Mesoscale analysis of dry shrinkage fractures in concrete repair systems using FEM and VEM

A novel numerical method that used a FEM coupled with a virtual element method was proposed to evaluate the drying shrinkage of concrete repair systems. The stress distribution, crack development of the concrete repair systems due to drying shrinkage were investigated using this method. (1) The mortar along the tangent direction of the aggregate boundary was subjected to the aggregate constraint, allowing shrinkage cracks to form easily. The overlay first developed a significant number of microcracks on surface, followed by debonding at both ends of the interface. (2) Owing to the confinement of the aggregate below the surface, the surface tensile stress of the overlay had a 'hump' distribution. After cracking, the surface was divided into several contraction zones, with tensile and compressive stresses applied to the boundary and interior of the contraction zone, respectively. (3) As the interface de-bonded, the tensile and shear stresses of the interface began to increase from both sides and moved inward. The rise in local compressive and shear stresses were induced by the constraint of the aggregate in the bonding interfacial region. (4) Tensile stress caused the first damage, and the shear stress caused interface debonding to evolve.