In-situ production of nano/micro particles in fresh concrete

Abstract

This study proposes a novel method to in-situ produce nanoparticles in fresh concrete using carbon dioxide gas. The new method can significantly enhance the sustainability of concrete through permanently storing carbon dioxide in concrete and increasing the performance of concrete. By using this method, calcium carbonate nanoparticles coated with a thin layer of silica can be in-situ produced in fresh concrete, which can not only serves as ideal nucleating sites for the hydration products of ordinary Portland cement, but also densifies the microstructure of the concrete. Synergistic effects between CO2 and cementitious material are also triggered by this method: 1) calcium carbonate produced by this method transforms from amorphous or metastable phase to stable phase so that calcium carbonate also functions as binding phase in concrete; and 2) calcium carbonate produced by this method changes the mineralogy of the hydrated cement to produce larger volume of hydration minerals and thereby to reduce porosity of the concrete or harder crystal to strengthen the concrete. Experimental studies show strength of concrete can be significantly increased by this method.