Comparative laboratory study of Sasobit and Aspha-Min additives in warm-mix asphalt

Warm-mix asphalt (WMA), which reduces the production temperatures (mixing and compaction) while maintaining the advantages of hot-mix asphalt (HMA), is becoming an attractive paving material. In this study, rheological properties of two commonly used performance grade (PG) binders (PG 64-22 and PG 70-28) were evaluated, with and without Sasobit and Aspha-Min additives. For PG 64-22,2%,3%, and 4% Sasobit additive reduced the mixing temperature of the pure binder from 163 degrees C to 147 degrees C (i.e., by 16 degrees C). In case of the PG 70-28, the reductions are 10 degrees C, 12 degrees C and 13 degrees C, respectively, for 2%, 3%, and 4% Sasobit additive. No significant decrease in mixing temperature by the Aspha-Min additive was observed in using the rotational viscometer. Evaluation of the binders on the basis of G*/sin(delta) demonstrates no negative effect on high-temperature grading due to high-temperature viscosity reduction. With the addition of 4% Sasobit additive, the high-temperature binder grading of PG 64 (actually PG 65) increases to PG 69, while 4% Sasobit additive improves the PG 70 (actually PG 75) to PG 80. No significant changes in grading were observed with the addition of the Aspha-Min additive. In fact, reduction in binder viscosity and improvement in binder grading without increasing the viscosity indicate two-way reductions (both direct and indirect) in production temperatures by the Sasobit additive. Finally, the Sasobit additive is found to decrease the asphalt pavement analyzer rut depths significantly, and these rut depths correlate well with the rutting factor G*/sin(delta). It was also observed that rutting potential decreases with decreasing mixing and compaction temperatures. Comparatively, a smaller reduction in rut depths was observed by adding the Aspha-Min additive.