Phosphogypsum-based calcination-free low-carbon cementing material and preparation method thereof

Abstract

The invention discloses a phosphogypsum-based calcination-free low-carbon cementing material and a preparation method thereof. The phosphogypsum-based calcination-free low-carbon cementing material comprises the following components in percentage by weight: 10%-35% of phosphogypsum, 10%-35% of desulfurized gypsum, 5%-20% of sewage treatment sludge, 10%-35% of fly ash, 10%-35% of yellow phosphorus slag and 5%-20% of phosphorus tailing slag. The total amount of the ardealite and the desulfurized gypsum is controlled within 45%, and the total amount of the fly ash and the yellow phosphorus slag is controlled within 45%. The technical problems that an existing phosphogypsum-based cementing material is low in early strength, poor in performance stability and high in cost are effectively solved through a multi-solid-waste synergistic compatibility design and a calcination-free process.

Description

Technical Field

[0001] The present invention relates to the technical field of phosphogypsum-based calcination-free low-carbon cementitious materials, and in particular to a phosphogypsum-based calcination-free low-carbon cementitious material and a preparation method thereof. Background Art

[0002] Phosphogypsum is an industrial solid waste generated during the production of phosphoric acid. Long-term storage not only consumes land resources but also poses a risk of leakage of pollutants such as phosphorus and fluorine, creating ecological and environmental pressures. Cementitious materials, a fundamental building block of construction engineering, require high-temperature calcination to produce traditional products, such as Portland cement, resulting in high carbon emissions. Against this backdrop, the development of low-carbon cementitious materials using phosphogypsum and other solid wastes as primary raw materials and a calcination-free process has become an important approach to repurposing solid waste and reducing carbon emissions in the building materials industry.

[0003] In the existing technology, the research on phosphogypsum-based cementitious materials mostly focuses on the utilization of single solid waste or simple compounding, such as mixing phosphogypsum with slag, fly ash, etc. and then preparing cementitious materials through calcination or adding strong alkaline activators such as sodium hydroxide and water glass. However, this type of technology has obvious limitations: on the one hand, in a single solid waste or simple mixed system, the components are prone to "antagonistic effects", such as the solubility of phosphogypsum. 、 It will be adsorbed on the active sites of slag or fly ash, inhibiting the hydration reaction process, resulting in low early strength of the material and large fluctuations in later strength; on the other hand, in order to break through the performance bottleneck, existing technologies often rely on high-temperature calcination or external strong alkali activators, which not only increases energy consumption and carbon emissions, but also reduces the durability of the material due to the introduction of strong alkali, such as alkali-aggregate reaction. At the same time, the use of high-purity activators increases the cost of raw materials, limiting industrial applications. In addition, some technologies attempt to use multiple solid wastes in a coordinated manner, but do not fully consider the complementarity between components. For example, the low impurity characteristics of desulfurized gypsum are not effectively used to dilute the harmful ions in phosphogypsum, or the micro-aggregate filling effect of ultrafine tailings is ignored, resulting in insufficient system density and difficulty in balancing strength and durability.

[0004] Therefore, how to solve the problems of low early strength, poor performance stability and high cost of phosphogypsum-based cementitious materials through the synergistic design of multiple solid wastes under the calcination-free process without the need for external activators or high-temperature treatment has become a key technical bottleneck in promoting its large-scale application. Summary of the Invention

[0005] The purpose of the present invention is to provide a phosphogypsum-based calcination-free low-carbon cementitious material and a preparation method thereof, so as to solve the problems of low early strength, poor performance stability and high cost of gypsum-based cementitious materials.

[0006] In a first aspect, the present application provides a phosphogypsum-based non-calcined low-carbon cementitious material, comprising the following components in the following proportions by weight: phosphogypsum 10-35%, desulfurization gypsum 10-35%, sewage treatment sludge 5-20%, fly ash 10-35%, yellow phosphorus slag 10-35%, and phosphorus tailings 5-20%; wherein the total amount of phosphogypsum and desulfurization gypsum is controlled to be within 45%, and the total amount of fly ash and yellow phosphorus slag is controlled to be within 45%.

[0007] Further, the phosphogypsum is washed with water , the water content .

[0008] Further, the desulfurization gypsum has a purity , .

[0009] Further, the sewage treatment sludge has a content of , and a water content .

[0010] Further, the yellow phosphorus slag has a fineness of 550-650 mesh, .

[0011] Further, the fly ash has an activity index , .

[0012] Further, the phosphorus tailings have a particle size , and a water content .

[0013] In a second aspect, the present application provides a preparation method of a phosphogypsum-based non-calcined low-carbon cementitious material, comprising the following steps: Step one, providing the following components in the following proportions by weight as raw materials: phosphogypsum 10-35%, desulfurization gypsum 10-35%, sewage treatment sludge 5-20%, fly ash 10-35%, yellow phosphorus slag 10-35%, and phosphorus tailings 5-20%; wherein the total amount of phosphogypsum and desulfurization gypsum is controlled to be within 45%, and the total amount of fly ash and yellow phosphorus slag is controlled to be within 45%; Step two, pretreating the raw materials, drying the phosphogypsum after washing to remove impurities to remove soluble impurities; mixing and aging the sewage treatment sludge after pressure filtration and crushing with the phosphogypsum to eliminate the risk of swelling; and ball milling the phosphorus tailings after washing and drying to ensure stable particle grading; Step three, putting all the pretreated raw materials into a grinding device according to the proportion, and then mixing twice to ensure uniformity.

[0014] Furthermore, in step 2, the phosphogypsum is washed and impurity-removed with a solid-liquid ratio of 1:3, stirred for 30 minutes and then dried to a moisture content of less than 5% to remove 70% of the soluble and The sewage sludge was filtered through a plate and frame filter to a moisture content of 15%, crushed to a particle size of <5mm, and then mixed with phosphogypsum and aged for 24 hours to eliminate free Swelling risk; wash the phosphorus tailings with water at a solid-liquid ratio of 1:2, dry them, and then ball-mill them to 550 mesh to ensure The particle ratio is ≥80%.

[0015] Furthermore, in step 3, the pre-treated raw materials are put into Ball mill, using 40% With 60% Steel ball grading, grinding for 45 minutes to 550-650 mesh, specific surface area Then, it was mixed for a second time in a twin-shaft paddle mixer for 5 minutes to ensure uniformity > 95%.

[0016] The present invention has the following beneficial effects: the present invention effectively solves the technical problems of low early strength, poor performance stability and high cost of existing phosphogypsum-based cementitious materials through the synergistic design of multiple solid wastes and the calcination-free process; the calcination-free process greatly reduces the carbon emissions of the production process, and a single ton of material can absorb a large amount of industrial solid waste, which has both environmental benefits and resource utilization value; in addition, the simplified pretreatment and curing process is compatible with existing equipment, and does not require high-temperature treatment or complex modification steps, which significantly reduces processing costs and industrialization thresholds, so that the material has economic feasibility while ensuring high performance, and is suitable for large-scale promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 This is a flow chart of the preparation method of the phosphogypsum-based calcination-free low-carbon cementitious material of the present invention. DETAILED DESCRIPTION

[0019] It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present application may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments. It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this application belongs.

[0020] The application provides a phosphogypsum-based non-calcined low-carbon cementing material, which comprises the following components in a weight ratio: 10%-35% of phosphogypsum, 10%-35% of desulfurization gypsum, 5%-20% of sewage treatment sludge, 10%-35% of fly ash, 10%-35% of yellow phosphorus slag and 5%-20% of phosphorus tailings slag; wherein the total amount of the phosphogypsum and the desulfurization gypsum is controlled to be within 45%, and the total amount of the fly ash and the yellow phosphorus slag is controlled to be within 45%.

[0021] Example one The phosphogypsum-based non-calcined low-carbon cementing material comprises the following components in a weight ratio: 30% of phosphogypsum, 10% of desulfurization gypsum, 8% of sewage treatment sludge, 25% of yellow phosphorus slag, 20% of fly ash and 7% of phosphorus tailings slag.

[0022] The core functions and key control indexes of the components are shown in Table 1.

[0023] Table 1: Raw material proportion, core function and key control index

[0024] The synergistic mechanism is reflected in the following three aspects: Alkaline activation and pozzolanic reaction: the sewage treatment sludge in the provides a sustained alkaline environment, destroys the glass structure of the yellow phosphorus slag and the fly ash, and makes the active , dissolve and react with to generate gel. The , in the yellow phosphorus slag has a 30% increase in hydration rate under alkaline conditions, and the 28-day hydration rate is more than 60%, contributing more than 60% of the strength.

[0025] Sulfate and ettringite formation: 30% of phosphogypsum + 10% of desulfurization gypsum provides sufficient , reacts with in the fly ash to form a stable sulfur-aluminum ratio, rapidly generates ettringite under an alkaline environment, and the needle-shaped crystals interweave to form an early strength skeleton, with a 3-day generation amount of 60-70%, guaranteeing the 3-day strength . The low-impurity characteristics of the desulfurization gypsum can dilute the in the phosphogypsum, avoiding its adsorption on the surface of ettringite to inhibit growth.

[0026] Microstructure densification: the ultra-fine particles of the phosphorus tailings slag fill the pores between the yellow phosphorus slag and the fly ash, reducing the porosity of the system from 18% to below 12%, and increasing the density by 15%. At the same time, the inert characteristics of the tailings slag buffer the particle size distribution fluctuations of the components, reducing the strength deviation to .

[0027] Performance indicators, expected values and comparison standards are shown in Table 2.

[0028] Table 2 Performance indicators, expected values and comparison standards

[0029] See Figure 1 , the embodiment of the application provides a kind of phosphogypsum-based non-calcined low-carbon cementing material preparation method, comprising the following steps: Step one, provide the following weight ratio of components as raw materials: phosphogypsum 30%, desulfurization gypsum 10%, sewage treatment sludge 8%, yellow phosphorus slag 25%, fly ash 20%, phosphorus tailings 7%.

[0030] Step two, pretreatment is carried out on the raw materials, and the phosphogypsum is dried after water washing to remove impurities; the sewage treatment sludge is mixed with the phosphogypsum after being pressed and broken to eliminate the risk of expansion; the phosphorus tailings are ball milled after water washing and drying to ensure stable particle size distribution.

[0031] Specifically, the phosphogypsum is removed by water washing process with solid-liquid ratio of 1:3, stirred for 30 minutes and dried to moisture content <5% to remove 70% of the soluble and ; the sewage treatment sludge is mixed with the phosphogypsum after being pressed to moisture content of 15% and broken to particle size <5mm for 24 hours to eliminate free expansion risk; the phosphorus tailings are ball milled to 550 mesh after water washing and drying at a solid-liquid ratio of 1:2 to ensure particle ratio ≥80%.

[0032] Step three, all pretreated raw materials are put into grinding equipment according to the ratio, and then mixed twice to ensure uniformity.

[0033] The grinding equipment can be selected according to the application scene requirements, such as ball mill, vertical mill or tube mill, etc. If applied to soft foundation treatment and other scenes with relatively low material performance requirements, tube mill or ball mill can meet the requirements; if used for concrete prefabricated components and other scenes with high material performance requirements, vertical mill production line can be considered for production to better guarantee the fineness and quality stability of the material.

[0034] Taking ball mill as an example, pretreated raw materials are put into ball mill according to the ratio, with 40% of and 60% of steel ball grading, grinding for 45 minutes to 550-650 mesh, specific surface area , and then mixed twice for 5 minutes by double-shaft paddle mixer to ensure uniformity >95%.

[0035] Example two The phosphogypsum-based non-calcined low-carbon cementing material comprises the following components in a weight ratio: phosphogypsum 10%, desulfurization gypsum 35%, fly ash 10%, yellow phosphorus slag 35%, sewage treatment sludge 5%, and phosphorus tailing slag 5%.

[0036] Embodiment three

[0037] The phosphogypsum-based non-calcined low-carbon cementing material comprises the following components in a weight ratio: phosphogypsum 35%, desulfurization gypsum 10%, fly ash 35%, yellow phosphorus slag 10%, sewage treatment sludge 5%, and phosphorus tailing slag 5%.

[0038] The present application solves three key problems. First, the environmental and resource waste problem of industrial solid waste storage, which cooperatively incorporates difficult-to-handle solid wastes such as phosphogypsum, phosphorus tailing slag, and desulfurization gypsum into the cementing material system, reduces the storage pressure, and taps the resource value; second, the problem that traditional cementing materials cannot simultaneously achieve high performance and low carbon, which reduces carbon emissions through the "non-calcined" process, and achieves high performance through component optimization; and finally, the bottleneck problem of solid waste resourceization industrialization, which reduces the addition of water reducing agents and activators by utilizing the synergistic effect of natural components, and reduces the industrialization threshold.

[0039] In terms of multi-solid waste synergy, the present application forms a synergistic network by retaining desulfurization gypsum and phosphorus tailing slag, alleviates the inhibition of impurities in phosphogypsum on hydration, and improves strength and durability; in terms of strength regulation mechanism in the non-calcined system, sewage treatment sludge is introduced to catalyze the hydration reaction, and organic matter improves the fluidity of the slurry, providing a new mechanism for strength regulation of the non-calcined system; the non-calcined process and 100% solid waste replacement achieve low carbon, component matching achieves high performance, no high-temperature equipment is needed, and the concentrated source of solid waste is conducive to industrialization. 、 The phosphogypsum-based non-calcined low-carbon cementing material of the present application can be widely used in multiple engineering fields, including roadbed construction in the field of road engineering, backfilling operation in the field of mine engineering, treatment and utilization of fluidized solid waste or solid waste foam lightweight soil in the field of solid waste treatment and resource utilization, soft soil foundation treatment engineering, and construction of water-stable base and cement concrete components in the field of infrastructure materials.

[0040] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A phosphogypsum-based calcined low-carbon cementitious material, characterized in that: It includes the following components in weight ratios: phosphogypsum 10%-35%, desulfurization gypsum 10%-35%, sewage treatment sludge 5%-20%, fly ash 10%-35%, yellow phosphorus slag 10%-35%, and phosphorus tailings slag 5%-20%; among which, the total amount of phosphogypsum and desulfurization gypsum is controlled within 45%, and the total amount of fly ash and yellow phosphorus slag is controlled within 45%.

2. The phosphogypsum-based calcination-free low-carbon cementitious material according to claim 1, characterized in that: After the phosphogypsum is washed , moisture content .

3. The phosphogypsum-based calcination-free low-carbon cementitious material according to claim 1, characterized in that: The purity of the desulfurized gypsum , .

4. The phosphogypsum-based calcination-free low-carbon cementitious material according to claim 1, characterized in that: The sewage treatment sludge content , moisture content .

5. The phosphogypsum-based calcination-free low-carbon cementitious material according to claim 1, characterized in that: The yellow phosphorus slag has a fineness of 550-650 mesh. .

6. The phosphogypsum-based calcination-free low-carbon cementitious material according to claim 1, characterized in that: The fly ash activity index , .

7. The phosphogypsum-based calcination-free low-carbon cementitious material according to claim 1, characterized in that: The particle size of the phosphorus tailings , moisture content .

8. A method for preparing a phosphogypsum-based calcination-free low-carbon cementitious material, characterized in that: The steps include: Step 1: providing the following components in weight ratio as raw materials: 10%-35% of phosphogypsum, 10%-35% of desulfurized gypsum, 5%-20% of sewage treatment sludge, 10%-35% of fly ash, 10%-35% of yellow phosphorus slag, and 5%-20% of phosphorus tailings; wherein the total amount of phosphogypsum and desulfurized gypsum is controlled within 45%, and the total amount of fly ash and yellow phosphorus slag is controlled within 45%; Step 2: Pre-treat the raw materials by washing the phosphogypsum with water, removing impurities, and then drying it to remove soluble impurities; filter-press and crush the sewage treatment sludge, then mix it with the phosphogypsum and age it to eliminate the risk of swelling; and wash and dry the phosphorus tailings and then ball-mill it to ensure a stable particle size distribution. Step 3: All the pre-treated raw materials are put into the grinding equipment according to the proportion and then mixed twice to ensure uniformity.

9. The method for preparing the phosphogypsum-based calcination-free low-carbon cementitious material according to claim 8, characterized in that: In step 2, the phosphogypsum is washed and impurity-removed with a solid-liquid ratio of 1:3, stirred for 30 minutes and then dried to a moisture content of less than 5% to remove 70% of the soluble and The sewage sludge was filtered through a plate and frame filter to a moisture content of 15%, crushed to a particle size of <5mm, and then mixed with phosphogypsum and aged for 24 hours to eliminate free Swelling risk; wash the phosphorus tailings with water at a solid-liquid ratio of 1:2, dry them, and then ball-mill them to 550 mesh to ensure The particle ratio is ≥80%.

10. The method for preparing the phosphogypsum-based calcination-free low-carbon cementitious material according to claim 8, characterized in that: In step 3, the pre-treated raw materials are put into Ball mill, using 40% With 60% Steel ball grading, grinding for 45 minutes to 550-650 mesh, specific surface area Then, it was mixed for a second time in a twin-shaft paddle mixer for 5 minutes to ensure uniformity > 95%.

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