Improved Method to Determine Young’s Modulus for Concrete Cylinder Using Electromechanical Spectrum: Principle and Validation

Abstract

Electromechanical impedance (EMI) has been used as an in-situ nondestructive testing (NDT) method for concrete material property testing, e.g., strength and Young’s modulus, for decades. However, current EMI methods for determining Young’s modulus require establishing a large database of conventional compressive testing results to correlate the EMI spectrum. Although they can track the development of Young’s modulus of concrete using statistical metrics, the EMI method cannot quantitively determine the Young’s modulus of concrete without referring to a reference state in the baseline database. EMI physical models usually consider the contribution of the host structure as mechanical impedance which is more localized than the global mechanical properties of the structure. However, very few studies have investigated the physical relation between mechanical impedance and Young’s modulus. Furthermore, the EMI spectrum is highly sensitive to the boundary condition of sensors which results in poor repeatability due to sensor variability. In this paper, a novel testing method EMI Resonance (EMI-R) is proposed and validated to quantitatively determine Young’s modulus of concrete cylinders through an integrated, theoretical, and experimental study. First, the eigen frequencies of a cylinder were tested using the EMI spectrum of a single lead zirconide titanite (PZT) sensor. Then, the Young’s modulus was calculated based on eigen frequencies. Finite element (FE) analysis and impact resonance (IR) tests were implemented for validation. Results showed good agreement between the newly proposed EMI resonance (EMI-R) method and the conventional IR test method. The results have confirmed that the newly proposed EMI-R method does not require any correlation of EMI spectrum to compression testing results. The influence of the variation of sensors is also diminished because of the inertness of PZT in the low frequency band.