Influence of Local Code Constraints on Embodied Carbon in Steel-Concrete Composite Bridges

With the strong intention to reduce carbon emissions in bridge construction, it has been popular to use alternative cementitious materials to replace a portion of traditional Portland Cement (PC). Supplementary cementitious materials (SCMs) such as slag, fly ash and silica fume are commonly used but there are contradicting attitudes towards how efficiently they reduce carbon emissions. One main reason is the uncertainty of the replacement ratio, as for the same volume of concrete, the content of SCMs and PC can differ significantly. The adoptable replacement ratios of SCMs is dependent on a countries’ codes, specifications and practices. This paper presents a review of the maximum and minimum replacement ratios of SCMs, from four different countries and standards. The paper will also present a series of concrete mix designs based on the standards and will compare the carbon emissions of concrete elements with steel elements, of an existing steel-concrete composite bridge.