Investigation of early-age concrete strength development using a contactless ultrasonic method

The compressive strength of early aged concrete was estimated using obtained shear modulus derived by leaky Rayleigh wave velocity. To obtain shear modulus without interference from other factors, a unique testing configuration was implemented using a contactless ultrasonic method, which offers the advantages of being non-invasive and non-destructive. A parametric study was conducted to examine the influence of material properties and air temperature on the development of leaky wave velocity in a joint half-space. The results indicate that shear modulus is the primary factor influencing the increase in leaky Rayleigh wave velocity, while density and Poisson’s ratio also impact wave velocity during the curing process. Experimental validation was carried out using pin penetration tests, compressive tests, and real-time measurements of Poisson’s ratio and density, along with the contactless ultrasonic method. The results indicate that the initial velocity of the leaky Rayleigh wave is significantly influenced by the stiffness of coarse aggregates, even when the compressive strength of the specimens is identical. Additionally, the relationship between compressive strength and shear modulus shows a strong linear correlation at early ages.