The detrimental effects of hardening in asphalt pavements were first recognized by pioneering pavement engineers in the 1900s and have been studied extensively during the last 70 years. This hardening process, referred to as asphalt aging, is generally defined as change in the rheological properties of asphalt binders/mixtures due to changes in chemical composition during construction and its service life period. Aging causes the asphalt material to stiffen and embrittle, which affects the durability and leads to a high potential for cracking. This paper presents the state of the art on asphalt and asphalt mixture aging and use of antioxidant additives to retard the aging. A picture of complex molecular structure of asphalt and its changes due to atmospheric condition and various protocols used to simulate aging in laboratory environment are also discussed. Emphasis is given on recent studies on simulation of aging of asphalt mixtures as there has been limited research on mixtures compared to the asphalt binder. Finally, this paper presents the application of antiaging techniques and its mechanism, use of various types of antioxidant additives to retard aging of asphalt and, hence, improve the performance of asphalt pavements.

Tire-pavement friction is a key component in road safety. Adhesion and hysteresis are the two main mechanisms that affect the friction between rubber tires and pavements. This study experimentally examined the relationship between rubber–pavement adhesion and friction. The adhesive bond energy between rubber and pavement surfaces was calculated by measuring the surface energy components of rubber and aggregates. The friction was measured in the laboratory using a dynamic friction tester. The results revealed that there is a fair correlation between the adhesive bond energy and measured coefficient of friction. A rubber–pavement system with higher adhesion provided higher friction at low speed. In addition, the results demonstrated that there is a strong correlation between rubber–pavement friction and rubber properties. Softer rubber provided higher friction and vice versa. The results of this study provide an experimental verification of the relationship between adhesion and pavement surface friction. The adhesive bond energy and rubber rheological properties could be incorporated in computational models to study tire-pavement friction in different conditions (e.g., speed and temperature).

Noise pollution due to highway traffic has drawn the attention of transportation agencies worldwide. Noise pollution is an irritant to residents, especially in urban areas near roads with high traffic volume. In addition to its adverse effects on the quality of life, traffic noise can induce stress that could lead to sleep disturbance and anxiety. Traditionally, noise barrier walls have been used for highways to mitigate traffic noise. However, using barrier walls as a noise abatement measure has proven to be very expensive. In addition to the cost, noise barrier walls are not always effective because they must break the line of sight to work properly, which is not always possible in case of intersections or driveways. Therefore, researchers especially from Europe and USA have been very proactive to reduce the noise at source. A number of research studies show traffic noise can be reduced by using an alternative surface type or changing texture of the pavement while complying with other requirements of sustainability, i.e., safety, structural durability, construction and maintenance costs. This paper presents a comprehensive review of the research conducted on this subject. A review of the tire-pavement noise generation and amplification mechanism, various traffic noise measurement methods and correlation among these methods, in addition to the abatement techniques used by various agencies to reduce pavement noise, is also presented.

The rheological properties of asphalt binders change with aging. Aging is accelerated at elevated temperatures due to binder oxidation, leading to fatigue cracking and eventually pavement failure under heavy and repeated traffic loading. This study examined the effect of various antioxidant additives and copolymers with antioxidant agents on retarding the aging of asphalt binders. The performance of antioxidants was evaluated at the binder and mastic levels. Two unmodified binders were tested and fine asphalt mixtures made with these binders and three different aggregates were prepared and evaluated. Fatigue characteristics of asphalt binders and fine portion of asphalt mixtures (FAM) were determined before and after aging and an aging index was defined to evaluate the effect of antioxidants and copolymers on aging. The results showed that certain antioxidants and copolymers such as Redicote AP, Solprene and Calprene may retard the aging and improve the rheological properties of the asphalt binders. In addition, the results of FAM testing confirmed the favourable effect of certain antioxidants on improving the resistance to fatigue. In addition, the type of aggregate was found to influence the rate of aging of asphalt mixtures.

Ageing of asphalt binders has a significant impact on the rheological properties of asphalt binders and thus affects the performance of asphalt pavements. The rate of binder ageing is accelerated at high temperatures. This study presented a case study on the effect of ageing of the asphalt binder properties in the State of Qatar where asphalt mixtures experience harsh environmental conditions of elevated temperatures. The researchers collected field cores from 5-year-old trial pavement sections in Qatar, recovered the binder and tested to evaluate the change in the rheological properties of the binders. Test results indicated that there is a significant effect of ageing on the rheological properties of asphalt binder in Qatar. This effect was more prominent in the wearing course of pavements and diminishes with the increase in pavement depth. Binders along the wheel path experienced less ageing compared to shoulder. Aggregate type and mix design methods were also found to be affecting the extent of ageing of asphalt binder in the field. Furthermore, the researchers found that the current practice of ageing asphalt binders in pressure ageing vessel (PAV) to simulate ageing in the field is not sufficient for the Qatar case. It is recommended to extend the PAV ageing period from the standard 20 h for a hot climate like Qatar and it might go up to about 70 h based on the results of this study.

The quality of the interfacial bonding between asphalt binder and aggregates plays a significant role in determining the durability of asphalt mixtures. Warm mix asphalt (WMA) modifiers have been used extensively in the last decade primarily to reduce production and compaction temperatures as well as to improve workability of asphalt mixtures. This study aimed to provide better understanding of the effects of these WMA modifiers on the interfacial bonding between asphalt binders and aggregates. The evaluation focused on measuring surface energy of binders in unaged and aged states and aggregates and then calculating energy parameters that describe the potential of a given asphalt-aggregate combination to resist fatigue cracking and moisture damage. Results show that the combination of asphalt-WMA additive, as well as the content applied of WMA additive has a significant impact on the fatigue cracking and moisture damage resistance. The results suggest that it is poor practice to use a given type and percentage of WMA modifier without regard for binder type. Instead, test methods are recommended to evaluate the compatibility of asphalt binder, WMA additive type/content, and aggregates for improved performance at different conditions.