3D mesoscale modelling of recycled aggregate concrete

Mesoscale modelling is a promising tool to analyse the phenomenological causes of mechanical failure of recycled aggregate concrete (RAC). Most mesoscale models of RAC are two-dimensional (2D) and 3D models are lacking. This prevents the full understanding of the behaviour of each mesoscopic phase. This paper presents a 3D model of RAC and analyses its mechanical behaviour based on mesoscale phenomena. The analyses concern three types of tests carried out in concrete specimens: uniaxial compressive, uniaxial tensile and splitting tensile strength tests. The mechanical response and fracture behaviour of each mesoscopic phase is analysed in relation to the response of RAC specimen. The comparisons between uniaxial behaviour of 3D and 2D modelling as well as between uniaxial and splitting tensile behaviour of RAC are presented. The main findings of the paper are: (1) the full curve of uniaxial stress-strain response from 3D modelling is comparable to that from 2D modelling for RAC (therefore, 2D models are validated for RAC modelling); (2) the overall behaviour of the concrete elements remains elastic regardless of the fracture development in the ITZ and attached mortar of recycled aggregates until damage propagates to the new mortar matrix; (3) a relationship between modelled uniaxial and splitting strength of RAC is established and validated.