Experimental investigation of the composite action between hollowcore slabs with machine-cast finish and concrete topping

Abstract

Hollowcore slabs are precast/prestressed concrete elements produced at a manufacturing plant before shipping to the job site. Following installation, a layer of concrete topping is usually cast to connect the slabs and to have a level surface. According to current North American design standards, the topping should not be considered to act compositely with the slabs except if their surface satisfies a strict roughness requirement. This paper evaluates if such restriction is justified for hollowcore slabs with machine-cast finish through an experimental program that involves pull-off, push-off and full-scale tests. The surface roughness was first evaluated. The peel (bond) and shear strengths of the interface between the slabs and the topping were then assessed using pull-off and push-off tests. Full-scale tests examined the overall behavior of the composite slabs. The tested composite slabs exhibited higher tensile and shear stresses than the limits set by North American design standards. Surface roughness threshold for machine-cast hollowcore slabs is estimated. The paper presents the initial evidence that hollowcore slabs with machine-cast surface can be considered to act compositely with the concrete topping.