Steric Hardening and the Ordering of Asphaltenes in Bitumen

Steric hardening is the hardening of bitumen over time at room temperature. It occurs after bitumen is melted, and it often leads to poor reproducibility in standard testing. Modulated differential scanning calorimetry shows that asphaltenes order when bitumen is cooled from the melt and that this phenomenon is time-dependent. This paper establishes the link between the ordering of the asphaltenes in bitumen and its steric hardening. It is suggested that at least 24 h elapse between the melting and pouring of bitumen and its subsequent testing by standardized methods.