Mechanical Evaluation of Asphalt Mixtures Containing Recycled Bituminous Membranes (RBMs)

Bituminous membranes (BMs) are mainly composed of a polymer-modified bituminous mastic (with filler addition) and reinforcement. In case one face is exposed to air, the external layer is an antiadhesive layer (covered with mineral chips). Because of aging and deterioration, BMs are removed from roofs or bridge decks and landfilled. Nowadays, only a few membrane producers are equipped with recycling plants to recycle BMs in new products, by reintroducing them in the production process. However, the presence of highly modified bitumen in recycled bituminous membranes (RBMs) makes them an interesting opportunity as a recycled component in asphalt pavement materials. The experimental program evaluated the introduction of RBM in asphalt mixtures to evaluate the effect on mechanical properties. The study involved three types of asphalt materials (i.e., mixtures for surface, binder and base layers), two polymer-modified bitumens typically used in Italy (Performance Grade (PG) 76-22 and PG 82-16) and the addition of RBMs containing atactic polypropylene polymer. The preliminary part of the study investigated the maximum dosage of RBMs in PG 76-22 bitumen, in order to obtain a bituminous blend whose properties can be considered intermediate between PG 76-22 and PG 82-16 binders. This part was conducted in terms of continuous performance grade. Consequently, the maximum RBM dosage was adopted to produce three asphalt materials comparing three bitumens (PG 82-16, PG 76-22, and PG 76-22 with RBMs). Asphalt mixtures were characterized in terms of indirect tensile strength, cracking properties, and complex modulus. Results showed that the use of RBMs in asphalt mixtures allows the reduction of around 10 % of the virgin binder used to produce asphalt materials for base, binder, and surface layers. However, the combined use of RBM and reclaimed asphalt pavement can lead to poor cracking resistance properties.