Study of recycled aggregate concrete mechanical behavior by FEM multiscale modeling

Abstract

This research project presents a numerical analysis proposal for recycled aggregate concrete (RAC), whose recycled aggregates are obtained from the crushing of demolition concrete. The tool to be developed facilitates the mechanical behavior evaluation of the RAC, verifying the feasibility of its use for structural purposes. Considering that in Brazil the current use of the material is still quite limited in comparison with other countries, this type of tool helps in a better understanding of the material nature. That way, the RAC can be used more widely and properly, bringing structural, economic and mainly environmental advantages, complementing the current waste management guidelines in the construction industry. Due to the occurrence of microscopic specificities, the CAR modeling requires a more refined scale model (mesoscale) to represent the altered properties of recycled aggregate due to its variable composition and the crushing process. The fracture mechanisms that occur at the interface of the aggregate with the concrete matrix are influenced by these factors, introducing nonlinearity to the mechanical problem. In order to represent this nonlinearity, the proposed modeling strategy uses the technique of finite element mesh fragmentation together with robust and stable constitutive models. This fragmentation technique is based on the use of finite elements with high aspect ratio, which can be used to represent the additional phases of this composite material, corresponding to the different mesoscale CR intrinsic interfacial transition zones (ZTIs), as well as potential pathways for the propagation of fractures. Constitutive models based on the mechanics of continuous damage will be used to represent the non-linear behavior of these different CR phases, which together with the cited fragmentation technique will be valuable tools for the study of the influence of RA on mechanical behavior of CAR. The validation of the methodology will occur through preliminary tests for calibration of parameters and later through simulations of more advanced cases of conventional recycled aggregate concrete carried out in experiments in which the qualitative and quantitative numerical results obtained will be compared with the respective experimental results from the literature. (AU)