Evaluation of Cement-Bitumen Treated Material bearing capacity by in-situ tests

Cement-bitumen treated materials (CBTM) are widely used for the rehabilitation of existing pavements and for the construction of new pavements as they offer several structural and environmental benefits. The structural performance of CBTM combines the advantages of ductility, typical of bituminous mixtures, with the high resistance typical of cement mixtures. Furthermore there is the advantage of producing a cold mixture using reclaimed asphalt in percentage that can reach 80-90% of total aggregates. Although CBTMs have been used with great success for several years, their structural performance has not been investigated in sufficient detail, and their structural design is mainly based on the experience of practi-tioners. For this reason, an extensive experimental study has been conducted to evaluate the structural charac-teristics of this materials. The experimental site of the “Pedemontana Lombarda” motorway in Lomazzo allowed to evaluate the CBTM bearing capacity evolution over time. For this purpose the dynamic elastic modulus was measured by means of LWD and FWD tests carried out during a 90 days curing period. The evolution of the dynamic modulus over time for LWD tests can be described by means of a logistic function. The model provides a good prediction of the dynamic modulus evolution in time with a R2 of the fitted functions greater than 0.9. The validation of the model on a different dataset confirm the validity of the proposed model and excluded over fitting issues.