Reclaimed asphalt pavement (RAP) has received much attention recently due to its increased use in hot mix asphalt (HMA) pavements to enhance pavement sustainability. The use of aged asphalt in RAP, which is highly oxidised and has lost its properties due to exposure to traffic loads and climatic conditions throughout its lifespan, can cause asphalt mixtures to stiffen and embrittle, thus negatively affecting the behaviour of asphalt mixtures. This issue may be resolved by including rejuvenating agents that can restore both physical and rheological properties of aged asphalt by increasing maltene fractions and decreasing asphaltene. However, the high restoration capacity of any kind of rejuvenating agent does not assure the durability of restored aged asphalt. This study explored the performance and durability of rejuvenated asphalt mixtures embedded with several types of rejuvenators identified from the extensive literature review. The study serves as a significant reference to predict future challenges in rejuvenating aged asphalt.

Evaluating the performance of rejuvenated asphalt mixes is crucial for pavement design and construction, as using a rejuvenator not only boosts recycling and contributes to positive effects on the environment but also increases the sensitivity to rutting and moisture. This study was executed to evaluate the effect of a warm mix asphalt (WMA) antistripping agent, namely nano-ZycoTherm, on the moisture-induced damage and rutting potential of asphalt mixtures containing 30% and 60% aged (RAP) binder and rejuvenated with 12% waste engine oil (WEO). For this purpose, the rutting resistance of asphalt mixes in wet and dry conditions was examined utilizing a loaded wheel tracker. In addition, the impacts of moisture on the performance of the mixtures were evaluated using different experiments, such as modified Lottman (AASHTO T283), resilient modulus, dynamic creep, aggregate coating and wheel tracking tests. Fourier transform infrared (FTIR) spectroscopy and thermogravimetric (TG) analysis were performed to identify the functional groups, which would be significant in terms of moisture damage, and to assess the thermal stability of binder samples, respectively. The results revealed that the rejuvenation of aged binder with WEO increases the moisture susceptibility of the mixtures; however, the addition of ZycoTherm was found to enhance the moisture resistance of WEO-rejuvenated mixtures. Furthermore, the results indicated that the WEO-rejuvenated mixtures modified with ZycoTherm exhibited a better rutting resistance in a wet condition compared to that of WEO-rejuvenated and conventional HMA mixtures. However, the rejuvenated mixtures modified with ZycoTherm showed poorer rutting performance in a dry condition. In summary, the adoption of the WMA antistripping agent, RAP binder and WEO rejuvenation techniques demonstrated satisfactory outcomes in terms of rutting resistance and moisture susceptibility, and also, these techniques are much less expensive to implement.

The reclaimed asphalt pavement (RAP) has become a moderately common practice in most countries; Hence, rejuvenating materials with RAP have earned publicity in the asphalt manufacturers, mainly due to the increasing raw material costs. In this study, the crumb rubber (CR) and waste frying oil (WFO) utilized as waste materials to restore the properties and enhance the rutting resistance of the RAP. Several physical, rheological, chemical properties of bituminous binders were tested. The result showed that the RAP bituminous binders incorporating WFO and CR decreased softening points and the increased penetration value; these translate to an increase in penetration index. Moreover, the viscosity of the WFO/CR combination reclaimed asphalt pavement binder showed better workability and stiffness, as well as a low storage stability temperature (less than 2.2 °C) with an acceptable loss upon heating. Without chemical reaction was observed between the waste-frying oil with the rubberized binder and the reclaimed asphalt pavement binder. Additionally, the WFO/CR rheological properties combined with the reclaimed asphalt pavement binder were comparable to the control sample. The incorporation of CR with WFO as a hybrid rejuvenator enhanced the rutting resistance. Therefore, the presence of WFO/CR has a considerable influence on the RAP binder properties while preserving a better environment and reducing pollution by reusing waste materials.

The crumb rubber (CR) recycled from waste tyres could be a viable alternative in achieving green pavements that offer exciting new markets to global investors. Adding CR into flexible pavements enhances their performance and ensures environmental sustainability. This paper will discuss the production variables, CR sizes and contents, blending techniques, optimum bitumen contents, morphology, standard characteristics, rheological characteristics, mechanical performance, greenhouse gas emissions, energy consumption and life cycle cost. This review study found that compared to traditional asphalt mixtures, the CR-modified asphalts had superior performance and longer service life. However, the dearth of information on several factors in CR asphalt production, including greenhouse gas emissions, energy consumption and life cycle cost during recycling, causes many agencies in the global asphalt industry to continue employing costly, energy-consuming additives such as styrene-butadiene-styrene (SBS) instead of CR to enhance asphalt.

The increase in the cost of virgin materials and the environmental sustainability have contributed to increasing the incentive to use asphalt mixtures containing high percentages of recycled asphalt pavement (RAP). However, the use of high percentage of RAP into virgin asphalt mixture could negatively affect the performance of some properties of asphalt mixtures. Thus, using an appropriate additive to offset the negative effect of RAP could lead to an increase in the amount of RAP in asphalt mixtures. Therefore, this study aimed to evaluate the effect of using glass fiber (GF) with different contents (0.0%, 0.1%, 0.2%, and 0.3%) as an additive on the performance of asphalt mixtures containing RAP materials (60%, 70%, and 80%) and rejuvenated with waste engine oil (WEO) i.e., 6%, 9%, and 12%. The performance of RAP mixtures incorporating GF was evaluated using the indirect tensile strength test (ITS), resilient modulus test, and moisture susceptibility test. Hamburg wheel track testing was done to evaluate the rutting performance of the 70% RAP mixture. The results showed that the GF modification enhanced the ITS, rutting resistance, moisture susceptibility, and resilient modulus of rejuvenated mixtures. It was also found that the GF content of 0.2% was the optimum.

Bitumen pavements play a critical role in modern transportation infrastructure, providing durable and reliable surfaces for roads and highways. However, traditional bitumen modifiers often rely on non-renewable resources and may contribute to environmental degradation. In response to the need for sustainable alternatives, this study explores the potential of utilizing sawdust (SD) and charcoal ash (CA) as bitumen modifiers. SD and CA were blended with bitumen grade 60/70 with 0% (control) and varied amounts of proportion using combination of SD and CA. Moreover, the sustainable modified bitumen mixture was assessed using the Marshall stability, indirect tensile strength and loss abrasion test. Specifically, adding 7SD0.5CA performs the best in stability as a sustainable modified bitumen mixture. The correlation between stability, tensile strength and loss abrasion for SD and CA modified bitumen mixture was significant, with a strong Coefficient of Determination (R2) of average 0.96 for all testing parameters. According to this study’s findings, the correlation of SD and CA content may improve the performance and engineering characteristics with respect to sustainable modified bitumen.