Effects of carbon-sequestering coral aggregate on pore structures and compressive strength of concrete

Abstract

CO₂ sequestration/storage shows considerable impacts on the pore structures and compressive strength of concrete. This paper presents a study in which coral aggregates were presoaked in Ca(OH)₂ slurries with different solid-to-liquid ratios (i.e. 0.2, 0.4, and 0.6 g/mL) followed by accelerated carbonation. The effects of CO₂ sequestration on the particle size distribution, cylinder compressive strength, water absorption, and apparent density of coral aggregate were investigated. The evolution of pore structures in coral aggregate concrete after CO₂ sequestration was also studied. Additionally, the effect of CO₂ sequestration on the development of compressive strength of coral aggregate concrete was explored. The results showed that CO₂ sequestration affected the properties of coral aggregate. Moreover, the porosity of CaCO₃ formed by CO₂ sequestration was the highest in the concrete. With the increase of solid-to-liquid ratio, the porosity of cement pastes and the CaCO₃ increased, and more big pores existed in the cement pastes and CaCO₃. Furthermore, the compressive strength of coral aggregate concrete when the solid-to-liquid ratio was 0.2 g/mL increased compared with that before CO₂ sequestration, but the compressive strength reduced when the ratio increased to 0.6 g/mL.