Shear strength of smooth unreinforced construction joints

Abstract

Synopsis The results of 60 tests on smooth unreinforced construction joints in concrete prisms are presented. Each specimen was subjected to loading which induced combined direct and shear stresses at the joint. It was found that shear was transmitted by a combination of ‘cohesion’ and ‘friction’. A slight dependence of the shear strength upon the age ofthe first pour of concrete at the time of the second pour was found. A relation for the shear strength of a smooth unreinforced construction joint is proposed as a function of concrete compressive strength and the associated direct stress at the joint.