Sustainable reinforced concrete design: The role of ultra-high performance concrete (UHPC) in life-cycle structural performance and environmental impacts

Ultra-high performance concrete (UHPC), an advanced type of concrete material that shows superior mechanical and durability performance, brings promises of reducing the material usage and increasing the life span of conventional concrete structures. However, the environmental benefits of adopting UHPC have not been well understood because of a lack of life-cycle comparison between UHPC and conventional concrete structures. To address this gap, a structural, corrosion, and carbon emissions analysis of UHPC and concrete beams of similar functions (i.e., strength and stiffness) was completed. In addition to adopting UHPC in the full section, a new composite beam concept was also proposed to have UHPC in the compression zone only. Based on finite element (FE) analysis, UHPC beams were designed to show similar stiffness and strength as the concrete beams while the cross-section areas were greatly reduced. Service life spans were then determined through a time-dependent multi-physics modeling framework. Subsequently, analysis regarding the material costs, initial and life-cycle carbon emission was done. The simulation results show that the composite beam can significantly reduce cross-sectional area and self-weight with less than 13% increase in material costs. The carbon emissions of the composite beam was over 25% lower than that of the concrete beam, both in the initial and life-cycle range. Additionally, full UHPC beams could show similar initial carbon emission and around 48% lower life-cycle carbon emissions compared to the concrete beams.