Numerical modeling of microcrack behavior in encapsulation-based self-healing concrete under uniaxial tension

Abstract

We investigated microcrack behavior in encapsulation-based self-healing concrete subjected to uniaxial tension by using finite element analysis. 3D circular capsule with particular shell thickness embedded in the mortar matrix samples was modeled. To represent potential cracks, zero thickness cohesive elements with bi-linear traction-separation law were pre-inserted into the initially generated meshes. Effects of fracture strength variation among the mortar matrix, the capsule, and the interface between them on crack nucleation, initiation, and propagation were investigated. The results showed that the mismatch among fracture strengths of the capsule, the mortar matrix, and the interface of them has a significant influence on crack nucleation, initiation, and propagation. Using similar fracture strength between capsule and mortar matrix, together with high fracture strength of their interface, will initiate a crack from the mortar matrix and then propagate directly into the capsule. This condition is the most favorable case in the capsule-based self-healing concrete since a capsule contained with a healing agent will likely fracture. Thus, the self-healing process in the concrete can be achieved effectively. In addition, the interface with lower fracture strength than the mortar matrix and the capsule strengths will initiate a crack from the interface and then leave the capsule intact. Hence, the self-healing mechanism could not be achieved. These results will become some valuable assets for the experimentalists to assist in their experimental works.