Robustness of Resonant Frequency Test for Strength Estimation of Concrete

Abstract

The resonant frequency test (RFT) of molded concrete specimens is a nondestructive test (NDT) method for indirect strength estimation based on the fundamental mode characteristic resonance frequency. In this article, experimental, numerical, and analytical studies were performed to assess the sensitivity of test results to various factors involved in RFT. These factors included vibration modes of the specimen, sensor attachment techniques, contact time of the hammer impact, location of the sensor on the specimen, length to diameter ratio (L/D), and cross-sectional shape of the specimen. Experimental study included concrete specimen preparation in the lab and real-time RFT measurements for robustness of some of the aforementioned factors. Computation models developed using numerical simulations were verified by laboratory test and analytical results. The finite element method–based code, ABAQUS, was employed for computational modeling. Statistical analyses of the experimental results and parametric studies of the computational modeling were used to quantify the effect of the aforementioned factors on uncertainties of strength estimates using RFT measurements. The contact time of the hammer impact and the L/D of the specimen were found to have considerable effect on test results and hence on the concrete strength estimates.