This research has accomplished a comparative rheological test on the unmodified and nanoclay modified bitumen. The results show that compared to unmodified bitumen, the nanoclay modification leads to changes in rheological parameter by increasing stiffness and decreasing the phase angle hence; it can also reduce aging effect on bitumen. Further, the comparison of the rutting parameter (G*/sind) shows that the nanoclay modification could increase the rutting resistance of bitumen where the improvement is dependent upon the type and amount of nanoclay.The fatigue resistance parameter (G*sind) at the low to medium temperature shows that the nanoclay modification reduces the fatigue life, however, it exhibits the same fatigue life as that of the unmodified bitumen after a particular ageing condition.

Post-consumer waste polymers are considered as environmental pollutants that should be reused as inexpensive materials. Also, there are resources of natural bitumen in several regions of Iran that can be used to modify bitumen. The purpose of this study is to investigate the possibility of obtaining penetration grade modified bitumen from vacuum bottom residue (VB) by adding various recycled waste polymers and non-polymer materials without air blowing VB. Following this concept, natural bitumen (NB), recycled waste polyethylene (PE), recycled waste latex, crump rubber modifier (CRM) and heavy vacuum slopes (HVS) were used. The formulation of mixing blends was determined by experimental design method using design-expert V.7.16 software. It was found that 40/50, 60/70 and 85/100 grades of penetration bitumen with improved performance grades, 82-40, 70-40 and 70-40, respectively, are producible using these materials, although, decreased ductility is observed almost for all the blends. A combination of 10% natural bitumen and 5% recycled latex with VB are considered as the best blend amongst all blends. The resulting modified 60/70 grade bitumen shows improved complex modulus in comparison with neat 60/70 bitumen and consequently it has increased resistance against permanent deformation (rutting). Also, the lowered Frass breaking point of this blend (-21°C) improved its low temperature performance (PG = 70-40). Unfortunately, when the crump rubber modifier particles are not well-dispersed and fine enough in bitumen matrix, there is an unexpected decreased ductility occurred in the blends.

Waste management is a major concern in petrochemical plants. Almost all types of wastes are used to modify bitumen. Following this concept polymer and non-polymer wastes of petrochemical production lines were used to modify bitumen. It was found that incorporation of the wastes separately or as a combination of some high performing polymer-modified bitumens are obtained. Almost all modifiers did not improve the low temperature properties of the modified bitumen and in some cases deteriorated this property. The low molecular weight polyethylene (LMP) and Nmethylpyrrolidone (NMP) wastes increase high temperature performance of bitumen, whereas styrene-butadiene rubber (SBR) waste improves low temperature performance at moderate concentrations. The best performance grades (PG) obtained by introducing these modifiers are PG = 106-10, PG = 76-22 and PG = 94-16 at a rate of 5% modification, respectively. The best performance grades obtained with mixtures of NMP and SBR were PG = 82-16 and PG = 76-22. The most useful performance grades resulted form incorporation of mixtures of LMP and SBR in bitumen were PG = 94-16 and PG = 100-10. In fact, mixtures of LMP and SBR wastes were found to be the most beneficial compositions for bitumen modification.

Pavement as a multi-layer structure is subjected to various distress mechanisms such as permanent deformation (Rutting) in its service time. Rutting resistance evaluation is one of the important components of pavement management system which plays a substantial role in the effective strategic development of pavement rehabilitation and maintenance. Improving the rheological properties of bitumen using one of the various additives is one of the practical approaches to reduce the rutting potential in the asphalt mixture. In this study, basic bitumen with an 85/100 penetration grade (PG58-22) was modified by 0.5, 1.0 and 1.5% poly phosphoric acid by weight of bitumen. The rutting resistance improvement of modified bitumen was investigated according to Superpave protocol. For this purpose, temperature sweep and frequency sweep tests were performed on all bitumen at 46, 52 and 58 oC. Also, rutting resistance improvement ratio was calculated based on the Superpave specification (|G*|/sind), Shenoy specification (|G*|/ [1- (1/sin d´tand)]) and zero shear viscosity. This ratio was employed to rank these specifications. The results of this study represent an improvement in rutting resistance of modified bitumen. According to specification ranking results, it can be concluded that zero shear viscosity has more potential and credibility to predict rutting damage occurrence as compared to Superpave specification and Shenoy specification

In this study an empirical model which can be used to predict the rutting parameter (G*/sinl5) for neat and powder rubber modified bitumen describes. The model was developed using 36 unique powder rubber modified bitumen combinations, rubber concentrations were varied at 5% intervals between 5 and 20%. The effects of powder rubber particle size on model accuracy were also studied; ultimately a model was produced with the capability of predicting rutting parameter values over a range of temperatures and rubber concentrations. By definition, the upper limit of the performance grade is dependent on the rutting parameter value; therefore, the relationship was also considered in terms of high end failure temperature. The Rubber Coefficient for rutting parameter (Rcg) was identified as an important parameter in the estimation of rutting parameter (G*/sind) with the addition of powder rubber. This term is a quantitative representation of the increase typically witnessed in rutting parameter values with the addition of powder rubber. Ambient ground powder rubber exhibited higher revalues than cryogenically ground particles. Additionally, 95% confidence intervals were generated for the predictive model thus providing a range of accuracy for the model. The resulting confidence intervals were approximately +/-1300 Pa; these confidence intervals were seen to capture 92.6% of the 462 data points used. Findings from this research suggest that the differences between cryogenic and ambient powder rubber bitumen are accurately described using the Rcg furthermore bitumen properties may be predicted using an empirical equation.

Polymer modified asphalt binders have been used for years to produce asphalt mixes with improved resistance to rutting، fatigue cracking، and thermal cracking. Special equipment and technique، which may not be always available، are required to produce polymer modified binders with desired engineering properties. Recently، a new approach is introduced to facilitate the use of polymers in asphalt mixtures. Polymer-binder additive، with 40% Styrene Butadiene Styrene [SBS]، produced in pellet form can be directly incorporated to the mix during production in asphalt plant without the need for any special equipment. Logistically، this new form of mix additive simplifies and expands the use of polymers even for small paving projects. However، due to the novelty of technology more research is required to assess its efficacy. In this paper stiffness، rutting، fatigue، and thermal cracking resistance properties of asphalt mixes modified with polymerized pellet are compared to the mixes containing unmodified and polymer modified binders. The effects of long-term oxidative aging on stiffness and strength of mixes were also evaluated. Result of this study showed that the polymerized pellet mix additive had similar effects as the SBS polymer modified binder in improving asphalt mix performance-related properties.