Piezoelectric ring actuator technique to monitor early-age properties of cement-based materials

Piezoelectric ring actuator technique (P-RAT) that uses shear wave velocity (VS) was initially developed as a non-destructive test for soil characterization. The P-RAT was successfully modified to be adapted for cement-based materials in previous research by the co-authors. In the current study, validation of the P-RAT was carried out by comparing VS test results to those of conventional tests used to evaluate early-age properties of cementitious materials. Conventional tests included monitoring variation in penetration resistance for mortar, Vicat needle for paste, calorimetry, and electrical conductivity with time at early ages. The validation involved testing paste and mortar mixtures prepared with ordinary Portland cement and water-to-cement ratios (w/c) of 0.35–0.50 and different types and dosage rates of chemical admixtures. Test results showed that derivation of VS-versus-time curve obtained from the P-RAT can be employed to determine setting time. The variations of VS with time resulted in similar behaviour as those of the variations of heat of hydration and electrical conductivity with time. Fundamental relationships between VS results of the P-RAT and conventional tests to monitor setting were established. An analytical model to estimate the w/c at early age was proposed using the VS approach.