day activity index (69.75%) and the highest 28-day activity index (76.34%) were achieved when the mass ratio of activator to high-titanium slag was 1:3. Therefore, an appropriate amount of activator can react with the mineral components in high-titanium slag, promoting its hydration and generating a CSH framework structure. Excessive activator may lead to excessive formation of calcium aluminate (C3A) hydration products, an imbalance in the ratio of calcium to silicon hydration products, and the generation of excessive soluble salts and Ca(OH)2. This results in increased porosity, decreased density, and ultimately reduced material strength. Conversely, insufficient activator leads to incomplete hydration of the cementitious material, generating fewer hydration products, particularly insufficient CSH and C3AH6 content in the high-titanium slag, which cannot effectively fill the pores within the cementitious material, resulting in decreased density.

[0071] 2. Grinding aid dosage To investigate the effect of grinding aid dosage on the specific surface area of ​​high-titanium slag, the compressive strength of high-titanium slag with different grinding aid dosages was measured. The test results showed that, comparing the mechanical properties after 7 days and 28 days, the mechanical properties were optimal with a grinding aid dosage of 0.2%: the compressive strength at 28 days was 6.51 MPa, and the flexural strength was 14.76 MPa. When the grinding aid dosage exceeded 0.2%, the mechanical properties of the material began to decline, and the decline increased with increasing dosage. At a grinding aid dosage of 0.5%, compared to 0.2%, the flexural strength decreased by 2.01 MPa, and the compressive strength decreased by 4.42 MPa, representing decreases of 30.88% and 29.95%, respectively. These results indicate that the grinding aid dosage significantly affects the mechanical properties and particle size distribution.

[0072] 3. Specific surface area To investigate the effect of different specific surface areas on the specific surface area of ​​high-titanium slag, the compressive strength of high-titanium slag with different specific surface areas was measured. The test results showed that as the specific surface area of ​​high-titanium slag increased from 450 m², the compressive strength of the slag increased.2 / kg further increased to 500 m 2 The material exhibits improved early strength but decreased later strength. This is because finer grinding of high-titanium slag increases its specific surface area, accelerating the synergistic hydration reaction between the high-titanium slag and gypsum crystals, leading to the formation of numerous hydration products in the early stages and enhancing early strength. However, excessively fine slag particles may cause the hydration reaction to be too rapid and incomplete, failing to fully utilize the reactive components in the cement and generating a large amount of non-hydration products, thus affecting the long-term performance of the material. Furthermore, excessively fine slag particles may loosen the internal pore structure of the cement paste, increasing the formation of microcracks. Therefore, although increasing the fineness of titanium slag helps improve early strength, excessive refinement of high-titanium slag may adversely affect the long-term mechanical properties of cementitious materials.

[0073] Characterization of materials in Experiment Example 4 The composite cementitious materials prepared in Examples 1-2 of this invention were subjected to microscopic characterization.

[0074] like Figure 3 As shown, SEM images (×5000 magnification) of the composite cementitious materials prepared in Examples 1-2 of this invention are displayed. A represents F1, the composite cementitious material prepared in Example 2 using modified phosphogypsum and modified high-titanium slag in a mass ratio of 1:9; B represents F4, the composite cementitious material prepared in Example 1 using modified phosphogypsum and modified high-titanium slag in a mass ratio of 4:6; and C represents F9, the composite cementitious material prepared in Example 2 using modified phosphogypsum and modified high-titanium slag in a mass ratio of 9:1. Figure 3 As shown in Figure A, the SEM images of the F1 group materials reveal that AFt crystals intertwine with CaSO4·2H2O to form a framework structure, with C6S2H3 and C6S6H type CSH gels generated in the high-titanium slag under the volcanic ash effect filling the voids. The hydration products gradually cement together, filling the pores and ultimately forming a dense structure, reducing the occurrence of cracks or voids. Therefore, the F1 group materials exhibit high strength and excellent durability. In contrast, the hydration products of the F4 group materials exhibit different characteristics. The SiO4 in the high-titanium slag... 2- and AlO4 3- With Ca in gypsum 2+The reaction generates a large amount of AFt crystals. This reaction proceeds fully, encapsulating and filling the voids in the matrix with CaSO4·2H2O crystals, thus enhancing the matrix's density. Furthermore, the generated CSH crystals further fill some of the pores, resulting in the F4 group material exhibiting better mechanical properties, particularly in terms of softening coefficient. In contrast, the hydration products of the F9 group material mainly consist of columnar or blocky CaSO4·2H2O, with only a small amount of CSH gel filling the pores. This results in a more porous and looser overall structure, leading to lower mechanical properties and a relatively lower softening coefficient. In summary, the F1 and F4 groups exhibit better mechanical and durability properties due to their denser hydration product structure, while the F9 group, with its looser structure, suffers from relatively poor mechanical properties. Therefore, the F1 and F4 groups outperform the F9 group, and the higher softening coefficient of the F4 group reflects its superior mechanical stability.

[0075] Performance characterization of composite cementitious materials in Example 5, Examples 1 and 2 The composite cementitious materials in Examples 1 and 2 of this invention were tested for compressive strength in water and air according to the method of prior art 2 (Qian Yaoli. Study on stability and long-term performance of high water-resistant gypsum composite cementitious materials [J]. Shanxi Architecture, 2018, 44(17):114-115); after 26 days of curing, they were dried at 60℃ and sealed, and carbonation experiments were conducted according to the method of prior art 3 (GB / T 50082-2009, Method for determination of fineness of cement particles [S]. Beijing: China Standards Press, 2020); dry and wet cycle experiments were conducted according to the method of prior art 4 (GB / T 11969-2020, Test method for performance of autoclaved aerated concrete [S]. Beijing: State Administration for Market Regulation, Standardization Administration of China, 2020.); and dry and wet cycle experiments were conducted according to the method of prior art 5 (GB 50574-2010, Unified technical specification for application of wall materials [S]. Beijing: China Building Industry Press, The freeze-thaw cycle experiment was conducted using the method described in 2010.

[0076] like Figure 5 The diagram shows the development of compressive strength of the composite cementitious materials in water and air in Examples 1 and 2 of this invention. F1 represents the composite cementitious material prepared in Example 2 with a mass ratio of 1:9 of modified phosphogypsum and modified high-titanium slag; F9 represents the composite cementitious material prepared in Example 2 with a mass ratio of 9:1 of modified phosphogypsum and modified high-titanium slag; and F4 represents the composite cementitious material prepared in Example 1 with a mass ratio of 4:6 of modified phosphogypsum and modified high-titanium slag. Figure 5It can be seen that after air curing for 28 days, the compressive strengths of the F9 group materials were 11.35 MPa and 3.27 MPa, respectively, which were 7.48% higher and 69.03% lower than the compressive strength at 28 days. The compressive strengths of the F4 group materials were 26.50 MPa and 21.24 MPa, respectively, which were 2.75% higher and 16.51% lower than the compressive strength at 28 days. The compressive strengths of the F1 group materials were 29.51 MPa and 26.19 MPa, respectively, which were 2.29% higher and 9.81% lower than the compressive strength at 28 days.

[0077] like Figure 6 The images shown depict the carbonization of the composite cementitious materials in Examples 1 and 2 of this invention. F1 represents the composite cementitious material prepared in Example 2 using modified phosphogypsum and modified high-titanium slag in a mass ratio of 1:9; F9 represents the composite cementitious material prepared in Example 2 using modified phosphogypsum and modified high-titanium slag in a mass ratio of 9:1; and F4 represents the composite cementitious material prepared in Example 1 using modified phosphogypsum and modified high-titanium slag in a mass ratio of 4:6. Figure 6 It can be seen that the carbonation resistance of the material gradually decreases with the increase of phosphogypsum content. After 3 days of curing in the carbonation chamber, the carbonation depth of all groups was 1.1 cm. After 28 days of curing, the carbonation depths of the three groups were 5.0 cm (F1), 7.2 cm (F4), and 10.8 cm (F9), respectively. Among them, group F9 showed a particularly significant increase in carbonation depth in the later stages of carbonation, with an increase of 9.7 cm. This phenomenon is due to the increased phosphogypsum content, which leads to the generation of more Ca(OH)2 in the alkaline environment of the cement-based material. Simultaneously, a large amount of calcium sulfate minerals are generated during cement hydration, exhibiting instability during carbonation, easily decomposing, and releasing OH-, which reacts with CO2 to generate CO3. 2- This accelerates the carbonization reaction. Therefore, with the increase of phosphogypsum content, the carbonization reaction inside the material becomes more significant, leading to an accelerated increase in carbonization depth, especially in the later stages of carbonization, where a more obvious carbonization extension trend is observed.

[0078] like Figure 7 The figures shown depict the morphological changes of the composite cementitious materials in Examples 1 and 2 under different wet-dry cycles. F1 represents the composite cementitious material prepared in Example 2 using modified phosphogypsum and modified high-titanium slag at a mass ratio of 1:9; F9 represents the composite cementitious material prepared in Example 2 using modified phosphogypsum and modified high-titanium slag at a mass ratio of 9:1; and F4 represents the composite cementitious material prepared in Example 1 using modified phosphogypsum and modified high-titanium slag at a mass ratio of 4:6. Figure 7It can be seen that the F9 group material exhibited significant surface peeling after 40 wet-dry cycles, i.e., at the fourth level. At the eighth level, the material surface underwent slight deformation, while at the ninth level, most of the material surface peeled off.

[0079] like Figure 8 The figure shows the effect of different wet-dry cycles on the quality of the composite cementitious materials in Examples 1 and 2, where A represents mass; B represents mass loss rate; F1 represents the composite cementitious material prepared in Example 2 with a mass ratio of 1:9 of modified phosphogypsum and modified high-titanium slag; F9 represents the composite cementitious material prepared in Example 2 with a mass ratio of 9:1 of modified phosphogypsum and modified high-titanium slag; and F4 represents the composite cementitious material prepared in Example 1 with a mass ratio of 4:6 of modified phosphogypsum and modified high-titanium slag.

[0080] like Figure 9 As shown in the figure, the effect of different wet-dry cycles on the compressive strength of the composite cementitious materials in Example 1 and Example 2 is illustrated. In this figure, A represents the compressive strength; B represents the erosion rate; F1 represents the composite cementitious material prepared in Example 2 with a mass ratio of 1:9 of modified phosphogypsum and modified high-titanium slag; F9 represents the composite cementitious material prepared in Example 2 with a mass ratio of 9:1 of modified phosphogypsum and modified high-titanium slag; and F4 represents the composite cementitious material prepared in Example 1 with a mass ratio of 4:6 of modified phosphogypsum and modified high-titanium slag.

[0081] Comprehensive analysis Figures 7-9 It was learned that Group F4 also showed a significant decrease in strength and mass at level six, at which point... The material's compressive strength was 27.09 MPa, its mass was 519.20 g, its erosion rate was 5.94%, and its mass loss rate was 3.79%. At level nine, the strength decreased to 22.60 MPa, the mass was 493.74 g, the erosion rate was 21.53%, and the mass loss rate was 8.92%. The F1 group material began to show surface flaking at level seven. With increasing wet-dry cycles, the flaking area gradually increased, but the material did not show significant deformation. At this stage, the material's compressive strength was 28.28 MPa, its mass was 522.54 g, its erosion rate was 11.35%, and its mass loss rate was 3.26%. This is because excessive phosphogypsum content leads to the formation of incompletely reacted CaSO4·0.5H2O and CaSO4 within the material. These components absorb water and expand during immersion, generating expansion stress that compresses the surrounding aggregates and reduces the adhesion between them. During the subsequent drying process, the compressive pressure of CaSO4·2H2O on the surrounding aggregate decreases as moisture evaporates, and the pore volume no longer expands. With repeated wet-dry cycles, the expansion and contraction of pores lead to the gradual expansion of cracks within the material, and multiple micropores gradually connect to form through cracks. This not only further weakens the material's bonding strength but also has a significant negative impact on the material's macroscopic mechanical and physical properties. As the number of wet-dry cycles increases, microcracks connect and expand, forming a network of cracks. The width and length of these cracks continuously increase, ultimately leading to severe gypsum particle detachment from the material surface.

[0082] like Figure 10 The images shown are physical diagrams illustrating the damage morphology of the composite cementitious materials in Examples 1 and 2 of this invention after freeze-thaw cycles. A represents F1, the composite cementitious material prepared in Example 2 using modified phosphogypsum and modified high-titanium slag in a mass ratio of 1:9; B represents F4, the composite cementitious material prepared in Example 1 using modified phosphogypsum and modified high-titanium slag in a mass ratio of 4:6; and C represents F9, the composite cementitious material prepared in Example 2 using modified phosphogypsum and modified high-titanium slag in a mass ratio of 9:1.

[0083] like Figure 11 As shown in the figure, the effect of different freeze-thaw cycle levels of the present invention on the compressive strength of the composite cementitious materials in Example 1 and Example 2 is illustrated, where A represents mass; B represents mass loss rate; F1 is the composite cementitious material prepared in Example 2 with a mass ratio of 1:9 of modified phosphogypsum and modified high-titanium slag; F9 is the composite cementitious material prepared in Example 2 with a mass ratio of 9:1 of modified phosphogypsum and modified high-titanium slag; and F4 is the composite cementitious material prepared in Example 1 with a mass ratio of 4:6 of modified phosphogypsum and modified high-titanium slag.

[0084] like Figure 12As shown in the figure, the effect of different freeze-thaw cycle levels of the present invention on the compressive strength of the composite cementitious materials in Example 1 and Example 2 is illustrated, where A represents mass; B represents mass loss rate; F1 is the composite cementitious material prepared in Example 2 with a mass ratio of 1:9 of modified phosphogypsum and modified high-titanium slag; F9 is the composite cementitious material prepared in Example 2 with a mass ratio of 9:1 of modified phosphogypsum and modified high-titanium slag; and F4 is the composite cementitious material prepared in Example 1 with a mass ratio of 4:6 of modified phosphogypsum and modified high-titanium slag.

[0085] analyze Figures 10-12 It was found that the F9 group samples failed after undergoing the fifth freeze-thaw cycle, i.e., 25 cycles, exhibiting severe damage, becoming extremely brittle, and showing a significant reduction in strength. The F4 and F1 groups failed at the eighth and tenth freeze-thaw cycles, respectively. Although the F7 group had a larger surface spalling area, the failure of both groups was due to cracking. With increasing freeze-thaw cycles, the mass loss rate gradually increased, reaching 11.78%, 12.64%, and 9.24% for the three groups at the failure cycle count, respectively. Mass loss primarily stemmed from surface spalling, with lower-strength materials more prone to surface peeling and damage during freeze-thaw cycles. Simultaneously, the compressive strength of the materials decreased with increasing freeze-thaw cycles, with the F1 group showing significantly higher compressive strength than the F4 group, which in turn showed higher strength than the F9 group. The damage to the composite cementitious material during freeze-thaw cycles mainly originated from the freezing and expansion of moisture caused by temperature changes, as well as the interaction between moisture migration in the pores and crack propagation. Specifically, when the temperature drops below freezing, water in the pores begins to freeze, increasing in volume and exerting pressure on the pore boundaries, leading to boundary rupture or detachment. Simultaneously, some unfrozen water migrates within the pores, exacerbating internal stress and further promoting crack propagation. With repeated freeze-thaw cycles, the material's microstructure is gradually compromised, resulting in decreased strength and toughness. Repeated freeze-thaw cycles not only damage pore walls but may also accelerate the development of microcracks through water migration, causing further material damage. After multiple freeze-thaw cycles, the material's pore structure becomes increasingly unstable, ultimately leading to a significant decrease in its mechanical properties and potentially even complete material failure.

[0086] In summary, the composite cementitious material of Example 1 exhibits good water resistance, but its compressive strength gradually decreases with prolonged hydration time, especially during water curing, where the compressive strength drops to 21.24 MPa after 90 days. This limits its application in cold regions or freeze-thaw environments. It also demonstrates good resistance to carbonation; after 3 days of heavy curing in a carbonization chamber, the carbonization depth is 1.1 cm, increasing to 7.2 cm after 28 days. Although this increase is slight, it remains superior to other similar materials. Furthermore, Example 1 also exhibits excellent weather resistance and freeze-thaw resistance, showing no significant performance degradation after 80 freeze-thaw cycles, demonstrating good antifreeze properties.

[0087] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for preparing a phosphogypsum-high-titanium slag solid waste-based composite cementitious material, characterized in that, The preparation method includes: (1) Mix the activator with the high-titanium slag and grind it to 450 m² / kg to obtain modified high-titanium slag; mix the phosphogypsum with water, allow it to initially solidify and then solidify, calcine it at 180 ℃, cool it naturally in the furnace, and age it to obtain modified phosphogypsum. The activator is any two or more of N2-methyl polyol grinding aids, NaOH, water glass, fly ash and slag; (2) Mix modified phosphogypsum and modified high-titanium slag, add water, allow initial solidification, and then allow final solidification to obtain phosphogypsum-high-titanium slag solid waste-based composite cementitious material.

2. The preparation method according to claim 1, characterized in that, In step (1), the activator is N2-methyl polyol grinding aid, NaOH, water glass, fly ash and slag.

3. The preparation method according to claim 2, characterized in that, The mass fractions of the N2-methyl polyol grinding aid, NaOH, water glass, fly ash, and slag are 0.2%, 1.5%, 0.5%, 17.8%, and 80%, respectively.

4. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of the activator to the high-titanium slag is (10~35):(65~90); the mass of the water is 0.5~0.65 of the mass of the phosphogypsum.

5. The preparation method according to claim 4, characterized in that, The activator is in a mass ratio of 1:3 to high-titanium slag; the water mass is 0.61 times the mass of phosphogypsum; the calcination time is 2 hours; and the aging time is 1 hour.

6. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of the modified phosphogypsum to the modified high-titanium slag is (1~9): (1~9).

7. The preparation method according to claim 6, characterized in that, The mass ratio of the modified phosphogypsum to the modified high-titanium slag is 4:

6.

8. The preparation method according to claim 1, characterized in that, In step (2), the mass of the water is 0.44 of the total mass of the composite cementitious material.

9. A phosphogypsum-high titanium slag solid waste-based composite cementitious material prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the phosphogypsum-high titanium slag solid waste-based composite cementitious material as described in claim 9 as a building material.

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