Structure of micro-crack population and damage evolution in concrete

摘要

Tensile behaviour of concrete is controlled by the generation and growth of micro-cracks.A 3D lattice model is used in this work for generating micro-crack populations.In the model,lattice sites signify solid-phase grains and lattice bonds transmit forces and moments between adjacent sites.The meso-scale features generating micro-cracks are pores located at the interfaces between solid-phase grains.In the model these are allocated to the lattice bonds with sizes dictated by an experimentally determined pore size distribution.Micro-cracks are generated by removal of bonds when a criterion based on local forces and pore size is met.The growing population of micro-cracks results in a non-linear stress-strain response,which can be characterised by a standard damage parameter.This population is analysed using a graph-theoretical approach,where graph nodes represent failed bonds and graph edges connect neighbouring failed bonds,i.e.coalesced micro-cracks.The evolving structure of the graph components is presented and linked to the emergent non-linear behaviour and damage.The results provide new insights into the relation between the topological structure of the population of micro-cracks and the macroscopic response of concrete.They are applicable to a range of quasi-brittle materials with similar dominant damage mechanisms.