Concrete manifactured with crushed asphalt as partial replacement of natural aggregates

The paper focuses on the re-use of crushed asphalt (or grinded asphalt, GA) as a partial replacement of natural aggregates for concrete manufacturing. Concrete mixtures were designed by considering up to 20% substitution of natural aggregates by GA. The rheological and mechanical properties of GA mixtures were compared to those of the reference concrete (RC) manufactured by using natural aggregates only. GA aggregates addition produced a positive effect on workability loss. The GA mixtures, however, showed a marked tendency to bleeding and segregation at the highest replacement percentage (20%). The GA led to a decrease in the concrete compressive strength (with respect that of RC) up to 50% due to the weakness of cement paste/recycled aggregate interface. To compensate this negative effect, a reduction of w/c for GA concretes was necessary. In any case, the maximum GA replacement was limited to 15% in order to avoid both rheological and mechanical underperformances. Moreover, reduction in w/c allows elastic modulus higher or equal to that of RC when GA replacement is 5 or 15%, respectively. A decrease of w/c allowed the GA concretes to show drying shrinkage values substantially similar to those of RC with the same cement factor. The experimental results confirmed the possibility of the partial substitution (max 15%) of natural aggregates with crushed asphalt for manufacturing of concrete.