Preparation method of harmless semi-hydrated phosphogypsum road base stabilizing material

Abstract

The application provides a preparation method of harmless semi-hydrated phosphogypsum road base stabilizing material, which takes semi-hydrated phosphogypsum generated in a semi-hydrated wet-process phosphoric acid process as raw material, modifies the semi-hydrated phosphogypsum once by using limestone powder or high-calcium fly ash, modifies the semi-hydrated phosphogypsum again by using quicklime after aging once, and uses the semi-hydrated phosphogypsum aged twice as road base stabilizing material, which forms the harmless semi-hydrated phosphogypsum road base stabilizing material after forced stirring, compaction and curing once. The harmless semi-hydrated phosphogypsum is realized by twice modification and twice aging, the performances of the prepared stabilizing material meet the requirements of most road base application scenes, and the harmful components of the leaching solution of the semi-hydrated phosphogypsum stabilizing material under rainwater scouring in the road base application do not exceed the requirements of relevant environmental protection standards, and the semi-hydrated phosphogypsum stabilizing material is pollution-free to the environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of road material applications, in particular to a harmless semi-hydrated phosphogypsum road base stabilizing material preparation method. BACKGROUND

[0002] Phosphogypsum is an industrial by-product of the wet-process phosphoric acid leaching process. For every ton of phosphoric acid produced, 4-6 tons of phosphogypsum will be generated. In 2021, China's phosphogypsum production was about 80 million tons, with a resource comprehensive utilization rate of 45.6%. Phosphogypsum stockpiling occupies a large amount of land resources. Harmful ingredients and heavy metal ions remain in phosphogypsum that have not been harmlessly treated, which may penetrate into the soil and groundwater through weathering and rainwater erosion, causing vegetation death, soil pollution, planting function degradation, and groundwater pollution, etc.; it is one of the factors that limit the sustainable development of phosphorus chemical industry, so it is necessary to strengthen the management and comprehensive utilization of phosphogypsum.

[0003] Current wet-process phosphoric acid production processes can be divided into semi-hydrated method, dihydrated method, and semi-hydrated-dihydrated method, etc. Phosphogypsum produced by different production processes has different compositions. The main component of phosphogypsum produced by semi-hydrated wet-process phosphoric acid process is CaSO4·1 / 2H2O (hereinafter referred to as "semi-hydrated phosphogypsum"), the main component of phosphogypsum produced by dihydrated wet-process phosphoric acid process is CaSO4·2H2O (hereinafter referred to as "dihydrated phosphogypsum"), and the phosphogypsum produced by semi-hydrated-dihydrated wet-process phosphoric acid process is a mixture of semi-hydrated phosphogypsum and dihydrated phosphogypsum. Due to the advantages of low energy consumption, high phosphoric acid concentration, etc., semi-hydrated wet-process is the development trend of future phosphoric acid production.

[0004] Road engineering construction, the cushion and base structure between the soil base and the pavement surface layer is about 50-100 cm thick, which requires a large amount of construction materials; using semi-hydrated phosphogypsum to prepare road base stabilizing materials can absorb large amounts of semi-hydrated wet-process phosphogypsum and fully utilize the air-hardening properties of semi-hydrated phosphogypsum.

[0005] Currently, there are only a few technologies developed for the application of hemihydrate phosphogypsum, such as CN 106915941 B discloses a method for preparing mine filling material using hemihydrate phosphogypsum, the method uses industrial by-product hemihydrate phosphogypsum, phosphorus tailings and cement as raw materials, and prepares the mine filling material by mixing the raw materials in a certain proportion, which uses hemihydrate phosphogypsum as cementing material, cement adjusts the pH value of the filling material, and provides part of the strength, and the phosphorus tailings are used as aggregate to prepare the mine filling material with high early strength, good bleeding property and good fluidity. CN 103771820A discloses a fresh hemihydrate phosphogypsum lime-fly ash pavement base material capable of improving the unconfined compressive strength of pavement foundation, the pavement base material is prepared from fresh hemihydrate phosphogypsum 20-80%, quicklime 3-10% and red or brown fly ash 10-75% by weight, the raw materials used in the method are mainly industrial by-products, which are used as road materials, not only can the hemihydrate phosphogypsum which is difficult to utilize can be utilized, but also can save land for storage, reduce cost, be beneficial to natural resource and environmental protection, and the construction process is simple and reliable, and is suitable for the construction of base and bottom base of general road and high-grade highway.

[0006] At present, there are few studies on the resource utilization of hemihydrate phosphogypsum for developing its air hardening performance, and the development of road base stabilizing material capable of large-scale consumption of hemihydrate phosphogypsum has important significance, with the core indexes of stable storage of raw materials, convenient construction, no pollution to environment and meeting the design performance indexes of products. SUMMARY

[0007] The present application provides a harmless hemihydrate phosphogypsum road base stabilizing material preparation method.

[0008] The present application provides a harmless hemihydrate phosphogypsum road base stabilizing material preparation method.

[0009] (1) first modification: the first modifier is added to the hemihydrate phosphogypsum for mixing, the amount of the first modifier is able to ensure that the pH value of the mixture leaching solution after the first modification is between 5.0-6.0. Since the pH value of the hemihydrate phosphogypsum leaching solution is about 3.0 when the hemihydrate phosphogypsum is not modified, there are a large amount of harmful substances, through the first modification, the pH value of the mixture leaching solution is controlled between 5.0-6.0, the mixture is aged while keeping stable, and no crystal transformation, caking and the like occur.(2) first aging: the mixture after the first modification is aged for 5-10 days. After the mixture after the first modification is aged for 5-10 days, the change amount of the hemihydrate phosphogypsum crystal water content in the mixture will exceed 0.5%, at this time, the crystal transformation time is accelerated, and caking and hardening are easy, so the first aging time is 5-10 days, and then the second modification is immediately performed.(3) second modification: the quicklime is added to the mixture after the first aging for mixing, the amount of the quicklime is able to ensure that the pH value of the mixture leaching solution after the second modification is between 8.0-9.0;(4) second aging: the mixture after the second modification is aged for 1-2 days. The second aging is mainly to solidify the harmful components.(5) forced stirring: water is added to the mixture after the second aging, so that the attached water content in the mixture after the second aging is between 16%-17%, and the forced stirring machine is used for mixing, and the mixing time is not less than 10 min. In the forced stirring process, the attached water content in the mixture after the second aging is ensured to be between 16%-17% through online detection.(6) compaction: the mechanical compaction method is used for construction forming, and the compaction coefficient is not less than 0.94;(7) curing: after the construction is completed, the film and the geotextile are used for covering and sealing, and the curing time is not less than 7 days, and the harmless hemihydrate phosphogypsum road base stable material is obtained. In the application, the hemihydrate phosphogypsum is the hemihydrate phosphogypsum generated in the hemihydrate wet-process phosphoric acid process.

[0010] Preferably, the first modifier is limestone powder, and the calcium carbonate content in the limestone powder is not less than 75%.

[0011] Preferably, the first modifier is high-calcium fly ash, and the calcium oxide content in the high-calcium fly ash is not less than 15%.

[0012] Preferably, the attached water content in the hemihydrate phosphogypsum is not higher than 17%.

[0013] Preferably, the calcium oxide content in the quicklime is not less than 75%.

[0014] Preferably, the first modifier is a mixture of high-calcium fly ash and limestone powder.

[0015] Preferably, in the primary modification, the primary modifier is added to the hemihydrate phosphogypsum in batches for mixing, and the pH value of the leaching liquid of the mixture after the primary modification is ensured to be between 5.0 and 6.0 through online detection. Due to the complex nature of the hemihydrate phosphogypsum, there may be uniformity problems, and through the batch addition of the primary modifier and the online detection of the pH value of the leaching liquid after the primary modification, the pH value of the leaching liquid of the mixture after the primary modification can be better controlled to be between 5.0 and 6.0.

[0016] Preferably, in the secondary modification, the quicklime is added to the mixture after the primary aging in batches, and the pH value of the leaching liquid of the mixture after the secondary modification is ensured to be between 8.0 and 9.0 through online detection. Due to the complex nature of the hemihydrate phosphogypsum, there may be uniformity problems, and through the batch addition of the quicklime and the online detection of the pH value of the leaching liquid after the secondary modification, the pH value of the leaching liquid of the mixture after the secondary modification can be better controlled to be between 8.0 and 9.0.

[0017] The beneficial effects of the present application are: (1) The resource utilization rate of the hemihydrate phosphogypsum is high, and the hemihydrate phosphogypsum is harmlessly treated through two modifications and two aging processes, which ensures that the harmful components in the leaching liquid of the hemihydrate phosphogypsum stable material under adverse conditions such as rainwater scouring in road base use do not exceed the requirements of relevant environmental protection standards, and there is no pollution to the environment. (2) By controlling the water content attached to the hemihydrate phosphogypsum and the pH value of the primary modification, the stable storage demand of the hemihydrate phosphogypsum can be realized, and the crystal transformation of the hemihydrate phosphogypsum during the primary aging storage period is controlled. (3) By using the primary modification method of the present application, the reaction rate of the hemihydrate phosphogypsum with water is limited within 5-10 days of the primary aging, the proportion of the hemihydrate phosphogypsum converted into dihydrate phosphogypsum can be controlled within 15%, and the phenomena such as caking during storage which are not conducive to application are effectively solved, at the same time, the air hardening performance of the hemihydrate phosphogypsum is effectively preserved and utilized, which greatly improves the performance indicators of the prepared road base stable material. (4) The 7-day unconfined compressive strength of the harmlessly treated hemihydrate phosphogypsum road base stable material prepared by the present application can reach 5.0 MPa at the highest, the strength has no loss after 4 times of dry-wet cycles, and the mass loss rate is not higher than 5%, and each performance meets the demand of most road base application scenarios. (5) Through online detection of the water content attached to the hemihydrate phosphogypsum and the pH value of the hemihydrate phosphogypsum after modification, the usage amount of the primary modifier and quicklime can be more accurately controlled to cope with the problems of poor uniformity of the hemihydrate phosphogypsum and real-time adjustment of the harmlessness process parameters. (6) The process of the present application is simple and feasible, the production cost is low, the resource utilization of the hemihydrate phosphogypsum can be realized on a large scale, and it has good environmental, economic and social benefits. DETAILED DESCRIPTION

[0018] The specific embodiments of the present application are described in detail below, but it should be understood that the protection scope of the present application is not limited by the specific embodiments.

[0019] Example 1

[0020] A preparation method of the harmless semi-hydrated phosphogypsum road base stabilizing material, comprising the following steps: (1) primary modification: adding a primary modifier into the semi-hydrated phosphogypsum for fully mixing, the adding amount of the primary modifier being able to ensure that the pH value of the leaching liquid of the mixture after the primary modification is 5.8; (2) primary aging: aging the mixture after the primary modification for 8 days; (3) secondary modification: adding quicklime into the mixture after the primary aging for fully mixing, the adding amount of the quicklime being able to ensure that the pH value of the leaching liquid of the mixture after the secondary modification is 8.5; (4) secondary aging: aging the mixture after the secondary modification for 2 days; (5) forced stirring: adding water into the mixture obtained after the secondary aging, so that the attached water content in the mixture obtained after the secondary aging is 16%, and using a forced stirrer for fully mixing, the mixing time being 10 min; (6) compaction: adopting a mechanical compaction method for construction forming, the compaction coefficient being 0.94; (7) curing: after the construction is completed, adopting a film and geotextile for covering and closed curing for 7 days, so that the harmless semi-hydrated phosphogypsum road base stabilizing material is obtained.

[0021] In the embodiment, the semi-hydrated phosphogypsum is the semi-hydrated phosphogypsum generated in a semi-hydrated wet-process phosphoric acid process, the semi-hydrated phosphogypsum is 70 parts, the primary modifier is 26 parts, and the quicklime is 3 parts in terms of weight fraction; the primary modifier is limestone powder, the calcium carbonate content in the limestone powder is 75%, and the calcium oxide content in the quicklime is 80%; and the attached water content in the semi-hydrated phosphogypsum is 17%.

[0022] Example 2

[0023] A preparation method of the harmless semi-hydrated phosphogypsum road base stabilizing material, comprising the following steps: (1) primary modification: adding a primary modifier into the semi-hydrated phosphogypsum for fully mixing, the adding amount of the primary modifier being able to ensure that the pH value of the leaching liquid of the mixture after the primary modification is 6.0; (2) primary aging: aging the mixture after the primary modification for 8 days; (3) secondary modification: adding quicklime into the mixture after the primary aging for fully mixing, the adding amount of the quicklime being able to ensure that the pH value of the leaching liquid of the mixture after the secondary modification is 8.0; (4) secondary aging: aging the mixture after the secondary modification for 2 days; (5) forced stirring: adding water into the mixture obtained after the secondary aging, so that the attached water content in the mixture obtained after the secondary aging is 17%, and using a forced stirrer for fully mixing, the mixing time being 12 min; (6) compaction: adopting a mechanical compaction method for construction forming, the compaction coefficient being 0.95; (7) curing: after the construction is completed, adopting a film and geotextile for covering and closed curing for 8 days, so that the harmless semi-hydrated phosphogypsum road base stabilizing material is obtained.

[0024] In the embodiment, the hemihydrate phosphogypsum is hemihydrate phosphogypsum produced in a hemihydrate wet-process phosphoric acid process, and the hemihydrate phosphogypsum is 76 parts, the primary modifier is 20 parts, and the quicklime is 4 parts; the primary modifier is a mixture of limestone powder and high-calcium fly ash, wherein the limestone powder is 16 parts, and the high-calcium fly ash is 4 parts; the content of calcium carbonate in the limestone powder is 75%, and the content of calcium oxide in the high-calcium fly ash is 16.2%; the content of calcium oxide in the quicklime is 80%. The content of attached water in the hemihydrate phosphogypsum is 16.5%.

[0025] Example 3

[0026] A preparation method of a harmless hemihydrate phosphogypsum road base stabilizing material, comprising the following steps: (1) primary modification: a primary modifier is added to hemihydrate phosphogypsum for sufficient mixing, and the addition amount of the primary modifier can ensure that the pH value of the leaching liquid of the mixture after primary modification is 5.0; (2) primary aging: the mixture after primary modification is aged for 5 days; (3) secondary modification: quicklime is added to the mixture after primary aging for sufficient mixing, and the addition amount of the quicklime can ensure that the pH value of the leaching liquid of the mixture after secondary modification is 9.0; (4) secondary aging: the mixture after secondary modification is aged for 1 day; (5) forced stirring: water is added to the mixture obtained after secondary aging, so that the content of attached water in the mixture obtained after secondary aging is 16.5%, and a forced stirrer is used for sufficient mixing, and the mixing time is 12 min; (6) compaction: a mechanical compaction method is used for construction and molding, and the compaction coefficient is 0.95; (7) curing: after construction, a film and a geotextile are used for closed curing for 8 days, to obtain the harmless hemihydrate phosphogypsum road base stabilizing material.

[0027] In the embodiment, the hemihydrate phosphogypsum is hemihydrate phosphogypsum produced in a hemihydrate wet-process phosphoric acid process, and the hemihydrate phosphogypsum is 76 parts, the primary modifier is 20 parts, and the quicklime is 4 parts; the primary modifier is a mixture of limestone powder and high-calcium fly ash, wherein the limestone powder is 16 parts, and the high-calcium fly ash is 4 parts; the content of calcium carbonate in the limestone powder is 75%, and the content of calcium oxide in the high-calcium fly ash is 16.2%; the content of calcium oxide in the quicklime is 80%. The content of attached water in the hemihydrate phosphogypsum is 16.5%.

[0028] Example 4

[0029] A preparation method of a harmless semi-hydrated phosphogypsum road base stabilizing material, comprising the following steps: (1) primary modification: adding a primary modifier to the semi-hydrated phosphogypsum for sufficient mixing, the amount of the primary modifier being able to ensure that the pH value of the leaching liquid of the mixture after the primary modification is 5.2; (2) primary aging: aging the mixture after the primary modification for 10 days; (3) secondary modification: adding lime to the mixture after the primary aging for sufficient mixing, the amount of the lime being able to ensure that the pH value of the leaching liquid of the mixture after the secondary modification is 8.7; (4) secondary aging: aging the mixture after the secondary modification for 1.5 days; (5) forced stirring: adding water to the mixture obtained after the secondary aging so that the attached water content in the mixture obtained after the secondary aging is 16.8%, and using a forced stirrer for sufficient mixing, the mixing time being 12 min; (6) compaction: using a mechanical compaction method for construction and molding, the compaction coefficient being 0.95; (7) curing: after the construction is completed, using a film and geotextile to cover and seal for curing for 10 days, thereby obtaining the harmless semi-hydrated phosphogypsum road base stabilizing material.

[0030] In the embodiment, the semi-hydrated phosphogypsum is semi-hydrated phosphogypsum generated in a semi-hydrated wet-process phosphoric acid process, the semi-hydrated phosphogypsum being 80 parts, the primary modifier being 11 parts, and the lime being 4.5 parts in terms of weight fraction; the primary modifier is high-calcium fly ash, the content of calcium oxide in the high-calcium fly ash being 15.5%; the content of calcium oxide in the lime being 80%. The attached water content in the semi-hydrated phosphogypsum is 16.5%.

[0031] Embodiment 5

[0032] A preparation method of a harmless semi-hydrated phosphogypsum road base stabilizing material, comprising the following steps: (1) primary modification: adding a primary modifier to the semi-hydrated phosphogypsum for sufficient mixing, the amount of the primary modifier being able to ensure that the pH value of the leaching liquid of the mixture after the primary modification is 5.8; (2) primary aging: aging the mixture after the primary modification for 7 days; (3) secondary modification: adding lime to the mixture after the primary aging for sufficient mixing, the amount of the lime being able to ensure that the pH value of the leaching liquid of the mixture after the secondary modification is 8.4; (4) secondary aging: aging the mixture after the secondary modification for 1.5 days; (5) forced stirring: adding water to the mixture obtained after the secondary aging so that the attached water content in the mixture obtained after the secondary aging is 16%, and using a forced stirrer for sufficient mixing, the mixing time being 13 min; (6) compaction: using a mechanical compaction method for construction and molding, the compaction coefficient being 0.96; (7) curing: after the construction is completed, using a film and geotextile to cover and seal for curing for 8 days, thereby obtaining the harmless semi-hydrated phosphogypsum road base stabilizing material.

[0033] In this embodiment, the hemihydrate phosphogypsum is hemihydrate phosphogypsum produced in a hemihydrate wet-process phosphoric acid process, and the hemihydrate phosphogypsum 82 parts, the primary modifier 15 parts, and the quicklime 2.5 parts are used according to the weight parts. The primary modifier is high-calcium fly ash, and the content of calcium oxide in the high-calcium fly ash is 20%. The content of calcium oxide in the quicklime is 85%. The content of attached water in the hemihydrate phosphogypsum is 16.3%.

[0034] Example 6:

[0035] A preparation method of a harmless hemihydrate phosphogypsum road base stabilizing material includes the following steps: (1) primary modification: a primary modifier is added to hemihydrate phosphogypsum twice for sufficient mixing, and in the mixing process, online detection is performed to ensure that the amount of the primary modifier added can make the pH value of the leaching liquid of the mixture after primary modification be 5.6; (2) primary aging: the mixture after primary modification is aged for 7 days; (3) secondary modification: quicklime is added to the mixture after primary aging twice for sufficient mixing, and in the mixing process, online detection is performed to ensure that the amount of the quicklime added can make the pH value of the leaching liquid of the mixture after secondary modification be 8.6; (4) secondary aging: the mixture after secondary modification is aged for 1.5 days; (5) forced stirring: water is added to the mixture obtained after secondary aging to make the content of attached water in the mixture obtained after secondary aging be 17%, and a forced stirrer is used for sufficient mixing, and the mixing time is 13 min; (6) compaction: a mechanical compaction method is used for construction and molding, and the compaction coefficient is 0.94; (7) curing: after the construction is completed, a film and a geotextile are used for closed curing for 7 days, and the harmless hemihydrate phosphogypsum road base stabilizing material is obtained.

[0036] In this embodiment, the hemihydrate phosphogypsum is hemihydrate phosphogypsum produced in a hemihydrate wet-process phosphoric acid process, and the hemihydrate phosphogypsum 84 parts, the primary modifier 16 parts, and the quicklime 4.5 parts are used according to the weight parts. The primary modifier is a mixture of limestone powder and high-calcium fly ash, the content of the limestone powder is 4.5 parts, the content of calcium carbonate in the limestone powder is 80%, the content of the high-calcium fly ash is 11.5 parts, and the content of calcium oxide in the high-calcium fly ash is 20%. The content of calcium oxide in the quicklime is 80%. The content of attached water in the hemihydrate phosphogypsum is 16%.

[0037] According to the Highway Asphalt Pavement Design Specification (JTG D50-2017), combined with the hardening characteristics of semi-hydrated gypsum and the requirements of environmental protection, the CBR value, CBR water swelling amount, 7d unconfined compressive strength, 28d strength after 4 times of dry-wet cycles after curing, mass loss rate, and harmful ingredient content of the leaching liquid of the stabilized material of each embodiment were detected, and the detection method was as follows: 1. The CBR value and CBR water swelling amount of the stabilized material were detected according to the Highway Soil Test Rules (JTG3430-2020). 2. The 7d unconfined compressive strength of the stabilized material was detected according to the Highway Engineering Inorganic Binder Stabilized Material Test Rules (JTG E51-2009). 3. The test piece was formed according to the Highway Engineering Inorganic Binder Stabilized Material Test Rules (JTG E51-2009), the test piece was cured for 28 days, then soaked in water for 24h, and then placed in a 40℃ oven for 24h, the above process was one dry-wet cycle, and the above cycle was repeated 4 times, the unconfined compressive strength and the mass of the test piece were tested, and the strength loss and the mass loss rate were calculated; the strength loss rate = (P0-P) / P0; in the formula: P0 is the strength before dry-wet cycle, and P is the strength after 4 times of dry-wet cycle; the mass loss rate = (M0-M) / M0; in the formula: M0 is the strength before dry-wet cycle, and M is the strength after 4 times of dry-wet cycle. 4. The sample for detecting the 28d unconfined compressive strength was used to prepare the leaching liquid by the Solid Waste Leaching Toxicity Leaching Method Horizontal Oscillation Method (HJ 557-2010). The concentrations of total phosphorus, fluoride and various heavy metals in the leaching liquid were detected, and the standard requirements of the Surface Water Environmental Quality Standard (GB 3838-2002) were detected. The detection results of the related properties of the stabilized materials of examples 1-6 are shown in the following table.

[0038] Table 1 Detection results of related properties of stabilized materials obtained in examples 1-6

[0039]

[0040] Note: The strength loss rate (%) after 4 times of dry-wet cycles after 28d curing is negative, that is, under the dry-wet cycle conditions detected in the application, the harmless semi-hydrated gypsum road base stabilized material has no strength loss and shows different degrees of increase.

Claims

1. A method for preparing a harmless hemihydrate phosphogypsum road base stabilizing material, characterized in that, The process includes the following steps: (1) Primary modification: The primary modifier is added to the hemihydrate phosphogypsum and mixed thoroughly. The amount of primary modifier added is sufficient to ensure that the pH value of the leachate of the mixture after primary modification is between 5.0 and 6.

0. The primary modifier is high-calcium fly ash, and the calcium oxide content in the high-calcium fly ash is not less than 15%. (2) Primary aging: The mixture after primary modification is aged for 5-10 days. (3) Secondary modification: Quicklime is added to the mixture after primary aging and mixed thoroughly. The amount of quicklime added is sufficient to ensure that the pH value of the leachate of the mixture after secondary modification is between 5.0 and 6.

0. 8.0-9.0; (4) Secondary aging: Aging the mixture after secondary modification for 1-2 days; (5) Forced mixing: Add water to the mixture obtained after secondary aging so that the water content in the mixture obtained after secondary aging is between 16%-17%, and use a forced mixer to mix thoroughly for a mixing time of not less than 10 minutes; (6) Compaction: Use mechanical compaction method to form the material, and the compaction coefficient is not less than 0.94; (7) Curing: After the construction is completed, cover and seal the material with film and geotextile for a curing time of not less than 7 days to obtain harmless hemihydrate phosphogypsum road base stabilization material.

2. The preparation method of a harmless hemihydrate phosphogypsum road base stabilizing material according to claim 1, characterized in that, The water content in the hemihydrate phosphogypsum is no higher than 17%.

3. The preparation method of a harmless hemihydrate phosphogypsum road base stabilizing material according to claim 1, characterized in that, The quicklime contains no less than 75% calcium oxide.

4. The method for preparing a harmless hemihydrate phosphogypsum road base stabilizing material according to claim 1, wherein in the primary modification, the primary modifier is added to the hemihydrate phosphogypsum in several batches for mixing, and the pH value of the leachate of the mixture after primary modification is ensured to be between 5.0 and 6.0 by online detection.

5. The method for preparing a harmless hemihydrate phosphogypsum road base stabilizing material according to claim 1, wherein in the secondary modification, quicklime is added to the mixture after primary aging in stages, and the pH value of the leachate of the mixture after secondary modification is ensured to be between 8.0 and 9.0 by online detection.

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