Application of polymer fibers in asphalt mixtures

As a high-strength, durable and lightweight reinforcing material, road fiber can significantly improve the mechanical properties of asphalt pavement, thereby extending the fatigue life of the pavement structure.

Severe early damage to asphalt pavement is related to external factors such as long-term heavy-duty traffic, geographical climate, and construction quality. Even if modified asphalt is used, severe early damage such as rutting still occurs, affecting the normal and safe driving of vehicles.As an internal factor, early damage is closely related to the material properties of the asphalt mixture itself. Therefore, in the current severe heavy-duty traffic and climate environment, how to optimize the structure of asphalt mixture and improve the performance of asphalt mixture is the core and key to solving asphalt pavement problems.

Fibers are usually divided into two categories: hard fibers and soft fibers. Hard fibers refer to steel fibers made by drawing, pulling, rolling, and cutting processes; soft fibers are made of synthetic fibers, which are also divided into polymer chemical fibers (such as polyester fibers). Ester fiber, polyacrylonitrile, etc.) and mineral fiber (asbestos fiber, glass fiber, basalt fiber, etc.) and lignin fiber. Among them, polymer fiber is one of the most commonly used road fibers.

1.Polymer fiber Polymer fiber can be divided into light yellow, white and other colors according to different raw materials, and must not have stains or impurities. The following mainly introduces polyacrylonitrile fiber and polyester fiber.

(1)Polyacrylonitrile fiber (acrylic fiber) is a synthetic fiber made by wet spinning of more than 85% acrylonitrile and other second and third monomer copolymers. It is a kind of fiber specially used for asphalt concrete "reinforcement, Reinforced" fiber.

(2)Polyester fiber (polyester) is a fiber produced by using raw materials extracted from petroleum, adding special additives, and using the "rotation-melting" method. It is mainly used as a fiber additive for asphalt concrete. Compared with other fiber additives, polyester fiber has good weather resistance and is extremely resistant to acids and most other chemicals.

(3)Improve the high temperature stability of the mixture. The asphalt adsorbed by the criss-crossed fibers increases the proportion of asphalt in the interface layer and reduces free asphalt, thereby increasing the viscosity and softening point of the asphalt mixture and improving the high-temperature stability of the mixture. Chang'an University once conducted tests on asphalt mixtures mixed with polyester fiber and asphalt mixtures without polyester fiber. The test results showed that the Marshall stability of the asphalt mixture mixed with polyester fiber was increased by nearly 36%, and its dynamic stability was improved by nearly 36%. Stability has been improved by nearly 65%.

(4) Improve the low-temperature cracking resistance of the mixture. The low-temperature performance of fiber-reinforced asphalt mixture has a certain relationship with the physical and chemical properties of the fiber. The test of polyester fiber asphalt mixture conducted by Chang'an University proved that polyester fiber can still maintain flexibility and high tensile strength at minus 40°C, and its low-temperature crack resistance is excellent.

(5)Improves the mix's resistance to water damage.

(6) Improve the fatigue cracking resistance of the mixture and enhance the durability of the mixture. Polymer fibers are added to the asphalt mixture to increase the elastic recovery performance and stiffness modulus of the mixture, which can effectively prevent the expansion of pavement cracks and prolong the time for material instability expansion and fracture to occur. Therefore, the fatigue strength of the material is improved. It has been greatly improved and the durability has been improved.