Method for preparing and curing ardealite cement stabilized macadam test piece matched with field construction

Abstract

The invention provides a preparation and curing method of an ardealite cement stabilized macadam test piece matched with site construction, and belongs to the technical field of traffic civil engineering. A test piece comprises the following components in percentage by mass: 2-4% of cement, 5-15% of phosphogypsum, 0.1-0.3% of super absorbent resin and 80-95% of aggregate gravel, a rotary compaction process is matched with field compaction energy for forming, the test piece is moved indoors for natural curing to a corresponding age, and additional humidification and moisture preservation measures are not needed. According to the test piece, the defects that in the traditional technology, test piece forming is disjointed with a site construction technology, and the water stability of phosphogypsum is insufficient due to high-humidity maintenance are effectively overcome, the unconfined compressive strength of the test piece cured to the seventh day is 5.8-6.2 MPa, the actual performance of a site material can be accurately reflected, the solid waste resource utilization value is achieved, and the test piece is suitable for road base construction quality control.

Description

TECHNICAL FIELD

[0002] The application belongs to the technical field of traffic civil engineering, and particularly relates to a phosphogypsum cement stabilized macadam test piece preparation and curing method matched with field construction. BACKGROUND

[0004] As an industrial by-product, phosphogypsum can be used to prepare cement stabilized macadam base materials to realize solid waste resource utilization and meet the green and environmentally-friendly development demand. However, the existing preparation and curing technology of phosphogypsum cement stabilized macadam test pieces matched with field construction has two key defects, which seriously restricts the engineering application guiding value.

[0005] Firstly, the existing test piece forming mostly adopts heavy compaction or static pressure process, while the field phosphogypsum cement stabilized macadam construction generally adopts rotary compaction equipment for paving and compaction. The mechanical action mode and energy transmission path of the two processes are significantly different, which leads to a large deviation of the core structural parameters such as density and porosity of the test piece from the field entity. The test data such as strength and durability based on the test piece cannot truly reflect the actual performance of the field material, and has very low reference value.

[0006] Secondly, phosphogypsum is an air-hardening cementitious material with poor water stability. When early hydration is incomplete, the un-solidified phosphogypsum will be seriously affected by water contact, which will affect the strength formation. The traditional curing needs to place the test piece in a high-humidity environment with a temperature of 20±2℃ and a relative humidity of ≥95%, which further increases the risk of phosphogypsum water contact, leading to the deviation of the strength development law from the field material, and making it difficult to accurately guide the engineering construction and quality control.

[0007] Therefore, it is urgent to develop a test piece preparation and curing method matched with the field construction process and coordinated with forming and curing, to realize the consistency of the test piece and the field entity material, and improve the reliability and engineering guiding value of the test data. SUMMARY

[0009] The application aims to overcome the above-mentioned deficiencies in the prior art, and provides a phosphogypsum cement stabilized macadam test piece matched with field construction and a self-curing method thereof, to solve the problem that the traditional phosphogypsum cement stabilized macadam test piece preparation method does not match the actual situation, and the traditional test piece curing method increases the risk of phosphogypsum water contact and affects the strength formation of the phosphogypsum cement stabilized macadam.

[0010] To achieve the above-mentioned purpose, the technical solutions adopted by the application are as follows:

[0011] A phosphogypsum cement stabilized macadam test piece suitable for field construction, comprising, in terms of mass fractions: cement 2-4%, phosphogypsum 5-15%, superabsorbent resin 0.1-0.3%, and aggregate macadam 80-95%.

[0012] Specifically, the superabsorbent resin is one of sodium acrylate-acrylamide copolymer or cross-linked sodium polyacrylate.

[0013] Specifically, the aggregate macadam is continuously graded macadam, and the particle size comprises 19-26.5 mm, 9.5-19 mm, 4.75-9.5 mm and 0-4.75 mm.

[0014] Another object of the present application is to provide a self-curing method of a phosphogypsum cement stabilized macadam test piece suitable for field construction, comprising the following steps:

[0015] S1, the cement, phosphogypsum, superabsorbent resin and aggregate macadam are respectively placed in a 105 DEG C oven, dried for 4-6 h to constant weight, and cooled to room temperature for standby, to obtain dried pretreated raw materials;

[0016] S2, the dried pretreated raw materials are weighed according to the mass fractions, and are uniformly dry-mixed in a mixer to obtain dry mixture m1;

[0017] S3, water with a mass of m1*0.01*w0 is added to the dry mixture m1, and is uniformly mixed to obtain wet mixture;

[0018] S4, the phosphogypsum cement stabilized macadam material is loaded into a test mold with an inner diameter of 150 mm and a height of 230 mm±10 mm in three layers by quartering method, and each layer is inserted and tamped along the test mold wall for not less than 10 times, and the total mass of the wet mixture satisfies the formula m=ρ dmax *V*K*(1+0.01*w0);

[0019] S5, through 3-5 groups of pretests, the target compaction times equivalent to the field compaction energy are determined, the test mold is fixed on a rotary compactor, and the wet mixture is compacted to a test piece height of 150 mm according to the target compaction times, and a cylindrical test piece is obtained by demolding;

[0020] S7, the demolded cylindrical test piece is moved and placed in a room for natural curing to a corresponding age, to obtain the phosphogypsum cement stabilized macadam test piece suitable for field construction.

[0021] Specifically, w0 in step S3 is the optimum water content of the phosphogypsum cement stabilized macadam material, which is determined by rotary compaction, and the value range is 6.0-6.8%, and preferably 6.3-6.5%.

[0022] Specifically, in step S4, the total mass of the wet mixture satisfies the formula m=ρ dmax ×V×K×(1+0.01×w0), where:

[0023] The ρ dmax The maximum dry density of the wet mixture is determined by rotary compaction, and its value ranges from 2.40 to 2.42 g / cm³. 3 The preferred value is 2.403~2.415 g / cm³. 3 ;

[0024] V represents the standard volume of the specimen, and the specimen volume V = πr²h = π × 7.5 2 ×15=2650.72cm 3 ;

[0025] K is a predetermined compaction degree consistent with the on-site construction, with a value range of 96-98%, preferably 97%.

[0026] Specifically, the phosphogypsum cement-stabilized crushed stone specimen is a cylinder with dimensions of 150mm × 150mm.

[0027] Specifically, the indoor natural maintenance process in step S7 does not require additional humidification or moisturizing measures.

[0028] Specifically, the unconfined compressive strength of the phosphogypsum cement-stabilized crushed stone specimens obtained in step S7 and adapted to on-site construction, after curing to the 7th day, is 5.8~6.2 MPa.

[0029] Specifically, the cement, phosphogypsum, superabsorbent resin and aggregate crushed stone all meet the requirements for cementitious materials in the "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering" JTGE51-2009.

[0030] Another objective of this invention is to provide a phosphogypsum cement-stabilized crushed stone specimen adapted to on-site construction, or a curing method for a phosphogypsum cement-stabilized crushed stone specimen adapted to on-site construction, and its application in the quality control of road base construction.

[0031] The beneficial effects of this invention are:

[0032] (1) The invention is adapted to on-site construction. The self-curing of phosphogypsum cement stabilized crushed stone specimens is efficient and reliable. It relies on the water retention properties of super absorbent resin to achieve natural self-curing indoors. No additional humidification and moisturizing measures are required. It avoids the defects of insufficient water stability of phosphogypsum caused by traditional high humidity curing. The curing process is simplified and highly compatible with the on-site curing environment.

[0033] (2) The phosphogypsum cement stabilized crushed stone specimen prepared by the present invention is highly compatible with the structure and performance of the on-site construction materials, and has significant compatibility. It can effectively solve the problem of the disconnect between traditional molding process and on-site construction, and can accurately reflect the real performance of on-site construction materials, providing a reliable quantitative basis for the quality control of road base construction.

[0034] (3) The mechanical properties of the phosphogypsum cement stabilized crushed stone adapted for on-site construction of the present invention meet the standards. The unconfined compressive strength after curing to the 7th day reaches 5.5~6.0MPa, which meets the strength requirements of the base course of high-grade highways and ensures the stability and durability of the engineering structure.

[0035] (4) The invention of the on-site construction-adapted phosphogypsum cement stabilized crushed stone specimen is green, environmentally friendly and economical. It makes resource utilization of industrial by-product phosphogypsum, reduces the pressure of solid waste disposal, simplifies the maintenance process, saves equipment and labor costs, and has both environmental and economic benefits. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the specific embodiments.

[0038] Example 1

[0039] A phosphogypsum cement-stabilized crushed stone specimen adapted for on-site construction, comprising, by mass parts, 195g of cement, 630g of phosphogypsum, 13g of superabsorbent resin and 5642g of aggregate crushed stone.

[0040] Cement is a commercial 42.5 type ordinary Portland cement made from limestone and clay as raw materials, which are mixed in a certain proportion, calcined in a vertical kiln similar to lime burning, and then ground into clinker.

[0041] The superabsorbent resin is a sodium acrylate-acrylamide copolymer.

[0042] Continuously graded aggregate is crushed stone obtained after crushing at a stone quarry, with particle sizes including 19-26.5mm, 9.5-19mm, 4.75-9.5mm and 0-4.75mm.

[0043] All raw materials meet the relevant requirements of the "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering" JTGE51-2009.

[0044] A self-curing method for phosphogypsum cement-stabilized crushed stone specimens adapted for on-site construction:

[0045] S1. Place cement, phosphogypsum, superabsorbent resin and aggregate crushed stone in an oven at 105℃ and dry for 4-6 hours until constant weight. Cool to room temperature for later use to obtain the dried pretreated raw materials.

[0046] S2. Weigh the dried pretreated raw materials according to the mass fractions, add 3% cement, 10% phosphogypsum, 0.2% superabsorbent resin and 86.8% aggregate crushed stone into the mixer and dry mix evenly to obtain 6500g of dry mixture.

[0047] S3. Add 6500 × 0.01 × w0 = 409.5 g of water to the obtained dry mixture m1, mix well to obtain a wet mixture; where w0 is the optimum moisture content of the phosphogypsum cement-stabilized crushed stone material, determined by rotary compaction, and is taken as 6.3%;

[0048] S4. The phosphogypsum cement-stabilized crushed stone material is divided into three layers using the quartering method and placed into a mold with an inner diameter of 150mm × a height of 230mm ± 10mm. Each layer is tamped along the mold wall at least 10 times. The total mass of the wet mixture satisfies the formula m = ρ dmax ×V×K×(1+0.01×w0)=6600g, where ρ dmax It is 2.415 g / cm³ 3 V is 2650.72cm 3 K is 97%;

[0049] S5. Determine the target compaction number equivalent to the on-site compaction energy through 3 to 5 sets of pre-tests, fix the mold on the rotary compactor, compact the wet mixture to a specimen height of 150mm according to the target compaction number, and demold to obtain a cylindrical specimen with a specification of 150mm×150mm.

[0050] S7. Demold the cylindrical specimens and place them indoors. Without additional humidification or moisturizing measures, allow them to cure naturally to the appropriate age to obtain the phosphogypsum cement-stabilized crushed stone specimens that are suitable for on-site construction.

[0051] Example 2

[0052] A phosphogypsum cement-stabilized crushed stone specimen adapted for on-site construction comprises, by mass parts, 195g of cement, 975g of phosphogypsum, 19.5g of superabsorbent resin and 5310.5g of aggregate crushed stone.

[0053] Cement is a commercial 42.5 type ordinary Portland cement made from limestone and clay as raw materials, which are mixed in a certain proportion, calcined into clinker in a vertical kiln similar to lime burning, and then ground.

[0054] The superabsorbent resin is cross-linked sodium polyacrylate.

[0055] Continuously graded aggregate is crushed stone obtained after crushing at a stone quarry, with particle sizes including 19-26.5mm, 9.5-19mm, 4.75-9.5mm and 0-4.75mm.

[0056] All raw materials meet the relevant requirements of the "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering" JTGE51-2009.

[0057] A self-curing method for phosphogypsum cement-stabilized crushed stone specimens adapted for on-site construction:

[0058] S1. Place cement, phosphogypsum, superabsorbent resin and aggregate crushed stone in an oven at 105℃ and dry for 4-6 hours until constant weight. Cool to room temperature for later use to obtain the dried pretreated raw materials.

[0059] S2. Weigh the dried pretreated raw materials according to the mass fractions mentioned above. Add 3% cement, 15% phosphogypsum, 0.3% superabsorbent resin and 81.7% aggregate crushed stone into a mixer and dry mix evenly to obtain 6500g of dry mixture.

[0060] S3. Add 6500 × 0.01 × w0 = 422.5 g of water to the obtained dry mixture m1, mix well to obtain a wet mixture; where w0 is the optimum moisture content of the phosphogypsum cement-stabilized crushed stone material, determined by rotary compaction, and is taken as 6.5%;

[0061] S4. The phosphogypsum cement-stabilized crushed stone material is divided into three layers using the quartering method and placed into a mold with an inner diameter of 150mm × a height of 230mm ± 10mm. Each layer is tamped along the mold wall at least 10 times. The total mass of the wet mixture satisfies the formula m = ρ dmax ×V×K×(1+0.01×w0)=6580g, where ρ dmax It is 2.403 g / cm³ 3 V is 2650.72cm 3 K is 97%;

[0062] S5. Determine the target compaction number equivalent to the on-site compaction energy through 3 to 5 sets of pre-tests, fix the mold on the rotary compactor, compact the wet mixture to a specimen height of 150mm according to the target compaction number, and demold to obtain a cylindrical specimen with a specification of 150mm×150mm.

[0063] S7. Demold the cylindrical specimens and place them indoors. Without additional humidification or moisturizing measures, allow them to cure naturally to the appropriate age to obtain the phosphogypsum cement-stabilized crushed stone specimens that are suitable for on-site construction.

[0064] Comparative Example 1

[0065] The difference from Example 1 is that the molding method is heavy compaction, as detailed below:

[0066] A phosphogypsum cement-stabilized crushed stone specimen adapted for on-site construction, comprising, by mass parts, 195g of cement, 630g of phosphogypsum, 13g of superabsorbent resin and 5642g of aggregate crushed stone.

[0067] Cement is a commercial 42.5 type ordinary Portland cement made from limestone and clay as raw materials, which are mixed in a certain proportion, calcined in a vertical kiln similar to lime burning, and then ground into clinker.

[0068] The superabsorbent resin is a sodium acrylate-acrylamide copolymer.

[0069] Continuously graded aggregate is crushed stone obtained after crushing at a stone quarry, with particle sizes including 19-26.5mm, 9.5-19mm, 4.75-9.5mm and 0-4.75mm.

[0070] All raw materials meet the relevant requirements of the "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering" JTGE51-2009.

[0071] A self-curing method for phosphogypsum cement-stabilized crushed stone specimens adapted for on-site construction:

[0072] S1. Place cement, phosphogypsum, superabsorbent resin and aggregate crushed stone in an oven at 105℃ and dry for 4-6 hours until constant weight. Cool to room temperature for later use to obtain the dried pretreated raw materials.

[0073] S2. Weigh the dried pretreated raw materials according to the mass fractions, add 3% cement, 10% phosphogypsum, 0.2% superabsorbent resin and 86.8% aggregate crushed stone into the mixer and dry mix evenly to obtain 6500g of dry mixture.

[0074] S3. Add 6500 × 0.01 × w0 = 409.5 g of water to the obtained dry mixture m1, mix well to obtain a wet mixture; where w0 is the optimum moisture content of the phosphogypsum cement-stabilized crushed stone material, determined by heavy compaction, and is taken as 7.3%;

[0075] S4. The phosphogypsum cement-stabilized crushed stone material is divided into three layers using the quartering method and placed into a mold with an inner diameter of 150mm × a height of 230mm ± 10mm. Each layer is tamped along the mold wall at least 10 times. The total mass of the wet mixture satisfies the formula m = ρ dmax ×V×K×(1+0.01×w0)=6544g, where ρ dmax It is 2.372 g / cm³ 3 V is 2650.72cm 3 K is 97%;

[0076] S5. Perform heavy compaction molding according to the method T0804-1994 in the "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering" JTGE51-2009. Compact the wet mixture to a specimen height of 150mm, and demold to obtain a cylindrical specimen with a specification of 150mm×150mm.

[0077] S7. Demold the cylindrical specimens and place them indoors. Without additional humidification or moisturizing measures, allow them to cure naturally to the appropriate age to obtain the phosphogypsum cement-stabilized crushed stone specimens that are suitable for on-site construction.

[0078] Comparative Example 2

[0079] The difference from Example 1 is that it does not contain superabsorbent resin and uses high-humidity curing, as detailed below:

[0080] A phosphogypsum cement-stabilized crushed stone specimen adapted for on-site construction, comprising, by mass parts, 195g of cement, 630g of phosphogypsum, and 5642g of aggregate crushed stone.

[0081] Cement is a commercial 42.5 type ordinary Portland cement made from limestone and clay as raw materials, which are mixed in a certain proportion, calcined in a vertical kiln similar to lime burning, and then ground into clinker.

[0082] The superabsorbent resin is a sodium acrylate-acrylamide copolymer.

[0083] Continuously graded aggregate is crushed stone obtained after crushing at a stone quarry, with particle sizes including 19-26.5mm, 9.5-19mm, 4.75-9.5mm and 0-4.75mm.

[0084] All raw materials meet the relevant requirements of the "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering" JTGE51-2009.

[0085] A self-curing method for phosphogypsum cement-stabilized crushed stone specimens adapted for on-site construction:

[0086] S1. Place cement, phosphogypsum, superabsorbent resin and aggregate crushed stone in an oven at 105℃ and dry for 4-6 hours until constant weight. Cool to room temperature for later use to obtain the dried pretreated raw materials.

[0087] S2. Weigh the dried pretreated raw materials according to the mass fractions, and put the cement, phosphogypsum and aggregate into the mixer and dry mix evenly to obtain 6467g of dry mixture.

[0088] S3. Add water with a mass of 6467 × 0.01 × w0 = 407.4 g to the obtained dry mixture m1, mix evenly to obtain a wet mixture; where w0 is the optimum moisture content of the phosphogypsum cement-stabilized crushed stone material, determined by rotary compaction, and is taken as 6.3%;

[0089] S4. The phosphogypsum cement-stabilized crushed stone material is divided into three layers using the quartering method and placed into a mold with an inner diameter of 150mm × a height of 230mm ± 10mm. Each layer is tamped along the mold wall at least 10 times. The total mass of the wet mixture satisfies the formula m = ρ dmax ×V×K×(1+0.01×w0)=6467g, where ρ dmax It is 2.366 g / cm³ 3 V is 2650.72cm 3 K is 97%;

[0090] S5. Determine the target compaction number equivalent to the on-site compaction energy through 3 to 5 sets of pre-tests, fix the mold on the rotary compactor, compact the wet mixture to a specimen height of 150mm according to the target compaction number, and demold to obtain a cylindrical specimen with a specification of 150mm×150mm.

[0091] S7. The cylindrical specimens obtained by demolding are placed indoors and cured with high humidity, with the temperature controlled at 20±2℃ and the relative humidity at ≥95%, until the corresponding age is reached, thus obtaining the phosphogypsum cement stabilized crushed stone specimens that are suitable for on-site construction.

[0092] Experimental Example 1

[0093] Physical performance compatibility verification experiment:

[0094] 1. Test subjects: Dry mixtures prepared in Example 1, Comparative Example 1, and Comparative Example 2 before compaction.

[0095] 2. Test methods: (1) Optimal moisture content and maximum dry density: Example 1, Example 2 and Comparative Example 2 adopted the rotary compaction method provided in Example 1, and Comparative Example 1 adopted the heavy compaction method of JTGE51-2009 T0804; (2) On-site benchmarking: Select a construction section of a high-grade highway, measure the moisture content of the mixture to be compacted on-site, measure the dry density of the solid after on-site compaction using the core drilling method, and measure the moisture content of the mixture to be compacted on-site at the same time, and use this as the benchmark for suitability evaluation.

[0096] 3. Evaluation index: Deviation rate between laboratory test parameters and field measured parameters:

[0097]

[0098] 4. The test results are shown in the table below:

[0099]

[0100] The test results show that the optimal moisture content of Example 1 deviates from the measured value by only 1.6%, and the maximum dry density deviates from the measured value by only 0.6%, which is highly consistent with the state of the materials on site. However, Comparative Example 1, due to the use of heavy compaction, has an optimal moisture content deviation of 17.7%, resulting in excessive moisture in the mixture and a disconnect from the actual conditions. Comparative Example 2, lacking superabsorbent resin, has a lower maximum dry density and insufficient compaction, failing to match the actual structural state on site. This demonstrates that the present invention, by determining parameters through rotary compaction and combining the synergistic effect of the superabsorbent resin formulation, minimizes the deviation between the physical parameters of the specimen and the measured values ​​on site, achieving a high degree of compatibility with the state of the materials on site and solving the problem of disconnection between parameters in traditional molding processes.

[0101] Experiment Example 2

[0102] Mechanical performance compliance verification experiment:

[0103] 1. Test subjects: Phosphogypsum-based stabilized crushed stone specimens obtained from Example 1, Comparative Example 1 and Comparative Example 2 after curing for 7 days.

[0104] 2. Test method: The test procedure is based on the "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering" JTGE51-2009.

[0105] 3. Evaluation criteria: According to the specifications for the base course of high-grade highways, the unconfined compressive strength is ≥4.0MPa, the splitting tensile strength is ≥0.6MPa, and the coefficient of variation is ≤15%.

[0106] 4. Compressive strength is shown in the table below:

[0107]

[0108] The test results above show that Comparative Example 1, due to the disconnect between the molding process and the actual site conditions, cannot reflect the true performance of the material on site; Comparative Example 2, due to the absence of superabsorbent resin and the use of high-humidity curing, suffers from impaired water stability of phosphogypsum and has the lowest strength. This proves that the mechanical properties of the phosphogypsum cement-stabilized crushed stone specimens provided by this invention, which are compatible with on-site construction, far exceed the specifications and are superior to traditional solutions. The specimens have stable strength and can effectively ensure the stability and durability of the base structure of high-grade highways.

[0109] Experimental Example 3

[0110] Water stability verification experiment of phosphogypsum

[0111] 1. Test subjects: Phosphogypsum-based stabilized crushed stone obtained from Example 1, Comparative Example 1, and Comparative Example 2 after curing for 7 days.

[0112] 2. Testing Method:

[0113] (1) Content of unhydrated phosphogypsum: The proportion of CaSO4·2H2O in the test specimen was detected by X-ray diffraction (XRD);

[0114] (2) Strength loss rate: The strength loss rate was calculated by comparing the high-humidity curing specimen of Comparative Example 2 with the naturally curing specimen of Example 1;

[0115] (3) Appearance: Observe whether the surface of the specimen is sandy, cracked, or softened.

[0116] 3. The experimental results are shown in the table below:

[0117]

[0118] The test results above show that Example 1, due to the use of natural curing and superabsorbent resin, achieved sufficient hydration of phosphogypsum, with only 8.2% being unhydrated, resulting in no strength loss and a good appearance. Comparative Example 1, although using natural curing, suffered from excessive moisture due to the molding process, leading to 12.5% ​​unhydrated phosphogypsum and slight sanding. Comparative Example 2, lacking superabsorbent resin and using high-humidity curing, ensured sufficient contact between the phosphogypsum and water, resulting in 18.7% unhydrated phosphogypsum, a strength loss of 29.3%, and cracking and softening. This demonstrates that the present invention, through the synergistic design of superabsorbent resin water retention and natural curing, effectively avoids the defect of insufficient water stability in phosphogypsum, ensuring the performance of the specimens.

[0119] Experiment Example 4

[0120] Gradation stability and field adaptability verification experiment

[0121] 1. Phosphogypsum-based stabilized crushed stone specimens obtained by curing for 7 days in Example 1 and Comparative Example 1; phosphogypsum-based stabilized crushed stone specimens obtained by curing for 7 days in Example 1, Comparative Example 1, and Comparative Example 2, and on-site solid core samples.

[0122] 2. Testing Methods

[0123] (1) Grading stability: The breakage rate of key sieve openings of 4.75 mm, 9.5 mm and 19 mm was measured;

[0124] (2) Field adaptability: The mechanical properties of the example and comparative specimens are compared with the performance of the field core sample (150mm×150mm), and the similarity is calculated.

[0125] 3. Evaluation indicators:

[0126] (1) Crushing rate = Pass rate after molding - Pass rate of original gradation;

[0127] (2) Similarity = .

[0128] 4. The test results are shown in the table below:

[0129] (1) Results of gradation stability:

[0130]

[0131] (2) Results of field adaptability

[0132]

[0133] The test results show that in the gradation stability test, the breakage rate of the key sieve openings in Example 1 was ≤3.9%, indicating a low degree of aggregate breakage and a gradation closer to that of the actual construction. In Comparative Example 1, due to the impact of heavy compaction, the breakage rate of the 19mm sieve openings reached 14.1%, indicating severe gradation damage. In the field compatibility test, the performance similarity between Example 1 and the field core sample exceeded 100%, accurately replicating the actual performance of the field material. The similarity between Comparative Example 1 and Comparative Example 2 was only 71.9% and 80.0%, respectively, failing to reflect the actual field conditions. This demonstrates that the present invention, through rotary compaction molding process, reduces the damage to the gradation caused by aggregate breakage, making the performance of the specimen highly consistent with the actual field entity, providing a reliable basis for quality control of road base construction.

[0134] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0135] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. Technical details not described in detail in this invention can all be implemented using any existing technology in the art. In particular, all technical features not described in detail in this invention can be implemented using any existing technology.

Claims

1. A phosphogypsum cement stabilized macadam test specimen adapted to field construction, characterized in that, According to the mass fraction, it comprises: cement 2-4%, phosphogypsum 5-15%, super absorbent resin 0.1-0.3%, and aggregate gravel 80-95%.

2. The phosphogypsum cement stabilized macadam test piece adapted to the site construction according to claim 1, characterized in that, The super absorbent resin is one of sodium acrylate-acrylamide copolymer or cross-linked sodium polyacrylate.

3. The phosphogypsum cement stabilized macadam test piece adapted to the site construction according to claim 1, characterized in that, The aggregate gravel is continuously graded gravel, and the particle size comprises 19-26.5 mm, 9.5-19 mm, 4.75-9.5 mm, and 0-4.75 mm.

4. An autogenous method of stabilizing a test specimen of phosphogypsum cement-bound aggregate adapted to site construction according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: S1, the cement, phosphogypsum, super absorbent resin and aggregate gravel are respectively placed in a 105℃ oven, dried for 4-6h to constant weight, and cooled to room temperature for standby, to obtain the dried pretreated raw materials; S2, the dried pretreated raw materials are weighed according to the mass fraction, and are put into a mixer for dry mixing to obtain a dry mixture m1; S3, water with a mass of m1×0.01×w0 is added to the dry mixture m1, and is mixed uniformly to obtain a wet mixture; S4, the phosphogypsum cement stabilized macadam material is loaded into a test mold with an inner diameter of 150 mm and a height of 230 mm ± 10 mm in three layers by quartering method, each layer is inserted and tamped along the test mold wall not less than 10 times, and the total mass of the wet mixture meets the formula m = p dmax × V × K × (1 + 0.01 × w0); S5, through 3-5 groups of pre-tests, the target compaction times equivalent to the field compaction energy are determined, the test mold is fixed on a rotary compactor, and the wet mixture is compacted to a test piece height of 150mm according to the target compaction times, and a cylindrical test piece is obtained by demolding; S7, the demolded cylindrical test piece is moved to a room for natural curing to the corresponding age to obtain the phosphogypsum cement stabilized gravel test piece adapted to the field construction.

5. An autogenous method of curing a phosphogypsum cement stabilized aggregate test specimen adapted for field construction according to claim 4, wherein, In the step S3, w0 is the optimum moisture content of the phosphogypsum cement stabilized gravel material, which is determined by rotary compaction, and the value range is 6.0-6.8%, preferably 6.3-6.5%.

6. An autogenous method of stabilizing a phosphogypsum cemented aggregate test specimen adapted for field construction according to claim 4, wherein, The total mass of the wet mixture in the step S4 satisfies the formula m=ρ dmax ×V×K×(1+0.01×w0), wherein: The ρ dmax The maximum dry density of the wet mixture is 2.40-2.42 g / cm 3 , preferably 2.403-2.415 g / cm 3 ; The V is the standard volume of the test piece, the volume of the test piece V = πr 2 h = π x 7.5 2 x 15 = 2650.72 cm 3 ; K is a predetermined compaction degree consistent with the field construction, and the value range is 96-98%, preferably 97%.

7. A phosphogypsum cement stabilized aggregate test specimen adapted for field construction according to any one of claims 4, characterized in that, The phosphogypsum cement stabilized gravel test piece has a specification of a cylindrical body with a size of 150mm×150mm.

8. A method of autogenous curing of phosphogypsum cement stabilized aggregate test specimens adapted for field construction according to claim 4, characterized in that, In the step S7, the process of indoor natural curing does not require additional humidification or moisturizing measures.

9. A method of autogenous curing of phosphogypsum cement stabilized aggregate test specimens adapted for field construction according to claim 4, characterized in that, The unconfined compressive strength of the phosphogypsum cement stabilized gravel test piece adapted to the field construction obtained in the step S7 is 5.8-6.2MPa at the 7th day.

10. Application of the phosphogypsum cement stabilized gravel test piece adapted to the field construction according to any one of claims 1-3, or the curing method according to any one of claims 4-9 in the quality control of road base construction.

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