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.