Reducing embodied carbon emissions of concrete modules in high-rise buildings through structural design optimisation

Abstract Modular buildings have been widely recognised as a solution for improving the sustainability of the construction industry. However, the implications of modular buildings for reducing embodied carbon (EC) have seldom been examined previously. This paper aims to quantify the EC reduction potentials of different structural designs of concrete modules in high-rise buildings. The study was conducted via a real case study with a high-rise modular building in Hong Kong. The EC of the concrete modules during the cradle-to-end-of-construction stage was assessed using process-based LCA method. Three critical structural and one material design variables were considered to optimise the structural design of modules in order to achieve the lowest possible EC, including concrete grades, rebar ratios in modules’ structural components, dimensions of modules’ structural components and low carbon concrete mix alternatives. Material quantities were extracted from the parametrically established BIM model of the modules using Dynamo software, followed by structural safety check according to Hong Kong’s codes. Results indicated that the feasible reduction potential of the modules with fixed external size could reach up to 27% compared to the design with highest EC emissions. Reducing components’ dimensions could reduce up to 20% EC of the modules with the same concrete grade. Adopting low carbon concrete could reduce 10%-13% EC of the modules on average for different concrete grades. The findings revealed a significant potential of EC reduction in concrete modules through structural design optimisation, providing a new direction for achieving low carbon modular buildings.