Cement-bitumen treated materials (CBTM) for cold regions: RAP aggregate source and low production temperatures

Abstract

The increase of asphalt price due to the energy crisis of the last years drove the development of cost-effective asphalt pavement recycling technologies. The limited availability of natural aggregates, the growing awareness about the environment and the increasing costs for handling milled materials, required innovative sustainable technics, such as cold in-place recycling (CIR) and the reuse of reclaimed asphalt pavement (RAP). In this context, cement-bitumen treated materials (CBTM) ensure benefits in terms of reliability, cost effectiveness and environmental sustainability. The main difference between CBTM and Hot Mix Asphalt (HMA) is that the lubricant effect in the first is given mostly by the water, while in the second case it is given by the heated bitumen. At the same time, the cohesion of CBTM is granted by the cooperation of bitumen emulsion (or foamed bitumen) and cement as binding agents. Since the RAP aggregate are the major component of the aggregate volume, it is believed that a study on the effect of different RAP sources is needed to improve the mix design process. Moreover, field experience shows that CBTM laydown at low temperatures (during cold seasons) seems to suffer a loss in mechanical properties. Hence, the main objective of this thesis is to understand the effect of RAP sources and of low production temperatures on CBTM properties. Results have shown that the RAP source does influence several CBTM properties. In fact, the RAP binder characteristics, as well as its affinity with the residual bitumen used in the emulsion, affect the properties of cold recycled materials not only during production (workability and compactability), but also during and after the curing period, where influence on the mechanical properties in the small strain and large strain domains were observed. Furthermore, the bitumen emulsion characteristics influence the production process at low temperatures. Results showed that the production of such materials at 5 °C (intended as mixing, transportation, laydown, compaction and curing) was possible. In this way the time available for production during the year increases, but, on the other hand, a stiffness loss of 30% was observed compared to mixtures produced at 25 °C. This should be taken into account during pavement design.

Date	28 Sept 2020
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Daniel Perraton (Supervisor), Alan Carter (Co-supervisor) & Andrea Graziani (Co-supervisor)