Sharif Digital Repository

Modification by crumb rubber is a useful means of improving the resistance of asphalt binders and mixtures against rutting, fatigue cracking, and low temperature cracking. Increase binder viscosity and decrease stability at high temperatures are accompanied by most modifiers, and crumb rubber is no exception. Recent research efforts have shown that development of cross bonds across polymer chains and sulfur can improve the storage stability of modified binders. Also, WMA additives can considerably decrease the binder viscosity. This research showed that addition of small amount of sulfur during the crumb rubber modification can improve the workability and storage stability of this binder.... 

Increased environmental concerns and high oil prices have encouraged highway agencies to maximize the use of recycled materials like Reclaimed Asphalt Pavements (RAP) in pavement construction. However, utilization of RAP has limited to low percentage, generally less than 25%. This is due aged, stiffer, and less strain tolerant asphalt binder in RAP. As the RAP proportion increases, a large amount of the aged binder will be introduced into the mixture. The excessive stiffness of HMA mixture tends to lead to less workable mixture. Studies were conducted to examine the effect of Sasobit on the workablility of high RAP mixtures. The results indicated while the utilization of Sasobit had improved... 

Recycled materials have been very much taken into consideration in recent years due to economic issues and the preservation of natural resources. Warm Mix Asphalt (WMA) is also of particular importance due to less energy use in construction and environmental compatibility. This study examines the compressive workability and resistance to low temperature crackings of warm mixt asphalt containing reclaimed asphalt pavement (up to 30% by weight of aggregate). Sasobit was used as an organic additive in 1.5% by weight of bitumen in warm mix asphalt. Two additives of crumb rubber modifiers (9, 15 and 18% by weight of bitumen) and hydrated lime (1.5 and 2% by weight of aggregate) were also used to...