Optimization of RAP and SASOBIT for Permanent Deformation and Moisture Damage of Asphalt Mixes

Abstract

Transportation infrastructure plays a substantial role in the everyday life of social beings. The preservation of this vast infrastructure needs appropriate and cost-effective design technique which depends upon the selection and proportion of binder and aggregate. To save precious aggregates Reclaimed Asphalt Pavement (RAP) recycling is one of critical need, which also reduces the use of expensive asphalt binder. The production temperature limits the amount of recycled Hot Mix Asphalt (HMA). Warm Mix Asphalt (WMA) technology offers the option of recycling at a reduced temperature than conventionally used, thus a higher percentage of RAP can be recycled, and saving energy and cutting CO2 emission. The purpose of this experimental study (funded by the Higher Education Commission of Pakistan) was to evaluate the effects of WMA additive (sasobit) on permanent deformation and moisture susceptibility of HMA containing RAP. The mixtures’ durability (moisture susceptibility) was measured by the Universal Testing Machine (UTM) performing Indirect Tensile Strength (ITS) test and permanent deformation (Rutting) by Hamburg Wheel Tracking (HWT) test. The mixes with five different percentages of RAP i.e. 0%, 15%, 25%, 35% and 50% were prepared and tested for volumetric properties according to Marshall Mix Design procedure, and then preparing samples with further addition of four different percentages of sasobit i.e. 0%, 1%, 2% and 3% of Optimum Bitumen Content (OBC) for each mentioned percentages of RAP for rutting and moisture damage testing. The rutting potential of mixes were improved by addition of either RAP or sasobit or both as compared to control asphalt mixes. But for lower percentages of RAP i.e. up to 15% highest rut resistance was observed at 2% sasobit addition and for higher percentages of RAP highest rut resistance was observed at 3% sasobit addition. On the other hand, increasing RAP and sasobit content increased the moisture susceptibility of mixes so best recommended combination is to use 30-40% RAP in addition of 3% sasobit as far as permanent deformation and moisture susceptibility criteria’s are concerned. Overall, sasobit seems to be a workable tool for dropping production temperatures that can be readily mixed with HMA. Reductions in production temperatures can probably decrease fuel costs, reduce emissions of CO2 and many other hazardous gases, extend the winter paving window and facilitate specialized applications, such as construction of airport runway, where quick opening to traffic is necessary.