Mechanical and fracture properties of concrete reinforced with recycled and industrial steel fibers using Digital Image Correlation technique and X-ray micro computed tomography

Paper presents investigation of fracture phenomenon in plain concrete and in concrete reinforced with both recycled steel fibers (RSF) and industrial steel fibers (ISF). The wedge splitting test (WST), which enables stable crack propagation for quasi-brittle materials, was carried out on 75 × 75 × 75 mm cube samples. Initially, fracture process zone development was investigated only on the surface of samples using Digital Image Correlation which is a non-destructive optical testing method. Furthermore, to analyse the 3D cracking phenomenon (formation, development, width, shape and curvature) X-ray micro computed tomography was used. Micro-CT images were taken during continuous deformation process - without unloading sample during scanning. X-ray micro-computed tomography was also used to visualise and characterise air voids and fibers (length, diameter and orientation) embedded in concrete. The mechanical properties of plain, RSF and ISF reinforced concrete in terms of compressive strength, tensile splitting strength, shrinkage, tensile and residual strength in 3-point bending were additionally described.