Carbon footprint of reinforced concrete columns with and without supplementary cementitious materials

Abstract

The construction sector consumes a large quantity of natural resources and generates a great deal of carbon dioxide emissions and wastes, affecting its sustainability. Replacing Portland cement with supplementary cementitious materials (SCM) could reduce the environmental impact. This paper examines the carbon footprint of reinforced concrete columns. It focuses on the influence of increasing the steel cross-section and reducing the clinker factor by replacing Portland cement with SCM. Eighteen concrete mixtures were selected and classified according to the specified compressive strength at 28 days of curing using binary and ternary blended cements. Columns were designed consisting of such concretes and employing different reinforcing steel cross-sections. The life cycle assessment was conducted on ISO 14040 standard. The embodied carbon dioxide (ECO2) of the reinforced concrete columns was determined. The results show that the higher the compressive strength of concrete, the lower the carbon footprint of the columns. Concretes with a high volume of SCM replacement and low compressive strength at 28 days do not show the lowest carbon footprint since it requires a greater volume of material to withstand the bearing capacity. The carbon footprint of the columns increases as the steel section increases. Furthermore, increasing the compressive strength of concrete is less beneficial for reducing the carbon footprint of the column when the steel cross-section is increased. Portland cement is the component material of concrete that contributes the most to the concrete carbon footprint, and steel has the highest ECO2/tonne. Replacing Portland cement with SCM reduces ECO2 at one point of the life cycle and may increase the material volume and ECO2 at another. The lowest carbon footprint of compressed reinforced concrete elements is achieved for the higher-strength concretes and the minimum steel cross-section.