High performance, low carbon concrete for building cladding applications

Abstract

High Performance Concrete (HPC) when reinforced with fibres (HPFRC) is often presented as an environmental improvement on typical reinforced concrete given that its higher strength means less material is required to resist the same forces. However, to achieve these high strengths, considerable proportions of cement, superplasticisers and discontinuous fibres are typically needed, all of which are manufactured using carbon-intensive processes. This article investigates the feasibility of HPFRC as a sustainability improvement on typical reinforced concrete for façade applications by developing novel low carbon HPFRC mixes and carrying out an embodied carbon analysis of a concrete cladding element constructed of those developed mixes. The environmentally improved HPFRC include coarse aggregates (to reduce cement paste volume), non-corrosive fibres (to eliminate the risk of corrosion) and a high dosage of supplementary cementitious material (to again minimise the cement content). Compressive strengths of 100 MPa and pre-cracking flexural strengths above 8 MPa were achieved. Importantly it was also found that the inclusion of resin coasted glass and basalt fibres (2.3% by volume) resulted in deflection hardening behaviour under flexural loading conditions. An environmental investigation found that the embodied carbon of a precast concrete facade can be reduced by 50% when using the presented fibre reinforced high performance concrete in place of typical reinforced concrete cladding.