Frequency-Dependent Damping Properties of Recycled Aggregate Concrete

Abstract

This study focused on the frequency-dependent damping properties of recycled aggregate concrete (RAC) and provided new insights into the damping mechanism of RAC. Cyclic compressive loadings at low frequencies were applied to RAC with five replacements of recycled coarse aggregate (RCA) to evaluate the damping properties of RAC. A nanoindentation test was conducted to investigate the nanomechanical properties of cementitious nanophases in RAC and analyze the damping mechanism. It is found that the damping parameters (loss factor, loss modulus, and hysteretic energy) of RAC decrease with the increasing loading frequency from 0.05 to 1.0 Hz. The damping of RAC is more frequency-sensitive than that of natural aggregate concrete (NAC). A linear relation among the damping parameters and the mortar content of RAC is established. With the increasing RCA replacement from 0% to 100%, the loss factor and hysteretic energy of RAC increase, and the loss modulus firstly increases and then decreases when the RCA replacement is larger than 50%. Nanoindentation results show that the mechanical hysteresis of cementitious nanophase in RAC is inversely proportional to the storage modulus, and the loss modulus is approximately proportional to the storage modulus. A decrease in mechanical hysteresis and hysteretic energy of cementitious nanophases with an increase in loading frequency may be the nanoscale mechanism for the frequency-dependent damping of RAC.