Application of Acoustic Tests for the Mechanical Characterization of Hollow Masonry Units

Abstract

Although the use of nondestructive mechanical characterizations has increased (especially resonant methods), standards do not provide a relation between natural frequencies and mechanical properties for complex geometries such as hollow masonry units. This study uses numerical modeling via finite-element analysis (FEA) and impact acoustic tests to evaluate the dynamic elastic modulus of hollow masonry units based on their vibration modes and frequencies. Static and ultrasonic tests defined the reference values for the elastic modulus and an experimental sample comprised of hollow clay and concrete blocks and half-blocks of different geometries and compressive strengths. The results show the values of elastic modulus obtained from ultrasonic, acoustic, and compressive tests were different due to peculiarities of each test. A numerical simulation enabled the determination of the geometrical constants, and an analytical model proposed related vibration frequency and dynamic elastic modulus values for units of regular geometries and provided a reliable approximation for geometrical constants.