A study on the mechanical behaviour of cement–bitumen treated materials

Full depth reclamation (FDR) of asphalt pavements has gained general appreciation because of its technical, economical and environmental advantages. Along with FDR, the use of cement–bitumen treated materials (CBTM) rapidly increased over the last 10 years even if the lack of well-established technical specifications and reliable in situ control procedures hinder the cost-effective use of this material. Specifications for CBTM are currently based on experience and do not consider all the relevant parameters that affect the mixture behaviour. In this study the influence of curing conditions, temperature and moisture on the mechanical behaviour of CBTM is investigated. The recycled material was sampled during the FDR operations carried out on the Italian A14 motorway. The effect of curing and temperature on stiffness, and resistance to repeated loading were evaluated using cyclic indirect tensile tests. Moisture susceptibility was assessed by means of indirect tensile strength tests. Results showed a temperature-dependent behaviour of CBTM and allowed to define a simple model to predict the stiffness modulus based on curing time and temperature. In addition, the resistance to repeated loading proved to be a significant factor for the mechanical characterization of tested materials. Finally, regardless of curing conditions, the mixtures showed good moisture resistance.