Estimating Embodied Carbon Reduction in Modular High-Rise Residential Buildings Through Low Carbon Concrete

Modular construction has attracted wide attention from both academia and industry and has been viewed as a novel approach to improve construction sustainability. Nevertheless, few studies have focused on examining the embodied carbon (EC) emissions of modular buildings. This paper aims to assess the EC of a modular concrete high-rise residential building case by comparing it with a conventional prefabricated building case in Hong Kong and examining the EC reduction efficiencies of several low carbon concrete solutions. The EC during the cradle-to-site stage of both building cases was assessed using the process-based life cycle analysis method. A total of 10 scenarios of different low carbon concrete solutions were set, and their EC reductions were compared. The EC per construction floor area for an averaged floor of the modular building case was quantified as 532.1 kgCO₂-eq/m², higher than that of the conventional prefabricated building case (558.1 kgCO₂-eq/m²). The largest EC reduction reached 23.8% in the modular building case, which was achieved by the combined use of rice husk ashes and the recycled concrete aggregates. Findings in this paper lay a good foundation for exploring novel low carbon concrete solutions for EC reduction of modular buildings in future research.