Research On Road Performance And Environmental And Economic Costs Of Fast-growing Grass Fiber Asphalt Mixtureby

In response to the construction of ecological civilization,adhere to the basic national policy of saving resources and protecting the environment.The use of fast-growing grass plants to prepare herbaceous fiber instead of lignin fiber is not only conducive to saving forest resources,but also reducing the waste of fast-growing grass plants and the CO₂ emissions after incineration.In this paper,moso bamboo and reed fast-growing grass were used to prepare fast-growing grass fibers and compared with lignin fibers prepared from Chinese fir as raw material.The physical properties,microstructure of lignin,bamboo and reed fibers were tested.Meanwhile,the physical and thermal properties of fiber asphalt mortar,road performance and micro structure of the fiber asphalt mixture were analyzed,and then,the reinforcement mechanism of the three fibers to the asphalt mortar and mixture were revealed.The comparative method was used to study the environmental and economic costs of the lignin and bamboo fibers from raw material production to asphalt pavement construction.The main research results of the paper are as follows:1)The technical indicators of moso bamboo fiber and reed fiber produced by physical methods meet the requirements of the specification.Lignin fiber has better thermal stability than bamboo fiber and reed fiber.The three types of fibers have different degrees of improvement on the thermal stability of the asphalt mortar.The order of improvement effect is reed fiber<bamboo fiber<lignin fiber.The low-temperature flexibility and elasticity of bamboo fiber are better than those of lignin and reed fibers,its asphalt mortar has the best low-temperature crack resistance.2)The gradation,optimal fiber content（0.4%）and optimal asphalt conotent of three kinds of fiber asphalt mixtures are determined.For SMA-13,the optimal asphalt content of lignin fiber,bamboo fiber and reed fiber asphalt mixture is 5.9%,6.5%and 6.2%respectively.For AC-13,the optimal asphalt content of lignin fiber,bamboo fiber and reed fiber asphalt mixture is 5.0%,5.3%and 5.0%respectively.3)The road performance of SMA-13 and AC-13 asphalt mixtures of lignin fiber,bamboo fiber,and reed fiber were measured.It was found that the road plant fiber can effectively improve the mechanical properties,high-temperature stability,low-temperature crack resistance,moisture stability and anti-aging properties of asphalt mixture.Bamboo fiber has the best effect on improving the moisture stability,low-temperature crack resistance and aging resistance of asphalt mixtures;lignin fiber has the best effect on improving the mechanical properties and high-temperature stability of asphalt mixtures.4)SEM micro-test results show that the fluffy protrusions at the ends of lignin fibers can provide stronger reinforcement in asphalt mixture.The adsorption of bamboo fibers on asphalt is stronger than lignin fiber and reed fiber.the uneven structure on the surface of the reed fiber can enhance the internal friction of the asphalt mixture.5)Analysis results of environmental and economic benefits of lignin fiber and bamboo fiber asphalt pavements during construction show that the environmental benefits of moso bamboo forest are better than that of Chinese fir forest,and the gap of environmental hazards between the two fiber asphalt mixtures during construction is extremely small.The economic benefits of moso bamboo forest during the two rotations are 49.3%higher than that of Chinese fir forest.The preparation cost of bamboo fiber is only 34.3%of that of lignin fiber.The construction cost of lignin fiber asphalt pavement is about 6.6%higher than that of bamboo fiber asphalt pavement.The use of fast-growing grass to prepare road plant fibers not only helps to reduce the consumption of forest resources and engineering costs,but also broadens the scope of plant fiber materials used in asphalt pavements.It is of great significance to improve the performance of asphalt pavement in our country,reduce the construction cost and protect the ecological environment.