Comparative assessment of embodied energy of recycled aggregate concrete

Concrete waste can be recycled to produce an aggregate product; referred to as recycled concrete aggregate (RCA). While RCA is mainly used as a road base filler material, it has the potential to replace natural coarse aggregate (NA) in structural concrete. In determining the environmental performance of the resultant concrete product from this substitution, referred to as recycled aggregate concrete (RAC) against its counterpart, natural aggregate concrete (NAC), it is important to consider the effects of the entire life cycle including the upstream processes associated with each. This paper evaluates “cradle-to-gate” embodied energy (EE) of RAC received at a construction site, in comparison to NAC, using the input-output-based hybrid approach, using an Australian context. The paper constructs a model to evaluate EE of RAC and analyses the incremental energy of RAC as opposed to NAC, to identify what contribute to the difference out of four primary factors discussed in previous research. It was found that the EE of RAC is marginally different to that of NAC by +2.1 to −1.1%, and the variation was subject to the magnitude and direction of the four factors considered. The mix composition, primarily the binder composition, was found to have the highest contribution to the difference, significantly standing out from the direct energy difference between RCA and NA, difference of sourcing distance between RCA and NA and the difference of direct manufacturing energy between RAC and NAC.