High-content phosphogypsum and shell aggregate compounded high-strength concrete and preparation method thereof

Abstract

The invention discloses high-content phosphogypsum and shell aggregate compounded high-strength concrete and a preparation method thereof.The preparation method comprises the steps that phosphogypsum serves as a binding material and aggregate at the same time to prepare the concrete, firstly, phosphogypsum ceramsite formed by high-temperature calcination of the phosphogypsum is subjected to an oxalic acid neutralization reaction and a quick lime precipitation reaction; then the ardealite ceramsite is crushed and screened, and is doped with shell powder to be used as coarse and fine aggregate. Through the physical and chemical double modification of the phosphogypsum ceramsite and the ternary synergistic effect of the shell aggregate, the comprehensive utilization rate of the phosphogypsum is greatly improved, and the mechanical property of the concrete is remarkably improved. The phosphogypsum doping amount of the prepared concrete reaches 37%, the 28-day compressive strength reaches 72.8 MPa, the performance requirements of building structure materials are met, high-valued and high-doping-amount resource utilization of industrial solid waste is achieved, and remarkable environmental benefits and economic benefits are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, in particular to a high-strength concrete with high-dosage phosphogypsum and shell aggregate and a preparation method thereof. BACKGROUND

[0002] Phosphogypsum is a typical solid waste produced in the process of wet-process phosphoric acid production, and its main chemical component is calcium sulfate dihydrate (CaSO4·2H2O), and it also contains a small amount of phosphorus, fluorine and heavy metals and other impurities. According to statistics, 4-6 tons of phosphogypsum will be produced simultaneously for every ton of phosphoric acid produced, and the global annual production is nearly 300 million tons. The current disposal method of domestic phosphogypsum is mainly stockpiling, and a small amount is used to produce building materials. Long-term open-air stockpiling not only occupies a large amount of land resources, but also may pollute the soil and groundwater system through leachate. Harmless disposal and resource utilization of phosphogypsum has become a key research direction in the field of solid waste management.

[0003] Domestic and foreign scholars actively explore the resource utilization of phosphogypsum, for example: using it as a cement retarder, producing gypsum board or roadbed materials, but these methods have low added value, limited absorption capacity, and far from realizing large-scale high-value utilization. In the field of concrete, existing technologies attempt to partially replace natural aggregate or cementitious materials with phosphogypsum, but due to its weak cementitious activity, the inhibitory effect of impurities on the cement hydration process, and the weak bonding of the aggregate-paste interfacial transition zone, the phosphogypsum dosage is generally limited to less than 20%; when the dosage is increased, the mechanical properties of the concrete are significantly degraded, and the 28-day compressive strength is usually difficult to exceed 40 MPa (such as patent CN118894664B).

[0004] In recent years, researchers have begun to focus on the potential of bio-based materials in the modification of concrete, such as shell waste, which can optimize the interfacial transition zone and improve the density due to its porous microstructure and micro-aggregate effect, but existing work has mostly focused on the single incorporation of shell powder into cement-based materials (such as patent CN118388181B), and has not systematically addressed the synergistic effect of industrial solid waste. In addition, the strategy of using phosphogypsum as both a cementitious material and an aggregate for high-dosage composite utilization is still a technical blank, especially the lack of a physical and chemical dual-modification method targeting the impurity characteristics of phosphogypsum and a ternary synergistic strengthening mechanism with shell aggregate. Therefore, developing a high-strength concrete preparation technology that can efficiently dispose of phosphogypsum and break through the strength bottleneck is urgently needed for high-value and high-dosage resource utilization of industrial solid waste, and is also a scientific problem that needs to be solved in the current field of building materials. SUMMARY

[0005] In order to overcome the deficiencies of the above existing background technologies, the present application provides a high-strength concrete with high-dosage phosphogypsum and shell aggregate and a preparation method thereof.

[0006] The present application is achieved by the following technical solutions: In a first aspect, the present application provides a high-strength concrete with high-dosage phosphogypsum and shell aggregate, the raw material components of the high-strength concrete including cementitious material, aggregate, additive and water; the cementitious material including cement, silica fume, mineral powder and phosphogypsum; the aggregate including phosphogypsum coarse aggregate, phosphogypsum fine aggregate, gravel and shell powder; wherein the comprehensive dosage of phosphogypsum ranges from 35% to 40% based on the total weight of the concrete, and the comprehensive dosage of phosphogypsum includes phosphogypsum as a cementitious component and phosphogypsum coarse aggregate and phosphogypsum fine aggregate as an aggregate component.

[0007] The above scheme defines the core formula of the high-strength concrete: cementitious material, aggregate component and phosphogypsum comprehensive dosage of 35-40%. It breaks through the dosage bottleneck of phosphogypsum, increases the comprehensive dosage of phosphogypsum to 35-40%, which is much higher than the upper limit of 20% in the prior art, greatly increases the consumption of industrial solid waste phosphogypsum, reduces the land occupation and soil and groundwater pollution problems caused by open-air storage, and realizes the high-value utilization of solid waste. It also takes into account the strength and environmental protection, through the synergy of the cement + silica fume + mineral powder + phosphogypsum cementitious system and the phosphogypsum aggregate + gravel + shell powder aggregate system, to solve the problem of mechanical property degradation of concrete caused by high-dosage phosphogypsum, and to lay the foundation for the preparation of high-strength concrete. At the same time, the use of phosphogypsum (industrial solid waste) and shell powder (biological solid waste) reduces the dependence on natural aggregate (such as natural sand and stone), conforms to the concept of circular economy, and reduces the resource consumption of building material production.

[0008] Cementitious system synergy mechanism: When phosphogypsum (CaSO4·2H2O) is used as a cementitious component, it can undergo secondary hydration reaction with mineral powder (containing active SiO2 and Al2O3) under the excitation of Ca(OH)2 generated by cement hydration, to generate C-S-H gel and ettringite; silica fume fills the pores of the cementitious system by virtue of its high specific surface area, enhances the density, and the three together with cement improve the cementitious strength. Aggregate-paste interface optimization mechanism: After neutralization with oxalic acid and treatment with quicklime, the soluble impurities on the surface of the phosphogypsum aggregate are effectively removed, forming a clean and neutral surface, which significantly enhances the bonding between the aggregate surface and the cement hydration products; shell powder (porous structure) can act as micro-aggregate to fill the gaps between aggregates, reduce interface defects, alleviate the problem of weak bonding caused by high-dosage phosphogypsum, and improve the overall mechanical properties.

[0009] As a preferred technical solution of the present application, the particle size of the phosphogypsum coarse aggregate ranges from 2.50 to 9.50 mm, the particle size of the phosphogypsum fine aggregate ranges from 1.25 to 2.50 mm, the particle size of the shell powder ranges from 1.25 to 2.50 mm, and the particle size of the gravel ranges from 5.00 to 9.50 mm.

[0010] The above scheme further limits the particle size range of the raw materials, optimizes the aggregate gradation, and forms a continuous gradation by limiting the particle sizes of the phosphogypsum coarse aggregate (2.50-9.50mm), fine aggregate (1.25-2.50mm), shell powder (1.25-2.50mm), and gravel (5.00-9.50mm), effectively filling the internal pores of the concrete, reducing the porosity, and improving the density. At the same time, the construction performance is improved, and the problem of "strong aggregation and poor fluidity" caused by the small particle size of the shell powder, which leads to a large specific surface area and high water absorption, is avoided. At the same time, it prevents the segregation caused by the uneven particle size of the phosphogypsum aggregate, ensures the uniformity of the concrete slurry, and reduces the shrinkage cracks in the later stage.

[0011] As a preferred technical solution of the present application, the raw material components of the high-strength concrete include, by weight: shell powder 0-60 parts, phosphogypsum fine aggregate 300-500 parts, phosphogypsum coarse aggregate 100-300 parts, gravel 300-500 parts, cement 300-450 parts, silica fume 20-50 parts, mineral powder 150-300 parts, phosphogypsum 150-200 parts, aluminate activator 0-5 parts, retarder 0-5 parts, polycarboxylate superplasticizer 7-15 parts, and water 150-250 parts.

[0012] The above scheme further limits the weight range of the raw materials, balances the performance and cost, and limits the weight range of the cement (300-450 parts), silica fume (20-50 parts), and mineral powder (150-300 parts) to maintain high-strength performance while ensuring a high dosage of phosphogypsum (35-40%). At the same time, the weight range of the additives (aluminate activator 0-5 parts, retarder 0-5 parts, and polycarboxylate superplasticizer 7-15 parts) can be adjusted to adjust the setting time, fluidity, and hydration rate of the concrete, and adapt to different construction scenarios.

[0013] Cementitious activity activation mechanism: aluminate activator (such as calcium aluminate) can accelerate the hydration reaction of phosphogypsum, promote the rapid generation of ettringite (aluminate reacts with sulfate and calcium ions), and compensate for the weak cementitious activity of phosphogypsum; silica fume (high-activity SiO2) reacts with Ca(OH)2 generated by cement hydration to generate more C-S-H gel, enhancing the strength of the cementitious system; mineral powder (active Al2O3, SiO2) extends the strength development period through secondary hydration, improving the late strength. Additive control mechanism: polycarboxylate superplasticizer reduces the zeta potential by adsorbing on the surface of cementitious particles, reducing particle agglomeration and improving slurry fluidity; retarder can form a complex with calcium ions, delaying the cement hydration process and avoiding early cracking caused by the mismatch between the hydration rates of phosphogypsum and cement; the dosage range of aluminate activator and retarder can balance the strength development rate and construction window period, ensuring stable concrete performance.

[0014] As a preferred technical solution of the present application, the raw material components of the high-strength concrete include, in parts by weight: 51.2 parts of shell powder, 415 parts of phosphogypsum fine aggregate, 190 parts of phosphogypsum coarse aggregate, 409 parts of crushed stone, 350 parts of cement, 46.8 parts of silica fume, 234 parts of mineral powder, 150 parts of phosphogypsum, 4 parts of aluminate activator, 1 part of retarder, 13.5 parts of polycarboxylate superplasticizer, and 171.6 parts of water.

[0015] The above scheme further specifies the specific preferred component ratio, which is a preferred scheme, and can make the total phosphogypsum content of the concrete reach 37%, and the 28-day compressive strength reach 72.8 MPa (far exceeding the upper limit of 40 MPa of the existing high-phosphogypsum-concrete), while considering the fluidity and durability, meeting the high-strength requirement of building structural materials. At the same time, the production fluctuation is reduced: the specific ratio provides precise parameters for industrial production, reduces the performance fluctuation caused by the deviation of raw material usage, facilitates batch production, and improves product stability.

[0016] In a second aspect, the present application provides a method for preparing the high-strength concrete with high content of phosphogypsum and shell aggregate, comprising the following steps: S1, preparation and modification of phosphogypsum aggregate: phosphogypsum is calcined at high temperature, screened to form phosphogypsum ceramsite, and then the phosphogypsum ceramsite is sequentially subjected to acid neutralization treatment and alkaline substance treatment, and then the treated phosphogypsum ceramsite is crushed and screened to obtain phosphogypsum coarse aggregate and phosphogypsum fine aggregate with a predetermined particle size; S2, mixing and stirring: the phosphogypsum coarse aggregate, the phosphogypsum fine aggregate, the crushed stone, the shell powder, the cement, the silica fume, the mineral powder, the phosphogypsum as the cementitious component, the admixture, and the water are mixed and stirred to form a uniform concrete slurry; S3, molding and curing: the concrete slurry is molded, and then cured.

[0017] The above scheme provides a method for preparing high-strength concrete, wherein the high-temperature calcination + acid neutralization + alkaline treatment of S1 can remove the soluble phosphorus, fluorine and heavy metal impurities in the phosphogypsum, and convert them into chemically stable, pH-neutral aggregate, avoiding the inhibition of cement hydration by impurities. The staged mixing and stirring of S2 can ensure that the aggregate, cementitious material and admixture are fully dispersed, avoiding local aggregation and reducing the risk of segregation; the wet heat curing + standard wet curing of S3 can accelerate the hydration reaction, improve the early strength and ensure the development of the late strength, and shorten the curing period.

[0018] Phosphogypsum modification mechanism: high temperature calcination makes phosphogypsum (CaSO4·2H2O) dehydrate to generate calcium sulfate hemihydrate or anhydrous calcium sulfate, improving the strength of aggregate; acid neutralization removes phosphorus (generating oxalate phosphorus precipitation) and fluorine (generating calcium fluoride precipitation); alkaline treatment neutralizes residual acid, adjusts pH to neutral, and avoids the inhibition of cement hydration in acidic environment. Curing mechanism: wet heat curing (50-60℃, ≥95% humidity) can improve the hydration reaction rate, accelerate the generation and growth of C-S-H gel and ettringite, and shorten the strength development time; standard wet curing (normal temperature and high humidity) can maintain the internal moisture of concrete, prevent water evaporation from interrupting the hydration reaction, ensure sufficient later hydration, and improve the strength stability.

[0019] As a preferred technical solution of the present application, in step S1, the acid liquid neutralization treatment is to soak the phosphogypsum ceramsite in a 0.1%-2% oxalic acid solution, the soaking time is 5-30 minutes, and the mass ratio of phosphogypsum ceramsite to oxalic acid solution is 1: (2-5).

[0020] The above-mentioned scheme further limits the acid liquid neutralization treatment method, which can efficiently remove impurities. By soaking in a 0.1%-2% oxalic acid solution, the soluble phosphorus and fluorine impurities in the phosphogypsum ceramsite can be removed specifically, reducing the inhibitory effect of impurities on cement hydration and improving the early strength of concrete. Avoiding secondary pollution: the precipitates (such as oxalate phosphorus and calcium fluoride) generated by the reaction of oxalic acid and impurities have high stability and are not easily dissolved, avoiding the pollution of impurities leaching to soil or groundwater during later use.

[0021] As a preferred technical solution of the present application, in step S1, the alkaline substance treatment is to mix the phosphogypsum ceramsite treated by acid liquid with quicklime after drying and stand for 5-10 days, and the mass ratio of phosphogypsum ceramsite to quicklime is 1: (0.5-2).

[0022] The above-mentioned scheme further limits the alkaline substance treatment method, which adjusts the pH to neutral, and the quicklime (CaO) can neutralize the residual oxalic acid of the phosphogypsum ceramsite and its own acidity, adjusting the pH to 7-8 to provide a suitable alkaline environment for subsequent cement hydration and avoid the inhibition of acidity on hydration. At the same time, the structure of phosphogypsum is stabilized, and the calcium oxalate precipitate generated by the reaction of quicklime and residual oxalic acid can fill the surface pores of the phosphogypsum ceramsite, improving the density and strength of the aggregate, and preventing the influence of oxalic acid dissolution on performance in the later period.

[0023] As a preferred technical solution of the present application, in step S2, the mixing and stirring is specifically: First, mix the shell powder, phosphogypsum fine aggregate, phosphogypsum coarse aggregate, and crushed stone evenly; Then, add cement, silica fume, mineral powder, phosphogypsum as a cementitious component, aluminate activator, and retarder, and continue to mix evenly; Finally, add water and polycarboxylate superplasticizer, and mix until the slurry is uniform.

[0024] The above scheme further limits the mixing and stirring step of each raw material, improves the uniformity of dispersion, first dry mixes the aggregate (shell powder, phosphogypsum coarse / fine aggregate, gravel), which can avoid aggregate agglomeration and ensure uniform dispersion of the aggregate; then add the cementitious material and admixture dry mixing, which can make the cementitious material wrap the surface of the aggregate; finally, wet mixing with water and water reducing agent, which can ensure the fluidity of the slurry and avoid segregation caused by excessive local moisture. At the same time, reduce the interface defect: the phased mixing can reduce the weak area of the aggregate-cementitious slurry interface, improve the interface bonding strength, and thus improve the overall strength of the concrete.

[0025] As a preferred technical solution of the present application, in step S3, the curing includes: First, wet heat curing: under the condition of temperature 50-60℃, relative humidity ≥95%, curing for 6-10 hours; Then, standard wet curing: continue to cure under normal temperature and high humidity conditions to the specified age.

[0026] The above scheme further limits the curing step of high-strength concrete, accelerates the development of early strength, and wet heat curing (50-60℃, ≥95% humidity) can improve the early strength of concrete in a short time (6-10 hours), shorten the demolding time, and improve the production efficiency. At the same time, ensure the stability of the later strength, standard wet curing (normal temperature and high humidity) can maintain the internal moisture of the concrete, ensure the full hydration reaction, avoid early cracking caused by water evaporation, and improve the later strength and durability (such as impermeability and frost resistance).

[0027] In a third aspect, the present application provides a building material product made of the high-strength concrete.

[0028] Compared with the prior art, the specific technical effects of the present application are summarized as follows: The original phosphogypsum is acidic, which is not conducive to the generation of a large amount of high-strength hydration products in the later stage, and water-soluble phosphorus and fluorine are more easily leached in an acidic environment, thereby easily affecting the early strength of the aggregate or concrete. After pretreatment of phosphogypsum with oxalic acid and quicklime, the phosphogypsum aggregate is pure, chemically stable, neutral in pH, safe and harmless, and can be directly used as a building raw material.

[0029] The particle grading of the broken shell adopted in the application is more in line with the requirements of the aggregate, can effectively reduce the porosity inside the concrete, and at the same time, can avoid the problems such as strong aggregation and poor fluidity caused by the too large specific surface area and high water absorption of the shell, is easier to be stirred uniformly, reduces the risk of segregation in the construction process, and can reduce the shrinkage cracks caused by uneven water distribution in the later period. In addition, the shell only needs to be washed and broken to be used, and the production cost is low, which is helpful to realize the resource utilization of solid waste materials, reduce the exploitation of natural resources and the landfill amount of solid waste, is in line with the concept of circular economy, and is suitable for batch production application. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 A preparation process flow chart of the high-strength concrete with high-mixing amount of phosphogypsum and shell aggregate. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the technical solutions of the present application, the preferred embodiments of the present application will be described below in combination with specific examples, but it should not be understood as a limitation on the patent, but only as an example.

[0032] In the following examples, the test methods or test methods are conventional methods unless otherwise specified; the reagents and materials are obtained from conventional commercial channels or prepared by conventional methods unless otherwise specified.

[0033] All raw materials in the embodiments of the present application are market known and commercially available chemical raw materials unless otherwise specified.

[0034] Example 1 As shown in the following table, a high-strength concrete with high-mixing amount of phosphogypsum and shell aggregate is prepared in this embodiment, including the following steps: Figure 1 S1, preparing shell powder: taking a certain amount of shell, crushing it, and sieving the shell powder with a particle size of 1.25-2.50mm by using a standard sieve.

[0035] ​S2, preparation of phosphogypsum aggregate: the phosphogypsum is placed in a high temperature environment for calcination treatment, and the phosphogypsum ceramic particles with a particle size range of 2-20 mm are prepared and selected. A certain mass of the phosphogypsum ceramic particles is weighed, and is soaked in an oxalic acid solution with a mass fraction of 0.5%, wherein the mass ratio of the phosphogypsum ceramic particles to the oxalic acid solution is set to 1:3. During the soaking process, the phosphogypsum ceramic particles are stirred. After soaking for 10 min, the phosphogypsum ceramic particles are taken out and dried in a ventilated place. After complete drying, the phosphogypsum ceramic particles are mixed with quicklime, and the mass ratio of the phosphogypsum ceramic particles to the quicklime is 1:1. After mixing, the mixture is left to stand for 7 days, and then the phosphogypsum ceramic particles are screened out from the quicklime. Subsequently, the removed phosphogypsum ceramic particles are crushed, and through screening operation, the crushed particles with a particle size of 1.25-2.50 mm are selected as the phosphogypsum fine aggregate, and the particles with a particle size of 2.50-9.50 mm are selected as the phosphogypsum coarse aggregate.

[0036] S3, preparation of phosphogypsum: the phosphogypsum is derived from by-products produced in the production process of phosphorus chemical industry, and the main component is CaSO4·2H2O. The organic matter and soluble impurities in the phosphogypsum are removed by water washing method.

[0037] S4, preparation of crushed stone: a certain mass of crushed stone is taken, crushed, and the particles with a particle size of 5.00-9.50 mm are screened out.

[0038] S5, according to the weight fraction, 51.2 parts of shell powder, 415 parts of phosphogypsum fine aggregate, 190 parts of phosphogypsum coarse aggregate, 409 parts of crushed stone, 350 parts of cement, 46.8 parts of silica fume, 234 parts of mineral powder, 150 parts of phosphogypsum, 4 parts of aluminate activator, 171.6 parts of tap water, 13.5 parts of polycarboxylic acid water reducer, and 1 part of retarder are weighed, mixed and stirred for 10-20 min, and then the slurry is loaded into the mold after uniform mixing.

[0039] S6, curing: after the concrete test block is demolded, it is immediately placed in a saturated hot and humid curing box with a temperature controlled at (55±2)℃ and a relative humidity of 98%, and is subjected to standard hot and humid curing for 8 hours. After the curing is completed, the concrete test block is transferred to a curing environment with a temperature of normal temperature and a relative humidity of high humidity for continuous curing until the expected time is reached.

[0040] Example two In this embodiment, a high-strength concrete with high content of phosphogypsum and shell aggregate is prepared, which comprises the following steps: S1, preparation of shell powder: a certain mass of shell is taken, crushed, and the particles with a particle size of 1.25-2.50 mm are screened out.

[0041] S2, preparing phosphogypsum aggregate: phosphogypsum raw materials are prepared and sieved into phosphogypsum ceramsite with a particle size range of 2-20 mm by high-temperature calcination process. A certain mass of phosphogypsum ceramsite is accurately weighed, and is placed in an oxalic acid solution with a mass fraction of 0.5% for soaking treatment. The mass ratio of phosphogypsum ceramsite to oxalic acid solution is set to 1:3. The phosphogypsum ceramsite is continuously stirred during the soaking process. After soaking for 10 minutes, the phosphogypsum ceramsite is taken out and dried in a ventilated place. After the phosphogypsum ceramsite is completely dried, it is mixed with quicklime at a mass ratio of 1:1. After mixing, the phosphogypsum ceramsite is taken out from the quicklime and sieved. Then, the taken-out phosphogypsum ceramsite is crushed and sieved by a standard sieve. The part with a particle size of 1.25-2.50 mm is used as phosphogypsum fine aggregate, and the part with a particle size of 2.50-9.50 mm is used as phosphogypsum coarse aggregate.

[0042] S3, preparing phosphogypsum: the phosphogypsum is derived from solid industrial waste produced in the wet-process phosphoric acid production process, and the main component is CaSO4·2H2O. Organic matter and soluble impurities in the phosphogypsum are removed by water washing method.

[0043] S4, preparing crushed stone: a certain mass of crushed stone is taken, crushed, and sieved to obtain a part with a particle size of 5.00-9.50 mm.

[0044] S5, according to the weight fraction, 40.1 parts of shell powder, 415 parts of phosphogypsum fine aggregate, 190 parts of phosphogypsum coarse aggregate, 409 parts of crushed stone, 350 parts of cement, 46.8 parts of silica fume, 234 parts of mineral powder, 150 parts of phosphogypsum, 4 parts of aluminate activator, 171.6 parts of tap water, 13.5 parts of polycarboxylic acid water reducer, and 1 part of retarder are weighed and mixed for 10-20 minutes. After the slurry is uniformly mixed, it is loaded into a mold.

[0045] S6, curing: after the concrete test block is demolded, it is immediately placed in a saturated humid heat curing box with a temperature controlled at (55±2)℃ and a relative humidity of 98%, and is subjected to standard humid heat curing for 8 hours. After the curing is completed, the concrete test block is transferred to a curing environment with a temperature of normal temperature and a relative humidity of high humidity for continuous curing until the expected time is reached.

[0046] Example three This example prepares a high-strength concrete with a high content of phosphogypsum and shell aggregate composite, which includes the following steps: S1, preparing shell powder: a certain mass of shell is taken, crushed, and sieved to obtain a part with a particle size of 1.25-2.50 mm.

[0047] S2, preparing phosphogypsum aggregate: phosphogypsum raw materials are prepared and sieved into phosphogypsum ceramsite with a particle size range of 2-20 mm by high-temperature calcination process. A certain mass of phosphogypsum ceramsite is accurately weighed, and is placed in an oxalic acid solution with a mass fraction of 0.5% for soaking treatment. The mass ratio of phosphogypsum ceramsite to oxalic acid solution is set to 1:3. During the soaking process, the phosphogypsum ceramsite is continuously stirred, and after soaking for 10 min, the phosphogypsum ceramsite is taken out and dried in a ventilated place. After the phosphogypsum ceramsite is completely dried, it is mixed with quicklime at a mass ratio of 1:1. After mixing, it is left to stand for 7 days, and the phosphogypsum ceramsite is taken out from the quicklime and sieved. Then, the taken-out phosphogypsum ceramsite is crushed and sieved by a standard sieve, and the part with a particle size of 1.25-2.50 mm is used as phosphogypsum fine aggregate, and the part with a particle size of 2.50-9.50 mm is used as phosphogypsum coarse aggregate.

[0048] S3, preparing phosphogypsum: the phosphogypsum is derived from solid industrial waste residues generated in the wet-process phosphoric acid production process, and the main component is CaSO4·2H2O. Organic matter and soluble impurities in the phosphogypsum are removed by water washing method.

[0049] S4, preparing crushed stone: a certain mass of crushed stone is taken, crushed, and sieved to obtain a part with a particle size of 5.00-9.50 mm.

[0050] S5, according to the weight fraction, 60 parts of shell powder, 415 parts of phosphogypsum fine aggregate, 190 parts of phosphogypsum coarse aggregate, 409 parts of crushed stone, 350 parts of cement, 46.8 parts of silica fume, 234 parts of mineral powder, 150 parts of phosphogypsum, 4 parts of aluminate activator, 171.6 parts of tap water, 13.5 parts of polycarboxylic acid water reducer, and 1 part of retarder are weighed, mixed for 10-20 min, and then the slurry is mixed uniformly and loaded into the mold.

[0051] S6, curing: after the concrete test block is demolded, it is immediately placed in a saturated humid heat curing box with a temperature controlled at (55±2)℃ and a relative humidity of 98%, and is subjected to standard humid heat curing for 8 hours. After the curing is completed, the concrete test block is transferred to a curing environment with a temperature of normal temperature and a relative humidity of high humidity for continuous curing until the expected time is reached.

[0052] Example Four This example prepares a high-strength concrete with a high content of phosphogypsum and shell aggregate, which includes the following steps: S1, preparation of phosphogypsum aggregate: the phosphogypsum is placed in a high temperature environment for calcination treatment, and phosphogypsum ceramsite with a particle size range of 2-20 mm is prepared and selected. A certain mass of the phosphogypsum ceramsite is weighed, and it is soaked in an oxalic acid solution with a mass fraction of 0.5%, wherein the mass ratio of phosphogypsum ceramsite to oxalic acid solution is set to 1:3. During the soaking process, the phosphogypsum ceramsite is stirred, and after 10 minutes, the phosphogypsum ceramsite is taken out of the oxalic acid solution and placed in a well-ventilated place to dry. After it is completely dried, it is mixed with quicklime, and at this time the mass ratio of phosphogypsum ceramsite to quicklime is 1:1. After mixing, it is left to stand for 7 days, and then the phosphogypsum ceramsite is sieved out of the quicklime. Then the removed phosphogypsum ceramsite is crushed, and by screening operation, the part with a particle size of 1.25-2.50 mm after crushing is selected as the phosphogypsum fine aggregate, and the part with a particle size of 2.50-9.50 mm is selected as the phosphogypsum coarse aggregate.

[0053] S2, preparation of phosphogypsum: the phosphogypsum is derived from by-products produced in the production process of phosphorus chemical industry, and the main component is CaSO4·2H2O. Organic matter and soluble impurities in the phosphogypsum are removed by water washing method.

[0054] S3, preparation of crushed stone: a certain mass of crushed stone is taken, crushed, and the part with a particle size of 5.00-9.50 mm is sieved out.

[0055] S4, according to the weight fraction, 466.2 parts of phosphogypsum fine aggregate, 190 parts of phosphogypsum coarse aggregate, 409 parts of crushed stone, 350 parts of cement, 46.8 parts of silica fume, 234 parts of mineral powder, 150 parts of phosphogypsum, 4 parts of aluminate activator, 171.6 parts of tap water, 13.5 parts of polycarboxylic acid water reducer and 1 part of retarder are weighed, and then mixed for 10-20 minutes. After the slurry is uniformly mixed, it is loaded into the mold.

[0056] S5, curing: after the concrete test block is demolded, it is immediately placed in a saturated hot and humid curing box with a temperature controlled at (55±2)℃ and a relative humidity of 98%, and subjected to standard hot and humid curing for 8 hours. After the curing is completed, the concrete test block is transferred to a curing environment with a temperature of normal temperature and a relative humidity maintained at a high humidity state for continuous curing until the desired time is reached.

[0057] Comparative Example One This comparative example prepares a kind of high content phosphogypsum and shell aggregate composite concrete, including the following steps: S1, preparation of shell powder: a certain mass of shell is taken, crushed, and the part with a particle size of 1.25-2.50 mm is sieved out.

[0058] S2, preparing phosphogypsum aggregate: the phosphogypsum is placed in a high temperature environment for calcination treatment, and the phosphogypsum ceramsite with a particle size range of 2-20 mm is prepared and screened as the phosphogypsum aggregate. A certain mass of the phosphogypsum ceramsite is weighed, and is soaked in an oxalic acid solution with a mass fraction of 0.5%, wherein the mass ratio of the phosphogypsum ceramsite to the oxalic acid solution is set to 1:3. During the soaking process, the phosphogypsum ceramsite is stirred, and after 10 minutes, the phosphogypsum ceramsite is taken out of the oxalic acid solution and is placed in a ventilated place to dry. After it is completely dried, it is mixed with quicklime, and at this time the mass ratio of the phosphogypsum ceramsite to the quicklime is 1:1. After mixing, it is left to stand for 7 days, and then the phosphogypsum ceramsite is screened out of the quicklime.

[0059] S3, preparing phosphogypsum: the phosphogypsum is derived from a by-product produced in the production process of phosphorus chemical industry, and the main component is CaSO4·2H2O. The organic matter and soluble impurities in the phosphogypsum are removed by water washing method.

[0060] S4, preparing crushed stone: a certain mass of crushed stone is taken, crushed, and the part with a particle size of 5.00-9.50 mm is screened.

[0061] S5, according to the weight fraction, 51.2 parts of shell powder, 605 parts of phosphogypsum ceramsite, 409 parts of crushed stone, 350 parts of cement, 46.8 parts of silica fume, 234 parts of mineral powder, 150 parts of phosphogypsum, 4 parts of aluminate activator, 171.6 parts of tap water, 13.5 parts of polycarboxylic acid water reducer, and 1 part of retarder are weighed, and are mixed for 10-20 minutes. After the slurry is uniformly mixed, it is loaded into the mold.

[0062] S6, curing: after the concrete test block is demolded, it is immediately placed in a saturated humid heat curing box with a temperature controlled at (55±2)℃ and a relative humidity of 98%, and is subjected to standard humid heat curing for 8 hours. After the curing is completed, the concrete test block is transferred to a curing environment with a temperature of normal temperature and a relative humidity of high humidity (relative humidity of 50% or more) for continuous curing until the expected time is reached.

[0063] Comparative Example Two This comparative example prepares a kind of concrete with high content of phosphogypsum and shell aggregate, including the following steps: S1, preparing shell powder: a certain mass of shell is taken, crushed, and the part with a particle size of 1.25-2.50 mm is screened with a standard sieve.

[0064] S2, preparation of phosphogypsum aggregate: the phosphogypsum is placed in a high temperature environment for calcination treatment, and phosphogypsum ceramsite with a particle size range of 2-20 mm is prepared and selected. Then the phosphogypsum ceramsite is crushed. Through screening, the part with a particle size in the range of 1.25-2.50 mm is selected as the phosphogypsum fine aggregate, and the part with a particle size in the range of 2.50-9.50 mm is selected as the phosphogypsum coarse aggregate.

[0065] S3, preparation of phosphogypsum: the phosphogypsum is derived from solid industrial waste produced in the process of wet-process phosphoric acid production, and the main component is CaSO4·2H2O. The organic matter and soluble impurities in the phosphogypsum are removed by water washing method.

[0066] S4, preparation of gravel: a certain amount of gravel is crushed, and the part with a particle size of 5.00-9.50 mm is screened.

[0067] S5, according to the weight fraction, 51.2 parts of shell powder, 415 parts of phosphogypsum fine aggregate, 190 parts of phosphogypsum coarse aggregate, 409 parts of gravel, 350 parts of cement, 46.8 parts of silica fume, 234 parts of mineral powder, 150 parts of phosphogypsum, 4 parts of aluminate activator, 171.6 parts of tap water, 13.5 parts of polycarboxylic acid water reducer and 1 part of retarder are weighed, and then mixed for 10-20 min. After the slurry is uniformly mixed, it is loaded into the mold.

[0068] S6, curing: after the concrete test block is demolded, it is immediately placed in a saturated humid heat curing box with a temperature controlled at (55±2)℃ and a relative humidity of 98%, and is subjected to standard humid heat curing for 8 hours. After the curing is completed, the concrete test block is transferred to a curing environment with a temperature of normal temperature and a relative humidity maintained in a high humidity state for continuous curing.

[0069] Comparative Example Three A high-strength concrete with high content of phosphogypsum and shell aggregate is prepared in this comparative example. Except that the phosphogypsum fine aggregate is completely replaced by the same amount of phosphogypsum coarse aggregate, the rest is the same as Example One.

[0070] Comparative Example Four A high-strength concrete with high content of phosphogypsum and shell aggregate is prepared in this comparative example. Except that the phosphogypsum coarse aggregate is completely replaced by the same amount of phosphogypsum fine aggregate, the rest is the same as Example One.

[0071] The shell content of Example One is 11%, and compared with Example One, the shell contents of Example Two, Example Three and Example Four are 9%, 13% and 0% respectively; compared with Example One, the phosphogypsum aggregate of Comparative Example One is not physically modified; compared with Example One, the phosphogypsum aggregate of Comparative Example Two is not chemically modified; compared with Example One, Comparative Example Three uses phosphogypsum coarse aggregate; compared with Example One, Comparative Example Four uses phosphogypsum fine aggregate.

[0072] Table 1 As can be seen from Table 1, when the shell content in the concrete prepared by the present application is 0%, 9%, 11% and 13%, the concrete strength reaches the highest when the shell content is 11%, and the 11% determined by the test is the optimal shell content; compared with Example 1, the phosphogypsum aggregate of Comparative Example 1 is not physically modified, and the results of the example show that the strength of Example 1 is 82.9% higher than that of Comparative Example 1, indicating that physical modification can effectively improve the strength; compared with Example 1, the phosphogypsum aggregate of Comparative Example 2 is not chemically modified, and the results of the example show that the strength of Example 1 is 34.3% higher than that of Comparative Example 2, indicating that chemical modification can effectively improve the strength. Compared with Example 1, Comparative Example 3 uses single phosphogypsum coarse aggregate, and Comparative Example 4 uses single phosphogypsum fine aggregate, and the results of the example show that the strength of Example 1 is higher than that of Comparative Examples 3 and 4, indicating that the mixed use of phosphogypsum coarse aggregate and phosphogypsum fine aggregate effectively improves the strength.

[0073] The present application successfully solves the technical bottleneck of high content application of phosphogypsum in concrete through the physical and chemical dual modification technology of phosphogypsum ceramsite and the ternary synergistic strengthening mechanism of shell aggregate. The example data show that when the phosphogypsum aggregate is chemically modified by oxalic acid neutralization reaction and lime precipitation reaction, and physically modified by crushing and screening, combined with the optimal shell content of 11%, high-strength concrete with a total phosphogypsum content of up to 37% can be prepared, and the 28-day compressive strength reaches 72.8 MPa.

[0074] The above is only a preferred embodiment of the present application, and it should be pointed out that the above preferred embodiment should not be regarded as a limitation of the present application, and the protection scope of the present application should be limited by the scope defined by the claims. For ordinary skilled persons in the art, several improvements and refinements can be made without departing from the spirit and scope of the present application, and these improvements and refinements should also be regarded as the protection scope of the present application.

Claims

1. A high-strength concrete composed of high-dosage phosphogypsum and shell aggregate, wherein the raw material components of the high-strength concrete include cementitious materials, aggregates, admixtures, and water; characterized in that, The cementitious material includes cement, silica fume, mineral powder, and phosphogypsum; the aggregate includes phosphogypsum coarse aggregate, phosphogypsum fine aggregate, crushed stone, and shell powder; wherein, based on the total weight of concrete, the comprehensive dosage of phosphogypsum ranges from 35% to 40%, and the comprehensive dosage of phosphogypsum includes phosphogypsum as a cementitious component and phosphogypsum coarse aggregate and phosphogypsum fine aggregate as aggregate components.

2. The high-strength concrete according to claim 1, characterized in that, The coarse phosphogypsum aggregate has a particle size range of 2.50-9.50 mm, the fine phosphogypsum aggregate has a particle size range of 1.25-2.50 mm, the shell powder has a particle size range of 1.25-2.50 mm, and the crushed stone has a particle size range of 5.00-9.50 mm.

3. The high-strength concrete according to claim 1 or 2, characterized in that, By weight, the raw material components of the high-strength concrete include: 0-60 parts shell powder, 300-500 parts phosphogypsum fine aggregate, 100-300 parts phosphogypsum coarse aggregate, 300-500 parts crushed stone, 300-450 parts cement, 20-50 parts silica fume, 150-300 parts mineral powder, 150-200 parts phosphogypsum, 0-5 parts aluminate activator, 0-5 parts retarder, 7-15 parts polycarboxylate superplasticizer, and 150-250 parts water.

4. The high-strength concrete according to claim 3, characterized in that, The raw material components of the high-strength concrete, by weight, include: 51.2 parts shell powder, 415 parts fine phosphogypsum aggregate, 190 parts coarse phosphogypsum aggregate, 409 parts crushed stone, 350 parts cement, 46.8 parts silica fume, 234 parts mineral powder, 150 parts phosphogypsum, 4 parts aluminate activator, 1 part retarder, 13.5 parts polycarboxylate superplasticizer, and 171.6 parts water.

5. A method for preparing high-strength concrete composed of high-dosage phosphogypsum and shell aggregate as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Preparation and modification of phosphogypsum aggregate: Phosphogypsum is calcined at high temperature and screened to form phosphogypsum ceramsite. The phosphogypsum ceramsite is then subjected to acid neutralization treatment and alkaline treatment in sequence. The treated phosphogypsum ceramsite is then crushed and screened to obtain phosphogypsum coarse aggregate and phosphogypsum fine aggregate with predetermined particle size. S2. Mixing and stirring: The phosphogypsum coarse aggregate, phosphogypsum fine aggregate, crushed stone, shell powder, cement, silica fume, mineral powder, phosphogypsum as a cementing component, admixtures and water are mixed and stirred to form a uniform concrete paste. S3. Molding and Curing: The concrete slurry is molded and then cured.

6. The method according to claim 5, characterized in that, In step S1, the acid neutralization treatment involves soaking the phosphogypsum ceramsite in an oxalic acid solution with a mass fraction of 0.1%-2% for 5-30 minutes, with the mass ratio of the phosphogypsum ceramsite to the oxalic acid solution being 1:(2-5).

7. The method according to claim 5, characterized in that, In step S1, the alkaline treatment involves drying the acid-treated phosphogypsum ceramsite and mixing it with quicklime, then letting it stand for 5-10 days. The mass ratio of phosphogypsum ceramsite to quicklime is 1:(0.5-2).

8. The method according to claim 5, characterized in that, The mixing and stirring in step S2 specifically involves: First, dry mix the shell powder, fine phosphogypsum aggregate, coarse phosphogypsum aggregate, and crushed stone evenly; Then add cement, silica fume, mineral powder, phosphogypsum as a cementitious component, aluminate activator and retarder, and continue to dry mix evenly; Finally, add water and polycarboxylate superplasticizer, and mix until the slurry is uniform.

9. The method according to claim 5, characterized in that, In step S3, the maintenance includes: First, perform humid heat curing: cure for 6-10 hours at a temperature of 50-60℃ and a relative humidity of ≥95%; Then, standard wet curing is carried out: continue curing under normal temperature and high humidity conditions until the specified age.

10. A building material product, characterized in that, It is made of high-strength concrete as described in any one of claims 1 to 4.

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