The Mechanism And Key Technology Research Of Plant Asphalt Half Flexible Base

Most structural form of our country highway and the road is the semi-rigid base asphalt pavement. In this kind of pavement, the main role of semi-rigid base material is to bear load. In semi-rigid base, there are some advantages such as high strength, low cost, better water stability etc. At the same time, due to drying shrinkage and temperature shrinkage, semi-rigid base would crack. This will reduce the bearing capacity of base and affect the service life of the pavement. It has been the research hotspot about how to decrease and inhibit the crack of base effectively. It usually uses dry shrinkage coefficient and temperature shrinkage coefficient to evaluate the crack resistance of semi-rigid base.Plant asphalt is a kind of by-product in the process of deep processing of biomass, which annual outputs is quite high, mainly used in the casting adhesive and water proof asphalt and other fields, or directly used as filling material to burn heavy oil. In order to enhance the crack resistance of semi-rigid base, this paper introduces the new materials which are environmental friendly and low price into the semi-rigid base to improve dry shrinkage coefficient and temperature shrinkage coefficient. Through the indoor experiments, study from the follow aspects:interaction mechanism between plant asphalt and cement, determination of the optimum asphalt content, plant asphalt on the cement mortar shrinkage’s improvement, plant asphalt reduces the strength of cement stabilized fine grained soil, plant asphalt improves dry shrinkage coefficient and temperature shrinkage coefficient of cement stabilized fine grained soil, effect of plant asphalt on the strength of cement stabilized macadam. It is found that when plant asphalt adds into the semi-rigid base, the strength loss greatly. The reason is plant asphalt oily molecules dispersed among the cement particles, hinder the hydration reaction of cement and produce a large number of bubbles when dissolution. The two factors make extremely unfavorable influences to the strength of semi-rigid base. In order to improve the ultimate strength, we put forward the use of additives and some measures. Through experiments, the asphalt emulsifier, silane coupling agent, concrete triethanolamine were investigation, finally we found the method of high temperature curing and NaOH can improve the ultimate strength of plant asphalt semi rigid base.The experimental results show that when the amount of plant asphalt is5%, the shrinkage rate of cement mortar can be improved35%; in cement stabilized soil, which content5%quality of plant asphalt, the dry shrinkage coefficient is improved8.5%, the temperature shrinkage coefficient is maximum improved30%, through the NaOH, the unconfined compressive strength can achieve87%to the control group at28d age. When plant asphalt added into cement stabilized macadam, with the dosage of plant asphalt decreased, the strength of cement stabilized macadam had increasing trend, combined with high temperature curing and NaOH alkali excitation, the ultimate strength of2%dose of plant asphalt, cement stabilized macadam can reach2.8MPa, if continue to reduce the dosage of plant asphalt, the strength of cement stabilized macadam can be improved and then it will meet the requirements of specification. Conclusion shows that plant asphalt can enhance the anti cracking performance of semi-rigid base materials.