Hydration and microstructural characterization of early-age cement paste with ultrasonic wave velocity and electrical resistivity measurements

Abstract

Various non-destructive monitoring methods have been proposed to evaluate the early-age characteristics of cement paste, including the setting time and hardening, but the corresponding microstructural approach has not been reported in investigations of hydration products with non-destructive approaches. This study evaluates the microstructural evolution for 24 h in fresh cement paste through two types of non-destructive measurements, namely, ultrasonic wave velocity and electrical resistivity, compared with setting time by Vicat needle test. Observable non-destructive parameters can reflect the generated cement hydrates and change the tortuous path in the porous material including setting time, but the results of both methods provide different critical times of obtained parameters. To identify the formed hydration products at specific points, XRD and TG analyses are performed around the setting time. As a result, calcium hydroxide occurred after solid percolation mainly induces decreasing porosity and water depercolation, and these physicochemical changes were discussed with the measured non-destructive parameters.