Transition Towards Low Carbon Concrete – Persuading Parameters

The transition of the concrete industry towards a low-carbon pathway not only requires optimized mix designs with lower clinker/cement content but also other interventions that could reduce the carbon footprint of concrete in its value chain. Current codes specify minimum cement contents for concrete mixes intended to preserve durability in various exposure classes, but the cement type is usually not specified. Codes also specify an increase in the amount of reinforcing steel required for reinforced concrete members with a matrix strength above 50 MPa, partially counteracting the potential carbon benefits of reducing the amount of concrete used for a given element employing high-strength concrete. This places two “hard” constraints on reinforced concrete design for minimum carbon per unit of structural performance. With these two practical constraints in place, in this paper, the influence of several materials and design parameters are discussed and assessed for the carbon reduction potential of concrete systems. The parameters considered are i) lowering the clinker content in concrete mixes whilst complying with the code-specified minimum cement content for required durability ii) producing better quality concrete e.g., by minimising the margin between target mean strength and required characteristic compressive strength and iii) reducing partial factors of safety for concrete at the design stage while assuming the minimum load requirements. It was quantified that there is a significant potential reduction in the carbon footprint of the concrete and the reinforced concrete element, when these parameters are varied from what is specified in the code.