Search

Warm mix asphalt (WMA) is increasingly recognised as a green paving technology in terms of energy saving and emission reduction. The reduction in mix production temperature associated with the WMA additives is very desirable from the environmental aspect. However, researchers and practitioners desire a comparable performance with hot mix asphalt (HMA). The major issue with WMA is their moisture susceptibility especially in the pavement early life. Therefore, this study aims at investigating moisture susceptibility of WMA using both laboratory characterisation and field performance compared to HMA. Three mixtures were investigated, namely; HMA mixture, foaming and Evotherm WMA mixture. The laboratory tests included; resilient modulus (MR), Indirect Tensile test, and Hamburg wheel tracking test. Test sections on Farm to Market FM 973 Highway near Austin, Texas, were constructed using these three mixtures. The results of field performance monitoring for five years are represented in this paper. Laboratory test results revealed small differences between measured dry and wet tensile strength and MR of HMA and WMA which shows some improvements using antistripping agents. The field performance evaluation showed that the Evotherm WMA mixture had the least transverse and reflected cracks while the HMA performed better in both ravelling and longitudinal cracking. [ABSTRACT FROM AUTHOR]

Understanding the performance of rejuvenated asphalt mixtures is critical for cleaner pavement design and construction, as the use of rejuvenators lead to environmental and economic benefits with the ability to increase recycling but promote rutting and moisture susceptibility at a high recycled binder ratio. Existing models have not systematically evaluated rejuvenated asphalt mixtures in terms of rutting performance from a mechanistic approach, and there is a lack of research related to the third stage of rutting induced by high-temperature moisture damage. To overcome these shortcomings, two-stage and three-stage mechanistic-empirical models based on viscoelastic stress-strain response were proposed in this study to predict and evaluate rutting and moisture susceptibility of rejuvenated asphalt mixtures. Wheel tracking tests in wet and dry conditions were performed on a virgin asphalt mixture (without recycled materials) and on rejuvenated asphalt mixtures (with recycled materials and rejuvenator), and the cumulative rutting curves were investigated. In addition, linear viscoelastic properties at a reference temperature were used as input parameters in a finite element model (FEM) to calculate the viscoelastic response of virtual specimens under repeated loading. The FEM results were then substituted into the proposed models to determine the material parameters for wet and dry conditions separately. Two prediction results were combined to determine the proportion of rutting caused by stripping in rejuvenated asphalt mixtures. Four indices were used in the evaluation of rutting in wet conditions. Based on the wheel tracking test results, the rejuvenated asphalt mixtures with the highest recycled material content performed worst in wet conditions and best in dry conditions, which indicates that anti-stripping agent might be necessary for rejuvenated asphalt mixtures. [ABSTRACT FROM AUTHOR]