Meso-level HPC analysis of concrete specimens subject to external sulfate attack, and computational aspects

Concrete is considered a heterogeneous material composed of aggregates enclosed by a mortar matrix.The Finite Element analysis is performed by inserting zero-thickness interface elements in between continuum elements along pre-selected paths representing main potential crack paths.These interface elements are equipped with a fracture-based constitutive law.In previous literature this approach has been shown to provide very realistic results in the study of concrete fracture.Moreover, remeshing becomes unnecessary by the a-priori insertion of these elements where the fracture capability is concentrated, and the problem of localized deformation in the continuum elements is also overcome.However, using this approach a duplication of nodes occurs along the surfaces where they are inserted, and this may lead to a very high computational effort.In recent years, the group of Mechanics of Materials (MECMAT) at the Universitat Politcnica de Catalunya (UPC) has devoted substantial effort to extend the applicability of such approach to a variety of coupled problems, and to increase its efficiency via Message Passing Interface (MPI) parallelization and Portable, Extensible Toolkit for Scientific Computation (PETSc) libraries.In particular, these improvements have also been applied to the 3-D analysis of concrete specimens subject to External Sulphate Attack (ESA).In this context, the paper describes the coupled Chemo-Mechanical (C-M) model, presents the latest results obtained with various meshes of progressively larger sizes, and shows the scalability of the parallel implementation developed.Additionally, the paper describes a new technique developed to reduce computation times, consisting of identification of continuum blocks surrounded by interface elements and eliminating internal nodes using a Schur complement scheme.The new strategy has only been implemented so far in sequential mode, but results are presented that lead to significant reduction in computation time, and work is under way to achieve full parallel version of this technique. INTRODUCTIONIn recent years there has been a growing interest in determining and understanding concrete degradation processes.In particular,