Direct Tensile Resistance of Mixtures Produced with Crumb Rubber Added by Dry Process

This study presents the results of direct tensile tests performed at three different temperatures on mixtures containing crumb rubber (CR). These tests were conducted on GB5® mixtures, which included varying percentages (0%, 2%, and 4% by mass) of crumb rubber. The crumb rubber was incorporated by dry process, partially replacing mineral aggregates. Additionally, two types of bitumens were used: a neat 35/50 bitumen and a styrene–butadiene–styrene (SBS)-modified bitumen. The results indicated that, for the mixtures with SBS-modified bitumen, there were no significant differences between the mixture without crumb rubber and the mixture with 2% of crumb rubber across the tested temperature range. However, when 4% crumb rubber was used, the resulting mixture displayed a reduced peak strain compared to the reference mixture without crumb rubber, and this trend was observed at all temperatures. For mixtures using neat 35/50 bitumen, the addition of crumb rubber led to a decrease in peak stress across all temperature conditions. Regarding the impact of the binder type, the study revealed that mixtures incorporating SBS polymer-modified bitumen generally exhibited comparable or higher peak stress values than those with neat 35/50 bitumen, given the same content of crumb rubber.