The Warm Mix Asphalt (WMA) technologies have gained increasing popularity in recent years because of its unique property to allow the reduction in mixing and compaction temperatures of Hot Mix Asphalt (HMA) mixtures without compromising the quality of the mix. On the other hand, one of the reasons for utilizing the Crumb Rubber Modified (CRM) asphalt mixtures is that it increases the durability of the pavement by reducing the cracking and rutting potential of the pavement. However the CRM mixtures require a high mixing and compaction temperatures compared to the conventional HMA. Since the temperature requirements for CRM mixtures are more critical during construction, WMA technologies are expected to reduce the production and compaction temperatures of CRM mixtures. Therefore, since this concept has not been studied in detail, an investigation of the binder and mixture properties of warm mix asphalt modified rubberized mixes was initiated.
This research evaluated the effects of Aspha-min® and Sasobit® on five different sources of CRM binders in terms of viscosity, complex modulus, and the asphalt binder characteristics after long term aging. Based on the statistical analysis it was concluded that the WMA additives have an effect on viscosity and regardless of the source of binder and additive, viscosity was increased with time after the additive was added to the binder. Sasobit® was found effective in decreasing the viscosity of the binder at 135 °C and increasing the failure temperature after short term aging. The G* Sinδ value was observed to be higher with both the additives indicating an increase in cracking potential compared to unmodified CRM binders. Additionally Sasobit® was found to increase the low temperature cracking potential of the binders irrespective of the binder source used, as binders containing Sasobit® showed lower m values.
To evaluate the effect of WMA additives on compaction temperature of the CRM mixtures, 192 specimens were prepared (two aggregate sources, four different compaction temperatures, four different types of binder and six repetitions). Based on the statistical analysis it was concluded that the WMA additives were able to reduce the required compaction temperatures by up to 20 °C to 30 °C to get the target air voids. It was observed that the addition of WMA increased the %VFA and decreased the %VMA irrespective of the aggregate source used in this study. Over 108 specimens were made to evaluate the engineering properties of the CRM mixtures, and it was concluded that WMA technologies have no negative effect on the CRM mixture’s engineering properties such as rutting, moisture susceptibility and resilient modulus (MR).
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