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. 二氧化碳封存对混凝土的孔结构和抗压强度有较大影响。本文首先将珊瑚骨料分别浸泡在固液比为0.2、0.4和0.6 g/mL的氢氧化钙悬浮液中，然后将浸泡后的骨料加速碳化。其次，研究了二氧化碳封存对珊瑚骨料的粒径分布、筒压强度、吸水率和表观密度的影响。再次，研究了二氧化碳封存后珊瑚骨料混凝土的孔结构演变。最后，探讨了二氧化碳封存对珊瑚骨料混凝土抗压强度发展的影响。结果表明，二氧化碳封存影响了珊瑚骨料的性能。其次，在混凝土中，通过二氧化碳封存形成的碳酸钙的孔隙率最高。随着固液比的增大，水泥基体和该碳酸钙的孔隙率逐渐增大，且水泥基体和该碳酸钙中存在更多的大孔。最后，当固液比为0.2 g/mL时，珊瑚骨料混凝土的抗压强度较二氧化碳封存前有所提高，但当固液比增加到0.6 g/mL时，其抗压强度有所降低。