Carbon Efficiency Comparison of FRP and Steel Bars for Reducing the Embodied Carbon of Concrete Structural Elements

Abstract

In recent years, FRP (Fibre-Reinforced Polymer) bars have been considered to be a promising alternative to conventional steel bars for reducing the CO₂ emissions of concrete structural elements, whilst their environmental performance compared to traditional steel bars requires quantitative assessment. This paper introduces a multi-level comparative framework to evaluate the carbon efficiency of FRP bars compared to steel bars, from the material level to the section level and structural element levels, leading to quantitative comparative outcomes useful for decision-making when selecting the most carbon-efficient rebar type for achieving the lowest embodied carbon (cradle-to-gate) of structural elements. Each comparison level has its applicability depending on the specific context of construction projects. Because relative environmental performance can vary significantly in function of material and environmental data, the developed comparative framework aims to provide the rigorous methodology to follow, which can be adapted to any construction project by updating material and environmental datasets, rather than declaring a universally superior rebar type. Steel and BFRP (basalt FRP) bars are compared, based on the assumed material and environmental data, as an example to demonstrate how to apply the proposed comparative formwork. Results indicate that the optimal solution depends mainly on the structural parameters (such as span and slab thickness) as well as the assumed carbon data. For prismatic elements, the optimal choice between steel and BFRP bar is strongly influenced by the selection of slab thickness. For non-prismatic elements, it is found that non-prismatic BFRP-reinforced slabs have 4.8%–14.4% lower CO₂ than non-prismatic steel-reinforced slabs and can save up to 63% of CO₂ compared to the traditional solution (prismatic steel-reinforced slabs) in the presented examples.