论文部分内容阅读
Bitumen/Asphalt is one of the main materials that is widely used by the pavement industry throughout the world.Flexible pavements primarily consist of two basic components,aggregate and Asphalt binder.Asphalt binder performance is largely dependent on the amount of loading and the temperature.In some area of Pakistan where temperature is high,rutting is the main problem that is faced in flexible pavement which is due to increase of loading and high temperature.With increase of Population,there is rapid increase in number of vehicle and the waste tire are problematic source of waste and is main concern for environment due to large volume production.To increase the strength of conventional Asphalt binder,researchers have used different additives to increase its strength.Waste scrap tire rubber is used to improve the properties of bitumen.Asphalt Rubber is used which is produced by blending Asphalt with rubber.By this,it provides dispose of scrap tires as these scrap tires are burned which is not environmental friendly.For this,Crumb rubber obtained was further grind to micro size mesh passing sieve no 150.In this study,Conventional testing was performed to check and compare the result between different percentage of Crumb Rubber（CR）.In this study,for aggregate selection,NHA class A was selected for aggregate gradation and bitumen penetration grade of 60/70 was used.By using Wet process,Crumb Rubber was mixed with asphalt to get the required blend.Four percentages（4%,8%,12%,and 16%）of Crumb Rubber by weight of asphalt binder was selected.Conventional testing which include penetration test,softening point test,and ductility test of HMA mixture.Fourier transform infrared spectroscopy（FTIR）was performed to examine the homogeneity and proper mixing of the Crumb Rubber in asphalt binder.Marshal stability test was performed to find Optimum binder content for different percentage of modified and unmodified binder.For it,75 samples were prepared to get result for each modified binder and the result were compared.Wheel tracking and dynamic modulus tests were used to evaluate the performance of Unmodified and Modified HMA mixtures.The results showed that modified binder performance improves significantly as compared to conventional asphalt.By using CR,it causes more stiffness to mixture which improves its high temperature performance by increasing rutting resistance and increasing dynamic modulus.