High-freezing-resistance cement stabilized macadam mixture and preparation method thereof

Abstract

The invention relates to a high-freezing-resistance cement stabilized macadam mixture and a preparation method thereof, and the high-freezing-resistance cement stabilized macadam mixture comprises the following raw materials in parts by mass except polypropylene fiber: 75 parts of coarse aggregate, 25 parts of fine aggregate, 5 parts of cement, 0.15-0.35 part of expanding agent, 0.1-0.25 part of latex powder, 0.05-0.1 part of water-absorbent resin, 5.89-6.12 parts of water according to the volume ratio of the polypropylene fiber to cement stabilized macadam (formed by mixing the raw materials) of (1-2): 1000. Compared with the prior art, the cement stabilized macadam mixture applicable to the road base in the Tibetan region, provided by the invention, has good anti-freezing performance after 5 times and 10 times of freezing and thawing cycles, the problem that a common cement stabilized macadam base is difficult to meet the anti-freezing performance of a Tibetan region is solved, and the applicable requirement of the road base in the Tibetan region is met.

Description

Technical Field

[0001] The invention relates to the intersecting field of material science and road engineering, and in particular relates to a high frost-resistant cement-stabilized crushed stone base material. Background Art

[0002] The main materials for road base in frozen soil areas are cement-stabilized materials such as cement-stabilized gravel and cement-stabilized crushed stone. Cement-stabilized crushed stone materials have the characteristics of high strength, good stability and high rigidity, and are often used in the base of high-grade highways. However, the freeze-thaw cycle in frozen soil areas is severe and the freeze-thaw action is frequent. This situation causes frequent changes in the internal liquid expansion pressure and penetration pressure of the mixture, which makes the strength of the road base continue to decline. Under the action of vehicle loads, ordinary cement-stabilized crushed stone is difficult to meet the strength requirements of the base, and is prone to settlement, cracking and other damage, which in turn accelerates the destruction of the pavement structure and shortens the service life of the road.

[0003] When building roads in heavily frozen areas, a technical problem that needs to be solved urgently is how to ensure that the road base material has sufficient antifreeze performance to meet the needs of long-term road use. Especially in high-altitude areas such as Tibet, ordinary cement-stabilized gravel base is prone to strength loss, settlement, cracking and other problems due to the influence of freeze-thaw cycles, resulting in a shortened road service life. In order to adapt to this harsh environment, it is necessary to develop a new type of high-freeze-resistant cement-stabilized gravel mixture, which not only maintains a high residual compressive strength ratio after multiple freeze-thaw cycles, but also needs to improve the material's antifreeze performance both chemically and physically. Summary of the invention

[0004] In view of the fact that ordinary cement-stabilized gravel base is difficult to meet the requirements of frost resistance of roads in Tibetan areas, the present invention proposes a high-frost resistance cement-stabilized gravel mixture and a preparation method thereof. The cement-stabilized material has good frost resistance, and the residual compressive strength ratio after 5 and 10 freeze-thaw cycles is greater than 70%, which meets the requirements of the residual compressive strength ratio of inorganic mixtures in heavy freezing areas, and solves the problem that the frost resistance of ordinary cement-stabilized gravel base of roads in Tibetan areas is difficult to meet the service life of the road.

[0005] The applicant believes in the process of conception that the calcium aluminate generated by the expansion agent causes the cement-stabilized gravel to produce micro-expansion, thereby improving the compactness of the cement-stabilized gravel. The dispersible latex powder has the characteristic of being able to be redispersed into a film when it meets water, and forms a latex film while the cement is hydrated, which prevents the transmission of water when cracks are generated. At the same time, its air entraining properties can improve the toughness and volume stability of cement mortar and concrete. Adding latex powder to cement-stabilized gravel can effectively improve its shrinkage, crack resistance and deformation resistance. Super absorbent resin has the characteristics of absorbing and releasing water, which can reduce the self-shrinkage deformation inside the cement-stabilized gravel, promote the large-scale generation of gel, make the internal structure of the specimen more compact, and improve the compressive strength of the cement-stabilized gravel. Polypropylene fiber has the advantages of high strength and good tensile elasticity, which can reduce the tensile stress of the cement-stabilized gravel when microcracks appear, thereby effectively extending the time for the cement-stabilized gravel base to resist freeze-thaw damage. The four materials of water-absorbent resin, dispersible latex powder, expansion agent and polypropylene fiber can play a positive role in the cement-stabilized gravel base from different levels, and are expected to improve the road performance of the base.

[0006] The technical solution of the present invention is achieved in this way:

[0007] In the first aspect, the present invention comprises a high frost resistance cement stabilized gravel mixture. Except for polypropylene fiber, the remaining raw materials are calculated by weight as follows: 75 parts of coarse aggregate, 25 parts of fine aggregate, 5 parts of cement, 0.15-0.35 parts of expansion agent, 0.1-0.25 parts of latex powder, 0.05-0.1 parts of water-absorbing resin, polypropylene fiber and cement stabilized gravel (mixed with the above raw materials) in a volume ratio of (1-2): 1000, and 5.89-6.12 parts of water.

[0008] Furthermore, the coarse aggregate has a particle size of 4.75 to 31.5 mm.

[0009] Furthermore, the particle size of the fine aggregate is 0-4.75 mm and ≠0.

[0010] Furthermore, the synthetic gradation after mixing the coarse aggregate and the fine aggregate satisfies:

[0011] The cement stabilized crushed stone prepared by the present invention adopts a dense skeleton structure, and the synthetic gradation is controlled. The percentage of passing through a sieve hole size of 31.5 mm is 100%, the percentage of passing through a sieve hole size of 26.5 mm is 95-100%, the percentage of passing through a sieve hole size of 19 mm is 68-86%, the percentage of passing through a sieve hole size of 9.5 mm is 38-58%, the percentage of passing through a sieve hole size of 4.75 mm is 22-42%, the percentage of passing through a sieve hole size of 2.36 mm is 18-30%, the percentage of passing through a sieve hole size of 0.6 mm is 8-15%, and the percentage of passing through a sieve hole size of 0.075 mm is 0-3%.

[0012] Furthermore, the cement is PO42.5R early strength Portland cement.

[0013] Furthermore, the expansion agent is UEA concrete expansion agent.

[0014] Furthermore, the dispersible latex powder is vinyl acetate-ethylene copolymer latex powder.

[0015] Furthermore, the water-absorbing resin has a mesh size of 120 to 180 meshes.

[0016] Furthermore, the fiber is polypropylene fiber with a length of 18 mm.

[0017] In a second aspect, the present invention provides a method for preparing the above-mentioned high frost resistance cement stabilized crushed stone mixture, comprising the following steps:

[0018] Step 1: Measure the coarse aggregate and fine aggregate by weight and mix them evenly;

[0019] Step 2: Add 45-55% water (i.e. 5.89-6.12 parts of 45-55wt%) and stir evenly;

[0020] Step 3: Add the swelling agent, latex powder, water-absorbing resin and fiber according to weight, and stir and mix evenly;

[0021] Step 4: Add the remaining water and cement, stir and mix evenly to obtain a cement-stabilized gravel mixture with high frost resistance.

[0022] Further, in step 1, the stirring time is 60 to 90 seconds;

[0023] In step 2, the stirring time is 60 to 90 seconds;

[0024] In step 3, the stirring time is 30 to 60 seconds;

[0025] In step 4, the stirring time is 120 to 150 seconds.

[0026] The present invention provides a high frost resistance cement stabilized crushed stone base material, which has the following advantages:

[0027] 1. The present invention considers the influence of expansion agent, latex powder, water-absorbing resin and fiber on the antifreeze performance of cement-stabilized crushed stone materials at different levels, and adds the four materials into cement-stabilized crushed stone to improve the antifreeze performance. On the chemical level, the expansion agent reacts with water to form calcium aluminate to improve the compactness; on the physical level, the water-absorbing resin absorbs and releases water to reduce self-shrinkage and generates gel to further increase the compactness; the latex powder forms a film when it meets water to prevent water transmission and improve toughness and volume stability; the polypropylene fiber can reduce the tensile stress of cement-stabilized crushed stone when microcracks appear.

[0028] 2. After five freeze-thaw cycles, the mass loss rate of the high frost-resistant cement-stabilized crushed stone material provided by the present invention is reduced from 0.38% to 0.16-0.28%, the compressive strength loss rate is reduced from 12.01% to 4.65-6.17%, the compressive rebound modulus loss rate is reduced from 8.59% to 6.6-7.9%, the elastic modulus loss rate is reduced from 10.02% to 7.5-8.9%, and the splitting strength loss rate is reduced from 15.41% to 8.6 After 10 freeze-thaw cycles, the mass loss rate was reduced from 0.43% to 0.2-0.32%, the compressive strength loss rate was reduced from 30.04% to 11.65-15.28%, the compressive rebound modulus loss rate was reduced from 26.7% to 15.2-15.6%, the elastic modulus loss rate was reduced from 23.48% to 16.8-18.9%, and the splitting strength loss rate was reduced from 26.99% to 16.5-21.8%. Compared with ordinary cement stabilized crushed stone, it has less loss and better performance under freeze-thaw conditions.

[0029] 3. The high frost resistance cement stabilized gravel material provided by the present invention has a freeze-thaw residual strength ratio of 84.72-88.35% after 10 freeze-thaw cycles, which meets the requirement that the residual strength ratio in the heavy frozen area of ​​the Tibetan area is greater than 70%, and solves the problem that the frost resistance of ordinary cement stabilized gravel base of Tibetan roads is difficult to meet the service life of the road. DETAILED DESCRIPTION

[0030] On the whole, the present invention provides a high frost resistance cement stabilized gravel mixture. Except for polypropylene fiber, the remaining raw materials are calculated by weight: 75 parts of coarse aggregate, 25 parts of fine aggregate, 5 parts of cement, 0.15-0.35 parts of expansion agent, 0.1-0.25 parts of latex powder, 0.05-0.1 parts of water-absorbing resin, polypropylene fiber and cement stabilized gravel (mixed with the above raw materials) in a volume ratio of (1-2): 1000, and 5.89-6.12 parts of water.

[0031] The present invention is further described below in conjunction with the embodiments. Any features such as preparation means, materials, structures or composition ratios not clearly described in this technical solution are regarded as common technical features disclosed in the prior art.

[0032] Example 1

[0033] Except for polypropylene fiber, the remaining raw materials are mixed by mass: 75 parts of coarse aggregate, 25 parts of fine aggregate, 5 parts of cement, 0.15 parts of expansion agent, 0.1 parts of latex powder, 0.05 parts of water-absorbing resin, polypropylene fiber and cement-stabilized crushed stone (mixed with the above raw materials) in a volume ratio of 1:1000, and 6.01 parts of water.

[0034] The cement is PO42.5R early strength silicate cement, the expansion agent is UEA concrete expansion agent, the dispersible latex powder is vinyl acetate-ethylene copolymer latex powder, the mesh number of the water-absorbing resin is 120 mesh, and the length of the polypropylene fiber is 18 mm.

[0035] The above-mentioned Example 1 was prepared as follows:

[0036] Step 1: Measure the coarse aggregate and fine aggregate by weight, and mix them evenly for 60 seconds;

[0037] The synthetic gradation after mixing coarse aggregate and fine aggregate satisfies the requirement of 100% passing through 31.5mm sieve, 98.9% passing through 26.5mm sieve, 72.1% passing through 19.0mm sieve, 49.5% passing through 9.5mm sieve, 35.1% passing through 4.75mm sieve, 18.9% passing through 2.36mm sieve, 8.3% passing through 0.6mm sieve and 2.8% passing through 0.075mm sieve.

[0038] Step 2: Add 50wt% of water and stir evenly for 60s;

[0039] Step 3: Add the swelling agent, latex powder, water-absorbing resin and fiber according to weight, stir and mix evenly for 60 seconds;

[0040] Step 4: Add the remaining water and cement, stir and mix evenly to obtain a cement-stabilized gravel mixture with high frost resistance. The stirring time is 120 seconds.

[0041] Example 2

[0042] Different from Example 1, except for the polypropylene fiber, the other raw materials are mixed by mass: 75 parts of coarse aggregate, 25 parts of fine aggregate, 5 parts of cement, 0.15 parts of expansion agent, 0.25 parts of latex powder, 0.1 parts of water-absorbing resin, polypropylene fiber and cement-stabilized crushed stone (mixed with the above raw materials) in a volume ratio of 1.5:1000, and 5.89 parts of water.

[0043] The preparation method is the same as Example 1.

[0044] Example 3

[0045] Different from Example 1, except for the polypropylene fiber, the other raw materials are mixed by mass: 75 parts of coarse aggregate, 25 parts of fine aggregate, 5 parts of cement, 0.35 parts of expansion agent, 0.1 parts of latex powder, 0.05 parts of water-absorbing resin, polypropylene fiber and cement-stabilized crushed stone (mixed with the above raw materials) in a volume ratio of 1.5:1000, and 5.97 parts of water.

[0046] The preparation method is the same as Example 1.

[0047] Example 4

[0048] Different from Example 1, except for the polypropylene fiber, the other raw materials are mixed by mass: 75 parts of coarse aggregate, 25 parts of fine aggregate, 5 parts of cement, 0.15 parts of expansion agent, 0.25 parts of latex powder, 0.05 parts of water-absorbing resin, polypropylene fiber and cement-stabilized crushed stone (mixed with the above raw materials) in a volume ratio of 2:1000, and 6.03 parts of water.

[0049] The preparation method is the same as Example 1.

[0050] Comparative Example 1

[0051] The cement stabilized crushed stone without adding expansion agent, latex powder, water-absorbing resin and polypropylene fiber is used as a comparative example, and includes the following components in parts by weight: 75 parts of coarse aggregate, 25 parts of fine aggregate, 5 parts of cement and 6.12 parts of water.

[0052] The preparation method is the same as Example 1.

[0053] For Examples 1 to 4 and Comparative Example 1, after static pressing and curing for 28 days according to the "Testing Procedure for Stabilized Materials of Inorganic Binders for Highway Engineering" (JTGE-51-2009), the test pieces were tested after 5 and 10 freeze-thaw cycles, respectively, and the test data were shown in Table 1:

[0054] Table 1 Test results of Examples 1 to 4 and Comparative Example 1

[0055]

[0056] It can be seen from Table 1 that compared with the cement stabilized macadam of the comparative example, the high frost resistance of the cement stabilized macadam of Examples 1 to 4 is significantly improved in frost resistance. After 5 freeze-thaw cycles, the mass loss rate is reduced from 0.38% to 0.16-0.28%, the compressive strength loss rate is reduced from 12.01% to 4.65-6.17%, the compressive rebound modulus loss rate is reduced from 8.59% to 6.6-7.9%, the elastic modulus loss rate is reduced from 10.02% to 7.5-8.9%, and the splitting strength loss rate is reduced from 15.41% to 8.6-14.6%; after 10 freeze-thaw cycles, the mass loss rate is reduced from 0.38% to 0.16-0.28%, the compressive strength loss rate is reduced from 12.01% to 4.65-6.17%, the compressive rebound modulus loss rate is reduced from 8.59% to 6.6-7.9%, the elastic modulus loss rate is reduced from 10.02% to 7.5-8.9%, and the splitting strength loss rate is reduced from 15.41% to 8.6-14.6%; Under freeze-thaw conditions, the mass loss rate decreased from 0.43% to 0.2-0.32%, the compressive strength loss rate decreased from 30.04% to 11.65-15.28%, the compressive rebound modulus loss rate decreased from 26.7% to 15.2-15.6%, the elastic modulus loss rate decreased from 23.48% to 16.8-18.9%, and the splitting strength loss rate decreased from 26.99% to 16.5-21.8%. The reduction in mass loss rate means that the cement-stabilized crushed stone base can maintain better integrity after freeze-thaw; the reduction in compressive strength loss rate means that the base can withstand higher loads without damage after freeze-thaw; the reduction in compressive rebound modulus loss rate and elastic modulus loss rate means that the base is more flexible after freeze-thaw, and can produce a certain deformation to offset stress when bearing loads to prevent brittle failure; the reduction in splitting strength loss rate means that the base has a stronger ability to resist splitting after freeze-thaw, and can absorb more energy during deformation to avoid fracture.

[0057] Evaluation results of antifreeze performance: compressive strength loss rate > compressive rebound modulus loss rate > splitting strength loss rate > elastic modulus loss rate > elastic modulus loss rate.

[0058] In summary, the high frost resistance cement stabilized gravel provided by the present invention has significantly reduced mass loss rate, compressive strength loss rate, compressive rebound modulus loss rate, elastic modulus loss rate and splitting strength loss rate after freeze-thaw compared with ordinary cement stabilized gravel, which can better meet the use scenarios of cement stabilized gravel base for severe freeze-thaw cycles in Tibetan areas.

[0059] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A high frost resistance cement stabilized gravel mixture, characterized in that: Including expansion agent, dispersible latex powder, water-absorbing resin, polypropylene fiber, cement-stabilized crushed stone, water; The cement stabilized crushed stone comprises, by weight: 75 parts of coarse aggregate, 25 parts of fine aggregate, 5 parts of cement, 0.15-0.35 parts of expansion agent, 0.1-0.25 parts of latex powder, and 0.05-0.1 parts of water-absorbing resin; The water is 5.89 to 6.12 parts by mass; The volume ratio of the polypropylene fiber to the cement-stabilized crushed stone is (1-2):1000.

2. The high frost resistance cement stabilized crushed stone mixture according to claim 1, characterized in that: The coarse aggregate particle size is 4.75 to 31.5 mm.

3. The high frost resistance cement stabilized crushed stone mixture according to claim 1, characterized in that: The particle size of the fine aggregate is 0-4.75 mm, and the particle size of the fine aggregate is not equal to 0.

4. The high frost resistance cement stabilized crushed stone mixture according to claim 1, characterized in that: The composite gradation after mixing the coarse aggregate and the fine aggregate satisfies: The percentage passing through the sieve hole size of 31.5 mm is 100%, the percentage passing through the sieve hole size of 26.5 mm is 95-100%, the percentage passing through the sieve hole size of 19 mm is 68-86%, the percentage passing through the sieve hole size of 9.5 mm is 38-58%, the percentage passing through the sieve hole size of 4.75 mm is 22-42%, the percentage passing through the sieve hole size of 2.36 mm is 18-30%, the percentage passing through the sieve hole size of 0.6 mm is 8-15%, and the percentage passing through the sieve hole size of 0.075 mm is 0-3%.

5. The high frost resistance cement stabilized crushed stone mixture according to claim 1, characterized in that: The cement is PO42.5R early strength Portland cement.

6. The high frost resistance cement stabilized crushed stone mixture according to claim 1, characterized in that: The expansion agent is UEA concrete expansion agent.

7. The high frost resistance cement stabilized crushed stone mixture according to claim 1, characterized in that: The dispersible latex powder is vinyl acetate-ethylene copolymer latex powder.

8. The high frost resistance cement stabilized crushed stone mixture according to claim 1, characterized in that: The mesh size of the water-absorbing resin is 120 to 180 meshes; The length of the polypropylene fiber is 18 mm.

9. A method for preparing a high frost resistance cement stabilized crushed stone mixture as claimed in any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1: Measure the coarse aggregate and the fine aggregate by weight, and stir and mix them evenly to obtain material A; Step 2: Add 45-55% water to the material A, stir and mix evenly to obtain material B; Step 3: adding the swelling agent, latex powder, water-absorbing resin and fiber according to weight into the material B, and uniformly stirring and mixing to obtain material C; Step 4: Add the remaining water and cement to the material C, stir and mix evenly to obtain a cement-stabilized gravel mixture with high frost resistance.

10. The method for preparing a high frost resistance cement-stabilized crushed stone mixture according to claim 9, characterized in that: In step 1, the stirring time is 60 to 90 seconds; In step 2, the stirring time is 60 to 90 seconds; In step 3, the stirring time is 30 to 60 seconds; In step 4, the stirring time is 120 to 150 seconds.

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