Thermo-rheological modelling of cement-bitumen treated materials in the small strain domain

Cold recycled materials (CRM) have been introduced as structural materials in road pavement structures thanks to their significant economical and environmental benefits. Among them, cement-bitumen treated materials (CBTM) are often employed because of both contributions given by bitumen (in form of emulsion) and cement. The first confers a bituminous behaviour, whereas the second ensures good short-term performance otherwise penalized by the presence of water. Water plays a fundamental role in providing workability of the mixture at the atmospheric production temperatures. Due to such peculiarities, CBTM mixtures require attention when rheological modelling is performed in the small strain domain. This paper provides an overview on the most common rheological model applied to bituminous mixtures (2S2P1D) and the main issues related to the application to CBTM mixtures are highlighted. Afterwards, another model is proposed from the literature, the DBN model, and applied to three mixtures. The mixtures were prepared to assess the effect of the bitumen emulsion used, as well as the type of curing conditions. Results showed that the DBN model seems to be an excellent tool for not only CBTM rheological modelling in the small strain domain and it is recommended for applications in wider experimental programs.