Preparation method of water-excited tough cold-mixed asphalt mixture

Abstract

The invention relates to a preparation method of a water-excited tough cold-mixed asphalt mixture, belongs to the field of asphalt pavement maintenance, and solves the problems that a traditional cold-mixed asphalt mixture is low in initial strength, slow in strength formation, poor in timeliness and poor in durability, volatile harmful substances exist, a common reactive cold-mixed asphalt mixture is high in cost, the reaction time cannot be controlled and the like. The preparation method comprises the following steps: firstly, adding a certain amount of reactive diluent and silane coupling agent into SBS modified asphalt to prepare diluted asphalt; then preparing a water-excited curing agent from metakaolin and Portland cement in proportion; and finally, uniformly mixing the diluted asphalt, the aggregate, the water-excited curing agent and the fiber according to an asphalt-aggregate ratio of 5.3% and a gradation median value of AC-13F to obtain the water-excited tough cold-mixed asphalt mixture. When the water-excited tough cold-mixed asphalt mixture is used, a preparation process of firstly watering and then compacting is adopted. The method has very important practical significance in the aspects of improving various properties of the cold-mixed asphalt mixture, improving the rapid maintenance and repair technical level of the asphalt pavement, protecting the environment and the like.

Description

Technical Field

[0001] The present application discloses a method for preparing a water-activated toughened cold-mix asphalt mixture, and belongs to the field of asphalt pavement maintenance. Background Art

[0002] In recent years, with the vigorous development of my country's transportation industry, the scale of highway construction has continued to expand, and the requirements for road quality and performance have also increased. Asphalt pavement has become the mainstream choice of graded pavement in my country with its advantages of high construction efficiency, good comfort and convenient maintenance. However, asphalt pavement is prone to gaps and cracks due to problems with the mixture itself and changes in the external environment during long-term use, eventually forming potholes. At present, pavement maintenance and repair technologies mainly include hot patching and cold patching. Traditional hot patching asphalt mixture has good road performance and high repair quality, but it has strict requirements on construction temperature and paving and compaction conditions. It cannot quickly and effectively repair pavement diseases in bad weather such as rain, and the construction consumes a lot of energy and produces greenhouse gases. Cold patching technology makes up for the shortcomings of hot patching. The construction process is simple and convenient at room temperature, with high safety, environmental protection and energy saving. It has gradually become the preferred method for repairing potholes in asphalt pavements.

[0003] Cold-mix asphalt mixture is a new type of road material that is mixed and paved at room temperature by mixing diluted asphalt binder with aggregates and additives with certain grading requirements in a certain proportion. Compared with traditional asphalt pavement construction technology, this technology realizes construction at room temperature and is not affected by temperature and season. It overcomes the drawbacks of traditional pavement resource waste and environmental pollution. It is suitable for emergency repair and daily maintenance of local damage such as potholes and cracks in roads under various climatic conditions, meets the technical requirements of "green construction", and has significant social and environmental benefits. Traditional cold patching methods mostly use solvent-based cold-mix asphalt mixtures, whose strength mainly depends on the volatilization of solvents such as petroleum solvents and the continuous rolling of wheels after opening to traffic. It pollutes the environment, has low initial strength and slow strength formation. Construction at room temperature makes it difficult to effectively compact the mixture, and when repairing potholes with water, the water will further reduce the durability of the cold-mix asphalt mixture.

[0004] In order to solve the problems of low early strength, environmental pollution and poor durability of traditional cold-mix asphalt mixtures, researchers use liquid petroleum asphalt mixed with polymers as a binder, add a certain proportion of curing agent when repairing the road surface, and prepare a reactive cold-mix asphalt mixture. The curing agent reacts with the polymer to form a spatial network solidified material, which provides molding strength and good performance. At present, the common reactive cold-mix asphalt mixtures are epoxy resins and polyurethanes. Among them, epoxy resin mixtures form insoluble and infusible three-dimensional network solid compounds through curing reaction at room temperature. The toughness of epoxy resin is relatively poor after curing and under low temperature conditions. Moreover, epoxy resin and asphalt are two substances with different polarities. They have poor compatibility under simple physical mixing conditions, resulting in uneven performance of the mixture. Polyurethane mixtures mix polyurethane prepolymers into diluted asphalt. As the diluent evaporates, the free isocyanate groups in the polyurethane, the active hydrogen components in the asphalt system and the moisture in the air undergo a curing reaction, and cross-linking and curing form strength, but the price of polyurethane materials is relatively high. In general, these two types of cold-mix asphalt mixtures are expensive, have complex preparation and construction requirements, cannot control the reaction time and process, and have a long curing time.

[0005] Therefore, the present application proposes a method for preparing a water-activated tough cold-mix asphalt mixture, which uses environmentally friendly unsaturated fatty acids as reactive diluents, introduces water-activated alkaline curing agents, and adds mineral materials, fibers, curing agents, and diluted asphalt in a reasonable oil-stone ratio to prepare a water-activated tough cold-mix asphalt mixture. When used, water is added for rolling, and the water-activated alkaline curing agent and water produce a "volcanic ash effect". At the same time, the diluent and the hydration reaction product react chemically to form strength, thereby achieving rapid hardening of the cold-mix asphalt mixture and rapid opening to traffic. The present application provides a green and efficient road repair material that is suitable for various construction conditions, significantly improves the maintenance and repair efficiency of asphalt pavements, and complies with the concept of "green transportation." Summary of the invention

[0006] (1) Technical issues

[0007] The purpose of this application is to provide a method for preparing a water-activated tough cold-mix asphalt mixture, so as to solve the problems of low initial strength, slow strength formation, poor timeliness, poor durability, presence of volatile harmful substances, high cost and difficult to control reaction time of traditional cold-mix asphalt mixtures, thereby promoting the development of convenient cold patching technology for asphalt pavements.

[0008] (2) Technical solution

[0009] In order to solve the problems of low initial strength, slow strength formation, poor timeliness, poor durability, presence of volatile harmful substances, high cost and difficult to control reaction time of conventional cold-mix asphalt mixtures, the present application first adds a reactive diluent and a silane coupling agent to styrene-butadiene-styrene block copolymer (SBS) modified asphalt to prepare diluted asphalt, then configures a water-activated curing agent in a certain proportion, and finally evenly mixes the diluted asphalt, mineral material, fiber and water-activated curing agent to obtain a water-activated tough cold-mix asphalt mixture. The technical solution of the present application is as follows: select SBS modified asphalt, add a certain amount of reactive diluent and silane coupling agent, and obtain diluted asphalt containing coupling agent after sufficient shear development; mix kaolin and ordinary Portland cement in a certain mass ratio to obtain a water-activated curing agent, and prepare a water-activated strong and tough cold-mix asphalt mixture with basalt coarse aggregate, limestone fine aggregate, mineral powder and basalt short fiber according to the grading and optimal asphalt dosage determined by the mix ratio design. The mixture is poured into the cleaned pit and evenly sprinkled with water and compacted, and then opened to traffic 1 hour later, which fully solves the problems of poor timeliness, poor durability and high cost of existing cold-mix asphalt mixtures.

[0010] (3) Beneficial effects

[0011] Long-term rainfall can easily lead to loose asphalt pavement, cracks and potholes, which has always been a difficult problem in road maintenance. The present application provides a method for preparing a water-activated tough cold-mix asphalt mixture, which promotes the rapid hardening of the cold-mix asphalt mixture and quickly forms strength through a chemical reaction between a water-activated diluent and a curing agent; the continuous dense gradation exactly the same as that of a hot-mix asphalt mixture is adopted, and the density is high after molding; a certain proportion of fiber is added to play a reinforcement role, and the toughness and crack resistance of the mixture are improved; its reaction mechanism is chemical cross-linking and curing, which solves the problem that traditional cold-mix asphalt mixtures are afraid of water erosion; the material can be used as soon as it is mixed, and can also be stored for a short period of time, which effectively improves the flexibility and convenience of construction; the present application does not contain any volatile diluents, has high environmental protection, and has very important practical significance for improving the technical level of asphalt pavement maintenance, improving the quality of road use, and environmental protection. DETAILED DESCRIPTION

[0012] The present application provides a method for preparing a water-activated tough cold mix asphalt mixture, and the specific implementation steps are as follows:

[0013] (1) A certain amount of SBS modified asphalt is heated to 180°C, and a reactive diluent accounting for 60% of the mass of the asphalt is added, wherein the reactive diluent is an unsaturated fatty acid, including ricinoleic acid, linoleic acid, and oleic acid. A mechanical stirrer is used to stir at 40 rpm for 15 minutes to fully disperse the reactive diluent in the asphalt, and then stirred at 200 rpm for 20 minutes. During the entire stirring process, the temperature of the asphalt is 150°C, and the asphalt is placed in an oven at 80°C for 30 minutes to obtain a diluted asphalt;

[0014] (2) adding 0.3% of silane coupling agent to the diluted asphalt prepared in step (1), performing shear stirring at 80° C. using a high-speed shearing machine, with a shear rate of 1000 rpm and a shear time of 20 min, and then placing the mixture in a 60° C. oven for 30 min to obtain a diluted asphalt containing a coupling agent;

[0015] (3) 4000 mesh metakaolin and 425 type ordinary Portland cement are mixed in a mass ratio of 1:2, stirred and mixed evenly in a mixing pot, and then ground in a ball mill for 5 minutes to obtain a water-activated curing agent for diluted asphalt;

[0016] (4) Take a certain amount of the diluted asphalt containing a coupling agent prepared in step (2), heat and soften it, and then keep it warm at 90°C. According to the median value of the AC-13F grading of the asphalt mixture, weigh basalt coarse aggregate, limestone fine aggregate, mineral powder and 0.3% of basalt fiber, add a water-activated curing agent accounting for 2% of the total mass of the mixture to replace part of the mineral powder, stir the mineral material and fiber at a speed of 40 rpm for 30 seconds, add the diluted asphalt containing a coupling agent according to the optimal oil-stone ratio of 5.3%, stir at a speed of 50 rpm for 50 seconds, then add the mineral powder and the water-activated curing agent, stir at a speed of 50 rpm for 40 seconds, mix evenly, cool to room temperature, and store in a sealed bag to obtain a water-activated tough cold mix asphalt mixture;

[0017] (5) According to the rutting test, low-temperature beam bending test and freeze-thaw splitting test methods in the "Test Procedure for Asphalt and Asphalt Mixtures for Highway Engineering" (JTG E20-2011), water accounting for 8% of the mass of the water-activated toughened cold mix asphalt mixture is added to stimulate the rutting plate specimens, beam specimens and Marshall specimens formed by the water-activated toughened cold mix asphalt mixture prepared in step (4). After the tests, the high temperature stability, low temperature crack resistance and water stability of the water-activated toughened cold mix asphalt mixture are evaluated, and the preparation method of the water-activated toughened cold mix asphalt mixture is determined.

Claims

1. A method for preparing a water-activated tough cold-mix asphalt mixture, characterized in that The specific steps of this method are as follows: (1) A certain amount of SBS modified asphalt is heated to 180°C, and a reactive diluent accounting for 60% of the mass of the asphalt is added, wherein the reactive diluent is an unsaturated fatty acid, including ricinoleic acid, linoleic acid, and oleic acid. A mechanical stirrer is used to stir at 40 rpm for 15 minutes to fully disperse the reactive diluent in the asphalt, and then stirred at 200 rpm for 20 minutes. During the entire stirring process, the temperature of the asphalt is 150°C, and the asphalt is placed in an oven at 80°C for 30 minutes to obtain a diluted asphalt; (2) adding 0.3% of silane coupling agent to the diluted asphalt prepared in step (1), performing shear stirring at 80° C. using a high-speed shearing machine, with a shear rate of 1000 rpm and a shear time of 20 min, and then placing the mixture in a 60° C. oven for 30 min to obtain a diluted asphalt containing a coupling agent; (3) 4000 mesh metakaolin and 425 type ordinary Portland cement are mixed in a mass ratio of 1:2, stirred and mixed evenly in a mixing pot, and then ground in a ball mill for 5 minutes to obtain a water-activated curing agent for diluted asphalt; (4) Take a certain amount of the diluted asphalt containing a coupling agent prepared in step (2), heat and soften it, and then keep it warm at 90°C. According to the median value of the AC-13F grading of the asphalt mixture, weigh basalt coarse aggregate, limestone fine aggregate, mineral powder and 0.3% of basalt fiber, add a water-activated curing agent accounting for 2% of the total mass of the mixture to replace part of the mineral powder, stir the mineral material and fiber at a speed of 40 rpm for 30 seconds, add the diluted asphalt containing a coupling agent according to the optimal oil-stone ratio of 5.3%, stir at a speed of 50 rpm for 50 seconds, then add the mineral powder and the water-activated curing agent, stir at a speed of 50 rpm for 40 seconds, mix evenly, cool to room temperature, and store in a sealed bag to obtain a water-activated tough cold mix asphalt mixture; (5) According to the rutting test, low-temperature beam bending test and freeze-thaw splitting test methods in the "Test Procedure for Asphalt and Asphalt Mixtures for Highway Engineering" (JTG E20-2011), water accounting for 8% of the mass of the water-activated toughened cold mix asphalt mixture is added to stimulate the rutting plate specimens, beam specimens and Marshall specimens formed by the water-activated toughened cold mix asphalt mixture prepared in step (4). After the tests, the high temperature stability, low temperature crack resistance and water stability of the water-activated toughened cold mix asphalt mixture are evaluated, and the preparation method of the water-activated toughened cold mix asphalt mixture is determined.