Repeatability Study on the Laboratory Production Process of Cement Bitumen Treated Materials with Foamed Bitumen

Cold recycled materials are mixes with high percentages of reclaimed asphalt (RA), while the binding phase is commonly composed of Portland cement and bitumen (emulsion or foam). The reproduction of such materials in the laboratory is an important issue for an accurate mix design, even more when applying a volumetric approach. Particularly, the lack of a specific control on the reliability of the foaming bitumen machine seems to hinder the potentiality of these mixtures. Hence, the goal of this study is to assess the composition variability of several batches produced in the laboratory starting from a specific cement-bitumen treated materials (CBTM) recipe and production procedure. An ignition oven was used to measure RA binder and the effective foamed bitumen amounts in produced specimens and a comparison between maximum dry density and theoretical maximum dry density was carried out. The results have shown that the volumetric approach is a suitable tool to obtain the desired volumetric properties in CBTM produced with foamed bitumen. A certain variability between the theoretical maximum dry density and the measured value can be caused by the variability of bitumen content in the mixture.