Anti-cracking water-resistant phosphogypsum road base material and preparation method thereof

Abstract

The application belongs to the technical field of building materials, and discloses an anti-cracking water-resistant phosphogypsum road base material and a preparation method thereof. The anti-cracking water-resistant phosphogypsum road base material comprises a base material and an additive, and the base material is composed of raw materials in the following proportions by weight: calcined phosphogypsum 15-25%, natural coarse aggregate 43-47%, natural fine aggregate 28-32%, and Portland cement 3-8%. The additive is a combination of a modifier, EVA emulsion, PU emulsion and water, and the mass ratio of the base material, the modifier, the EVA emulsion, the PU emulsion and the water is 100:1.1-2.6:0.25-2:0.25-2:4-11. The application utilizes the organic gelation of EVA and PU emulsion to limit the shrinkage of cement mortar, especially the early self-shrinkage deformation within 28 days, thereby effectively reducing the cracking problem caused by the dry shrinkage and temperature shrinkage of the road base material, and effectively maintaining the stability of the cementitious material system, the compressive strength and other mechanical properties of the phosphogypsum and the road base material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building materials, and particularly relates to an anti-cracking and water-resistant phosphogypsum road base material and a preparation method thereof. BACKGROUND

[0002] Phosphogypsum is an industrial waste residue produced in the process of decomposing phosphate ore with sulfuric acid and extracting phosphoric acid by chemical enterprises, and the main component of the phosphogypsum is CaSO4·2H2O. The main pollution impurities include a small amount of phosphoric acid, calcium phosphate, P2O5 phosphate and fluorides, etc., and the phosphogypsum is usually in the form of dark gray moist powder. If the phosphogypsum is discarded in the natural environment, on the one hand, a large amount of land resources is occupied, and on the other hand, the phosphogypsum is easily penetrated into the ground through physical and chemical actions such as weathering and rain, causing pollution of surface water and shallow groundwater, and further causing air pollution through the water cycle in nature. Therefore, how to properly dispose of the phosphogypsum solid waste and realize resource utilization has very important social significance and engineering value.

[0003] The properties of the phosphogypsum are similar to those of the powder mineral aggregate commonly used in road materials, and the phosphogypsum can be used as a road material to effectively solve the problem of phosphogypsum storage. However, how to improve the water stability and frost resistance of the phosphogypsum road base material and the service life of the phosphogypsum road base material is closely related to the modification of the phosphogypsum and the inorganic cementitious material composite powder stabilization system.

[0004] Application No. 202211536774.7 discloses a pavement base material based on organic-inorganic cementitious material for stabilizing phosphogypsum and recycled aggregate and a preparation method thereof. The pavement base material is prepared from cement-based cementitious material, calcined phosphogypsum, natural fine aggregate, natural coarse aggregate, potassium silicate, calcium stearate emulsion, polymer emulsion and water as main raw materials. The cement-based cementitious material, calcined phosphogypsum, natural fine aggregate and natural coarse aggregate constitute a consolidation component.

[0005] The above-mentioned patent lacks the ability to resist crack development, and is prone to cracking problems caused by dry shrinkage and temperature shrinkage of the road base material. SUMMARY

[0006] The purpose of the present application is to provide an anti-cracking and water-resistant phosphogypsum road base material and a preparation method thereof to solve the cracking problem caused by dry shrinkage and temperature shrinkage of the existing road base material. The organic cementation of EVA emulsion and PU emulsion is used to limit the shrinkage of cement mortar, especially to reduce the early self-shrinkage deformation within 28 days, effectively reducing the cracking problem caused by dry shrinkage and temperature shrinkage of the road base material. The pavement base material has low shrinkage and strong water resistance, can effectively maintain the mechanical properties such as compressive strength of the cementitious material system, and can also have the ability of water damage resistance and frost-thaw cracking resistance of the pavement base material.

[0007] To achieve the above object, the technical scheme adopted by the present application is:

[0008] The first object of the present application is to provide an anti-cracking water-resistant phosphogypsum road base material, which comprises a base material and an additive, wherein the base material is composed of the following raw materials in percentage by weight: calcined phosphogypsum 15-25%, natural coarse aggregate 43-47%, natural fine aggregate 28-32%, and silicate cement 3-8%; and the additive is a combination of a modifier, EVA emulsion, PU emulsion, and water, wherein the mass ratio of the base material, the modifier, the EVA emulsion, the PU emulsion, and the water is 100:1.1-2.6:0.25-2:0.25-2:4-11.

[0009] Further, the EVA emulsion is ethylene-vinyl acetate copolymer, the solid content of which is 30-50%, and the pH value of which is 6.0-7.0.

[0010] Further, the PU emulsion is polyurethane emulsion, the solid content of which is 30-50%, and the pH value of which is 7.0-9.0.

[0011] Further, the modifier is a combination of potassium silicate and calcium stearate emulsion, and the mass ratio of the potassium silicate and the calcium stearate emulsion is 1.0-2.2:0.1-0.4.

[0012] Further, the solid content of the calcium stearate emulsion is 25-45%, and the pH value of which is 8-11.

[0013] Further, the preparation method of the calcined phosphogypsum comprises the following steps:

[0014] After washing the phosphogypsum with water, the phosphogypsum is calcined, and then cooled and crushed to obtain the calcined phosphogypsum, wherein the particle size of the calcined phosphogypsum is ≤0.3mm.

[0015] Further, the calcination temperature is 100-180℃, and the time is 1-2h.

[0016] Further, the natural coarse aggregate is limestone, the particle size of which is 4.75-19mm, the bulk density of which is 1590-1781kg / m 3 , the crushing index of which is 8-11%, and the water absorption of which is 0-1%; the natural fine aggregate is natural river sand, the particle size of which is 4.75-19mm, the bulk density of which is 1517-1581kg / m 3 , the water absorption of which is 6-9%, and the water content of which is 1.5-5%; and the silicate cement is cement or a mixture of cement and mineral admixtures, wherein the mineral admixtures are one or more of fly ash, lime, and mineral powder.

[0017] Further, the limestone and natural river sand are used in a grading manner, wherein the mass ratio of limestone with a particle size of 13-19mm, limestone with a particle size of 9-13mm, limestone with a particle size of 4.75-13mm, natural river sand with a particle size of 1.18-4.75mm, natural river sand with a particle size of 1.18-2.36mm and natural river sand with a particle size of 0-1.18mm is 15:13:20:11:7:34.

[0018] The second object of the present application is to provide a preparation method of the anti-cracking water-resistant phosphogypsum road base material, comprising the following steps:

[0019] The components are weighed according to the percentage by weight; the silicate cement and water are stirred and mixed uniformly to form a mixture A; the calcined phosphogypsum, modifier, EVA emulsion and PU emulsion are mixed and stirred uniformly and then left to stand to obtain a mixture B; the mixture A, the mixture B, natural coarse aggregate and natural fine aggregate are stirred uniformly to obtain the anti-cracking water-resistant phosphogypsum road base material.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] (1) The EVA emulsion and PU emulsion of the present application can reduce the average pore size in the base material and slightly reduce the total porosity, so that the closed pores formed can prevent internal water loss and external water erosion. Not only can the mechanical properties such as the compressive strength of the phosphogypsum and the road base material be effectively maintained, but also the water damage resistance and freeze-thaw cracking resistance of the road base material can be achieved, thereby prolonging the service life.

[0022] (2) The organic cementation of the EVA emulsion and PU emulsion of the present application can limit the shrinkage of the cement mortar, especially the early-age self-shrinkage deformation, thereby effectively reducing the cracking problem caused by the dry shrinkage and temperature shrinkage of the road base material.

[0023] (3) The EVA emulsion and PU emulsion of the present application can realize the large-scale resource utilization of phosphogypsum and natural coarse aggregate in the road base material through the synergistic cementation of the EVA emulsion, PU emulsion and cementitious materials, thereby alleviating the problems of extreme shortage of natural coarse aggregate and phosphogypsum storage, and having significant environmental, economic and social benefits. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0025] It should be noted that the professional terms used in the present application are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present application. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the following embodiments of the present application can be purchased from the market or prepared by the existing method.

[0026] The anti-cracking water-resistant phosphogypsum road base material comprises a base material and an additive, and the base material is composed of raw materials in the following weight percentages: calcined phosphogypsum 15-25%, natural coarse aggregate 43-47%, natural fine aggregate 28-32%, and Portland cement 3-8%; the additive is a combination of a modifier, EVA emulsion, PU emulsion and water, wherein the mass ratio of the base material, the modifier, the EVA emulsion, the PU emulsion and the water is 100:1.1-2.6:0.25-2:0.25-2:4-11.

[0027] The present application utilizes the hydration reaction of inorganic cementitious material and the physicochemical reaction of EVA emulsion to compound and cement the calcined phosphogypsum, increases the amount of hydration products such as hydrated calcium silicate and hydrated calcium aluminate in the mixture, reduces the problems of swelling and softening of phosphogypsum when it meets water and water absorption, promotes better bonding capacity of rubber and hardened cement mortar, enhances the compactness of microstructure, and achieves the goal of strength growth; the use of EVA emulsion in cooperation with cementitious material can reduce the early hydration heat of cement-based material, the loss of emulsion water during the hydration process of cement forms a polymer film which plays a role of "microfiber" to limit shrinkage, improves the shrinkage performance at 28d, and to a certain extent, reduces the stability of inorganic cementitious material for pavement base, which is conducive to reducing the cracking phenomenon caused by dry shrinkage, temperature shrinkage and load stress of base material; based on the stabilizing effect of the rubber emulsion in cooperation with cementitious material, the potential ability of improving the mechanical strength and durability of the pavement base material containing phosphogypsum can be improved.

[0028] The EVA emulsion and PU emulsion used in the present application make the base layer have better flexibility compared with SBR emulsion, and SBR emulsion can promote the generation of ettringite which has a negative impact on strength during the cement hydration reaction, reduces its anti-cracking performance, and weakens the expected goal of SBR emulsion to reduce the stiffness of base material and enhance the anti-cracking performance. While delaying the early hydration of cement, the two emulsions of the present application can improve the late strength of base material and significantly improve its ability to resist crack development.

[0029] In a specific embodiment, the EVA emulsion is ethylene-vinyl acetate copolymer, the solid content of which is 30-50%, and the pH value is 6.0-7.0.

[0030] In a specific embodiment, the PU emulsion is polyurethane emulsion, the solid content of which is 30-50%, and the pH value is 7.0-9.0.

[0031] In one specific embodiment, the modifier is a combination of potassium silicate and calcium stearate emulsion, and the mass ratio of the potassium silicate and the calcium stearate emulsion is 1.0-2.2:0.1-0.4.

[0032] In one specific embodiment, the calcium stearate emulsion has a solid content of 25-45% and a pH value of 8-11.

[0033] In one specific embodiment, the preparation method of the calcined phosphogypsum comprises the following steps:

[0034] After washing the phosphogypsum with water, the phosphogypsum is calcined, and after the calcination is completed, the phosphogypsum is cooled and crushed to obtain a calcined phosphogypsum, and the particle size of the calcined phosphogypsum is ≤0.3 mm. More specifically, the calcination temperature is 100-180°C, and the time is 1-2 h.

[0035] In one specific embodiment, the natural coarse aggregate is limestone, the particle size is 4.75-19 mm, the bulk density is 1590-1781 kg / m 3 , the crushing index is 8-11%, and the water absorption is 0-1%; the natural fine aggregate is natural river sand, the particle size is 4.75-19 mm, the bulk density is 1517-1581 kg / m 3 , the water absorption is 6-9%, and the water content is 1.5-5%; the Portland cement is cement or a mixture of cement and mineral admixtures, and the mineral admixtures are one or more of fly ash, lime, and mineral powder. More specifically, the cement is P.O 42.5 ordinary Portland cement, the apparent density is 3.3 g / cm 3 , the water requirement for standard consistency is 25.9%, the initial setting time is 217 min, and the final setting time is 283 min.

[0036] In one specific embodiment, the limestone and the natural river sand are used in a graded manner, and the mass ratio of limestone with a particle size of 13-19 mm, limestone with a particle size of 9-13 mm, limestone with a particle size of 4.75-13 mm, natural river sand with a particle size of 1.18-4.75 mm, natural river sand with a particle size of 1.18-2.36 mm, and natural river sand with a particle size of 0-1.18 mm is 15:13:20:11:7:34.

[0037] The preparation method of the above-mentioned anti-cracking and water-resistant phosphogypsum road base material comprises the following steps:

[0038] The components are weighed according to the percentage by weight; the Portland cement and the water are stirred and mixed uniformly to form a mixture A; the calcined phosphogypsum, the modifier, and the EVA emulsion and the PU emulsion are mixed and stirred uniformly and then left to stand to obtain a mixture B; and the mixture A, the mixture B, the natural coarse aggregate, and the natural fine aggregate are stirred and mixed uniformly to obtain the anti-cracking and water-resistant phosphogypsum road base material.

[0039] The EVA emulsion and PU emulsion provided by the present application reduce the average pore size in the base material and slightly reduce the total porosity, forming closed pores that prevent internal water loss and external water erosion. Not only can the mechanical properties of the phosphogypsum and road base material, such as compressive strength, be effectively maintained, but the road base material can also have the ability to resist water damage and freeze-thaw cracking, prolonging its service life. The organic gelation of the EVA emulsion and PU emulsion limits the shrinkage of the cement mortar, especially the early self-shrinkage deformation within 28 days, effectively reducing the cracking problem caused by the drying and temperature shrinkage of the road base material.

[0040] In the following examples, the physical and mechanical properties of the phosphogypsum and road base material were tested according to the Highway Geotechnical Test Procedures (JTG E400-2007), Highway Engineering Inorganic Material Binder Stabilized Material Test Procedures (JTGE51-2009), and other test methods.

[0041] The following comparative examples and examples use 20wt% phosphogypsum to replace the aggregate within the full gradation range, and the aggregate gradation composition of the base material is shown in Table 1.

[0042] Table 1 Aggregate gradation composition of road base material in comparative examples and examples

[0043]

[0044]

[0045] The following is further illustrated by specific implementation.

[0046] Example 1

[0047] A crack-resistant and water-resistant phosphogypsum road base material, comprising a base material and an additive, the base material being composed of the following raw materials in weight percentage: calcined phosphogypsum 20%, limestone 45%, natural river sand 30%, cement 5%; the additive being potassium silicate, calcium stearate emulsion, EVA emulsion, PU emulsion, and water, the mass ratio of the base material, potassium silicate, calcium stearate emulsion, EVA emulsion, PU emulsion, and water being 100:2.2:0.32:0.75:0.25:6.33. The EVA emulsion is an ethylene-vinyl acetate copolymer with a solid content of 35% and a pH value of 6.5. The PU emulsion is a polyurethane emulsion with a solid content of 40% and a pH value of 8. The calcium stearate emulsion has a solid content of 40% and a pH value of 10.

[0048] The preparation method of the calcined phosphogypsum comprises the following steps: firstly, the phosphogypsum is washed with water and filtered, then the phosphogypsum is calcined at a temperature of 150 DEG C for 1 hour, and the calcined phosphogypsum is obtained after natural cooling and screening, wherein the particle size of the calcined phosphogypsum is less than or equal to 0.3 mm.

[0049] The limestone has a particle size of 4.75-19 mm, a volume density of 1637 kg / m 3 , a crushing index of 9.5%, and a water absorption of 0.5%; the natural river sand has a particle size of 4.75-19 mm, a volume density of 1541 kg / m 3 , a water absorption of 6.79%, and a water content of 2.4%; the limestone and the natural river sand are in a continuous grading mode, and the limestone in a particle size of 13-19 mm accounts for 15% of the total mass, the limestone in a particle size of 9-13 mm accounts for 13% of the total mass, and the limestone in a particle size of 4.75-13 mm accounts for 20% of the total mass; the fine sand in a particle size of 0-1.18 mm accounts for 34% of the total mass, the medium sand in a particle size of 1.18-2.36 mm accounts for 7% of the total mass, and the coarse sand in a particle size of 1.18-4.75 mm accounts for 11% of the total mass.

[0050] The preparation method of the anti-cracking and water-resistant phosphogypsum road base material comprises the following steps:

[0051] S1, the components of the base material are weighed according to the weight percentage: 20% of the calcined phosphogypsum, 45% of the limestone, 30% of the natural river sand, and 5% of the cement; the components of the additive are weighed according to the weight percentage based on 100% of the weight of the base material: 2.2% of potassium silicate, 0.32% of calcium stearate emulsion, 0.75% of EVA emulsion, 0.25% of PU emulsion, and 6.33% of water;

[0052] S2, the cement and the water are stirred and mixed uniformly to form a mixture A; the calcined phosphogypsum, the potassium silicate, the calcium stearate emulsion, the EVA emulsion, and the PU emulsion are mixed and stirred uniformly and then left to stand to obtain a mixture B; the mixture A, the mixture B, the limestone, and the natural river sand are stirred uniformly to obtain the anti-cracking and water-resistant phosphogypsum road base material.

[0053] Example 2

[0054] The anti-cracking water-resistant phosphogypsum road base material comprises a base material and an additive, the base material is composed of raw materials in the following weight percentages: calcined phosphogypsum 20%, limestone 45%, natural river sand 30%, cement 5%; the additive is potassium silicate, calcium stearate emulsion, EVA emulsion, PU emulsion and water, and the mass ratio of the base material, potassium silicate, calcium stearate emulsion, EVA emulsion, PU emulsion and water is 100:2.2:0.32:0.5:0.5:6.33. The EVA emulsion is ethylene-vinyl acetate copolymer, the solid content of which is 35%, and the pH value is 6.5. The PU emulsion is polyurethane emulsion, the solid content of which is 40%, and the pH value is 8. The solid content of the calcium stearate emulsion is 40%, and the pH value is 10.

[0055] The preparation method of the calcined phosphogypsum comprises the following steps: firstly, washing and filtering phosphogypsum, then calcining at a temperature of 150 DEG C for 1 h, and obtaining the calcined phosphogypsum after natural cooling and screening, the particle size of the calcined phosphogypsum is less than or equal to 0.3 mm.

[0056] The particle size of the limestone is 4.75-19 mm, the bulk density is 1637 kg / m 3 , the crushing index is 9.5%, and the water absorption is 0.5%; the particle size of the natural river sand is 4.75-19 mm, the bulk density is 1541 kg / m 3 , the water absorption is 6.79%, and the water content is 2.4%; the limestone and the natural river sand are in a continuous grading mode, the mass percentage of the limestone with a particle size of 13-19 mm is 15%, the mass percentage of the limestone with a particle size of 9-13 mm is 13%, and the mass percentage of the limestone with a particle size of 4.75-13 mm is 20%, as shown in Table 1; the mass percentage of the fine sand with a particle size of 0-1.18 mm is 34%, the mass percentage of the medium sand with a particle size of 1.18-2.36 mm is 7%, and the mass percentage of the coarse sand with a particle size of 1.18-4.75 mm is 11%, as shown in Table 1.

[0057] The preparation method of the anti-cracking water-resistant phosphogypsum road base material comprises the following steps:

[0058] S1, weighing the components of the base material according to the weight percentages: calcined phosphogypsum 20%, limestone 45%, natural river sand 30%, cement 5%; weighing the components of the additive according to the weight percentages: potassium silicate 2.2%, calcium stearate emulsion 0.32%, EVA emulsion 0.5%, PU emulsion 0.5% and water 6.33% based on 100% of the weight of the base material;

[0059] S2, cement and water are stirred and mixed uniformly to form mixture A; calcined phosphogypsum, potassium silicate, calcium stearate emulsion, EVA emulsion and PU emulsion are mixed and stirred uniformly to form mixture B; the mixture A, the mixture B, limestone and natural river sand are stirred and mixed uniformly to obtain the anti-cracking and water-resistant phosphogypsum road base material.

[0060] Example 3

[0061] An anti-cracking and water-resistant phosphogypsum road base material, comprising a base material and an additive, wherein the base material is composed of the following raw materials in percentage by weight: calcined phosphogypsum 20%, limestone 45%, natural river sand 30%, cement 5%; the additive is potassium silicate, calcium stearate emulsion, EVA emulsion, PU emulsion and water, and the mass ratio of the base material, potassium silicate, calcium stearate emulsion, EVA emulsion, PU emulsion and water is 100:2.2:0.32:0.25:0.75:6.33. The EVA emulsion is ethylene-vinyl acetate copolymer with a solid content of 40% and a pH value of 6.5. The PU emulsion is polyurethane emulsion with a solid content of 40% and a pH value of 8. The calcium stearate emulsion has a solid content of 40% and a pH value of 10.

[0062] The preparation method of the calcined phosphogypsum comprises the following steps: firstly, washing and filtering phosphogypsum, then calcining at a temperature of 150℃ for 1h, and naturally cooling and screening the calcined phosphogypsum after calcination to obtain the calcined phosphogypsum with a particle size of ≤0.3mm.

[0063] The particle size of the limestone is 4.75-19mm, the bulk density is 1637kg / m 3 , the crushing index is 9.5%, and the water absorption is 0.5%; the particle size of the natural river sand is 4.75-19mm, the bulk density is 1541kg / m 3 , the water absorption is 6.79%, and the water content is 2.4%; the natural river sand is in a continuous grading mode; the limestone and the natural river sand are in a continuous grading mode, and the composition mass ratio is that the percentage of the limestone with a particle size of 13-19mm is 15%, the percentage of the limestone with a particle size of 9-13mm is 13%, and the percentage of the limestone with a particle size of 4.75-13mm is 20%, as shown in Table 1; the composition mass ratio is that the percentage of the fine sand with a particle size of 0-1.18mm is 34%, the percentage of the medium sand with a particle size of 1.18-2.36mm is 7%, and the percentage of the coarse sand with a particle size of 1.18-4.75mm is 11%, as shown in Table 1.

[0064] The preparation method of the anti-cracking and water-resistant phosphogypsum road base material comprises the following steps:

[0065] S1, the base material components are weighed by percentage by weight: calcined phosphogypsum 20%, natural coarse aggregate 45%, natural river sand 30%, cement 5%; the components of the additive are weighed by percentage by weight based on 100% of the weight of the base material: potassium silicate 2.2%, calcium stearate emulsion 0.32%, EVA emulsion 0.25%, PU emulsion 0.75% and water 6.33%;

[0066] S2, the cement and water are stirred and mixed uniformly to form mixture A; the calcined phosphogypsum, potassium silicate, calcium stearate emulsion, EVA emulsion and PU emulsion are mixed and stirred uniformly and then left to stand to obtain mixture B; the mixture A, mixture B, natural coarse aggregate and natural fine aggregate are stirred and mixed uniformly to obtain the anti-cracking and water-resistant type phosphogypsum road base material.

[0067] Example 4

[0068] An anti-cracking and water-resistant type phosphogypsum road base material, comprising a base material and an additive, the base material is composed of raw materials in the following weight percentages: calcined phosphogypsum 20%, limestone 45%, natural river sand 30%, cement 5%; the additive is potassium silicate, calcium stearate emulsion, EVA emulsion, PU emulsion and water, and the mass ratio of the base material, potassium silicate, calcium stearate emulsion, EVA emulsion, PU emulsion and water is 100:2.2:0.32:2:1:6.33. The EVA emulsion is ethylene-vinyl acetate copolymer with a solid content of 40% and a pH value of 6.5. The PU emulsion is polyurethane emulsion with a solid content of 40% and a pH value of 8. The calcium stearate emulsion has a solid content of 40% and a pH value of 10.

[0069] The preparation method of the calcined phosphogypsum comprises the following steps: first, the phosphogypsum is washed and filtered with water, then calcined at a temperature of 150℃ for 1h, and after the calcination is completed, the calcined phosphogypsum is obtained by natural cooling and screening, and the particle size of the calcined phosphogypsum is ≤0.3mm.

[0070] The particle size of the limestone is 4.75-19mm, the bulk density is 1637kg / m 3 , the crushing index is 9.5%, and the water absorption rate is 0.5%; the particle size of the natural river sand is 4.75-19mm, the bulk density is 1541kg / m 3 , the water absorption rate is 6.79%, and the water content is 2.4%; the limestone and the natural river sand are in a continuous grading mode, and the composition mass ratio is that the percentage of limestone with a particle size of 13-19mm is 15%, the percentage of limestone with a particle size of 9-13mm is 13%, and the percentage of limestone with a particle size of 4.75-13mm is 20%, as shown in Table 1; the composition mass ratio is that the percentage of fine sand with a particle size of 0-1.18mm is 34%, the percentage of medium sand with a particle size of 1.18-2.36mm is 7%, and the percentage of coarse sand with a particle size of 1.18-4.75mm is 11%, as shown in Table 1.

[0071] A preparation method of a water-resistant and anti-cracking phosphogypsum road base material, comprising the following steps:

[0072] S1, each component of the base material is weighed by percentage: 20% of calcined phosphogypsum, 45% of limestone, 30% of natural river sand, and 5% of cement; the components of the additive are weighed by percentage based on 100% of the weight of the base material: 2.2% of potassium silicate, 0.32% of calcium stearate emulsion, 2% of EVA emulsion, 1% of PU emulsion, and 6.33% of water;

[0073] S2, the cement and water are stirred and mixed uniformly to form a mixture A; the calcined phosphogypsum, potassium silicate, calcium stearate emulsion, EVA emulsion, and PU emulsion are mixed and stirred uniformly and then left to stand to obtain a mixture B; the mixture A, the mixture B, the natural coarse aggregate, and the natural fine aggregate are stirred and mixed uniformly to obtain the water-resistant and anti-cracking phosphogypsum road base material.

[0074] Example 5

[0075] A water-resistant and anti-cracking phosphogypsum road base material, comprising a base material and an additive, wherein the base material is composed of the following raw materials by weight percentage: 20% of calcined phosphogypsum, 45% of limestone, 30% of natural river sand, and 5% of cement; the additive is potassium silicate, calcium stearate emulsion, EVA emulsion, PU emulsion, and water, and the mass ratio of the base material, potassium silicate, calcium stearate emulsion, EVA emulsion, PU emulsion, and water is 100:2.2:0.32:1:1:6.33. The EVA emulsion is an ethylene-vinyl acetate copolymer with a solid content of 40% and a pH value of 6.5. The PU emulsion is a polyurethane emulsion with a solid content of 40% and a pH value of 8. The calcium stearate emulsion has a solid content of 40% and a pH value of 10.

[0076] A preparation method of calcined phosphogypsum, comprising the following steps: first, washing and filtering phosphogypsum, then calcining at a temperature of 150℃ for 1h, and naturally cooling and sieving after calcination to obtain calcined phosphogypsum with a particle size of ≤0.3mm.

[0077] The particle size of the limestone is 4.75-19mm, the bulk density is 1637kg / m 3 , the crushing index is 9.5%, and the water absorption rate is 0.5%; the particle size of the natural river sand is 4.75-19mm, the bulk density is 1541kg / m 3, the water absorption is 6.79%, the moisture content is 2.4%; the limestone and the natural river sand are in a continuous grading mode, the limestone with a size of 13-19 mm accounts for 15%, the limestone with a size of 9-13 mm accounts for 13%, the limestone with a size of 4.75-13 mm accounts for 20%, as shown in Table 1; the fine sand with a size of 0-1.18 mm accounts for 34%, the medium sand with a size of 1.18-2.36 mm accounts for 7%, and the coarse sand with a size of 1.18-4.75 mm accounts for 11%, as shown in Table 1.

[0078] The preparation method of the anti-cracking and water-resistant phosphogypsum road base material comprises the following steps:

[0079] S1, the components of the base material are weighed according to the percentage by weight: calcined phosphogypsum 20%, limestone 45%, natural river sand 30%, cement 5%; the components of the additive are weighed according to the percentage by weight based on 100% of the weight of the base material: potassium silicate 2.2%, calcium stearate emulsion 0.32%, EVA emulsion 1%, PU emulsion 1% and water 6.33%;

[0080] S2, the cement and water are stirred and mixed uniformly to form a mixture A; the calcined phosphogypsum, potassium silicate, calcium stearate emulsion, EVA emulsion and PU emulsion are mixed and stirred uniformly and then left to stand to obtain a mixture B; the mixture A, the mixture B, the natural coarse aggregate and the natural fine aggregate are stirred and mixed uniformly to obtain the anti-cracking and water-resistant phosphogypsum road base material.

[0081] Example 6

[0082] An anti-cracking and water-resistant phosphogypsum road base material, comprising a base material and an additive, the base material is composed of raw materials in the following weight percentages: calcined phosphogypsum 20%, limestone 45%, natural river sand 30%, cement 5%; the additive is potassium silicate, calcium stearate emulsion, EVA emulsion, PU emulsion and water, and the mass ratio of the base material, potassium silicate, calcium stearate emulsion, EVA emulsion, PU emulsion and water is 100:2.2:0.32:1:2:6.33. The EVA emulsion is ethylene-vinyl acetate copolymer, the solid content of which is 40% and the pH value is 6.5. The PU emulsion is polyurethane emulsion, the solid content of which is 40% and the pH value is 8. The solid content of the calcium stearate emulsion is 40-40% and the pH value is 10.

[0083] The preparation method of the calcined phosphogypsum comprises the following steps: first, the phosphogypsum is washed and filtered, then calcined at a temperature of 150℃ for 1h, and the calcined phosphogypsum is obtained after natural cooling and screening, the particle size of the calcined phosphogypsum is ≤0.3mm.

[0084] The particle size of the limestone is 4.75-19mm, the bulk density is 1637kg / m 3The crushing index is 9.5%, and the water absorption rate is 0.5%; the particle size of the natural river sand is 4.75-19 mm, and the bulk density is 1541 kg / m³. 3 The water absorption rate is 6.79% and the moisture content is 2.4%. The limestone and natural river sand are continuously graded, with the following mass ratios: limestone (13-19 mm) accounts for 15%, limestone (9-13 mm) accounts for 13%, and limestone (4.75-13 mm) accounts for 20% (see Table 1); fine sand (0-1.18 mm) accounts for 34%, medium sand (1.18-2.36 mm) accounts for 7%, and coarse sand (1.18-4.75 mm) accounts for 11% (see Table 1).

[0085] A method for preparing crack-resistant and water-resistant phosphogypsum road base material includes the following steps:

[0086] S1. Weigh the following components of the base material by weight percentage: calcined phosphogypsum 20%, limestone 45%, natural river sand 30%, cement 5%; weigh the following components of the additives by weight percentage based on 100% of the base material: potassium silicate 2.2%, calcium stearate emulsion 0.32%, EVA emulsion 1%, PU emulsion 2%, and water 6.33%;

[0087] S2. Cement and water are mixed evenly to form mixture A; calcined phosphogypsum, potassium silicate, calcium stearate emulsion, EVA emulsion and PU emulsion are mixed evenly and left to stand to obtain mixture B; mixture A, mixture B, natural coarse aggregate and natural fine aggregate are mixed evenly to obtain crack-resistant and water-resistant phosphogypsum road base material.

[0088] Comparative Example 1

[0089] A cement-based road base material comprises the following raw materials in weight percentages: 57% natural coarse aggregate, 38% natural river sand, 5% cement, and 7.26% water.

[0090] The natural coarse aggregate has a particle size of 4.75–19 mm and a bulk density of 1637 kg / m³. 3 The crushing index is 9.5%, and the water absorption rate is 0.5%; the particle size of the natural fine aggregate is 4.75-19 mm, and the bulk density is 1541 kg / m³. 3 The water absorption rate is 6.79% and the moisture content is 2.4%. The limestone and natural river sand are continuously graded, with the following mass ratios: limestone (13-19 mm) accounts for 15%, limestone (9-13 mm) accounts for 13%, and limestone (4.75-13 mm) accounts for 20% (see Table 1); fine sand (0-1.18 mm) accounts for 34%, medium sand (1.18-2.36 mm) accounts for 7%, and coarse sand (1.18-4.75 mm) accounts for 11% (see Table 1).

[0091] The preparation method of the road base material comprises the following steps:

[0092] S1, each component is weighed according to the percentage by weight: limestone 57%, natural river sand 38%, cement 5%, and water 7.26%;

[0093] S2, the cement and water are stirred and mixed uniformly to form a mixture A; the mixture A, the limestone and the natural river sand are stirred uniformly to obtain the cement-based road base material.

[0094] Comparative Example 2

[0095] The cement-based stable phosphogypsum road base material comprises a base material and an additive, the base material is composed of raw materials in the following weight percentages: calcined phosphogypsum 20%, limestone 45%, natural river sand 30%, and cement 5%; the additive is water, and the mass ratio of the base material to water is 100:6.33.

[0096] The preparation method of the calcined phosphogypsum comprises the following steps: firstly, the phosphogypsum is washed and filtered with water, then calcined at a temperature of 150℃ for 1h, and the calcined phosphogypsum is obtained after natural cooling and screening, and the particle size of the calcined phosphogypsum is ≤0.3mm.

[0097] The particle size of the limestone is 4.75-19mm, the bulk density is 1637kg / m 3 , the crushing index is 9.5%, and the water absorption rate is 0.5%; the limestone is in a continuous grading mode; the particle size of the natural river sand is 4.75-19mm, the bulk density is 1541kg / m 3 , the water absorption rate is 6.79%, and the water content is 2.4%; the natural river sand is in a continuous grading mode, and the limestone and the natural river sand are in a continuous grading mode, and the composition mass ratio is that the percentage of the limestone with a particle size of 13-19mm is 15%, the percentage of the limestone with a particle size of 9-13mm is 13%, and the percentage of the limestone with a particle size of 4.75-13mm is 20%, as shown in Table 1; the composition mass ratio is that the percentage of the fine sand with a particle size of 0-1.18mm is 34%, the percentage of the medium sand with a particle size of 1.18-2.36mm is 7%, and the percentage of the coarse sand with a particle size of 1.18-4.75mm is 11%, as shown in Table 1.

[0098] The preparation method of the cement-based stable phosphogypsum road base material comprises the following steps:

[0099] S1, each component of the base material is weighed according to the percentage by weight: calcined phosphogypsum 20%, natural coarse aggregate 45%, natural river sand 30%, and cement 5%; 6.33% of water is weighed according to the percentage by weight based on 100% of the weight of the base material;

[0100] S2, cement and water are stirred and mixed uniformly to form a mixture A; the mixture A, calcined phosphogypsum, limestone, natural river sand are stirred and mixed uniformly to obtain a cement-based stabilized phosphogypsum road base material.

[0101] Comparative Example 3

[0102] A cementitious material stabilized phosphogypsum road base material, comprising a base material and an additive, the base material is composed of raw materials in the following weight percentages: calcined phosphogypsum 20%, limestone 45%, natural river sand 30%, cement 5%; the additive is potassium silicate, calcium stearate emulsion and water, and the mass ratio of the base material, potassium silicate, calcium stearate emulsion and water is 100:2.2:0.32:6.33. The EVA emulsion is ethylene-vinyl acetate copolymer with a solid content of 40% and a pH value of 6.5. The PU emulsion is polyurethane emulsion with a solid content of 40% and a pH value of 8. The preparation method of the calcined phosphogypsum comprises the following steps: first, the phosphogypsum is washed and filtered, then calcined at a temperature of 150℃ for 1h, and after calcination, the calcined phosphogypsum is obtained by natural cooling and screening, and the particle size of the calcined phosphogypsum is ≤0.3mm.

[0103] The particle size of the limestone is 4.75-19mm, the bulk density is 1637kg / m 3 , the crushing index is 9.5%, and the water absorption is 0.5%; the particle size of the natural river sand is 4.75-19mm, the bulk density is 1541kg / m 3 , the water absorption is 6.79%, and the moisture content is 2.4%; the limestone and the natural river sand are in a continuous grading mode, and the composition mass ratio is that the percentage of limestone with a particle size of 13-19mm is 15%, the percentage of limestone with a particle size of 9-13mm is 13%, and the percentage of limestone with a particle size of 4.75-13mm is 20%, as shown in Table 1; the composition mass ratio is that the percentage of fine sand with a particle size of 0-1.18mm is 34%, the percentage of medium sand with a particle size of 1.18-2.36mm is 7%, and the percentage of coarse sand with a particle size of 1.18-4.75mm is 11%, as shown in Table 1.

[0104] A preparation method of a cementitious material stabilized phosphogypsum road base material, comprising the following steps:

[0105] S1, the components of the base material are weighed according to the following weight percentages: calcined phosphogypsum 20%, limestone 45%, natural sand 30%, and cement 5%; the components of the additive are weighed according to the following weight percentages based on 100% of the weight of the base material: potassium silicate 2.2%, calcium stearate emulsion 0.32%, and water 6.33;

[0106] S2, cement and water are stirred and mixed uniformly to form mixture A; the calcined phosphogypsum, potassium silicate are stirred and mixed uniformly and then left to stand to obtain mixture B; the mixture A, the mixture B, natural coarse aggregate and natural fine aggregate are stirred and mixed uniformly to obtain the roadbed material of cemented phosphogypsum.

[0107] Comparative Example 4

[0108] A crack-resistant and water-resistant phosphogypsum roadbed material, which comprises a base material and an additive, wherein the base material is composed of the following raw materials in percentage by weight: calcined phosphogypsum 20%, limestone 45%, natural river sand 30%, cement 5%; the additive is potassium silicate, calcium stearate emulsion, EVA emulsion and water, and the mass ratio of the base material, potassium silicate, calcium stearate emulsion, EVA emulsion and water is 100:2.2:0.32:1:6.33. The EVA emulsion is ethylene-vinyl acetate copolymer, the solid content of which is 40% and the pH value is 6.5. The calcium stearate emulsion has a solid content of 40% and a pH value of 10.

[0109] The preparation method of the calcined phosphogypsum comprises the following steps: firstly, the phosphogypsum is washed and filtered with water, and then calcined at a temperature of 150℃ for 1h; after the calcination is completed, the calcined phosphogypsum is naturally cooled and sieved to obtain the calcined phosphogypsum, and the particle size of the calcined phosphogypsum is ≤0.3mm.

[0110] The particle size of the limestone is 4.75-19mm, the bulk density is 1637kg / m 3 , the crushing index is 9.5%, and the water absorption is 0.5%; the particle size of the natural river sand is 4.75-19mm, the bulk density is 1541kg / m 3 , the water absorption is 6.79%, and the water content is 2.4%; the limestone and the natural river sand are in a continuous grading mode, and the component mass ratio is that the percentage of the limestone with a particle size of 13-19mm is 15%, the percentage of the limestone with a particle size of 9-13mm is 13%, and the percentage of the limestone with a particle size of 4.75-13mm is 20%, as shown in Table 1; the component mass ratio is that the percentage of the fine sand with a particle size of 0-1.18mm is 34%, the percentage of the medium sand with a particle size of 1.18-2.36mm is 7%, and the percentage of the coarse sand with a particle size of 1.18-4.75mm is 11%, as shown in Table 1.

[0111] The preparation method of the crack-resistant and water-resistant phosphogypsum roadbed material comprises the following steps:

[0112] S1, the components of the base material are weighed according to the percentage by weight: calcined phosphogypsum 20%, limestone 45%, natural river sand 30%, and cement 5%; the components of the additive are weighed according to the percentage by weight based on 100% of the weight of the base material: potassium silicate 2.2%, calcium stearate emulsion 0.32%, EVA emulsion 1%, and water 6.33%;

[0113] S2, cement and water are stirred and mixed uniformly to form mixture A; calcined phosphogypsum, potassium silicate, calcium stearate emulsion, EVA emulsion are mixed and stirred uniformly to form mixture B; the mixture A, the mixture B, limestone and natural river sand are stirred and mixed uniformly to obtain the anti-cracking and water-resistant phosphogypsum road base material.

[0114] Comparative Example 5

[0115] An anti-cracking and water-resistant phosphogypsum road base material, comprising a base material and an additive, wherein the base material is composed of the following raw materials in percentage by weight: calcined phosphogypsum 20%, limestone 45%, natural river sand 30%, cement 5%; the additive is potassium silicate, calcium stearate emulsion, PU emulsion and water, and the mass ratio of the base material, potassium silicate, calcium stearate emulsion, PU emulsion and water is 100:2.2:0.32:1:6.33. The PU emulsion is polyurethane emulsion with solid content of 40% and pH value of 8. The calcium stearate emulsion has solid content of 40% and pH value of 10.

[0116] The preparation method of the calcined phosphogypsum comprises the following steps: firstly, washing and filtering phosphogypsum, then calcining at 150℃ for 1h, and naturally cooling and screening to obtain the calcined phosphogypsum with particle size ≤0.3mm.

[0117] The particle size of the limestone is 4.75-19mm, the bulk density is 1637kg / m 3 , the crushing index is 9.5%, and the water absorption is 0.5%; the limestone is in continuous gradation; the particle size of the natural river sand is 4.75-19mm, the bulk density is 1541kg / m 3 , the water absorption is 6.79%, and the water content is 2.4%; the natural river sand is in continuous gradation; the limestone and the natural river sand are in continuous gradation, and the mass ratio of the components is that the percentage of the limestone with particle size of 13-19mm is 15%, the percentage of the limestone with particle size of 9-13mm is 13%, and the percentage of the limestone with particle size of 4.75-13mm is 20%, as shown in Table 1; the percentage of the fine sand with particle size of 0-1.18mm is 34%, the percentage of the medium sand with particle size of 1.18-2.36mm is 7%, and the percentage of the coarse sand with particle size of 1.18-4.75mm is 11%, as shown in Table 1.

[0118] A preparation method of an anti-cracking and water-resistant phosphogypsum road base material, comprising the following steps:

[0119] S1, weighing the components of the base material in percentage by weight: calcined phosphogypsum 20%, limestone 45%, natural river sand 30%, cement 5%; weighing the components of the additive in percentage by weight based on 100% of the weight of the base material: potassium silicate 2.2%, PU emulsion 0.25% and water 6.33%;

[0120] S2. Cement and water are mixed evenly to form mixture A; calcined phosphogypsum, potassium silicate and PU emulsion are mixed and stirred evenly and left to stand to obtain mixture B; mixture A, mixture B, limestone and natural river sand are mixed evenly to obtain crack-resistant and water-resistant phosphogypsum road base material.

[0121] The road base materials obtained in Examples 1-6 and Comparative Examples 1-5 were subjected to the following performance tests, and the results are shown in Tables 2-5.

[0122] 1. Unconfined compressive strength test

[0123] It will be made by static pressing according to test procedure T 0843. The standard specimens, with a compaction degree >98%, are placed in a standard curing room (20℃±2, humidity >95%) and cured to the required age. On the last day of the curing period, the specimens are taken out and soaked in water at 20℃±2 for 24 hours. After removing them and wiping the surface moisture with a soft cloth, an unconfined compressive strength test is performed at a loading rate of 1 mm / min. Six parallel specimens are used, and their representative values ​​are taken.

[0124] 2. Dry and wet cycle test

[0125] According to ASTM D559, each set of specimens was immersed in a 20°C water bath for 1 day and dried in a 40°C oven for 1 day. The entire process was considered a complete wet-dry cycle. The wet-dry cycle test was terminated after 5 wet-dry cycles.

[0126] 3. Freeze-thaw cycle test

[0127] According to test procedure T 0858, each group of specimens was placed in a -18℃ low-temperature chamber for 16 hours, ensuring a gap of at least 20mm around the specimen to facilitate cold air circulation. After the freezing test, the specimens were immediately removed and placed in a 20℃ water bath for thawing for 8 hours. After thawing, a second freeze-thaw cycle was performed. The freeze-thaw cycle test was terminated after 5 freeze-thaw cycles.

[0128] 4. Drying Shrinkage Test

[0129] According to test procedure T 0854, a beam specimen was used. After curing for 7 days, a shrinkage test was conducted. The specimen was placed on a shrinkage apparatus, and the shrinkage deformation value was measured using a dial indicator. Three standard specimens were reserved for measuring the water loss rate. The shrinkage test was conducted daily for the first week, then every two days thereafter. After 30 days, the dial indicator readings were taken on the 40th, 60th, and 90th days. The moisture content of the specimen was determined at each reading.

[0130] Table 2 Unconfined compressive strength of base materials at 7d and 28d

[0131]

[0132]

[0133] Table 2 shows the 7-day and 28-day unconfined compressive strength of the phosphogypsum-containing base material. As shown in Table 2, compared to Examples 1-5, the 7-day unconfined compressive strength of the base material prepared in Comparative Example 3 is relatively weaker, while the 28-day strength of the base material prepared in Comparative Example 5 shows a significant improvement. This indicates that the EVA emulsion introduced in this invention has an inhibitory effect on early strength, while the PU emulsion is beneficial to the overall strength development of the base material. Examples 1-3 show that as the EVA emulsion content decreases and the PU emulsion content increases, the early mechanical strength of the base material does not decrease but instead shows an increasing trend. Its long-term strength significantly increases with the increase of the PU emulsion content. Examples 4-6 show that increasing the content of the two emulsions has no effect on the early strength of the base material, but the later strength is improved to a certain extent.

[0134] Table 3. Water stability coefficient of base materials

[0135]

[0136]

[0137] Table 3 shows the water stability coefficients of the phosphogypsum-containing base material. Examples 1-6 and Comparative Examples 1-5 show that appropriate amounts of EVA and PU emulsions significantly improve the water stability of the base material. Table 3 also shows that the strength of Examples 1-3 significantly increased after wet-dry cycling, with a substantial increase in their water stability coefficients, indicating strong overall water stability. The water stability coefficients of Examples 4-6 decreased, indicating that excessive amounts of EVA and PU emulsions did not significantly improve the water stability of the base material. The water stability coefficient was positively correlated with the independent use of EVA emulsion, while the effect of using PU emulsion alone was not significant. When both are used synergistically in appropriate amounts, the water stability performance of the base material is significantly enhanced; excessive use reduces the improvement. Therefore, appropriate amounts of EVA and PU emulsions have a certain effect on improving the water resistance of the phosphogypsum base material.

[0138] Table 4. Residual strength loss ratio of base materials after freeze-thaw cycles

[0139]

[0140] Table 4 is the residual strength loss ratio of the base material containing phosphogypsum after freeze-thaw cycle. As shown in Table 4, the residual strength loss ratio of Comparative Examples 4 and 5 is not significantly improved after 5 freeze-thaw cycles, which indicates that the use of EVA emulsion and PU emulsion alone has little effect on reducing the compressive strength loss of the gelled material stabilized phosphogypsum and pavement base material. As shown in Examples 1-6, the appropriate amount of EVA and PU emulsion can effectively improve the residual strength loss ratio, improve the frost resistance and reduce the problem of freeze-thaw cracking. As shown in Examples 1-6, the appropriate amount of EVA emulsion and PU emulsion can better play the anti-freezing performance of the base material and significantly improve the water resistance.

[0141] Table 5 total shrinkage and dry shrinkage coefficient

[0142] No. Total shrinkage (mm) coefficient of dry shrinkage (10 -6 )]]> Comparative Example 1 0.425 86.89 Comparative Example 2 0.397 81.33 Comparative Example 3 0.312 72.36 Comparative Example 4 0.267 57.46 Comparative Example 5 0.297 59.14 Example 1 0.233 52.77 Example 2 0.191 49.81 Example 3 0.261 56.33 Example 4 0.227 54.17 Example 5 0.187 49.13 Example 6 0.229 53.07

[0143] Note: 1. The total shrinkage is the average reading of the dial gauge; 2. The dry shrinkage coefficient is In the formula, α d is the dry shrinkage coefficient, ε i is the i-th dry shrinkage strain, is the i-th water loss rate.

[0144] The dry shrinkage coefficient represents the sensitivity of the material volume change to the water loss, which is essentially the sensitivity coefficient of the material to water. The greater the dry shrinkage coefficient of the material, the greater the sensitivity of the material to water, and the poorer the crack resistance. Table 5 is the total shrinkage and dry shrinkage coefficient of the dry shrinkage test. As shown in Table 5, the use of EVA emulsion and PU emulsion alone can reduce the shrinkage of the base material, and the effect of EVA emulsion is greater. As shown in Examples 1-6, the appropriate amount of EVA emulsion and PU emulsion can significantly reduce the shrinkage, but excessive use has no obvious effect on the anti-shrinkage performance of the base material. The addition of EVA emulsion and PU emulsion reduces the porosity and increases the content of small pores in the material, thereby reducing the shrinkage.

[0145] Example 7

[0146] A crack-resistant and water-resistant phosphogypsum road base material, comprising a base material and an additive, wherein the base material is composed of the following raw materials in weight percentage: calcined phosphogypsum 15%, limestone 47%, natural river sand 32%, cement 6%; the additive is potassium silicate, calcium stearate emulsion, EVA emulsion, PU emulsion and water, and the mass ratio of the base material, potassium silicate, calcium stearate emulsion, EVA emulsion, PU emulsion and water is 100:1:0.4:1:2:11. The EVA emulsion is ethylene-vinyl acetate copolymer with a solid content of 35% and a pH value of 6.5. The PU emulsion is polyurethane emulsion with a solid content of 40% and a pH value of 8. The solid content of the calcium stearate emulsion is 40% and the pH value is 10.

[0147] The preparation method of the calcined phosphogypsum comprises the following steps: firstly, the phosphogypsum is subjected to water washing and filtration, and then is subjected to calcination at a temperature of 150 DEG C for 1 h, and after the calcination is completed, the calcined phosphogypsum is obtained by natural cooling and screening, and the particle size of the calcined phosphogypsum is less than or equal to 0.3 mm.

[0148] The particle size of the limestone is 4.75-19 mm, the bulk density is 1637 kg / m 3 , the crushing index is 9.5%, and the water absorption is 0.5%; the particle size of the natural river sand is 4.75-19 mm, the bulk density is 1541 kg / m 3 , the water absorption is 6.79%, and the water content is 2.4%; the limestone and the natural river sand are in a continuous grading mode, and the component mass ratio of the limestone is that the percentage of the limestone with a particle size of 13-19 mm is 15%, the percentage of the limestone with a particle size of 9-13 mm is 13%, and the percentage of the limestone with a particle size of 4.75-13 mm is 20%, as shown in Table 1; the component mass ratio of the natural river sand is that the percentage of the fine sand with a particle size of 0-1.18 mm is 34%, the percentage of the medium sand with a particle size of 1.18-2.36 mm is 7%, and the percentage of the coarse sand with a particle size of 1.18-4.75 mm is 11%.

[0149] The preparation method of the anti-cracking and water-resistant phosphogypsum road base material comprises the following steps:

[0150] S1, the components of the base material are weighed according to the percentage by weight: 15% of the calcined phosphogypsum, 47% of the limestone, 32% of the natural river sand, and 6% of the cement; the components of the additive are weighed according to the percentage by weight based on 100% of the weight of the base material: 1% of potassium silicate, 0.4% of calcium stearate emulsion, 1% of EVA emulsion, 2% of PU emulsion, and 11% of water;

[0151] S2, the cement and the water are stirred and mixed uniformly to form a mixture A; the calcined phosphogypsum, the potassium silicate, the calcium stearate emulsion, the EVA emulsion, and the PU emulsion are mixed and stirred uniformly and then are left to stand to obtain a mixture B; the mixture A, the mixture B, the limestone, and the natural river sand are stirred and mixed uniformly to obtain the anti-cracking and water-resistant phosphogypsum road base material.

[0152] Experiments prove that the characterization data of the anti-cracking and water-resistant phosphogypsum road base material obtained in the embodiment have no substantial difference from those in Example 6.

[0153] Example 8

[0154] The anti-cracking water-resistant phosphogypsum road base material comprises a base material and an additive, the base material is composed of raw materials in the following weight percentages: calcined phosphogypsum 25%, limestone 43%, natural river sand 28%, cement 4%; the additive is potassium silicate, calcium stearate emulsion, EVA emulsion, PU emulsion and water, and the mass ratio of the base material, potassium silicate, calcium stearate emulsion, EVA emulsion, PU emulsion and water is 100:1.5:0.1:1:2:4. The EVA emulsion is ethylene-vinyl acetate copolymer, the solid content of which is 35%, and the pH value is 6.5. The PU emulsion is polyurethane emulsion, the solid content of which is 40%, and the pH value is 8. The solid content of the calcium stearate emulsion is 40%, and the pH value is 10.

[0155] The preparation method of the calcined phosphogypsum comprises the following steps: firstly, washing and filtering phosphogypsum, then calcining at a temperature of 150 DEG C for 1 h, and obtaining the calcined phosphogypsum after natural cooling and screening, the particle size of the calcined phosphogypsum is less than or equal to 0.3 mm.

[0156] The particle size of the limestone is 4.75-19 mm, the bulk density is 1637 kg / m 3 , the crushing index is 9.5%, and the water absorption is 0.5%; the particle size of the natural river sand is 4.75-19 mm, the bulk density is 1541 kg / m 3 , the water absorption is 6.79%, and the water content is 2.4%; the limestone and the natural river sand are in a continuous grading mode, and the component mass ratio is that the percentage of the limestone with a particle size of 13-19 mm is 15%, the percentage of the limestone with a particle size of 9-13 mm is 13%, the percentage of the limestone with a particle size of 4.75-13 mm is 20%, and the percentage of the fine sand with a particle size of 0-1.18 mm is 34%, the percentage of the medium sand with a particle size of 1.18-2.36 mm is 7%, and the percentage of the coarse sand with a particle size of 1.18-4.75 mm is 11%.

[0157] The preparation method of the anti-cracking water-resistant phosphogypsum road base material comprises the following steps:

[0158] S1, weighing the components of the base material according to the weight percentages: calcined phosphogypsum 25%, limestone 43%, natural river sand 28%, cement 4%; weighing the components of the additive according to the weight percentages: potassium silicate 1.5%, calcium stearate emulsion 0.1%, EVA emulsion 1%, PU emulsion 2% and water 4%, based on 100% of the weight of the base material;

[0159] S2, mixing and stirring the cement and water uniformly to form a mixture A; mixing and stirring the calcined phosphogypsum, potassium silicate, calcium stearate emulsion, EVA emulsion and PU emulsion uniformly and standing to obtain a mixture B; mixing and stirring the mixture A, the mixture B, the limestone and the natural river sand uniformly to obtain the anti-cracking water-resistant phosphogypsum road base material.

[0160] The experiment proves that the characterization data of the anti-cracking water-resistant phosphogypsum road base material obtained in the embodiment has no substantial difference with that of Example 6.

[0161] It should be noted that when the present application involves a numerical range, both endpoints of each numerical range and any number between the two endpoints can be selected. Since the same steps and examples are used, the preferred embodiments are described in the present application to prevent redundancy. Although the preferred embodiments of the present application have been described, those skilled in the art can make additional changes and modifications to the embodiments once they know the basic inventive concept. Therefore, the appended claims are intended to include the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0162] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application also intends to include these modifications and variations.

Claims

1. A crack-resistant and water-resistant phosphogypsum road base material, characterized in that, The product includes a base material and additives. The base material is composed of the following raw materials in weight percentages: 15-25% calcined phosphogypsum, 43-47% natural coarse aggregate, 28-32% natural fine aggregate, and 3-8% silicate cement. The additives are a composition of modifier, EVA emulsion, PU emulsion, and water, wherein the mass ratio of the base material, modifier, EVA emulsion, PU emulsion, and water is 100:1.1-2.6:0.25-2:0.25-2:4-11. The calcination temperature of the calcined phosphogypsum is 100-180℃. The modifier is a composition of potassium silicate and calcium stearate emulsion, wherein the mass ratio of potassium silicate to calcium stearate emulsion is 1.0~2.2:0.1~0.

4.

2. The crack-resistant and water-resistant phosphogypsum road base material according to claim 1, characterized in that, The EVA emulsion is an ethylene-vinyl acetate copolymer with a solid content of 30-50% and a pH value of 6.0-7.

0.

3. The crack-resistant and water-resistant phosphogypsum road base material according to claim 1, characterized in that, The PU emulsion is a polyurethane emulsion with a solid content of 30-50% and a pH value of 7.0-9.

0.

4. The crack-resistant and water-resistant phosphogypsum road base material according to claim 1, characterized in that, The calcium stearate emulsion has a solid content of 25-45% and a pH value of 8-11.

5. The crack-resistant and water-resistant phosphogypsum road base material according to claim 1, characterized in that, The preparation method of the calcined phosphogypsum includes the following steps: After washing the phosphogypsum with water, it is calcined. After calcination, it is cooled and pulverized to obtain calcined phosphogypsum with a particle size ≤0.3mm.

6. The crack-resistant and water-resistant phosphogypsum road base material according to claim 5, characterized in that, The calcination time is 1-2 hours.

7. The crack-resistant and water-resistant phosphogypsum road base material according to claim 1, characterized in that, The natural coarse aggregate is limestone with a particle size of 4.75~19mm and a bulk density of 1590~1781kg / m³. 3 The crushing index is 8-11%, and the water absorption rate is 0-1%; the natural fine aggregate is natural river sand with a particle size of 0-4.75 mm and a bulk density of 1517-1581 kg / m³. 3 It has a water absorption rate of 6-9% and a moisture content of 1.5-5%. The silicate cement is cement or a mixture of cement and mineral admixtures, wherein the mineral admixtures are one or more of fly ash, lime, and mineral powder.

8. The crack-resistant and water-resistant phosphogypsum road base material according to claim 7, characterized in that, The limestone and natural river sand are graded, wherein the mass ratio of limestone with a particle size of 13-19 mm, limestone with a particle size of 9-13 mm, limestone with a particle size of 4.75-13 mm, natural river sand with a particle size of 2.36-4.75 mm, natural river sand with a particle size of 1.18-2.36 mm, and natural river sand with a particle size of 0-1.18 mm is 15:13:20:11:7:

34.

9. A method for preparing the crack-resistant and water-resistant phosphogypsum road base material according to claim 1, characterized in that, Includes the following steps: Weigh each component by weight percentage; mix silicate cement and water evenly to form mixture A; mix calcined phosphogypsum, modifier, EVA emulsion and PU emulsion evenly and let stand to obtain mixture B; mix mixture A, mixture B, natural coarse aggregate and natural fine aggregate evenly to obtain crack-resistant and water-resistant phosphogypsum road base material.

Images