Effect of gradation on volumetric and mechanical properties of cold recycled mixtures (CRM)

In recent times, recycling using cold bituminous mixtures has become one of the most interesting techniques in pavement engineering from sustainability aspect. This study focuses on the clarification of the steps concerned with the cold mixture mix design to determine the initial aggregate gradation of the mixture. The study has been developed involving procedures followed in Canada and Italy. In both the cases, three different gradations, normally employed in the production of traditional bituminous mixtures, were compared. The effect conferred by the gradation type has been studied in terms of workability, compactability and mechanical properties. Results show that in both the procedures the gradation influenced the workability and the compaction behaviour of the mixtures studied. At the same time, in terms of mechanical properties, the gradation influenced the strength of the final mixture in only one of the procedures applied.