Effects of pretreatment methods on the properties of recycled aggregates and prepared concrete under CO2-curing

Abstract

In this study, the standard CO2-curing, CO2-curing with pre-saturated Ca(OH)2 immersion and CO2-curing with cement slurry pre-wrapping as enhancement methods for recycled aggregates (RAs) and prepared concrete were investigated. The fundamental properties of the cured RAs were measured. The effects of different treatment methods on the stress-strain curve, capillary water absorption property and chloride penetrability of the prepared concrete were explored. Moreover, the pore structure analysis, scanning electron microscope, X-ray diffraction and thermo-gravimetric analysis were conducted on the RAs and prepared concrete. The results indicated that (1) the qualities of the carbon treated RAs with different pretreatment methods were improved by the formation of CaCO3, which filled the pores and micro-cracks from the microstructural analysis. (2) The mechanical properties of the prepared concrete were enhanced with more brittle behavior. (3) The permeability, pore structure, microstructure and chloride resistance of the cured RAC improved significantly. (4) The CO2-curing with pre-saturated Ca(OH)2 immersion method recorded the highest enhancing efficiency due to the addition of calcium ion.