A micromechanical lattice model to describe the fracture behaviour of engineered cementitious composites

Engineered cementitious composites (also called pseudo-ductile cementitious composites or strain-hardening cement-based composites), a special class of high performance fiber-reinforced cementitious composites, exhibit a tensile strain-hardening response with a superior ductility (which is the result of the development of multiple stable micro-cracks bridged by fibers) in comparison to normal concrete or other fiber-reinforced concretes. In the present paper, the fracture propagation in engineered cementitious composites (ECC) under tensile loading is analysed using a two-dimensional lattice model. A regular triangular lattice model (formed by pin-joined truss elements) accounting for the actual multiphase structure (at the meso-scale level) of the material is developed, and an automatic image processing procedure for phase detection is adopted. The trusses are assumed to have a linear elastic behavior in compression, whereas in tension a linear elastic behavior up to a first cracking stress is followed by a linear piecewise post-cracking curve with softening branches. Some numerical results related to ECC tensile specimens are presented along with those of a standard fiber-reinforced cementitious composite and of a plain concrete for comparison.