Mixed-mode fracture in lightweight aggregate concrete by using a moving mesh approach within a multiscale framework

Lightweight aggregate concrete (LWAC) has gained popularity as an alternative to ordinary concrete for structural purposes, due to its higher strength-to-weight ratio. The present work aims to present novel numerical results of complete failure simulations performed on pre-cracked beams made of LWAC, subjected to a mixed-mode fracture test. To this end, an innovative simulation algorithm for crack propagation within a multiscale framework has been adopted, specifically conceived for predicting micro-cracking in quasi-brittle heterogeneous materials under general loading conditions; such a strategy allows to take into account both the continuous crack propagation along a non-prescribed path and the crack penetration through a material interface. Path tracking for continuous crack propagation has been performed by using an advanced geometry optimization method coupling a moving mesh approach and a gradient-free optimization solver, whereas crack penetration has been simulated by means of a simplified re-initiation criterion at the interface, involving a material characteristic length. Several numerical experiments have been carried out, in order to investigate the influence of the Young's modulus of lightweight aggregates on the peak and post-peak behavior. These results have been validated by comparing them with those obtained from fully homogenized analyses based on the LEFM approach.