Conventional stone mastic asphalt (SMA) is being increasingly used in highways and expressways because it provides high rutting resistance, good skid resistance, and noise reduction for heavily trafficked roads. However, the conventional SMA mixture requires high mixing and compacting temperatures to create a suitable coating between the polymer-modified asphalt and large size of aggregate. Warm-mix asphalt (WMA) technology is being extended to provide significant economic benefits when applied to heat sensitive mixture, such as polymer-modified mixture, to reduce mixing and compacting temperatures. In this study, the performance characteristics of SMA–WMA mixture using new polyethylene wax-based WMA additive were evaluated against the conventional SMA mixture without additive, in terms of the moisture susceptibility, viscoelastic properties, rutting resistance at high temperature, fatigue resistance, and crack resistance at low temperature. The mix design was carried out in the laboratory for the conventional SMA mixture, and a similar composition was adopted for the SMA–WMA mixture (with the incorporation of 1.5 % WMA additive in the asphalt binder weight), in order to evaluate the influence of the performance characteristics of the resulting SMA mixture. Drain-Down and Cantabro test results of SMA–WMA mixture meet the requirement of the relevant criteria. Compared to the conventional SMA, the mixtures containing WMA additive show superior performance in moisture susceptibility, rutting resistance at high temperature, fatigue resistance at intermediate temperature, and crack resistance at low temperature. Therefore, this implies that the WMA additive is effective in reducing the production temperature, without compromising the performance of the SMA–WMA mixture.

Several warm-mix asphalt (WMA) technologies have been developed and implemented worldwide. Because of the reduced production and compaction temperatures of WMA mixtures, WMA technology can reduce energy consumption, carbon dioxide emission, and asphalt oxidation as well as extend the paving season, increase hauling distance, and create a better working environment. A wax-based WMA additive called low-energy and low–carbon-dioxide asphalt pavement (LEADCAP), has been developed by the Korea Institute of Construction Technology and Kumho Petrochemical and is the first WMA additive developed in South Korea. This paper introduces the characteristics of this newly developed WMA additive and presents the performance evaluation of WMA with LEADCAP. To evaluate the performance of the WMA mixture with LEADCAP additive, the Superpave® mix design, moisture susceptibility test, and mechanical test were performed. Common hot-mix asphalt and a WMA mixture with Sasobit additive were also evaluated for comparison. Sasobit is also a wax-based additive and is well-known. Mechanical tests included the dynamic modulus test, the direct tension fatigue test, and the triaxial repeated loading permanent deformation test. From the limited data obtained in this study, it was concluded that LEADCAP could be effectively used in WMA mixtures and that the performance of WMA with LEADCAP could be expected to be comparable to that of hot-mix asphalt and WMA with Sasobit additive.

The production of warm mix asphalt (WMA) mixtures with high percentages of reclaimed asphalt pavement (RAP) is gaining attention as a way to save costs and efficiently utilize existing resources. However, WMA must perform at least as well as hot mix asphalt (HMA) before it can be used as a replacement for HMA. In this study, the performance of a WMA mixture with a high percentage of RAP (40 % RAP) and a WMA additive (1.5 % of binder weight) that works as a rejuvenator was evaluated and compared with the performance of a HMA mixture with the same amount of RAP in order to evaluate the effects of the WMA rejuvenator. These mixtures were evaluated in terms of fatigue cracking using the simplified viscoelastic continuum damage (S-VECD) model and in terms of rutting using the triaxial stress sweep (TSS) test. In addition, layered viscoelastic pavement analysis for critical distresses (LVECD) was used to predict the fatigue resistance of these mixtures for future use. The WMA rejuvenator was found to improve the mixing and compaction ability of the WMA mixture. Also, compared to the HMA mixture, the WMA mixture showed better fatigue resistance, but the rejuvenator found to have an adverse effect on the rutting resistance of the mixture.

This study presents a laboratory evaluation on rutting resistance of Open Graded Friction Course (OGFC) mixes made with different polymer modifiers and coarse aggregate sizes. For this research work, six mix designs for three polymer modifiers (3% SBS modified, 6% LDPE modified, and 12% rubber modified) and two aggregate sizes (13 mm and 10 mm) were carried out to determine the optimum asphalt contents. The OGFC specimens were fabricated using the Superpave gyratory compactor at a compaction level of 50 gyrations. The air void contents and final rut depths of the mixtures were measured by the Corelok system and the Asphalt Pavement Analyzer (APA), respectively. In general, the results indicated that the polymer modifier plays an important role in the rutting resistance of the OGFC mixes used in this study. With respect to the coarse aggregate size, it was found to have little effect on the rutting potential.