Parametric optimisation of two-way slabs on beams for early-stage low-carbon design

Abstract

Floor systems contribute nearly 75% of the embodied carbon emissions associated with the superstructure of buildings, underscoring the need to identify early-stage design parameters that can reduce embodied emissions while still adhering to traditional design guidelines. This study investigates the potential for minimising embodied carbon in reinforced concrete two-way slabs on beams through a parametric grid search approach. The design space was systematically varied by adjusting slab thickness, concrete grade, reinforcement ratios, and spans ranging from 4 m to 10 m. From all generated designs meeting flexural, serviceability, and detailing requirements, those with the lowest cradle-to-gate carbon emissions were selected. Results indicate that carbon savings of approximately 3–50% can be achieved compared to conventional Eurocode-based designs, with greater reductions observed as the span increases. The most efficient configurations featured thinner slabs, lower concrete grades, and higher reinforcement densities. Emission factor variations only moderately affected embodied emissions, even at 100% changes, while optimal parameters remained stable throughout. Based on these findings, a set of early-stage design charts is proposed to aid the development of low-carbon slab systems under varying load and grid conditions.