Influence of Different Warm Mix Additives on Characteristics of Warm Mix Asphalt

Abstract

The interest in minimising fuel consumption and greenhouse gas emissions among road specialists is increasing. Thus, methods for reducing asphalt concrete mixing and compaction temperatures by a few tens of degrees Celsius without compromising the long-term performance has become a topic of significant interest. This study is focused on the analysis of warm mix asphalt (WMA) prepared with locally available materials in order to determine the suitable technology applicable to the specific traffic and climatic conditions of Romania. WMA was prepared using different warm mix additives (organic additives, chemical additive, and synthetic zeolite) at different mixing and compaction temperatures, and bitumen blends with these additives were analysed by carrying out the dynamic shear rheometer test and evaluating the penetration index. In conclusion it was noted that most additives did not lead to a significant change of bitumen`s characteristics, but the organic additive had a big influence on the bitumen`s properties. The characteristics of WMA are very similar to those of HMA. The mixing and compaction temperatures could be reduced by approximately 40 °C when WMA was blended with the additives without compromising the performance of the asphalt mixture, compared to hot mix asphalt.

Environmental Impact Assessment of Different Warm Mix Asphalts

“…Figures 1 and 2 show the values of the Marshall stability and flow for all the asphalt mixtures at the mentioned temperatures (T1-T3). In these figures the horizontal lines represent the reference values obtained for the Marshall stability and Marshall flow for HMA [36]. The Marshall stability values for all the WMA mixtures were close for all investigated cases, but lower than the values obtained for HMA.…”

“…The percentages of additives and synthetic zeolite were recommended by suppliers. The asphalt mixture dosage and the efficiency of additives used were confirmed by laboratory tests on binders and asphalt mixtures [36,37].…”

“…The synthetic zeolite is a sodium aluminium silicate that has been hydro-thermally crystallized. The crystallization is approximately 21% water by mass which is released from the zeolite structure in the temperature range of 85-180 • C [36].…”

“…For all the asphalt mixtures, Marshall stability and flow, stiffness modulus, resistance to permanent deformation (creep characteristics), and water sensitivity were determined [36].…”

“…Marshall stability helps to determine the optimum binder content and analysing the high-temperature behaviour of the bituminous layer under traffic loads. The flow index represents the deformation reached by the vertical diameter of the specimen at failure [36]. A low Marshall stability and a high Marshall flow shows a low stability at high temperatures for the asphalt mixture.…”