Compressive fatigue behavior of compound concrete containing demolished concrete lumps

This research focused on the uniaxial compressive fatigue behavior of compound concrete (CC) made of fresh concrete (FC) and demolished concrete lumps (DCLs) distinctly larger than conventional recycled aggregates. Sixty cylindrical and three planar specimens were tested under constant-amplitude sinusoidal loading. Digital image correlation was employed to monitor the initiation and propagation of cracks on the specimens. The variances in the dissipated energy, Poisson's ratio, fatigue modulus and longitudinal residual strain of the cylindrical specimens with the number of cycles are discussed. Linear formulas describing the relationship between secondary strain rate and fatigue life are presented. The results indicate that there is no distinct difference in fatigue life between CC and conventional concrete, though the lateral expansion of CC under such loading is greater. The replacement ratio of DCLs can hardly influence the secondary strain rate of CC. The interfaces between DCLs and FC are not evident weak zones in CC. (C) 2019 Elsevier Ltd. All rights reserved.