New insight into self-antifoaming effect of entrained CO2 bubbles in fresh cement paste

Abstract

A new insight into self-antifoaming effect of CO₂ bubble was proposed by exploring the evolution of entrained CO₂ bubbles in fresh cement paste. The disappearance process of CO₂ bubbles was observed, resulting in the reduction of air content. The evolution of CO₂ bubbles eventually formed two kinds of pore structures: hollow spherical shell structure (HSS) and interior filled spherical shell structure (IFSS). It was evidenced by the rich area of CaCO₃ at the outline of CO₂ bubble and the interior formation of hydration products. Meanwhile, self-antifoaming effect of CO₂ bubble promoted the microstructural build-up of fresh cement paste and enhanced the mechanical property of hardened cement paste. Fresh cement paste with CO₂ bubbles had stronger elasticity and higher volume resistance, corresponding to the faster rise of storage modulus. The compressive strength of hardened cement paste was increased from 29.6 MPa to 37.3 MPa with a porosity reduction of 6%.