Early-stage assessment of drying shrinkage in Portland limestone cement concrete using nonlinear ultrasound

Second harmonic generation (SHG), a nonlinear ultrasonic technique, holds great promise for reliable structural health management owing to its nondestructive detection of early-stage damage evolution in cement-based materials. Utilizing the SHG technique, this study focuses on elucidating the contribution of limestone to dimensional stability under drying shrinkage in cement-based materials. Specifically, the acoustic nonlinearity parameter ?? obtained from the SHG is used, together with uniaxial strain and mass reduction, to characterize the microstructural condition near the surface (???50 mm) of Portland limestone cement (PLC, Type IL) concrete, which is compared to ordinary Portland cement (OPC, Type I/II) concrete. In both PLC and OPC specimens, ?? increases remarkably compared with other measured parameters (i.e., change in mass, strain). This demonstrates the sensitivity of this approach to the microstructural modification caused by drying shrinkage, allowing for the discrimination in performance of PLC and OPC