Polymerized MDI modified recycled concrete aggregate asphalt mixture and preparation method thereof

Abstract

The invention discloses a polymerized MDI modified recycled concrete aggregate asphalt mixture and a preparation method thereof, and belongs to the field of road building materials. The polymeric MDI modified recycled concrete aggregate asphalt mixture is prepared from recycled concrete aggregate, polymeric MDI, asphalt, mineral stone and filler. By using the polymerized MDI modified asphalt, the defect that the recycled concrete aggregate is insufficient in water damage resistance when being applied to an asphalt pavement is overcome. On one hand, an isocyanate group in the polymeric MDI has relatively high reaction activity and can react with active hydrogen in asphalt to generate polyurethane or polyurea; on the other hand, the polymerized MDI can chemically react with moisture in the air to form stable chemical bonds; therefore, the adhesion performance of the asphalt and the recycled concrete aggregate is improved, and the water damage resistance is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of road construction materials, and particularly relates to a polymer MDI-modified recycled concrete aggregate asphalt mixture and a preparation method thereof. Background Art

[0002] The resource utilization of recycled cement concrete has become a major research focus at home and abroad. There are many studies on the recycling of cement concrete pavements. A relatively conventional disposal method is to crush and screen waste cement concrete slabs to form recycled aggregates of different particle sizes, and use the recycled aggregates in cement concrete as highway pavement structures or other components to study their road performance and durability, or use the recycled aggregates in highway cement stabilized materials as the base or subbase.

[0003] Compared with mineral aggregates, recycled concrete aggregates have a higher water absorption rate, while their wear resistance, mechanical properties and density are lower. In recent years, the research and application of recycled concrete aggregates in asphalt pavements have gradually increased. At present, there are many studies evaluating the influence of recycled concrete aggregates on the performance of asphalt concrete. Since the surface of recycled concrete aggregates is rougher and can absorb more asphalt, the optimal asphalt dosage will increase. Mills Beale found that with the increase of recycled concrete aggregates, the rutting resistance of asphalt concrete decreases. Xu Jiazhou disclosed that coarse recycled concrete aggregates were used to replace different proportions of granite aggregates by equal mass to prepare asphalt mastic asphalt mixtures. By comprehensively considering the optimal asphalt dosage, Marshall stability, impact strength, resilient modulus and splitting strength through experiments, the recommended optimal dosage of recycled concrete aggregates was 40%. However, some studies (Pérez, 2017) have confirmed that the use of recycled aggregates has an adverse effect on the performance of asphalt concrete, which may lead to a decrease in the resilient modulus of asphalt concrete, deterioration of low-temperature crack resistance, especially a decrease in the water damage resistance. How to overcome these problems is still a technical bottleneck restricting the application of recycled concrete aggregates in asphalt pavements. Therefore, it is urgent to develop a recycled concrete aggregate asphalt mixture with strong water damage resistance. Summary of the Invention

[0004] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a polymer MDI-modified recycled concrete aggregate asphalt mixture and a preparation method thereof to increase the adhesion performance between asphalt and recycled concrete aggregates and improve their water damage resistance.

[0005] The technical solution of the present invention to solve the above technical problems is as follows: providing a polymer MDI-modified recycled concrete asphalt mixture, which comprises the following raw materials in parts by mass: 20-60 parts of recycled concrete aggregates, 1-10 parts of polymer MDI, 100-150 parts of asphalt, 40-80 parts of mineral aggregates and 3-8 parts of fillers.

[0006] Further, it includes raw materials in the following parts by mass: 20 parts of recycled concrete aggregate, 3 parts of polymeric MDI, 100 parts of asphalt, 80 parts of mineral stone, and 3 parts of filler.

[0007] Further, the polymeric MDI is a diphenylmethane diisocyanate polymer containing 2 - 3 functional groups.

[0008] Further, the recycled concrete aggregate is recycled aggregate obtained by crushing cement pavement concrete and building concrete.

[0009] Further, the particle size of the mineral stone is 0.075 mm.

[0010] Further, the filler is mineral powder, and the particle size of the mineral powder is < 0.075 mm.

[0011] The present invention also provides a preparation method of the above - mentioned polymeric MDI - modified recycled concrete asphalt mixture, which includes the following steps: (1) Prepare polymeric MDI - modified asphalt: First, heat the asphalt to a flowing state, add polymeric MDI, and stir evenly to obtain it; (2) Heat the recycled concrete aggregate and the mineral stone separately, and then stir the recycled concrete aggregate and the mineral stone evenly; (3) Add the polymeric MDI - modified asphalt and the filler obtained in step (1) to the product obtained in step (2), and stir evenly to obtain it.

[0012] Further, in step (2), the heating temperature is 160 - 180 °C, and the heating time is 4 - 6 h.

[0013] The present invention has the following beneficial effects: By using polymeric diphenylmethane diisocyanate (polymeric MDI) to modify asphalt, the present invention improves the defect of insufficient water damage resistance performance when recycled concrete aggregate is applied to asphalt pavement. On the one hand, the isocyanate groups in polymeric MDI have high reaction activity and can react with the active hydrogen in asphalt to generate polyurethane or polyurea; on the other hand, polymeric MDI can also chemically react with the moisture in the air to form stable chemical bonds; thus increasing the adhesion performance between asphalt and recycled concrete aggregate and improving its water damage resistance performance. Specific Embodiments

[0014] The principles and features of the present invention are described below in conjunction with embodiments. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention. For those not specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are followed. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0015] Example 1: A polymer MDI-modified recycled cement concrete asphalt mixture, comprising the following raw materials in parts by mass: 20 parts of recycled concrete aggregate, 3 parts of polymer MDI, 100 parts of asphalt, 80 parts of mineral stone, and 3 parts of filler; its preparation method comprises the following steps: (1) First, heat the asphalt to a flowing state, then add polymer MDI, and mix evenly by mechanical stirring to obtain polymer MDI-modified asphalt; (2) Heat the recycled concrete aggregate and the mineral stone at 160 °C for 4 h respectively, and then stir the recycled concrete aggregate and the mineral stone in a mixing pot for 180 s; (3) Add the polymer MDI-modified asphalt obtained in step (1) to the product obtained in step (2), stir for 90 s to evenly coat the asphalt on the surface of the aggregate, and finally add the filler and stir for 90 s to make the entire asphalt mixture reach a uniform state.

[0016] Example 2: A polymer MDI-modified recycled cement concrete asphalt mixture, comprising the following raw materials in parts by mass: 40 parts of recycled concrete aggregate, 5 parts of polymer MDI, 120 parts of asphalt, 60 parts of mineral stone, and 5 parts of filler; its preparation method comprises the following steps: (1) First, heat the asphalt to a flowing state, then add polymer MDI, and mix evenly by mechanical stirring to obtain polymer MDI-modified asphalt; (2) Heat the recycled concrete aggregate and the mineral stone at 160 °C for 4 h respectively, and then stir the recycled concrete aggregate and the mineral stone in a mixing pot for 90 s; (3) Add the polymer MDI-modified asphalt obtained in step (1) to the product obtained in step (2), stir for 120 s to evenly coat the asphalt on the surface of the aggregate, and finally add the filler and stir for 120 s to make the entire asphalt mixture reach a uniform state.

[0017] Example 3: A polymer MDI-modified recycled cement concrete asphalt mixture, comprising the following raw materials in parts by mass: 60 parts of recycled concrete aggregate, 3 parts of polymer MDI, 150 parts of asphalt, 80 parts of mineral stone, and 3 parts of filler; its preparation method comprises the following steps: (1) First, heat the asphalt to a flowing state, then add polymer MDI, and mix evenly by mechanical stirring to obtain polymer MDI-modified asphalt; (2) Heat the recycled concrete aggregate and the mineral stone at 160 °C for 4 h respectively, and then stir the recycled concrete aggregate and the mineral stone in a mixing pot for 300 s; (3) Add the polymer MDI modified asphalt obtained in step (1) to the product obtained in step (2), stir for 60 s to evenly coat the asphalt on the surface of the aggregate, and finally add the filler and stir for 60 s to make the entire asphalt mixture reach a uniform state.

[0018] Comparative Example 1: A recycled cement concrete asphalt mixture, comprising the following raw materials in parts by mass: 20 parts of recycled concrete aggregate, 100 parts of asphalt, 80 parts of mineral stone, and 3 parts of filler; its preparation method comprises the following steps: (1) Heat the recycled concrete aggregate and the mineral stone separately at 160 °C for 4 h, and then stir the recycled concrete aggregate and the mineral stone in a mixing pot for 180 s; (2) Add asphalt to the product obtained in step (1), stir for 90 s to evenly coat the asphalt on the surface of the aggregate, and finally add the filler and stir for 90 s to make the entire asphalt mixture reach a uniform state.

[0019] Comparative Example 2: A recycled cement concrete asphalt mixture, comprising the following raw materials in parts by mass: 40 parts of recycled concrete aggregate, 120 parts of asphalt, 60 parts of mineral stone, and 5 parts of filler; its preparation method comprises the following steps: (1) Heat the recycled concrete aggregate and the mineral stone separately at 160 °C for 4 h, and then stir the recycled concrete aggregate and the mineral stone in a mixing pot for 90 s; (2) Add asphalt to the product obtained in step (1), stir for 120 s to evenly coat the asphalt on the surface of the aggregate, and finally add the filler and stir for 120 s to make the entire asphalt mixture reach a uniform state.

[0020] Comparative Example 3: A recycled cement concrete asphalt mixture, comprising the following raw materials in parts by mass: 60 parts of recycled concrete aggregate, 150 parts of asphalt, 80 parts of mineral stone, and 3 parts of filler; its preparation method comprises the following steps: (1) Heat the recycled concrete aggregate and the mineral stone separately at 160 °C for 4 h, and then stir the recycled concrete aggregate and the mineral stone in a mixing pot for 300 s; (2) Add asphalt to the product obtained in step (1), stir for 60 s to evenly coat the asphalt on the surface of the aggregate, and finally add the filler and stir for 60 s to make the entire asphalt mixture reach a uniform state.

[0021] Perform performance tests on the recycled concrete aggregate asphalt mixtures prepared in Examples 1-3 and Comparative Examples 1-3: Use the recycled concrete aggregate asphalt mixtures prepared in Examples 1-3 and Comparative Examples 1-3 to make Marshall specimens, specifically as follows: Use a Marshall compactor to make standard cylindrical Marshall specimens with a size of Φ101.6mm×63.5mm. The test method is the method for fabricating asphalt mixture specimens (JTG E20-2011 (T0702), compaction method); then conduct a freeze-thaw splitting test with reference to the asphalt mixture freeze-thaw splitting test (JTG E20-2011 (T0729)). The test results are shown in Table 1: Table 1 Results of the freeze-thaw splitting test Project Splitting strength before freeze-thaw / MPa Splitting strength after freeze-thaw / MPa Freeze-thaw splitting strength ratio / % Example 1 1.22 1.10 90.2 Example 2 1.19 1.03 86.6 Example 3 1.13 0.92 81.4 Comparative Example 1 1.08 0.82 75.9 Comparative Example 2 1.02 0.73 71.6 Comparative Example 3 0.97 0.65 67.0 The freeze-thaw splitting test can effectively evaluate the water damage resistance of asphalt mixtures. The "Technical Specifications for Construction of Highway Asphalt Pavements" (JTG F40-2004) in China requires that the freeze-thaw splitting strength ratio be not less than 75%. As can be seen from Table 1, the freeze-thaw splitting strength ratios of the polymer MDI-modified recycled cement concrete asphalt mixtures provided in Examples 1-3 of the present invention are 90.2%, 86.6%, and 81.4% respectively, which are significantly higher than the freeze-thaw splitting strength ratios of the recycled cement concrete asphalt mixtures in Comparative Examples 1-3 (75.9%, 71.6%, and 67.0% respectively). Thus, it can be seen that the polymer MDI-modified recycled cement concrete asphalt mixture of the present invention can effectively improve the water damage resistance of the recycled concrete aggregate asphalt mixture.

[0022] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A polymerized MDI modified recycled concrete asphalt mixture, characterized in that: The invention comprises the following raw materials in parts by weight: 20-60 parts of recycled concrete aggregate, 1-10 parts of polymerized MDI, 100-150 parts of asphalt, 40-80 parts of mineral stone and 3-8 parts of filler.

2. The polymerized MDI modified recycled concrete asphalt mixture according to claim 1, characterized in that: The raw materials include the following parts by mass: 20 parts of recycled concrete aggregate, 3 parts of polymerized MDI, 100 parts of asphalt, 80 parts of mineral stone and 3 parts of filler.

3. The polymerized MDI modified recycled concrete asphalt mixture according to claim 1 or 2, characterized in that: The polymeric MDI is a diphenylmethane diisocyanate polymer having 2-3 functionalities.

4. The polymerized MDI modified recycled concrete asphalt mixture according to claim 1 or 2, characterized in that: The recycled concrete aggregate is recycled aggregate obtained by crushing cement pavement concrete and building concrete.

5. The polymerized MDI modified recycled concrete asphalt mixture according to claim 1 or 2, characterized in that: The particle size of the mineral stone is 0.075 mm.

6. The polymerized MDI modified recycled concrete asphalt mixture according to claim 1 or 2, characterized in that: The filler is mineral powder, and the particle size of the mineral powder is less than 0.075 mm.

7. The method for preparing the polymerized MDI modified recycled concrete asphalt mixture according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) Preparation of polymerized MDI modified asphalt: first heat the asphalt to a fluid state, add polymerized MDI and stir evenly to obtain; (2) heating the recycled concrete aggregate and the mineral stone separately, and then mixing the recycled concrete aggregate and the mineral stone evenly; (3) Adding the polymerized MDI modified asphalt and filler obtained in step (1) to the product obtained in step (2), stirring evenly, to obtain a product.

8. The preparation method according to claim 7, characterized in that: The heating temperature in step (2) is 160-180° C. and the heating time is 4-6 hours.