Cracking Resistance Characterisation of Reclaimed Asphalt

To maximise the use of reclaimed asphalt (RA), it is necessary to understand better its behaviour and more specifically its cracking properties. It is evident that the cracking resistance of mixtures containing RA will depend greatly on the ageing state of the RA binder. The aim of this chapter is to propose a new methodology based on which different RA materials are assessed in terms of their ageing state by means of their resistance to cracking. Four different RA materials are prepared into mixtures (with 100% RA), together with a reference AC 10 mixture, and their cracking resistance is evaluated by means of indirect tensile strength (ITS) testing. The suitability of the cracking tolerance index (CTindex) to characterise RA mixtures is explored. The results of this study demonstrate that the CTindex shows very low values, making it difficult to discriminate between the different ageing states. For this purpose, a new index to track the brittle behaviour of RA, namely, the cracking-based brittleness index (CBI), is proposed. CBI is a promising index with lower variability compared to the CTindex (i.e. max 21% coefficient of variation (COV) for CBI and max 50% COV for CTindex) and with higher discriminative power.