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By following up on the effect of rubber, which has recently been widely used as a direct additive to the asphalt binder or to the concrete mix as a percentage of the weight of the aggregate. The success of the effect of this type of admixture on improving the modified asphalt binder in addition to the modified concrete mix has been investigated. As it was noted the importance of following the asphalt properties due to the increasing use of crumb rubber modifiers in asphalt mixtures, there is a more position to check their rheological and physical properties comprehensively. In general, the performance of the asphalt rubber binder is affected by the rubber crumb content and mixing conditions. This research used 40/50 asphalt grade and Crumb Rubber additives with contents (5, 10, 15, and 20%). The main objectives of this study were to investigate the physical and rheological properties of rubber-modified asphalt binder and mixture. These purposes were achieved by testing HMA samples using the Marshall test approach to determine (Marshall stability and flow and void properties) and measuring the retained Marshall stability and DSR and Viscosity test. Sample testing showed that when recycled rubber was used as modifiers for asphalt mixes, the mixture became more stable, had a higher bulk specific gravity, and had less flow value and air voids. This infers that using recycled rubber can enhance the rutting resistance of bituminous mix.

This study aimed to determine how various concentrations of warm mix asphalt (WMA) additives can affect the rheological and physical characteristics of asphalt cement. Bitumen was modified by the chemical additive PAWMA® with an addition ratio of (0.2, 0.4, and 0.6), while the organic additives, Sasobit® and Kaowax®, were added at concentrations of (2, 4, and 6%) by the weight of bitumen. Bitumen hardness, softness, temperature susceptibility, viscosity, and elastic behavior have all been measured using a variety of physical and rheological tests, such as the penetration degree, softening point, penetration index, rotational viscosity, and dynamic shear rheology. This study showed that bitumen physical and rheological properties were affected differently according to the type and percentage of the WMA additive employed. The PAWMA additive, for instance, raised the bitumen penetration while Sasobit® and Kaowax® decreased the bitumen penetration degree. The inverse occurred for the softening point values. All WMA additives lowered bitumen viscosity values. Results from a dynamic shear rheometer (DSR) showed that the rutting index value (G*/Sin) rose, indicating improved rutting resistance.

Bituminous concrete mixture is the most widely used structural layer in flexible pavements. The surface layer of the paving is exposed to repeated loads in addition to changes in temperature, especially during the summer, when the temperature approaches the softness point of the asphalt binder, and therefore, it is subject to multiple types of failure, especially rutting. The properties of asphalt binder and asphalt mixtures can be improved by using various additives. Coconut shell powder, made from the dried husk of coconut fruit, is a popular addition in many industries. As a result of its high strength and stability, this waste material can be recycled into functional structural components such as composite material reinforcement. This study was conducted to evaluate the performance of coconut husk as very fine particles passing through sieve number 200 (0.075 mm) to modify the asphalt binder. The modifier was added at rates of (0, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10) by the weight of asphalt binder. Two asphalt binder types, 80/100 and 40/50 penetration grade, were used in this study. All asphalt samples were tested for penetration, softening point, rotational viscosity, and dynamic shear rheology. The results showed that the modified samples had better physical and rheological properties compared to the base asphalt binders. However, (7-8%) replacement of coconut husk powder, regardless of the base asphalt binder, yielded the best performance among the modified binders. In conclusion, coconut powder has significant potential as a road-building material due to its impact on the viability of the road construction sector. [ABSTRACT FROM AUTHOR]

All over the world, highway traffic is increasing rapidly, as is the population and the road network. The country's maximum and minimum temperatures also vary greatly. Moreover, the pavements are subjected to various types of damage. Pavement binders and mixtures are a constant area of research and development for scientists and engineers. Adding fibers to bituminous mixes may improve the properties of fatigue and strength of the material. Natural fibers may be used to improve asphalt mixtures performance due to their inherent compatibility with asphalt cement and excellent mechanical properties. Also, the high stone content and relatively high asphalt content in SMA mixture led to the occurrence of drain-down of the asphalt mastic from the mixture, and this problem requires the use of stabilizing additives such as cellulose fibers, mineral fibers, or polymers to mitigate this problem and ensure long-term performance. The most public sort of stabilizing additives is cellulose fiber. Overall, natural fibers in stone mastic asphalt mixes are discussed in this paper. An additional focus is on how asphalt concrete will be affected by natural fibers, mixing techniques, and managerial decisions. According to the review, the stabilizing and strengthening impact of natural fibers on the performance of asphalt mixes have been extensively researched. Natural fibers can significantly increase the rut and flow resistance of asphalt mixtures. Adding natural fibers to pavement can increase structural resistance to pavement distress. [ABSTRACT FROM AUTHOR]