Experimental Study of Temperature Cracking Susceptibility and Direct Tensile Resistance of Mixtures Produced with Crumb Rubber Added by Dry Process

ABSTRACT In this study, the influence of crumb rubber added by dry process is investigated on the resistance to the thermal cracking and direct tensile resistance of bituminous mixtures. Thermal stress restrained specimen tests (TSRST) and direct tensile tests were performed on six different mixtures. The two reference mixtures are GB5-type bituminous mixtures containing recycled asphalt pavement. The four other mixtures are the same GB5 in which mineral coarse aggregates are replaced by 4 % and 8 % of crumb rubber (on the mixture volume) with a 4/8-mm grain size distribution. Additionally, two types of bitumen were used: a neat 35/50 bitumen and a styrene-butadiene-styrene (SBS) modified bitumen. A good repeatability of experimental results is observed for all materials. From the TSRST tests performed, some differences can be seen between the six mixtures as the mixtures containing crumb rubber show lower values of peak stress and failure temperatures compared with the reference mixtures without crumb rubber. Direct tensile tests showed no significant differences between the mixture with 2 % crumb rubber and SBS-modified bitumen and the mixture without crumb rubber and SBS-modified bitumen. However, at 4 % crumb rubber, peak strain decreased across all temperatures compared with the reference. Mixtures with neat 35/50 bitumen experienced decreased peak stress with crumb rubber addition across all temperatures. Overall, mixtures with SBS-modified bitumen generally exhibited comparable or higher peak stress values than those with neat 35/50 bitumen, given equivalent crumb rubber content.