Evaluation of mortar film thickness of dry process crumb rubber modified warm mix asphalt concrete utilizing 2-dimensional images

Abstract

Asphalt mortar film thickness and its distribution are accepted to be strong parameters that affect the durability and performance of asphalt mixtures. This study focuses on the effects of the Warm Mix Asphalt (WMA) additive, production temperatures, and compaction effort on the distribution of mortar film thickness in dry process crumb rubber modified mixtures. Utilizing image analysis, not only mortar film thickness distribution but also its distribution for each aggregate size fraction was analyzed. It is revealed that the difference in mixture preparation procedures and aggregate size fractions significantly affects the distribution and variation of mortar film thickness. Moreover, to relate between cracking and the mortar film thickness, indirect tensile strength tests are performed at three different temperatures. A good correlation was only built between cracking resistance and average mortar film thickness at −10 °C. Therefore, it can be concluded that the mortar film thickness cannot be solely used as an indicator of performance. However, it can be still generalized that thicker and variable mortar film thickness weakens the aggregate interlock and low-temperature cracking resistance.