Fracture energy approach to characterize concrete crack surface roughness and shear stiffness

In many concrete structural applications, such as concrete pavements, joints or cracks are relied upon to transfer load between adjacent slabs in order to better distribute the stresses in the material. This study has developed a new method to characterize the shear transfer ability of preexisting concrete cracks and joints. The measured concrete surface roughness and fracture energy (G_F) were related to a concrete mixtures ability to transfer shear load across a preexisting cracked surface. The wedge splitting test (WST) was used to obtain the concrete's fracture energy. A modified method for determining G_F based on WST is presented. A novel laser profilometer was implemented for quantifying the three-dimensional cracked concrete surface characteristics. The fracture energy was found to characterize both the physical and mechanical properties of the concrete crack face better than previously used surface parameters. In addition, the surface roughness of the concrete crack was related to the fracture energy at the time of cracking, whereas its ability to transfer shear load or shear stiffness was more related to the fracture energy at 28-day age.