Preparation method of retarded cement stabilized macadam and paving method of base layer of retarded cement stabilized macadam

Abstract

The invention relates to the technical field of cement stabilized macadam, and provides a preparation method of retarded cement stabilized macadam, which comprises the following steps: mixing and stirring cement, ardealite, epoxy methylsiloxane, polyacrylamide and graded stone according to the weight ratio of (4-6): (5-10): (1-3): (2-3): (77-88) to obtain a dry material; adding 3-7 parts by weight of water into the dry material, and stirring to obtain the retarded cement stabilized macadam; the base layer paving method comprises the following steps: construction preparation; blending the retarded cement stabilized macadam; transporting the retarded cement stabilized macadam; paving a delayed coagulation cement stabilized macadam base layer; compacting the delayed coagulation stabilized macadam base layer; performing joint treatment; after continuous pressing is completed, emulsified asphalt can be directly sprayed for curing, geotechnical cloth can also be adopted for covering and watering for curing, and the curing time is not less than 7 days. The invention has the advantages of green industrial waste and high added value utilization, and can shorten the construction period of the pavement base layer and guarantee the integrity of the structural layer, thereby prolonging the service life of the pavement and reducing the maintenance cost.

Description

Technical Field

[0001] The invention relates to the technical field of cement stabilized gravel, and in particular to a preparation method of slow-setting cement stabilized gravel and a method for paving a base layer thereof. Background Art

[0002] Cement-stabilized crushed stone is widely used in the base construction of asphalt pavement and cement pavement in my country due to its advantages in bearing capacity, durability, stability and economy. For high-grade highways such as expressways, first-class highways and second-class highways, in order to ensure the bearing capacity and durability of the pavement structure, a thicker cement-stabilized crushed stone base is often designed, and its thickness can reach 30~40 cm or 45~60 cm. Traditionally, for thicker cement-stabilized crushed stone bases, my country has adopted a layered construction process, dividing the base into two or three layers for construction, and the compaction thickness of each layer is controlled within the range of 15~20 cm. After the cement-stabilized crushed stone is prepared, transported, paved and compacted in the factory, it is then heat-insulated and moisturized for 7 days. Only after it has the initial strength can the construction and curing of the next layer of cement-stabilized crushed stone be carried out; thus, the construction and curing are repeated until the designed thickness is reached. Therefore, the layered construction process has the disadvantages of long construction period and consumption of construction machinery and manpower; and because the layered construction interface is the weak surface of the pavement structure, it is easy to cause interlayer sliding, which has a negative impact on the service life of the pavement.

[0003] The "layered paving, layered compaction, and one-time maintenance" process, that is, the three-layer continuous paving construction process, has the advantages of saving the lower layer curing time, reducing costs and avoiding weak interfaces in the base layer. However, this solution requires the use of cement with a long initial setting time to prepare cement-stabilized gravel. The ordinary cement-stabilized gravel materials currently used do not have the conditions for the implementation of three-layer continuous paving due to their short initial setting time.

[0004] Therefore, in view of the above problems, a method for preparing slow-setting cement-stabilized crushed stone and a method for paving the base layer thereof are proposed to solve the above problems. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention develops a method for preparing slow-setting cement stabilized gravel and a method for paving a base layer thereof. The present invention provides a method for preparing slow-setting cement stabilized gravel, and forms a method for paving a slow-setting cement stabilized gravel base layer accordingly. The present invention has the advantages of green and high value-added utilization of industrial waste, and can shorten the construction period of the road base layer, ensure the integrity of the structural layer, thereby extending the life of the road surface and reducing the maintenance cost.

[0006] The technical solution of the present invention to solve the technical problem is: the present invention provides a method for preparing slow-setting cement-stabilized crushed stone, comprising the following steps: (1) Cement, phosphogypsum, epoxymethylsiloxane, polyacrylamide and graded stone are mixed and stirred in a weight ratio of 4-6 parts: 5-10 parts: 1-3 parts: 2-3 parts: 77-88 parts to obtain a dry material; (2) Add 3 to 7 parts by weight of water to the dry material in step (1) and stir to obtain slow-setting cement-stabilized gravel.

[0007] As an optimization, the cement in step (1) is ordinary Portland cement, slag Portland cement or pozzolanic Portland cement, and the strength grade of the cement is 32.5 or 42.5.

[0008] As an optimization, the phosphogypsum in step (1) is phosphogypsum powder treated by a water washing method.

[0009] A method for paving a base of slow-setting cement-stabilized crushed stone prepared by any of the preparation methods described above, comprising the following steps: S1. Construction preparation; S2, slow setting cement stabilized gravel mixing; S3, slow setting cement stabilized gravel transportation; S4. Spread the slow-setting cement-stabilized gravel base; S5. Compact the slow-setting stable gravel base; S6, seam treatment; S7. After continuous compaction, you can directly spread emulsified asphalt for curing, or you can use geotextile to cover and sprinkle water for curing.

[0010] As an optimization, in S1, construction measurement is carried out, and side piles are measured and placed on the lower bearing layer to control the elevation; the surface of the lower bearing layer is cleaned and watered before paving.

[0011] As an optimization, in S3, dump trucks are used to transport the slow-setting cement-stabilized gravel mixture, and the slow-setting cement-stabilized gravel mixture is covered with tarpaulins.

[0012] As an optimization, in S4, the slow-setting cement-stabilized gravel mixture is fully prepared before paving. The transporter drives to 20-30 cm in front of the paver, and the paver pushes the transporter to unload and pave. The paving speed is 1.5-2 m / min. During the paving process, the paving thickness needs to be checked at 3 locations every 10 m and recorded.

[0013] As an optimization, in S5, compaction includes three stages: initial compaction, repeated compaction and final compaction. Each stage follows the principle of "light first, heavy later, slow first, fast later, from bottom to high", and is rolled successively in the order of construction. The length of each rolling is controlled at 50-80 m, overlapping 1 / 2 wheel width; when the roller is rolling, the rolling sections are clearly layered and trapezoidal in shape, and obvious boundary marks are set. At the same time, the water content of the slow-setting cement-stabilized gravel mixture is adjusted and controlled in time.

[0014] As an optimization, in S6, for the transverse joints, a seam cutter is used to cut the seams; after cutting, the debris is promptly removed and wiped clean with a wet cloth; for the longitudinal joints, a roller is used to roll them.

[0015] The effects provided in the summary of the invention are only the effects of the embodiments, rather than all the effects of the invention. The above technical solution has the following advantages or beneficial effects: The solid waste phosphogypsum produced in the wet phosphoric acid process is used as a retarder for cement-stabilized gravel after being washed with water to remove harmful impurities. A method for preparing retarded cement-stabilized gravel is proposed, and a three-layer continuous paving construction process for a retarded cement-stabilized gravel base is formed accordingly. The present invention has the advantages of green and high value-added utilization of industrial waste, and can shorten the construction period of the road base and ensure the integrity of the structural layer, thereby extending the life of the road surface and reducing the maintenance cost. DETAILED DESCRIPTION

[0016] In order to clearly illustrate the technical features of this solution, the present invention is described in detail below through specific implementation methods. The disclosure below provides many different embodiments or examples to implement different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described below. In addition, the present invention may repeat reference numbers and / or letters in different examples. This repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed.

[0017] A method for preparing slow-setting cement-stabilized crushed stone comprises the following steps: (1) Cement, phosphogypsum, epoxymethylsiloxane, polyacrylamide and graded stone are mixed and stirred in a weight ratio of 4-6 parts: 5-10 parts: 1-3 parts: 2-3 parts: 76-85 parts to obtain a dry material; (2) Add 3 to 7 parts by weight of water to the dry material in step (1) and stir to obtain slow-setting cement-stabilized gravel.

[0018] In step (1), the cement is ordinary Portland cement, slag Portland cement or pozzolanic Portland cement, and the strength grade of the cement is 32.5 or 42.5.

[0019] The phosphogypsum in step (1) is phosphogypsum powder treated by a water washing method.

[0020] The slow setting mechanism of cement stabilized crushed stone is: (1) Using phosphogypsum, a solid waste generated in the production of phosphoric acid, as a retarder for retarded cement to stabilize crushed stone; (2) The phosphogypsum is pre-washed to remove impurities such as phosphorus, fluorine and metallic elements, and then dried in an oven at 40-60°C before use to avoid the negative impact of impurities on the strength of cement-stabilized gravel.

[0021] Table 1 Changes in the composition of phosphogypsum before and after washing and drying (3) Using gypsum (CaSO 4 ) and calcium aluminate (3CaO·Al 2 O 3 ) undergoes hydration reaction to generate hydrated calcium sulphoaluminate (3CaO·Al 2 O 3 ·3CaSO 4 ·(30~32)H 2 O, namely ettringite); in the preparation process of slow-setting cement stabilized gravel, adding epoxymethylsiloxane is helpful for the formation of cement particles; and the surface of silicate cement is prone to form a porous structure, and the addition of epoxymethylsiloxane helps ettringite to adhere to the surface of cement particles, fill the pores, and hinder the contact between cement and water; after polyacrylamide is mixed with cement, it is conducive to the formation of cement-coated stone particles, and maintains the evaporation rate of water in cement, combined with epoxymethylsiloxane, so as to achieve the purpose of slow setting.

[0022] The quality and specifications of slow-setting cement-stabilized crushed stone comply with the requirements of the Technical Specifications for Highway Pavement Base Construction (JTG / T F20-2015), and the gradation design is carried out according to the gradation range in Table 2: Table 2 Grading range of slow-setting cement stabilized crushed stone Example 1: Preparation of slow-setting cement-stabilized crushed stone a Graded stone, 77 parts; C32.5 ordinary Portland cement, 4 parts; phosphogypsum, 5 parts; epoxymethylsiloxane: 3 parts; polyacrylamide: 3 parts; mix and stir evenly to obtain dry material, add 3 parts of water, stir evenly, and obtain slow-setting cement stabilized gravel a.

[0023] Example 2: Preparation of slow-setting cement-stabilized crushed stone b 84 parts of graded stone; 5 parts of C32.5 ordinary Portland cement; 6.5 parts of phosphogypsum; 2 parts of epoxymethylsiloxane; 2 parts of polyacrylamide; mix and stir evenly to obtain dry material, add 4.5 parts of water, stir evenly to obtain slow-setting cement-stabilized gravel b.

[0024] Example 3: Preparation of slow-setting cement-stabilized crushed stone c 85.3 parts of graded stone; 4.5 parts of C32.5 slag silicate cement; 6 parts of phosphogypsum; 1 part of epoxymethylsiloxane; 2 parts of polyacrylamide; mix and stir evenly to obtain dry material, add 4.2 parts of water, stir evenly to obtain slow-setting cement-stabilized gravel b.

[0025] Example 4: Preparation of slow-setting cement-stabilized crushed stone d 88 parts of graded stone; 6 parts of C32.5 slag silicate cement; 10 parts of phosphogypsum; 1 part of epoxymethylsiloxane; 3 parts of polyacrylamide; mix and stir evenly to obtain dry material, add 7 parts of water, stir evenly to obtain slow-setting cement-stabilized gravel b.

[0026] The aggregate gradations of Examples 1-4 are shown in Table 3. Table 3 Aggregate gradation of Examples 1-4 Comparative Example 1: The difference from Example 1 is that this comparative example does not contain phosphogypsum, epoxymethylsiloxane and polyacrylamide.

[0027] Comparative Example 2: The difference from Example 2 is that this comparative example does not contain phosphogypsum.

[0028] Comparative Example 3: The difference from Example 3 is that this comparative example does not contain epoxymethylsiloxane.

[0029] Comparative Example 4: The difference from Example 4 is that this comparative example does not contain polyacrylamide.

[0030] Comparative Example 5: The difference from Example 1 is that the phosphogypsum in this comparative example is not treated by water washing.

[0031] The 7d unconfined compressive strength test method of the slow-setting cement stabilized crushed stone prepared in Test Examples 1-4 and Comparative Examples 1-5 refers to the "Test Code for Inorganic Binder Stabilized Materials for Highway Engineering" (JTG 3441-2024), and the shrinkage coefficient and temperature shrinkage coefficient test methods refer to the "Test Method for Drying Shrinkage Cracking Performance of Cement Mortar and Concrete" (GB / T 29417-2012). The results are shown in Table 4.

[0032] Table 4 Test results of slow-setting cement stabilized gravel of Examples 1-4 and Comparative Examples 1-5 After preparation, the 7-day unconfined compressive strength test results with different delay times are shown in Table 5.

[0033] Table 5 7-day unconfined compressive strength test results of delayed-setting cement-stabilized crushed stone A method for paving a base of slow-setting cement-stabilized crushed stone prepared by any of the preparation methods described above, comprising the following steps: S1. Construction preparation; S2. Mixing of retarded cement stabilized gravel; the aggregate gradation should strictly follow the laboratory design mix ratio, and the moisture content should be increased by about 1~2% compared with the laboratory design result, so that the moisture content of the retarded cement stabilized gravel after being transported to the site for paving is close to its optimal moisture content. Strictly control the water addition time and the feeding rate of the mixer to ensure that the mixture is uniform and the color is consistent, and there is no white material; S3, slow setting cement stabilized gravel transportation; S4. Spread the slow-setting cement-stabilized gravel base; S5. Compact the slow-setting stable gravel base; S6, seam treatment; S7. After continuous compaction, emulsified asphalt can be directly spread for curing, or geotextile can be used for covering and watering for curing. The curing time should be no less than 7 days.

[0034] In S1, construction measurements are carried out, and side piles are measured and placed on the lower bearing layer to control the elevation. The surface of the lower bearing layer is cleaned to ensure that there is no debris, and water is sprinkled before paving to prevent excessive local moisture and facilitate bonding between layers.

[0035] In S3, dump trucks are used to transport slow-setting cement-stabilized gravel mixtures, and care is taken to keep the weight of each truckload of mixtures basically the same; the transportation capacity should be adapted to the mixing capacity and have a surplus to ensure construction continuity; the slow-setting cement-stabilized gravel mixture is covered with tarpaulin to reduce moisture evaporation.

[0036] In S4, the slow-setting cement-stabilized gravel mixture is fully prepared before paving. The transporter drives to 20-30 cm in front of the paver, shifts to neutral and is directed by a dedicated person to unload. The paver pushes the transporter to unload and pave. The paving speed is 1.5-2m / min. During the paving process, the paving thickness needs to be checked at 3 locations every 10 m and recorded. When one paver is paving about 5 m, another paver enters the site. The two pavers are paved synchronously with a distance of 5-10 m between them. After each vehicle is finished paving, the spilled mixture needs to be cleaned up in time to prevent the paver from rolling over and increasing the thickness.

[0037] In S5, compaction includes three stages: initial compaction, repeated compaction and final compaction. Each stage follows the principle of "light first, heavy later, slow first, fast later, from bottom to high", and is rolled successively in the order of construction. The length of each rolling is controlled at 50-80 m, overlapping 1 / 2 wheel width. When the roller is rolling, the rolling sections are clearly layered and trapezoidal in shape, and obvious boundary marks are set. At the same time, the water content of the slow-setting cement-stabilized crushed stone mixture is adjusted and controlled in time until it approaches the optimal water content.

[0038] The initial compaction is carried out by using a single steel wheel vibratory roller with one pass of static compaction followed by one pass of vibration, or by using a double steel wheel roller with one pass of static compaction, with the speed controlled at 1.5-1.7 km / h; When recompacting, use a heavy roller to perform one pass with weak vibration, at a speed of 1.8-2.5 km / h, and then perform three passes with strong vibration, at a speed of 1.8-2.5 km / h; The final compaction is carried out using a double steel wheel roller, with static compaction for no less than 1 time, and the speed is controlled at 1.5-1.7 km / h, until there are no wheel marks left.

[0039] Among them, in S4 and S5, three times of paving and three times of compaction are carried out respectively. After the first layer of slow-setting stabilized gravel base is paved, the first layer of slow-setting stabilized gravel base is compacted, and then the second layer is paved and compacted, and finally the third layer is paved and compacted. The paving and compaction of each layer are carried out according to the steps in S4 and S5.

[0040] In S6, for transverse joints, a seam cutter is used to cut the seams; after cutting, the debris is promptly removed and wiped clean with a wet cloth; for longitudinal joints, a roller is used to roll the seams to avoid misalignment.

[0041] Although the above describes the specific implementation methods of the invention, it does not limit the scope of protection of the invention. Based on the technical solution of the present invention, various modifications or variations that can be made by those skilled in the art without creative work are still within the scope of protection of the present invention.

Claims

1. A method for preparing slow-setting cement-stabilized crushed stone, Its characteristics are: Includes the following step, (1) Cement, phosphogypsum, epoxymethylsiloxane, polyacrylamide and graded stone are mixed and stirred in a weight ratio of 4-6 parts: 5-10 parts: 1-3 parts: 2-3 parts: 77-88 parts to obtain a dry material; (2) Add 3 to 7 parts by weight of water to the dry material in step (1) and stir to obtain slow-setting cement-stabilized gravel.

2. The method for preparing slow-setting cement-stabilized crushed stone according to claim 1, Its characteristics are: In step (1), the cement is ordinary Portland cement, slag Portland cement or pozzolanic Portland cement, and the strength grade of the cement is 32.5 or 42.

5.

3. The method for preparing slow-setting cement-stabilized crushed stone according to claim 1, Its characteristics are: The phosphogypsum in step (1) is phosphogypsum powder treated by a water washing method.

4. A method for laying a base layer of slow-setting cement-stabilized crushed stone prepared by the preparation method according to any one of claims 1 to 3, Its characteristics are: Use the following steps, S1. Construction preparation; S2, slow setting cement stabilized gravel mixing; S3, slow setting cement stabilized gravel transportation; S4. Spread the slow-setting cement-stabilized gravel base; S5. Compact the slow-setting stable gravel base; S6, seam treatment; S7. After continuous compaction, you can directly spread emulsified asphalt for curing, or you can use geotextile to cover and sprinkle water for curing.

5. The method for laying the base layer according to claim 4, Its characteristics are: In S1, construction measurement is carried out, and side piles are measured and placed on the lower bearing layer to control the elevation; the surface of the lower bearing layer is cleaned and watered before paving.

6. The method for laying a base layer according to claim 4 is characterized in that: in S3, a dump truck is used to transport the slow-setting cement-stabilized gravel mixture, and the slow-setting cement-stabilized gravel mixture is covered with a tarpaulin.

7. The method for paving the base layer according to claim 4 is characterized in that: in S4, the slow-setting cement-stabilized gravel mixture is ensured to be fully prepared before paving, the conveyor drives to 20-30 cm in front of the paver, and the paver pushes the conveyor to unload and pave, the paving speed is 1.5-2 m / min, and the paving thickness needs to be checked at 3 locations every 10 m during the paving process and recorded.

8. The method for laying the base layer according to claim 4, Its features are: S5 In the process, compaction includes three stages: initial compaction, repeated compaction and final compaction. Each stage follows the principle of "light first, heavy later, slow first, fast later, from bottom to high", and is rolled successively in the order of construction. The length of each rolling is controlled at 50-80 m, overlapping 1 / 2 wheel width. When the roller rolls, the rolling sections are clearly layered and trapezoidal in shape, and obvious boundary marks are set. At the same time, the water content of the slow-setting cement stabilized gravel mixture is adjusted and controlled in time.

9. The method for laying the base layer according to claim 4 is characterized in that: in S6, for the transverse joints, a seam cutter is used to cut the seams; after cutting the seams, the debris is promptly removed and wiped clean with a wet cloth; and for the longitudinal joints, a roller is used to roll the seams.

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