Study On Gradation Optimization Design And Technical Performance Of Asphalt Mixture At High Temperature And Rainfall

Asphalt pavements have been widely used along with the fast development of highway in China. more and more asphalt pavements are facing early damages such as rut and water damage etc at high temperature and rainfall. Wherefore a study on high temperature stability and water-resistant capability of asphalt mixture is of all-important operation significance to the asphalt pavement construction at temperature and rainfall.According to the special function requirements of different layers in the pavement, the author has proposed gradation optimization methods of asphalt mixture at high temperature and rainfall, and carried out an in-depth research on high temperature performance and water stability of asphalt mixture through choosing a scientific and reasonable evaluation index on the basis of the current deficiencies in high temperature stability evaluation and water stability evaluation of asphalt mixture.In this paper, the author has designed and developed a dynamic water scouring system and a new permeameter, and conducted the dynamic water scouring tests, the penetration shear tests, the national rutting tests, Hamburg Wheel-tracking Device (HWTD) tests, the traditional permeability tests and the Air permeability tests. The results proved that asphalt mixtures after gradation optimization perform much better than asphalt mixtures which have not gradation optimization in the aspect of anti-dynamic water scouring, anti-shear performance, high temperature stability and waterproof properties; the effective asphalt film thickness of asphalt mixture is an important factor in affecting asphalt mixture's anti- dynamic water scouring ability and performance at high temperature;Ï„max in suspension close-grained structure mixture would increase with the increasement of the nominal maximum size of aggregate; HWTD tests can distinguish different types of asphalt mixtures'performance at high temperature very well; the increasing extent of performance at high temperature increases with the increasement of the nominal maximum size of aggregate when using modified asphalt. Through regression analysis of HWTD results and the penetration shear test results, it comes to a conclusion that the penetration shear test can be used to evaluate asphalt mixture's performance at high temperature. The feasibility of dynamic water scouring system was validated on the base of good correlation between HWTD results and scouring splitting ratio. In addition, the author proposed a new mix proportion design idea based on dynamic water scouring tests at high temperature and rainfall.There is a good nonlinear correlation beteween the result of air permeameter and traditional permeameter, air permeameter can better evaluate permeability performance of different asphalt mixtures, to asphalt concrete, permeability increases with the increasement of NMAS and permeability of mix decreases with the increasement of asphalt content.Through the application of the asphalt mixtures after gradation optimization, the paper can draw a conclusion that the design method of ATB-30 mixture which considers gradation uniformity can well solve the aggregate segregation phenomenon which occurrs in large stone asphalt mix construction; mixtures using CAVF and modified SMA design methods have superior pavement performance.