High-water-resistance anhydrous-semi-hydrated phosphogypsum phosphorus slag masonry mortar and preparation method thereof

Abstract

The invention provides high-water-resistance anhydrous-semi-hydrated phosphogypsum phosphorus slag masonry mortar and a preparation method thereof. The high-water-resistance anhydrous-semi-hydrated phosphogypsum phosphorus slag masonry mortar is prepared from the following raw materials: anhydrous phosphogypsum, semi-hydrated phosphogypsum, a gypsum modifier, Portland cement, granular yellow phosphorus slag, a polycarboxylate superplasticizer, a defoaming agent and water. By scientifically compounding the anhydrous-semi-hydrated phosphogypsum and various auxiliary components, high-proportion resource utilization of industrial solid wastes is realized, and finally, the masonry mortar which has excellent thermal insulation property, mechanical strength, binding power and water resistance, is convenient to construct, is controllable in cost and is green and environment-friendly is provided; the application limitation and the solid waste treatment problem of a traditional material are broken through. The invention further provides a preparation method of the high-water-resistance anhydrous-semi-hydrated phosphogypsum phosphorus slag masonry mortar.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a high water-resistant anhydrous-semi-hydrated phosphogypsum slag masonry mortar and its preparation method. Background Technology

[0002] As a crucial basic industry, the phosphate chemical industry generates a large amount of phosphogypsum solid waste during the production of core products such as phosphoric acid and phosphate fertilizers. Currently, the main method of treating phosphogypsum is stockpiling. However, due to natural factors such as rainwater runoff, stockpiled phosphogypsum is easily dispersed with the filtrate, leading to the leakage of pollutants such as phosphorus, acidic substances, and heavy metals, which in turn pollute the soil and groundwater, causing a series of serious environmental pollution problems and placing enormous pressure on ecological and environmental governance. At the same time, phosphogypsum itself has excellent thermal insulation properties and is currently widely used in gypsum board manufacturing and other fields. However, due to its insufficient water resistance, its application is limited to indoor dry environments, failing to fully realize its material potential and resulting in a waste of industrial solid waste resources.

[0003] In the field of construction engineering, masonry mortar, as a key cementing material, directly affects the stability, durability, and construction efficiency of building structures. Traditional cement mortar is currently the most widely used masonry material, but it has many inherent defects: insufficient thermal insulation performance, making it difficult to meet the energy-saving and emission-reducing requirements of modern buildings; long construction cycles and slow hardening speed, affecting project progress; at the same time, its production process consumes a large amount of raw materials, which not only increases production costs but also leads to high carbon emissions, contradicting the current green building development concept. To solve these problems, the industry has attempted to use phosphogypsum to prepare new building mortars. Related patents have included products such as phosphogypsum-based plastering mortar, thermal insulation mortar, and self-leveling mortar. However, these mortars generally suffer from low strength and insufficient water resistance, making them unsuitable for complex usage environments such as "wet areas" in buildings, thus limiting the large-scale application of phosphogypsum in the construction field.

[0004] Anhydrous phosphogypsum, after high-temperature calcination, exhibits superior fluidity and water resistance compared to ordinary hemihydrate phosphogypsum. Its plate-like crystals hydrate to form short columnar dihydrate gypsum crystals, resulting in better volume stability. Hemihydrate phosphogypsum, on the other hand, possesses rapid hardening speed and strong bonding strength. A reasonable blend of these two materials, combined with industrial solid waste phosphate slag to prepare masonry mortar, holds promise for achieving complementary performance advantages. However, optimizing the ratio of anhydrous to hemihydrate phosphogypsum, selecting suitable modifiers and additives, and resolving compatibility and structural stability issues that may arise during the blending process are crucial technical challenges. The ultimate goal is to prepare a masonry mortar that combines excellent thermal insulation, mechanical strength, bonding strength, and water resistance, while simultaneously achieving a high proportion of resource utilization from industrial waste, reducing production costs and carbon emissions. Summary of the Invention

[0005] This invention aims to solve at least one of the aforementioned technical problems existing in the prior art. To this end, this invention provides a high-water-resistant anhydrous-hemihydrate phosphogypsum and slag masonry mortar, aiming to address multiple technical problems existing in the prior art: on the one hand, it addresses the shortcomings of traditional cement mortar, such as insufficient thermal insulation performance, long construction cycle, high production cost and carbon emissions, as well as the common problems of low strength, insufficient water resistance, and difficulty in adapting to complex usage environments such as wet areas in buildings, such as existing phosphogypsum-based plastering mortars, thermal insulation mortars, and self-leveling mortars; on the other hand, it solves the environmental and resource dilemma caused by the large-scale accumulation of phosphogypsum solid waste generated by the phosphate chemical industry, resulting in soil and groundwater pollution and resource waste. Through the scientific compounding of anhydrous-hemihydrate phosphogypsum and various auxiliary components, a high proportion of industrial solid waste is utilized for resource recovery. Ultimately, it provides a masonry mortar that combines excellent thermal insulation performance, mechanical strength, adhesion, and water resistance, and is convenient to construct, cost-effective, and environmentally friendly, breaking through the application limitations of traditional materials and the difficulties in solid waste treatment.

[0006] The present invention also provides a method for preparing a highly water-resistant anhydrous-hemihydrate phosphogypsum slag masonry mortar.

[0007] The first aspect of the present invention provides a highly water-resistant anhydrous-hemihydrate phosphogypsum slag masonry mortar, the raw materials of which include anhydrous phosphogypsum, hemihydrate phosphogypsum, gypsum modifier, silicate cement, granular yellow phosphorus slag, polycarboxylate superplasticizer, defoamer and water.

[0008] The high water-resistant anhydrous-hemihydrate phosphogypsum and phosphorus slag masonry mortar of the present invention has at least the following beneficial effects: With superior overall performance and adaptability to multiple application scenarios, this masonry mortar achieves complementary performance advantages through a scientifically proportioned blend of anhydrous phosphogypsum, hemihydrate phosphogypsum, and various auxiliary components. Anhydrous phosphogypsum exhibits excellent fluidity and water resistance, while the short columnar dihydrate gypsum crystals formed after hydration enhance volume stability. Hemihydrate phosphogypsum hardens quickly and has strong adhesion; the combination of these two components gives the product excellent thermal insulation, mechanical strength, and adhesion. Test results show that the mortar's initial fluidity exceeds 180mm, its 28-day compressive strength surpasses 30MPa, reaching the M30 strength standard, with a water absorption rate of only 3.90%-4.32% and a softening coefficient of 0.86~0.91. After D25 freeze-thaw cycles, both strength and mass loss remain low, demonstrating excellent water resistance and freeze-thaw resistance. This breaks the limitation of traditional phosphogypsum-based materials being suitable only for dry indoor environments, extending its application to complex scenarios such as "wet areas" in buildings.

[0009] High-value utilization of industrial solid waste, environmentally friendly: The raw materials contain over 98% anhydrous and semi-hydrated phosphogypsum and granular yellow phosphorus slag, which effectively disposes of large quantities of industrial solid waste generated by the phosphate chemical industry. This formulation not only solves the soil and groundwater pollution problems caused by phosphogypsum stockpiling, but also replaces a large amount of natural resources in traditional mortar, reducing the environmental pressure caused by resource extraction and solid waste stockpiling, while also reducing carbon emissions during product production, aligning with the concepts of green building and sustainable development.

[0010] Convenient and efficient construction with significant cost advantages: The rapid hardening characteristics of hemihydrate phosphogypsum, combined with optimized component ratios, significantly shorten the construction cycle, improve on-site construction efficiency, and reduce labor costs; Granular yellow phosphorus slag, as a solid waste aggregate, replaces traditional raw materials such as quartz sand, and the application of a high proportion of industrial solid waste significantly reduces material production costs; The synergistic effect of polycarboxylate superplasticizer (water reduction rate of 30~40%) and organosilicon defoamer reduces water consumption and porosity, ensuring mortar density while further optimizing construction operability, facilitating factory production and on-site construction promotion.

[0011] The formula is scientific and reasonable, and the performance is stable and reliable: the dosage range of each component has been precisely optimized. The gypsum modifier (mainly composed of calcium oxide and basalt fiber) can stimulate the potential activity of phosphogypsum, refine the structure and improve crack resistance. Silicate cement further enhances water resistance. Granular yellow phosphorus slag is evenly dispersed in the slurry to resist drying shrinkage. The synergistic effect of each component ensures the performance stability and reliability of the mortar under different usage environments. It effectively solves the technical pain points of traditional cement mortar, such as poor heat insulation, long construction period and high carbon emissions, as well as the low strength and insufficient water resistance of existing phosphogypsum-based mortar.

[0012] According to some embodiments of the present invention, the product comprises, by weight: Anhydrous phosphogypsum: 300-600 parts Hemihydrate phosphogypsum: 50-300 parts Gypsum modifier: 30-50 parts Silicate cement: 20-40 parts Granular yellow phosphorus slag: 1400-1800 parts Polycarboxylate superplasticizer: 2-10 parts Defoamer: 1-5 parts Water: 200-300 servings.

[0013] According to some embodiments of the present invention, the product comprises, by weight: Anhydrous phosphogypsum: 348-557 parts Hemihydrate phosphogypsum: 70-278 parts Gypsum modifier: 34-48 parts, Silicate cement: 20-34 parts Granular yellow phosphorus slag: 1400-1740 parts Polycarboxylate superplasticizer: 2-4 parts Defoamer: 1-2 parts Water: 209-223 portions.

[0014] According to some embodiments of the present invention, the anhydrous phosphogypsum is prepared by firing undisturbed phosphogypsum at a high temperature of 800~1200℃.

[0015] Anhydrous phosphogypsum, after being fired at high temperatures of 800~1200℃, exhibits excellent fluidity and water resistance. The short columnar dihydrate gypsum crystals formed after hydration enhance its volume stability.

[0016] According to some embodiments of the present invention, the anhydrous phosphogypsum is fired at high temperature for 1-3 hours.

[0017] According to some embodiments of the present invention, the hemihydrate phosphogypsum is fired at a high temperature of 150~300℃.

[0018] Hemihydrate phosphogypsum is fired at high temperatures of 150~300℃, resulting in rapid hardening and strong adhesion. The combination of these two materials gives the product excellent thermal insulation, mechanical strength, and adhesion.

[0019] According to some embodiments of the present invention, the high-temperature firing time of the hemihydrate phosphogypsum is 1-3 hours.

[0020] Anhydrous phosphogypsum, obtained through high-temperature calcination at a specific temperature, not only exhibits superior fluidity and water resistance compared to hemihydrate phosphogypsum, but its plate-like crystals also generate short columnar dihydrate gypsum crystals upon hydration, resulting in even better volume stability. The preparation of masonry mortar using anhydrous-hemihydrate phosphogypsum compounded with phosphorus slag fully combines the advantages of anhydrous phosphogypsum (good fluidity, strong water resistance, and volume stability after hydration) with the characteristics of hemihydrate phosphogypsum (rapid hardening and strong bonding). The resulting masonry mortar product possesses excellent thermal insulation, mechanical strength, bonding ability, and water resistance, facilitating both factory production and on-site construction, effectively shortening the construction cycle and reducing labor costs. Notably, the total proportion of phosphogypsum and phosphorus slag in this product exceeds 98%, achieving a high proportion of resource utilization of industrial waste, conserving natural resources, reducing environmental pollution from industrial solid waste stockpiling, and significantly lowering material production costs.

[0021] According to some embodiments of the present invention, the main components of the gypsum modifier are calcium oxide and basalt fiber. It can activate the potential activity of anhydrous phosphogypsum, combining its own hydraulic characteristics with phosphogypsum to form a hydraulic hydration product. Simultaneously, it can improve the structural crack resistance through basalt fiber, refine the structure by filling pores with micropowder, reduce water penetration, and thus reduce water absorption and enhance water resistance.

[0022] According to some embodiments of the present invention, the silicate cement includes type PO.42.5 cement. This not only activates the potential activity of anhydrous phosphogypsum but also improves the water resistance of the product.

[0023] According to some embodiments of the present invention, the fineness modulus of the granular yellow phosphorus slag is 3.1-3.8. Lightweight phosphorus slag aggregate can resist the drying shrinkage of cementitious materials and be uniformly dispersed in the slurry, improving product stability and uniformity. Moreover, using solid waste phosphorus slag as aggregate can significantly reduce material costs.

[0024] According to some embodiments of the present invention, the water reduction rate of the polycarboxylate superplasticizer is 30-40%. This can reduce water consumption, decrease porosity, and enhance density.

[0025] According to some embodiments of the present invention, the defoamer is an organosilicon defoamer. It can solve the performance defects caused by "harmful air bubbles" during the preparation and molding of masonry mortar, and enhance its density.

[0026] A second aspect of the present invention provides a method for preparing a high water-resistant anhydrous-hemihydrate phosphogypsum slag masonry mortar according to the first aspect of the present invention, comprising the following steps: S1: According to the formula, the anhydrous phosphogypsum, hemihydrate phosphogypsum, gypsum modifier, silicate cement, granular yellow phosphorus slag and defoamer are mixed evenly in proportion to obtain a premix; the water-reducing agent is added to water and stirred evenly to obtain a premix liquid. S2: The premixed material and the premixed liquid are mixed and stirred to obtain the high water-resistant anhydrous-semi-hydrated phosphogypsum slag masonry mortar.

[0027] The preparation method of highly water-resistant anhydrous-hemihydrate phosphogypsum and phosphorus slag masonry mortar has at least the following beneficial effects: The process is simple, efficient, and suitable for large-scale production: the method completes mortar preparation through only three core steps: premix preparation, premix liquid preparation, and mixing of the two. The process is clear, easy to understand, and convenient to operate, requiring no complex equipment or special process conditions. It is suitable for both factory mass production and meeting the rapid mixing needs of on-site construction, significantly improving production and construction efficiency. The separate preparation of the premix and premix liquid avoids uneven reaction or poor dispersion of components when directly mixed, ensuring uniform mixing of raw materials and preventing negative impacts on product performance.

[0028] Precise and controllable proportions ensure stable product performance: The steps clearly specify the weighing and mixing of raw materials according to specific proportions, which can accurately control the dosage ratio of anhydrous phosphogypsum, hemihydrate phosphogypsum and various additives. This fully leverages the synergistic advantages of anhydrous phosphogypsum's strong water resistance and volume stability with hemihydrate phosphogypsum's rapid hardening and strong bonding force. At the same time, it ensures that auxiliary components such as gypsum modifiers and polycarboxylate superplasticizers play an efficient role, so that the prepared masonry mortar always maintains excellent and stable thermal insulation performance, mechanical strength, water resistance and construction fluidity, avoiding inconsistent product quality due to process fluctuations.

[0029] Reduced production energy consumption and costs, green and environmentally friendly: The process does not require harsh reaction conditions such as high temperature and high pressure, and the stirring treatment only takes 3-5 minutes. It also adopts indoor natural curing method, which greatly reduces energy consumption and maintenance costs in the production process. At the same time, the method uses industrial solid waste such as phosphogypsum and phosphate slag, which account for more than 98% of the raw materials, as the main raw materials. Through scientific preparation process, it realizes a high proportion of resource utilization of solid waste, which not only reduces the environmental pollution caused by industrial solid waste stockpiling, but also replaces a large amount of natural resources in traditional mortar, which is in line with the green and low-carbon production concept.

[0030] Optimizing component fusion and enhancing overall product performance: The method of first mixing solid raw materials into a premix and liquid additives with water into a premixed liquid, followed by secondary mixing and stirring, promotes the full dissolution and uniform dispersion of polycarboxylate superplasticizer in the slurry, ensuring that its high water reduction rate of 30-40% is fully utilized, effectively reducing mortar porosity and enhancing density; at the same time, it avoids the defoaming effect attenuation caused by direct contact between defoamer and other solid components, enabling it to efficiently eliminate harmful bubbles during the preparation process, further improving the structural density, water resistance, and freeze-thaw resistance of the mortar, ultimately achieving an optimized upgrade of the product's overall performance.

[0031] According to some embodiments of the present invention, the stirring time is 3-5 minutes. Attached Figure Description

[0032] Figure 1 This is a picture of the mortar from Example 1. Detailed Implementation

[0033] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0034] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0035] Unless otherwise specified, "room temperature" in this invention means 25℃±5℃.

[0036] Unless otherwise specified, "about" in this invention means that the allowable error is within ±2%.

[0037] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0038] In the example: Anhydrous phosphogypsum comes from Guizhou Phosphate (Group) Co., Ltd.

[0039] The hemihydrate phosphogypsum comes from Guizhou Phosphate (Group) Co., Ltd.

[0040] The gypsum modifier was purchased from Hunan Tieke Track Technology Co., Ltd.

[0041] The silicate cement was PO.42.5 grade cement, purchased from Anhui Conch Cement Co., Ltd.

[0042] The fineness modulus of the granular yellow phosphorus slag is 3.5-3.8, and it was purchased from Guizhou Phosphate (Group) Co., Ltd.

[0043] The water-reducing agent is a polycarboxylate water-reducing agent, purchased from Bernuo New Materials (Beijing) Technology Co., Ltd.

[0044] The defoamer is an organosilicon defoamer, purchased from Dongguan Defeng Defoamer Co., Ltd.

[0045] Example 1 A highly water-resistant anhydrous-hemahydrate phosphogypsum and phosphorus slag masonry mortar, the raw materials by weight are: 557 parts anhydrous phosphogypsum, 70 parts hemihydrate phosphogypsum, 48 parts gypsum modifier, 20 parts silicate cement, 1400 parts granular yellow phosphorus slag, 2 parts polycarboxylate superplasticizer, 1 part defoamer, and 209 parts water.

[0046] Anhydrous phosphogypsum is made by firing raw phosphogypsum at 800℃ for 2 hours.

[0047] The hemihydrate phosphogypsum was fired at 150℃ for 2 hours.

[0048] The specific preparation method includes the following steps: (1) After weighing anhydrous phosphogypsum, hemihydrate phosphogypsum, gypsum modifier, silicate cement, granular yellow phosphorus slag and defoamer, mix them evenly in proportion, pour them into a mixer and dry mix for 1-2 minutes to ensure that the materials are fully mixed to obtain premixed material. (2) Add the weighed water-reducing agent to the water and stir thoroughly to ensure that the water-reducing agent is fully dissolved to obtain a premixed liquid; then pour the premixed liquid into the mixer of the premixed material and stir at a stirring speed of 165 r / min for 3-5 min to obtain a high water-resistant anhydrous-hemihydrate phosphogypsum slag masonry mortar. Actual product as shown Figure 1 As shown.

[0049] Example 2 A highly water-resistant anhydrous-hemahydrate phosphogypsum and phosphorus slag masonry mortar, the raw materials by weight are: 487 parts anhydrous phosphogypsum, 139 parts hemihydrate phosphogypsum, 48 parts gypsum modifier, 20 parts silicate cement, 1400 parts granular yellow phosphorus slag, 2 parts polycarboxylate superplasticizer, 1 part defoamer, and 209 parts water.

[0050] Anhydrous phosphogypsum is made by firing raw phosphogypsum at 800℃ for 2 hours.

[0051] The hemihydrate phosphogypsum was fired at 150℃ for 2 hours.

[0052] The specific preparation method includes the following steps: (1) After weighing anhydrous phosphogypsum, hemihydrate phosphogypsum, gypsum modifier, silicate cement, granular yellow phosphorus slag, lime powder and defoamer, mix them evenly in proportion, pour them into a mixer and dry mix for 1-2 minutes to ensure that the materials are fully mixed to obtain premixed material. (2) Add the weighed water-reducing agent to the water and stir thoroughly to ensure that the water-reducing agent is fully dissolved to obtain a premixed liquid; then pour the premixed liquid into the mixer of the premixed material and stir at a stirring speed of 165r / min for 3-5 minutes to obtain a high water-resistant anhydrous-semi-hydrated phosphogypsum slag masonry mortar.

[0053] Example 3 A highly water-resistant anhydrous-hemahydrate phosphogypsum and phosphorus slag masonry mortar, the raw materials by weight are: 418 parts anhydrous phosphogypsum, 209 parts hemihydrate phosphogypsum, 48 parts gypsum modifier, 20 parts silicate cement, 1400 parts granular yellow phosphorus slag, 3 parts polycarboxylate superplasticizer, 2 parts defoamer, and 209 parts water.

[0054] Anhydrous phosphogypsum is made by firing raw phosphogypsum at 800℃ for 2 hours.

[0055] The hemihydrate phosphogypsum was fired at 150℃ for 2 hours.

[0056] The specific preparation method includes the following steps: (1) After weighing anhydrous phosphogypsum, hemihydrate phosphogypsum, gypsum modifier, silicate cement, granular yellow phosphorus slag, lime powder and defoamer, mix them evenly in proportion, pour them into a mixer and dry mix for 1-2 minutes to ensure that the materials are fully mixed to obtain premixed material. (2) Add the weighed water-reducing agent to the water and stir thoroughly to ensure that the water-reducing agent is fully dissolved to obtain a premixed liquid; then pour the premixed liquid into the mixer of the premixed material and stir at a stirring speed of 165r / min for 3-5 minutes to obtain a high water-resistant anhydrous-semi-hydrated phosphogypsum slag masonry mortar.

[0057] Example 4 A highly water-resistant anhydrous-hemahydrate phosphogypsum and phosphorus slag masonry mortar, the raw materials by weight are: 348 parts anhydrous phosphogypsum, 278 parts hemihydrate phosphogypsum, 48 parts gypsum modifier, 20 parts silicate cement, 1400 parts granular yellow phosphorus slag, 4 parts polycarboxylate superplasticizer, 2 parts defoamer, and 209 parts water.

[0058] Anhydrous phosphogypsum is made by firing raw phosphogypsum at 800℃ for 2 hours.

[0059] The hemihydrate phosphogypsum was fired at 150℃ for 2 hours.

[0060] The specific preparation method includes the following steps: (1) After weighing anhydrous phosphogypsum, hemihydrate phosphogypsum, gypsum modifier, silicate cement, granular yellow phosphorus slag, lime powder and defoamer, mix them evenly in proportion, pour them into a mixer and dry mix for 1-2 minutes to ensure that the materials are fully mixed to obtain premixed material. (2) Add the weighed water-reducing agent to the water and stir thoroughly to ensure that the water-reducing agent is fully dissolved to obtain a premixed liquid; then pour the premixed liquid into the mixer of the premixed material and stir at a stirring speed of 165r / min for 3-5 minutes to obtain a high water-resistant anhydrous-semi-hydrated phosphogypsum slag masonry mortar.

[0061] Comparative Example 1 Prepared according to the method of Example 1 in CN119504222A.

[0062] Comparative Example 2 Prepared according to the method of Example 1 in CN120682006A.

[0063] Comparative Example 3 Prepared according to the method of Example 1 in CN119751007A, the difference from Example 1 is that the gypsum used is desulfurized anhydrite.

[0064] Performance testing According to the "Standard for Test Methods of Basic Performance of Building Mortar" (JGJ / T70-2009), the mortars of Examples 1 to 4 and Comparative Examples 1 to 3 were filled into molds and compacted by vibration. After the specimens hardened and solidified, they were demolded. After demolding, the specimens were naturally cured for 28 days to obtain mortar test blocks.

[0065] Initial fluidity, 28-day flexural strength, 28-day compressive strength, 28-day water absorption, 28-day softening coefficient, and freeze-thaw resistance of the masonry mortar obtained in the examples and comparative examples were tested at the corresponding ages. The results are shown in Table 1.

[0066] Table 1

[0067] As shown in Table 1, the masonry mortars prepared in Examples 1-4 contain up to 98% solid waste such as phosphogypsum and phosphorus slag, which can realize the large-scale disposal of industrial solid waste, saving natural resources and reducing environmental pollution.

[0068] Based on the performance test results of each embodiment, the product exhibits excellent overall performance. Specifically: The initial flowability of the masonry mortar exceeded 180 mm, and its 28-day compressive strength surpassed 30 MPa, reaching the strength standard of M30 grade masonry mortar. Simultaneously, its water absorption rate was controlled between 3.90% and 4.32%, its softening coefficient was 0.91 to 0.96, and after D25 freeze-thaw cycles, the strength loss was only 14.4% to 18.2%, and the mass loss was as low as 1.33% to 2.34%. These data indicate that the prepared masonry mortar not only possesses excellent water resistance but also maintains good structural strength even in low-temperature environments.

[0069] Compared to the comparative cases, this invention makes extensive use of solid waste materials, and the product has superior workability and water resistance. Furthermore, using solid waste phosphorus slag instead of quartz sand can resist the drying shrinkage of cementitious materials and ensure uniform dispersion in the slurry, improving product stability and uniformity while reducing material costs.

[0070] Overall, the product of this invention can effectively dispose of large quantities of industrial solid waste, conserve natural resources, and reduce carbon emissions and production costs. Furthermore, the product has a short construction period and exhibits superior performance in terms of thermal insulation, mechanical strength, adhesion, and water resistance.

[0071] Compared with the prior art, the advantages of the present invention are as follows: In existing technologies, traditional cement mortar suffers from problems such as insufficient thermal insulation performance, long construction period, high cost, and high carbon emissions. The types of plastering mortar, thermal insulation mortar, and self-leveling mortar prepared using phosphogypsum generally suffer from low strength and insufficient water resistance, making them difficult to apply in humid environments.

[0072] Phosphogypsum and phosphate slag are industrial solid wastes. Phosphogypsum possesses excellent thermal insulation properties. Anhydrous phosphogypsum, obtained through high-temperature calcination, not only exhibits superior fluidity and water resistance compared to building gypsum, but also produces short columnar dihydrate gypsum crystals after hydration, resulting in better volume stability. Using anhydrous-hemihydrate phosphogypsum and phosphate slag to prepare masonry mortar can comprehensively leverage the excellent fluidity, water resistance, and hydration-after-hydration volume stability of anhydrous phosphogypsum, as well as the rapid hardening and strong bonding properties of hemihydrate phosphogypsum. This product boasts superior thermal insulation, strength, bonding strength, and water resistance, facilitating production operations, shortening construction cycles, and reducing labor costs. Furthermore, the product utilizes over 98% phosphogypsum and phosphate slag, significantly utilizing industrial waste, conserving natural resources, reducing environmental pollution, and substantially lowering material costs.

[0073] It should be noted that in this invention, the anhydrous phosphogypsum is prepared by firing undisturbed phosphogypsum at a high temperature of 800-1200℃. If fired at 750℃, the undisturbed phosphogypsum cannot meet the performance requirements of this invention for anhydrous phosphogypsum. The core reason is that the temperature does not reach the critical threshold for dehydration and crystal transformation of phosphogypsum, resulting in product performance defects. The specific analysis is as follows: Firstly, incomplete dehydration may result in residual hemihydrate / dihydrate gypsum. The inventors discovered that the dehydration process of phosphogypsum (mainly composed of dihydrate gypsum CaSO4·2H2O) is temperature-dependent: 1.5 molecules of water of crystallization are removed at 150-300℃ to form hemihydrate gypsum (CaSO4·2H2O), while complete removal of water of crystallization and conversion to anhydrous gypsum (type III or type II anhydrous gypsum) is only achieved at 800-1200℃. 750℃ falls within the transition range from hemihydrate to anhydrous gypsum, making complete dehydration impossible, resulting in a large amount of residual hemihydrate gypsum and undecomposed dihydrate gypsum in the product. This residual gypsum containing water of crystallization leads to uneven volume shrinkage during subsequent mortar hydration, reducing volume stability, and failing to fundamentally improve water resistance (hemihydrate / dihydrate gypsum has poor water resistance).

[0074] The crystal structure was not optimized, resulting in insufficient key performance characteristics. The high temperature of 800~1200℃ is not only a dehydration process but also a crucial stage for the reconstruction of anhydrous gypsum crystals, promoting the transformation of plate-like crystals into short columnar dihydrate gypsum precursors, thus improving fluidity and volume stability. At 750℃, the energy threshold for crystal transformation was not reached, resulting in anhydrous gypsum crystals with a loose structure and numerous defects. The fluidity was far lower than that of products fired at high temperatures (this invention requires an initial fluidity exceeding 180mm), and the density of the structure formed after hydration was insufficient, directly leading to the mortar's compressive strength and water resistance (water absorption rate, softening coefficient) failing to meet standards.

[0075] Poor synergy with the compound system. This invention achieves complementary performance of water resistance and rapid hardening bonding through the compounding of anhydrous and hemihydrate phosphogypsum. The product fired at 750℃ has incomplete dehydration and poor crystal properties, which not only fails to give full play to the water resistance advantage of anhydrous gypsum, but also disrupts the synergistic effect with other components (gypsum modifier, silicate cement, phosphate slag) due to the uncontrollable proportion of residual hemihydrate gypsum. This leads to a decrease in core indicators such as overall mortar strength and freeze-thaw resistance, making it unsuitable for complex scenarios such as wet building areas.

[0076] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A highly water-resistant anhydrous-hemahydrate phosphogypsum and phosphorus slag masonry mortar, characterized in that, The raw materials for preparation include anhydrous phosphogypsum, hemihydrate phosphogypsum, gypsum modifier, silicate cement, granular yellow phosphorus slag, polycarboxylate superplasticizer, defoamer, and water.

2. The high water-resistant anhydrous-hemihydrate phosphogypsum slag masonry mortar according to claim 1, characterized in that, By weight, it includes: Anhydrous phosphogypsum: 300-600 parts Hemihydrate phosphogypsum: 50-300 parts Gypsum modifier: 30-50 parts Silicate cement: 20-40 parts Granular yellow phosphorus slag: 1400-1800 parts Polycarboxylate superplasticizer: 2-10 parts Defoamer: 1-5 parts Water: 200-300 servings.

3. The high water-resistant anhydrous-hemahydrate phosphogypsum slag masonry mortar according to claim 2, characterized in that, By weight, it includes: Anhydrous phosphogypsum: 348-557 parts Hemihydrate phosphogypsum: 70-278 parts Gypsum modifier: 34-48 parts, Silicate cement: 20-34 parts Granular yellow phosphorus slag: 1400-1740 parts Polycarboxylate superplasticizer: 2-4 parts Defoamer: 1-2 parts Water: 209-223 portions.

4. The high water-resistant anhydrous-hemihydrate phosphogypsum and phosphorus slag masonry mortar according to any one of claims 1 to 3, characterized in that, The anhydrous phosphogypsum is produced by firing raw phosphogypsum at a high temperature of 800~1200℃.

5. The high water-resistant anhydrous-hemihydrate phosphogypsum and phosphorus slag masonry mortar according to any one of claims 1 to 3, characterized in that, The hemihydrate phosphogypsum is fired at a high temperature of 150~300℃.

6. The high water-resistant anhydrous-hemihydrate phosphogypsum slag masonry mortar according to any one of claims 1 to 3, characterized in that, The silicate cement includes type PO.42.5 cement.

7. The high water-resistant anhydrous-hemihydrate phosphogypsum slag masonry mortar according to any one of claims 1 to 3, characterized in that, The fineness modulus of the granular yellow phosphorus slag is 3.1-3.

8.

8. The high water-resistant anhydrous-hemihydrate phosphogypsum slag masonry mortar according to any one of claims 1 to 3, characterized in that, The water reduction rate of the polycarboxylate superplasticizer is 30-40%.

9. The high water-resistant anhydrous-hemihydrate phosphogypsum and phosphorus slag masonry mortar according to any one of claims 1 to 3, characterized in that, The defoamer is an organosilicon defoamer.

10. A method for preparing a high water-resistant anhydrous-hemihydrate phosphogypsum slag masonry mortar as described in any one of claims 1 to 9, characterized in that, Includes the following steps: S1: According to the formula, the anhydrous phosphogypsum, hemihydrate phosphogypsum, gypsum modifier, silicate cement, granular yellow phosphorus slag and defoamer are mixed evenly in proportion to obtain a premix. The polycarboxylate superplasticizer is added to water and stirred evenly to obtain a premix liquid. S2: The premixed material and the premixed liquid are mixed and stirred to obtain the high water-resistant anhydrous-semi-hydrated phosphogypsum slag masonry mortar.

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