A laboratory investigation on Dense Bituminous Macadam containing different fractions of coarse and fine RAP

Abstract

The present investigation promotes the usage of RAP for developing countries like India where hot mix asphalt is still the most popular and utilized technology. Dense Bituminous Macadam (DBM) mixes were prepared with different proportions (50% & 100%) of coarse RAP (C), fine RAP (F) and total RAP (T) obtained from two different sources separately. This approach was adopted owing to the fact that uncontrolled milling is still the most practically doable method for reclaiming RAP. The optimum proportion of RAP for DBM mixes was decided based upon several strength and durability properties. It was found that C mixes demand higher quantity of virgin asphalt followed by F and T mixes for achieving the desirable volumetric properties. T mixes were found to have the highest Marshall Stability value whereas rest of the mixes could attain comparable stability value. Similarly, the rutting performance of all the mixes was significantly higher than the control mix; however, F mixes showed comparable performance to T mixes. On the other hand, both the individual fractions of RAP had comparable moisture resistance (tensile strength ratio) to the control mix, whereas, total fraction mixes could not meet the minimum specified limits. Even the abrasion resistance of C and F mixes in standard condition was higher than the control mix. The results indicated that natural coarse and fine aggregates may be replaced completely by coarse RAP and fine RAP, respectively, for preparation of DBM mixes without much affecting the performance-related properties. Also, this combination would provide a cost saving of about 40%. © 2018