A phosphorous slag-based cementitious material, a preparation method and application thereof

Abstract

This invention discloses a phosphorus slag-based cementitious material, its preparation method, and its application, specifically relating to the field of cementitious materials technology. The cementitious material, by weight, comprises the following components: 60-90 parts phosphorus slag powder; 5-25 parts fly ash; 5-15 parts activator; 0.25-1.5 parts early-strength agent; and 0.2-0.5 parts water-reducing agent; wherein the specific surface area of ​​the phosphorus slag powder is 400-550 m². 2 / kg, particle size (D) 90 The particle size is 20-40 μm; the early-strength agent is selected from at least one of iron salts and aluminum salts. This invention uses phosphorus slag micro-powder with a specific specific surface area as the main substrate, with a high dosage, combined with fly ash, activator, early-strength agent, and water-reducing agent to obtain phosphorus slag-based cementitious materials. By optimizing the physical properties of the phosphorus slag micro-powder and constructing a suitable composite activator-early-strength system, the 28-day compressive strength of the cementitious material reaches over 61.0 MPa, achieving a balance between "high phosphorus slag content" and "high strength".

Description

Technical Field

[0001] This invention relates to the field of cementitious materials technology, specifically to a phosphorus slag-based cementitious material, its preparation method, and its application. Background Technology

[0002] In the phosphorus chemical industry chain, the treatment and resource utilization of solid waste has always been a key issue for the industry's sustainable development. As one of the largest solid wastes generated in this industry chain, the high-value utilization of phosphorus slag has attracted much attention. Using phosphorus slag as a major cementing component in mine backfill materials is a key technological path to achieve its high-value utilization. However, mine backfill technology mainly relies on cement as a cementing agent. For example, the high-content phosphorus slag micro-powder cementitious material disclosed in Chinese patent CN111233355A, although it can meet the strength requirements, has high energy consumption and high carbon emissions during cement use, which contradicts the concept of sustainable development.

[0003] In search of alternatives, existing technologies attempt to partially replace cement with phosphate slag. However, due to the low activity and unreasonable particle size distribution of phosphate slag, problems such as insufficient early strength of the backfill and slurry sedimentation and segregation often occur, which not only affect the backfilling efficiency but also limit its large-scale application in high-concentration and high-strength backfilling projects.

[0004] Chinese patent CN1792973A discloses a gypsum tailings cementitious material. This technology primarily utilizes gypsum tailings blended with finely ground slag / phosphate slag to prepare a cementless cementitious material under the action of activators such as lime and alum powder. While this method achieves solid waste utilization, the system highly relies on the large amount of dihydrate gypsum in the gypsum tailings as the main cementing component, constructing a strength framework through the generation of ettringite. In this system, phosphate slag exists only as an auxiliary active material (maximum only 40%), and it has not undergone refined gradation control tailored to the characteristics of phosphate slag. Limited by the brittleness and long-term stability of gypsum-based materials, the 28-day compressive strength of this system is typically only around 40 MPa, making it difficult to meet the requirements of higher strength engineering structural materials.

[0005] Further analysis of existing technologies reveals that removing cement or reducing calcium sulfate content drastically decreases the strength of phosphorus slag-based materials. For example, the strength of the filling material in Chinese patent CN103964804A is typically below 15 MPa. Although Chinese patent CN119490313A employs a composite activator and aluminum salt early-strength agent, its yellow phosphorus slag content is still only 20-40 parts, and its filling material strength is similarly low. This indicates that simply applying the fineness requirements of traditional cement concrete (such as only requiring a specific surface area >350 m²) is ineffective. 2Neither the use of phosphate slag ( / kg) nor the use of traditional activator systems can achieve high-strength cementitious properties while completely eliminating cement and significantly reducing gypsum dependence. In particular, when the content of phosphate slag is increased to more than 60%, the existing activators and fineness control methods not only fail to improve strength, but also lead to a surge in water demand and a loose structure, making it difficult to form a dense hardened body.

[0006] Therefore, how to achieve a balance between high phosphorus slag content and high strength without the need for cement or large amounts of gypsum, by optimizing the physical properties of phosphorus slag and constructing a suitable composite activation-early strength system, has become a technical challenge that urgently needs to be overcome in this field. Summary of the Invention

[0007] Therefore, the present invention provides a phosphorus slag-based cementitious material, its preparation method and application, to solve the problems in the prior art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: According to a first aspect of the present invention, a phosphorus slag-based cementitious material comprises, by weight, the following components: 60-90 parts phosphorus slag powder; 5-25 parts fly ash; 5-15 parts activator; 0.25-1.5 parts early-strength agent; and 0.2-0.5 parts water-reducing agent; wherein the specific surface area of ​​the phosphorus slag powder is 400-550 m². 2 / kg, particle size (D) 90 )20-40μm; the early strength agent is selected from at least one of iron salt and aluminum salt.

[0009] Furthermore, the mass ratio of calcium carbide slag to sodium sulfate in the activator is (1-1.5):1.

[0010] The main component of carbide slag is Ca(OH)2, which releases OH- after ionization in water. - It can increase the pH value of the cementation system, destroy the glassy structure in the phosphorus slag powder, and release active silica-alumina components; the released Si and Al ions react with Ca... 2+ The combination generates cementitious products such as hydrated calcium silicate (CSH gel) and hydrated calcium aluminate (CAH), which are cross-linked through hydrogen and ionic bonds to form a three-dimensional network structure. In the yellow phosphorus slag-calcium hydroxide system, SO4 ionized from sodium sulfate... 2- It will react with free Ca in the system 2+ AlO2 - The C-(A)-SH gel on the surface of yellow phosphorus slag undergoes the following two reactions to further generate ettringite, which plays an early strength role.

[0011] AlO2 - +Ca 2+ +OH -+SO4 2- →3CaO·Al2O3·3CaSO4·32H2O 3CaO·Al2O3·6H2O+3(CaSO4·2H2O)+20H2O→3CaO·Al2O3·3CaSO4·32H2O In addition, SO4 in sulfate activators 2- SiO4 can be encapsulated in C-(A)-SH gel 4- A portion was displaced and reacted with Ca outside the encapsulation layer. 2+ The reaction continues to generate C-(A)-SH gel, allowing the hydration reaction to continue fully and further improving the strength properties.

[0012] Furthermore, the early strength agent is a mixture of iron salt and aluminum salt in a mass ratio of (0-1):1.

[0013] Furthermore, the iron salt is selected from at least one of basic ferric sulfate, polyferric sulfate, and ferric chloride; the aluminum salt is selected from at least one of aluminum chloride, polyaluminum chloride, aluminum sulfate, and polyaluminum sulfate. As an example, the aluminum salt is aluminum sulfate.

[0014] Furthermore, the water-reducing agent is selected from at least one of lignin sulfonate-based water-reducing agents, polycarboxylate water-reducing agents, and naphthalene-based water-reducing agents.

[0015] Furthermore, the lignin sulfonate-based water-reducing agent is selected from at least one of sodium lignin sulfonate and calcium lignin sulfonate; the polycarboxylate water-reducing agent is selected from at least one of polyester-type PCE and polyether-type PCE; and the naphthalene-based water-reducing agent is selected from naphthalene sulfonate formaldehyde condensate.

[0016] Furthermore, the phosphorus slag powder is obtained by ball milling yellow phosphorus slag at a speed of 260-300 rpm.

[0017] The phosphorus slag powder of this invention is yellow phosphorus slag powder. Yellow phosphorus slag is a byproduct of the production of yellow phosphorus by the electric furnace process. By crushing the yellow phosphorus slag and then ball milling it (preferably at a ball milling speed of 260-300 rpm), a specific surface area of ​​400-550 m² can be obtained. 2 Phosphate slag powder with a particle size of 20-40μm (laser particle size analyzer) and a density of / kg (Burney method).

[0018] Yellow phosphorus slag: Waste residue discharged from the thermal yellow phosphorus process. The main components of yellow phosphorus slag are CaO (44%-52%) and SiO2 (38%-45%). Its internal structure is amorphous (glassy), and its content is usually as high as 85%-95%, which is the fundamental reason for its potential activity.

[0019] Fly ash contains a large amount of silica and alumina, which, after dissolving in an alkaline environment, provides additional silica and alumina monomers, which, together with the Ca released from phosphorus slag, contribute to its overall benefits. 2+ The reaction generates C-(A)-SH gel, enhancing the system's strength. Simultaneously, the active Al2O3 in fly ash promotes the depolymerization of the silica-oxygen network in the phosphorus slag, shortening the setting time. Furthermore, fly ash improves the pore structure, and its synergistic effect with phosphorus slag significantly enhances the material's mechanical properties, durability, and sustainability.

[0020] According to a second aspect of the present invention, a method for preparing a phosphorus slag-based cementitious material as described above includes the following steps: mixing phosphorus slag powder, fly ash, activator, early strength agent and water-reducing agent according to the proportion for 18-24 hours to obtain the phosphorus slag-based cementitious material.

[0021] According to a third aspect of the present invention, an application of a phosphorus slag-based cementitious material as described above in mine backfilling is provided.

[0022] Furthermore, the phosphorus slag-based cementitious material is mixed with aggregate and water to form a filling slurry, which is then transported to the goaf of the mine for filling.

[0023] Furthermore, the aggregate is selected from at least one of phosphogypsum, phosphate tailings, and waste rock; the mass ratio of the aggregate to the phosphate slag-based cementitious material is (4-6):1.

[0024] Furthermore, the mass concentration of the filling slurry is 65-72%.

[0025] The present invention has the following advantages: This invention uses phosphorus slag powder with a specific surface area as the main base material, with a high dosage, combined with fly ash, activator, early strength agent, and water-reducing agent to obtain phosphorus slag-based cementitious materials. This is achieved by optimizing the physical properties of the phosphorus slag powder (specific surface area 400-550 m²). 2 / kg, particle size D 90 The phosphorus slag-based cementitious material has a thickness of 20-40 μm and a suitable composite activation-early strength system is constructed, enabling the 28-day compressive strength of the cementitious material to reach over 61.0 MPa, achieving a balance between "high phosphorus slag content" and "high strength". Furthermore, the phosphorus slag-based cementitious material of this invention exhibits a short setting time and rapid early strength development, meeting the engineering requirements for cemented backfilling in mines.

[0026] The phosphorus slag-based cementitious material system of this invention is completely free of cement components, with a yellow phosphorus slag content of over 60%, achieving a complete replacement for traditional cement. Using phosphorus slag powder and fly ash as the main cementitious components, combined with inherent mine waste such as phosphogypsum and phosphorus tailings as aggregates, it can utilize large quantities of industrial solid waste throughout the entire chain, achieving "waste treatment with waste." This significantly reduces dependence on traditional cement, reduces the environmental pressure caused by solid waste accumulation, and significantly lowers raw material and production costs, aligning with the concept of green development. It boasts high solid waste utilization and significant environmental and economic benefits.

[0027] This invention employs a calcium carbide slag-sodium sulfate composite activator. Through the synergistic effect of alkali activation and sulfate activation, it effectively disrupts the glassy structure of phosphorus slag, continuously promoting the hydration reaction and generating CSH gel and ettringite. The alkaline environment provided by the calcium carbide slag can destroy the glassy structure in the phosphorus slag powder, releasing active silica-alumina components; the SO4 provided by sodium sulfate... 2- Then with free Ca in the system 2+ AlO2 - The reaction produces ettringite, and SO42- 2- SiO4 can be encapsulated in C-(A)-SH gel 4- A portion is displaced, allowing the hydration reaction to continue fully.

[0028] This invention, combined with iron / aluminum salt early-strength agents, accelerates early hydration and shortens setting time. The iron and aluminum salts work synergistically with the composite activator to rapidly generate ettringite and iron cementitious phases, further densifying the structure. Fly ash supplements the silica-alumina source and optimizes the pore structure, ultimately achieving early strength and high strength.

[0029] The preparation process of this invention only requires mixing and grinding the components according to the specified ratio for 18-24 hours, without the need for complex processes such as high-temperature calcination. It has low energy consumption and simple equipment requirements. The fineness of the phosphorus slag powder is precisely controlled by ball milling (ball milling speed 260-300 rpm), and the proportion of each component is flexibly adjustable, which facilitates large-scale mass production and has good industrialization prospects.

[0030] This invention is specifically designed for mine backfilling. It exhibits excellent compatibility with existing mine aggregates such as phosphogypsum and phosphate tailings, resulting in backfill slurries with good stability and low bleeding rate. The proportions can be flexibly adjusted according to the strength, cost, and setting time requirements of different mining projects, effectively solving the problems of insufficient early strength and slurry sedimentation and segregation in existing backfill materials, thus ensuring mine safety. Detailed Implementation

[0031] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0032] Unless otherwise specified in the embodiments of this invention, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available products; different manufacturers and models of raw materials do not affect the implementation of the technical solution or the achievement of the technical effect of this invention.

[0033] Yellow phosphorus slag: Yellow phosphorus slag produced by electric furnace process in Guizhou's phosphorus chemical industry. Main chemical components: CaO 46.5%, SiO2 41.2%, Al2O3 3.8%, P2O5 2.1%.

[0034] Phosphorus slag powder: After drying yellow phosphorus slag at 110℃ for 24 hours, it is ball-milled using a planetary ball mill. The rotation speed and ball milling time are controlled to obtain phosphorus slag powder with different specific surface areas and particle sizes.

[0035] Fly ash: Grade II fly ash, specific surface area 380 m² 2 / kg, water requirement ratio 98%.

[0036] Calcium carbide slag: A by-product of a calcium carbide plant, with a Ca(OH)2 content of 86% and a residue of 8% on an 80μm sieve.

[0037] Sodium sulfate: Industrial grade sodium sulfate, Na2SO4 content ≥98%.

[0038] Aluminum sulfate: Industrial grade, Al2(SO4)3·18H2O content ≥99%.

[0039] Polyferric sulfate: Industrial grade, total iron content ≥18%.

[0040] Sodium lignosulfonate: Industrial grade, water reduction rate ≥12%.

[0041] Polycarboxylate superplasticizer: powder, water reduction rate ≥25%, meeting the requirements of GB / T 8077-2012 "Test Method for Homogeneity of Concrete Admixtures" standard. This invention uses Jiangsu Subote, PCA®-VIII series polycarboxylate high-performance superplasticizer; The naphthalene-based water-reducing agent is a naphthalene sulfonate formaldehyde condensate, which conforms to GB / T 8077 standard and has a water reduction rate of ≥15%. This invention uses FDN-F high-efficiency water-reducing agent produced by Shandong Hongyi Technology.

[0042] Example 1 Phosphorus slag powder: Yellow phosphorus slag was placed in an oven and dried at 105-110℃ for 24 hours until the moisture content was ≤1%. After cooling, it was set aside for use. The dried yellow phosphorus slag was then ball-milled using a planetary ball mill at a speed of 265 rpm, a ball-to-material ratio of 10:1, and a milling time of 20 hours to obtain phosphorus slag powder. The specific surface area of ​​this phosphorus slag powder was measured to be 450 m² / g. 2 / kg (Burney method), particle size D 90 The particle size is 28 μm (laser particle size analyzer method).

[0043] Raw materials: 75 parts phosphorus slag powder; 15 parts fly ash; 5.0 parts calcium carbide slag + 4.0 parts sodium sulfate; 0.8 parts aluminum sulfate; 0.35 parts polycarboxylate superplasticizer.

[0044] Preparation method: The above-weighed phosphorus slag powder, fly ash, carbide slag, sodium sulfate, aluminum sulfate and polycarboxylate superplasticizer are placed in a mixer and mixed for 24 hours to ensure that the components are fully mixed and uniform, so as to obtain phosphorus slag-based cementitious material powder.

[0045] Example 2 The difference from Example 1 is as follows: Phosphorus slag powder: Yellow phosphorus slag was pulverized and then ball-milled at 280 rpm for 18 hours to obtain a specific surface area of ​​400 m². 2 / kg, particle size (D) 90 The phosphorus slag powder is 33μm in size.

[0046] Raw materials: 60 parts of phosphorus slag powder; 25 parts of fly ash; 2.5 parts of calcium carbide slag + 2.5 parts of sodium sulfate; 0.25 parts of aluminum sulfate; 0.2 parts of sodium lignosulfonate.

[0047] Everything else is the same as in Example 1.

[0048] Example 3 The difference from Example 1 is as follows: The ball milling speed was 280 rpm, and the ball milling time was 24 hours, resulting in a specific surface area of ​​550 m². 2 / kg, particle size (D) 90 The phosphorus slag powder is 15μm in size.

[0049] Raw materials: 90 parts of phosphorus slag powder; 5 parts of fly ash; 8.0 parts of calcium carbide slag + 7.0 parts of sodium sulfate; 1.5 parts of aluminum sulfate; 0.5 parts of polycarboxylate superplasticizer.

[0050] Everything else is the same as in Example 1.

[0051] Example 4 The difference from Example 1 is as follows: Raw materials: 70 parts of phosphorus slag powder; 20 parts of fly ash; 4.0 parts of calcium carbide slag + 3.5 parts of sodium sulfate; 0.6 parts of polyferric sulfate; 0.3 parts of sodium lignosulfonate.

[0052] Everything else is the same as in Example 1.

[0053] Example 5 The difference from Example 1 is as follows: Raw materials: 80 parts of phosphorus slag powder; 10 parts of fly ash; 6.0 parts of calcium carbide slag + 5.0 parts of sodium sulfate; 0.5 parts of aluminum sulfate + 0.5 parts of polyferric sulfate; 0.4 parts of FDN-F.

[0054] Everything else is the same as in Example 1.

[0055] Example 6 The difference from Example 1 is as follows: Raw materials: 85 parts of phosphorus slag powder; 8 parts of fly ash; 7.0 parts of calcium carbide slag + 6.0 parts of sodium sulfate; 1.0 part of polyaluminum chloride; 0.4 parts of sodium lignosulfonate.

[0056] Everything else is the same as in Example 1.

[0057] Comparative Example 1 The difference from Example 1 is as follows: Raw materials: 55 parts of phosphorus slag powder; 10 parts of fly ash; 4.2 parts of calcium carbide slag + 4.2 parts of sodium sulfate; 1.3 parts of aluminum sulfate; 0.3 parts of sodium lignosulfonate.

[0058] Everything else is the same as in Example 1.

[0059] Comparative Example 2 The difference from Example 1 is as follows: Phosphorus slag powder: Yellow phosphorus slag was pulverized and then ball-milled at 265 rpm for 16 hours to obtain a specific surface area of ​​350 m². 2 / kg, particle size (D) 90 The phosphorus slag powder is 40μm in size.

[0060] Raw materials: 80 parts of phosphorus slag powder; 10 parts of fly ash; 4.2 parts of calcium carbide slag + 4.2 parts of sodium sulfate; 1.3 parts of aluminum sulfate; 0.3 parts of sodium lignosulfonate.

[0061] Everything else is the same as in Example 1.

[0062] Comparative Example 3 The difference from Example 1 is as follows: Phosphorus slag powder: Yellow phosphorus slag was pulverized and then ball-milled at 265 rpm for 26 hours to obtain a powder with a specific surface area of ​​600 m². 2 / kg, particle size (D) 90 () is 10μm phosphorus slag powder.

[0063] Raw materials: 80 parts of phosphorus slag powder; 10 parts of fly ash; 4.2 parts of calcium carbide slag + 4.2 parts of sodium sulfate; 1.3 parts of aluminum sulfate; 0.3 parts of sodium lignosulfonate.

[0064] Everything else is the same as in Example 1.

[0065] Comparative Example 4 The difference from Example 1 is as follows: Raw materials: 80 parts of phosphorus slag powder; 10 parts of fly ash; 8.4 parts of calcium carbide slag; 1.3 parts of aluminum sulfate; 0.3 parts of sodium lignosulfonate.

[0066] Everything else is the same as in Example 1.

[0067] Comparative Example 5 The difference from Example 1 is as follows: Raw materials: 80 parts of phosphorus slag powder; 10 parts of fly ash; 8.4 parts of sodium sulfate; 1.3 parts of aluminum sulfate; 0.3 parts of sodium lignosulfonate.

[0068] Everything else is the same as in Example 1.

[0069] Comparative Example 6 The difference from Example 1 is as follows: Raw materials: 80 parts of phosphorus slag powder; 10 parts of fly ash; 4.2 parts of calcium carbide slag + 4.2 parts of sodium sulfate; 0.3 parts of sodium lignosulfonate.

[0070] Everything else is the same as in Example 1.

[0071] Comparative Example 7 The difference from Example 1 is as follows: Raw materials: 80 parts of phosphorus slag powder; 10 parts of fly ash; 8.4 parts of sodium sulfate; 1.3 parts of triethanolamine; 0.3 parts of sodium lignosulfonate.

[0072] Everything else is the same as in Example 1.

[0073] Comparative Example 8 The difference from Example 1 is as follows: Raw materials: 80 parts of phosphorus slag powder; 10 parts of fly ash; 4.2 parts of calcium carbide slag + 4.2 parts of sodium sulfate; 1.3 parts of alum stone powder; 0.3 parts of sodium lignosulfonate.

[0074] Everything else is the same as in Example 1.

[0075] Comparative Example 9 The difference from Example 1 is as follows: Raw materials: 70 parts of phosphorus slag powder; 4.0 parts of calcium carbide slag + 3.5 parts of sodium sulfate; 0.6 parts of polyferric sulfate; 0.3 parts of sodium lignosulfonate.

[0076] Everything else is the same as in Example 1.

[0077] Comparative Example 10 The difference from Example 1 is as follows: Raw materials: 70 parts of phosphorus slag powder; 20 parts of fly ash; 4.0 parts of calcium carbide slag + 3.5 parts of sodium sulfate; 0.6 parts of polyferric sulfate.

[0078] Everything else is the same as in Example 1.

[0079] Comparative Example 11 The difference from Example 1 is as follows: Raw materials: 60 parts phosphorus slag powder; 30 parts cement; 8 parts fly ash; 4.0 parts calcium carbide slag + 3.5 parts sodium sulfate; 0.6 parts polyferric sulfate; 0.3 parts sodium lignosulfonate.

[0080] Everything else is the same as in Example 1.

[0081] Comparative Example 12 The difference from Example 1 is as follows: Raw materials: 60 parts of phosphorus slag powder; 20 parts of gypsum; 10 parts of fly ash; 4.0 parts of carbide slag + 3.5 parts of sodium sulfate; 1.3 parts of aluminum sulfate; 0.3 parts of sodium lignosulfonate.

[0082] Everything else is the same as in Example 1.

[0083] Test Example 1 Mortar strength test: According to GBT17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)": Weigh phosphorus slag-based cementitious material, standard sand and water in a mass ratio of 2:6:1 and mix them in a cement mortar mixer. Then pour the mixture into a mold (40mm×40mm×160mm), vibrate to form the shape, and place it in a curing box for curing (temperature maintained at 20±1℃, relative humidity not less than 90%) for 3 to 28 days. Test the compressive and flexural properties of the cured test blocks. The test was conducted using an integrated compression and flexural strength testing machine. Flexural strength: Three-point bending method, loading rate 50 N / s; Compressive strength: tested using a half-block after flexural stress, with a loading rate of 2.4 kN / s; Setting time test: Referring to GB / T 1346-2011 "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement", the initial setting time and final setting time were determined using a Vicat apparatus.

[0084] The results are shown in Table 1.

[0085] Table 1 Performance test results of phosphorus slag-based cementitious materials

[0086] Table 1 shows that the phosphate slag-based cementitious materials prepared in Examples 1-6 exhibit significantly better 3-day and 28-day compressive and flexural strengths than those in Comparative Examples 1-9. In particular, Examples 1 and 3 show 28-day compressive strengths exceeding 60 MPa, meeting the standards for high-strength cement. This demonstrates that the component design and parameter optimization of this invention can effectively improve the mechanical properties of cementitious materials. Comparative Example 1, by reducing the phosphate slag powder content to 55 parts, resulted in a significant decrease in 28-day compressive strength to 48.5 MPa. This proves that when the phosphate slag content, as the main active component, is below 60 parts, it cannot form a sufficient cementitious skeleton, leading to a significant decrease in strength. (Specific surface area 350 m²) 2 At a concentration of / kg, the activation is insufficient, resulting in a 3-day strength of only 8.5 MPa and a 28-day strength of only 35.2 MPa, with an excessively long setting time. Specific surface area: 600 m² / kg. 2 At a concentration of / kg, although the early reaction was rapid, the increased water demand led to structural defects, and the 28-day strength was actually lower than that of Example 1, and the energy consumption was too high and uneconomical. Using only carbide slag or sodium sulfate resulted in extremely low strength (approximately 30 MPa at 28 days) and excessively long setting time, indicating that the "alkali + sulfate" dual-activation system is indispensable. Without aluminum sulfate (Comparative Example 6) or replacing it with triethanolamine (Comparative Example 7) or alum powder (Comparative Example 8), the early strength decreased significantly, failing to meet the requirements for rapid demolding or early support. Comparative Example 9 (without fly ash) showed a significant decrease in strength, indicating that the micro-aggregate effect and secondary hydration reaction of fly ash are crucial for a dense structure. Comparative Example 3 had a specific surface area of ​​600 m². 2 The concentration of particles exceeding the upper limit ( / kg) leads to a surge in water demand, particle agglomeration, and a loose structure in the hardened body. The 28-day compressive strength is only 40.0 MPa, which is significantly lower than the strength level of 61.0 MPa or above in the preferred range of this invention. At the same time, it causes excessively rapid setting, increased energy consumption, and deterioration of the fluidity and freeze-thaw resistance of the filling slurry.

[0087] Test Example 2 Test methods for filling material performance: Take the phosphorus slag-based cementitious material powder prepared in Examples 1-6 and Comparative Examples 1-12 above, and mix it with aggregate (phosphogypsum) and water to prepare filling slurry. The mass ratio of aggregate to cementitious material is 5:1, and the mass concentration of filling slurry is 68% (in line with the actual needs of mine filling). After stirring evenly, it is ready for use.

[0088] Slurry concentration calculation: Concentration = (cementing material + aggregate) / (cementing material + aggregate + water) × 100%.

[0089] According to the "Cementitious Materials for Mine Backfilling" (GB / T 35164-2017), the following performance tests were conducted on each sample: Compressive strength: Tested using an integrated compression and flexural strength testing machine, with a loading rate of 0.5-1.0 kN / s, GB / T 50081-2019; Slump: The slurry is poured into a slump cone, lifted up and the vertical drop height is measured, GB / T 50080-2016; Bleeding rate: After the slurry is placed in a container and allowed to stand, the amount of water separated is measured, GB / T 50080-2016; Freeze resistance: Strength loss rate (%) after 25 freeze-thaw cycles using the rapid freezing method, GB / T 50082-2009.

[0090] Table 2 Test results of filling slurry and filling material performance

[0091] As shown in Table 2, the slump of Examples 1-6 was between 220-260 mm, and the bleeding rate was between 2.5%-3.2%, indicating that the slurry had good fluidity and did not segregate, making it very suitable for pipeline pumping backfill. The 28-day backfill strength of Examples 1-6 was between 3.05-3.85 MPa, meeting the requirements for the stability of goaf areas in mine backfilling (usually >1-2 MPa). Comparative Example 1: Insufficient phosphorus slag content led to increased slurry bleeding rate and decreased strength. Comparative Examples 2-3: The specific surface area of ​​phosphorus slag powder deviated from the optimal range, resulting in decreased slump, increased bleeding rate, and poorer frost resistance. Comparative Examples 4-5: Using a single activator resulted in extremely low strength of the filling body and a significant decrease in frost resistance. Comparative Example 6: Lacking an early-strength agent resulted in insufficient early strength, failing to meet the aging requirements for filling construction. Comparative Examples 7-8: Replacing the type of early-strength agent resulted in strength and frost resistance inferior to the examples. Comparative Example 9: Lacking fly ash resulted in decreased slurry fluidity and strength. Comparative Example 10: Lacking a water-reducing agent resulted in a significant decrease in slump, affecting pipeline transportation. Comparative Example 11: While adding cement improves mechanical properties, it contradicts the core design concept of this invention, which is completely cement-free. Furthermore, cement raw materials are expensive, have high carbon emissions, and low solid waste utilization. Comparative Example 12, with the addition of a large amount of gypsum, combined with phosphogypsum aggregate, resulted in a double excess of gypsum, which reduced the alkalinity of the system and hindered the activation of the phosphogypsum glass body. This led to a comprehensive deterioration in mechanical properties, water resistance, and volume stability. The mortar strength was lower than that of ordinary cement, and the filling strength, softening coefficient, and drying shrinkage were all significantly worse, indicating that the performance was not excellent. Neither of these measures meets the core design concept of this invention: high phosphogypsum content, no cement, low gypsum dependence, and green, low-cost resource utilization.

[0092] Test Example 3 Physical and mechanical performance testing: Referring to GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures" and GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete", the following tests were conducted on the filling body specimens prepared from phosphorus slag-based cementitious materials: Softening coefficient: Test method: According to GB / T 50081-2019, the test blocks were divided into two groups. One group was naturally cured, and the other group was soaked in water for 48 hours before testing the compressive strength. Softening coefficient = saturated strength / dry strength. Shrinkage rate: Test method: Refer to GB / T 50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete", measure the length change of the test block within 28 days and calculate the drying shrinkage rate; Vertical expansion ratio: Test method: Refer to GB / T 50119-2013 "Technical Specification for Application of Concrete Admixtures" to measure the vertical expansion of the test block within 24 hours; Scalability: Test method: Refer to GB / T 50080-2016 to test the slump spread of the filling slurry (when the slump is >220mm, the spread is used to characterize the fluidity).

[0093] The results are shown in Table 3.

[0094]

[0095] As shown in Table 3, the softening coefficients of Examples 1-6 are between 0.86 and 0.92, exhibiting high strength retention after water immersion and excellent water resistance; the 28-day drying shrinkage rate is ≤0.38‰, indicating minimal drying shrinkage deformation, which effectively reduces the risk of cracking in the filling material and ensures structural integrity; the vertical expansion rate is 0.06% to 0.10%, with moderate micro-expansion compensating for drying shrinkage deformation and further improving the compactness of the filling material; the spread is controlled at 540-620mm, matching the slump performance, and the slurry has excellent workability and pumping fluidity, making it suitable for different mine filling construction conditions.

[0096] In contrast, Comparative Examples 1-3, due to low phosphorus slag content or phosphorus slag powder specific surface area deviating from the optimal range of 400-550 m² / kg, showed a significant decrease in softening coefficient, an increase in drying shrinkage, and insufficient vertical expansion effect, resulting in deteriorated overall durability. Comparative Examples 4-5, using only calcium carbide slag or sodium sulfate for activation, failed to form a synergistic activation effect, resulting in extremely low softening coefficient, significantly large drying shrinkage deformation, and no vertical micro-expansion compensation effect, making the filling body prone to shrinkage and cracking. Comparative Example 6 lacked a dedicated early-strength component, and Comparative Examples 7-8, replacing it with non-ferrous / aluminum salt early-strength components, both resulted in a weak hydration process, manifested as a decrease in softening coefficient and an increase in drying shrinkage. Comparative Example 9, without fly ash, lacked the synergistic effect of micro-aggregate filling and secondary hydration, leading to a simultaneous deterioration in water resistance and volume stability. Comparative Example 10, without the addition of a water-reducing agent, showed poor particle dispersibility in the slurry and a significant reduction in spread, which was unfavorable for pipeline pumping construction.

[0097] Comparative Example 11, which incorporates ordinary Portland cement, exhibits superior mechanical and durability properties, but contradicts the core design concept of this invention: completely cement-free and with high solid waste utilization. Furthermore, cement raw materials are expensive, production generates significant carbon emissions, and the utilization rate of solid waste is low, failing to align with the green, low-carbon, and resource-based development approach. Comparative Example 12, with its additional large amount of gypsum, creates an excessive gypsum superposition effect with the phosphogypsum aggregate, reducing the system's alkalinity and inhibiting the activation of the phosphogypsum glassy phase. This results in the mortar's 28-day compressive strength being lower than the 42.5 MPa strength grade of ordinary cement, and a comprehensive deterioration in the filling body's strength, water resistance, volumetric shrinkage, and expansion properties, significantly worsening its mechanical and durability properties. Neither of these examples fulfills the original research and development goals and engineering application positioning of this invention: high phosphogypsum content, cement-free, low gypsum dependence, low cost, and full solid waste resource utilization.

[0098] Test Example 4 Heavy metal testing was performed on the mortar test blocks in Examples 1-6, referring to the methods in "Identification Standard for Hazardous Waste - Leaching Toxicity Identification GB 5085.3-2007" and "Leaching Toxicity Leaching Method for Solid Waste - Horizontal Oscillation Method HJ / T 557-2010". The experimental results are shown in Table 4.

[0099] Table 4. Leaching toxicity test results of phosphorus slag-based cementitious materials

[0100] As shown in Table 4, the leaching concentrations of heavy metals such as copper, cadmium, lead, chromium, and mercury in Examples 1-6 were all 0 or close to 0, far below the limits specified in the "Identification Standard for Hazardous Waste". This proves that the hydration products (CSH gel, etc.) of this cementitious material can effectively encapsulate and solidify any heavy metals that may be present in the raw materials. Although phosphate slag and phosphogypsum themselves contain fluorine, the inorganic fluoride leaching amounts in Examples 1-6 (15.97-26.86 mg / L) are far below the limit of 100 mg / L. This indicates that the alkaline environment provided by the carbide slag not only stimulates activity but also converts soluble fluoride into insoluble calcium fluoride (CaF2) precipitate, achieving harmless solidification.

[0101] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A phosphorus slag-based cementitious material, characterized in that, The cementitious material comprises, by weight, the following components: 60-90 parts of phosphorus slag powder; 5-25 parts of fly ash; 5-15 parts of activator; 0.25-1.5 parts of early strength agent; and 0.2-0.5 parts of water-reducing agent; wherein the specific surface area of ​​the phosphorus slag powder is 400-550 m². 2 / kg, particle size (D) 90 )20-40μm; the early strength agent is selected from at least one of iron salt and aluminum salt.

2. The phosphorus slag-based cementitious material according to claim 1, characterized in that, The mass ratio of calcium carbide slag to sodium sulfate in the activator is (1-1.5):

1.

3. The phosphorus slag-based cementitious material according to claim 1, characterized in that, The early strength agent is a mixture of iron salt and aluminum salt in a mass ratio of (0-1):

1.

4. The phosphorus slag-based cementitious material according to claim 3, characterized in that, The iron salt is selected from at least one of basic ferric sulfate, polyferric sulfate, and ferric chloride; the aluminum salt is selected from at least one of aluminum chloride, polyaluminum chloride, aluminum sulfate, and polyaluminum sulfate.

5. The phosphorus slag-based cementitious material according to claim 1, characterized in that, The water-reducing agent is selected from at least one of lignin sulfonate-based water-reducing agents, polycarboxylate water-reducing agents, and naphthalene-based water-reducing agents.

6. The phosphorus slag-based cementitious material according to claim 5, characterized in that, The lignin sulfonate-based water-reducing agent is selected from at least one of sodium lignin sulfonate and calcium lignin sulfonate; the polycarboxylate water-reducing agent is selected from at least one of polyester-type PCE and polyether-type PCE; and the naphthalene-based water-reducing agent is selected from naphthalene sulfonate formaldehyde condensate.

7. The phosphorus slag-based cementitious material according to claim 1, characterized in that, The phosphorus slag powder is obtained by ball milling yellow phosphorus slag at a speed of 260-300 rpm.

8. A method for preparing a phosphorus slag-based cementitious material as described in any one of claims 1-7, characterized in that, The process includes the following steps: According to the specified ratio, mix and grind phosphorus slag powder, fly ash, activator, early strength agent and water-reducing agent for 18-24 hours to obtain phosphorus slag-based cementitious material.

9. The application of a phosphorus slag-based cementitious material as described in any one of claims 1-7 in mine backfilling.

10. The application according to claim 9, characterized in that, The phosphorus slag-based cementitious material is mixed with aggregate and water to form a filling slurry, which is then transported to the goaf of the mine for filling.

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