This study investigated the effects of carbon nanotubes (CNT) as a binder modifier on the performance properties of asphalt binders and storage stability of polymer modified binders. Performance characteristics of CNT modified binders were investigated through physical and rheological tests such as penetration index (PI), viscosity temperature susceptibility (VTS), temperature susceptibility (TS), and frequency sweep tests. Furthermore, the influence of CNT on storage stability of styrene-butadiene-styrene (SBS) modified binders was investigated by measuring rheological properties like separation index (SI), separation ratio ($R_s$ ), degradation ratio ($R_d$ ), and softening point difference (SPD) of the triple nanocomposite. The results indicated that the addition of CNT decreased PI, TS, and VTS and improved physical and rheological properties of the asphalt binder. Also, the results showed a significant relationship between the CNT content and PI, TS, and VTS in CNT modified binders. Regarding storage stability, adding CNT to the SBS modified binder resulted in improved stability, indicating a strong interaction between the asphalt binder and SBS polymer.

Bitumen as a main and efficient material in the behavior of hot mix asphalt (HMA) already has attracted the attention of various researchers. Bitumen modification with polymeric and nonpolymeric materials was considered one of the main research subjects relevant to increasing road life cycles. Crumb rubber is one of the appropriate bitumen modifiers due to its desired properties, and it also helps to reduce environmental pollution. In the current research, two types of mesh, crumb rubber (mesh of Nos. 14 and 50), with three different percentages (10, 15, and 20%), have been mixed with three types of bitumen, and the obtained results have been investigated on high-temperature (HT), intermediate-temperature (IT), low-temperature (LT), and viscosity properties. Also, in order to investigate the impact of aging on stated parameters, test results on bitumen samples modified by crumb rubber, before and after aging, have been studied.

The effects of interface condition on the life of flexible pavements have been determined. The methodology consists of implementing a previously derived interface constitutive model into the Kenlayer programme to compute the stresses and strains in typical flexible road structures. The shell transfer functions for fatigue cracking and terminal serviceability were used to estimate the pavement life. The behaviour of in‐service pavements indicates that the condition of the bonding between pavement layers plays an important role in the road structures performance. Premature failure of road sections due to layer separation, leading to redistribution of stresses and strains in the pavement structure, is often encountered, especially in areas where the vehicles are more likely to apply horizontal forces. In computing the critical stresses and strains, most of the mechanistic design procedures of flexible pavement structures consider that pavement layers are completely bonded or completely unbounded.

In this study Cyclogen, Rapiol and waste cooking oil was used as rejuvenators to improve properties of aged bitumen. The effects of these rejuvenators on asphalt mixtures containing 50% of reclaimed asphalt pavement specimens was evaluated using dynamic creep, resilient modulus, low temperature fracture energy and moisture susceptibility tests and the results was compared to recycled mixtures without rejuvenator and control HMA mixtures. The results showed that the rejuvenators are effective in alleviating the aging effect of RAP bitumen. Waste cooking oil performed better than other studied rejuvenators followed by Cyclogen and Rapiol. However, moisture resistance was impaired when rejuvenators were used.