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Minimising Embodied Carbon in Concrete Floors



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Jayasinghe Arachchige, Amila Sankalpa 


Limiting global warming has become an internationally agreed target to stop the rapid and devasting consequences of climate change. Though reducing CO2 emissions is the path forward, a substantial component of the emissions stems from the processes related to the construction industry. The manufacture of cement alone accounts for 6% of global CO2 emissions. A significant challenge arises as CO2 reduction objectives must be achieved alongside the increasing demand for infrastructure caused by rapid urbanisation.

This thesis explores how exploring different design solutions by varying design parameters, analysing alternative construction forms, and optimising shapes can reduce the embodied carbon of steel-reinforced concrete floors. Four interconnected optimisation studies are illustrated in this thesis: (1) shape optimisation of reinforced concrete beams using a parametric design approach to achieve practical and technically feasible solutions, considering deflection performance; (2) parametric optimisation for reinforced concrete flat slabs, coupled with a finite element model to estimate non-linear long-term deflections; (3) simultaneous optimisation of the cost and carbon emissions of concrete floors using different conventional slab designs; and (4) comparing the potential carbon savings of different optimisation strategies for concrete floors against the timeline for potential implementation. Possible variations of the optimisation outcomes depending on the selected embodied carbon coefficients and cost rates are also analysed.

Shape optimised construction methods offer solutions with the minimum embodied carbon for a given set of design criteria in the long term. In the ascending order of possible reductions in embodied carbon, concrete floors can be optimised in the short term by: (1) minimising section depth to satisfy deflection limitations; (2) adopting low-strength concrete in flexural members; (3) analysing conventional alternative slab types; and (4) optimising column layouts. Nonlinear relationships observed in optimisation methods highlight key design aspects to target for maximum reductions in embodied carbon. The conclusions reached herein are presented as a set of guidelines for structural engineers to minimise the embodied carbon of concrete floor designs.





Orr, John


Concrete Structures, Design Optimisation, Embodied Carbon, Structural Analysis, Sustainable Construction


Doctor of Philosophy (PhD)

Awarding Institution

University of Cambridge
Churchill Jafar PhD Studentship from The Cambridge Commonwealth, European & International Trust