Enhancing the sustainability and mechanical properties of ultra-high-performance concrete through CO2 sequestration

Abstract

Carbon dioxide (CO2)-consuming ultra-high-performance concrete (CC-UHPC) is a sustainable, high-performance material distinguished by its excellent mechanical properties and carbon sequestration capabilities. This study proposes an optimal type of mixing water for CC-UHPC, utilizing nano-sized bubbles known for their superior physical characteristics and efficient element transport. Experimental results reveal that these nano-sized bubbles generate additional gel pores by collapsing micro-scale pores within the UHPC matrix, thereby enhancing compressive strength. The increased nano-scale porosity also improves the equivalent bond strength between the embedded steel fibers and the matrix, inducing a slip-hardening response. Furthermore, the presence of nanosized bubbles promotes the formation of numerous microcracks-approximately 10 mu m in size-significantly boosting the tensile strain capacity of CC-UHPC. Notably, CC-UHPC prepared with CO2-capturing nano-sized bubbles in the mixing water exhibited both high CO2 uptake capacity and improved fiber bond strength, thereby achieving the dual goals of sustainability and superior mechanical performance.