The Effect of Aggregate Shape and Configuration to the Concrete Behavior

Abstract

It has long been acknowledged that the behaviour of concrete is influenced by the properties of its constitutive materials. The geometry of aggregates is believed to contribute to the strength and stress-strain relationship of concrete. However, advanced studies are still required to quantify the effect of such factor in determining the behaviour of concrete. This research was aimed at investigating the effect of aggregate shape and configuration on the stress-strain relationship of concrete. Four types of specimens were investigated. There was one single coarse aggregate with different shape placed in the centre part of the specimens. The specimens were subject to uni-axial compression and both the load and displacement were measured. The experiments were conducted at the Structural and Material Laboratory of Diponegoro University in Semarang. The results show that the specimen with a diamond shaped aggregate results in the lowest compressive strength. However, the initial tangent stiffness of all specimens is almost identical up to 25% of its ultimate strength. Finite element analyses were carried out to study stress distribution in the specimens. The results show that the stresses are concentrated at the corner of the aggregates. This stress concentration initiates cracks at the Interfacial Transition Zone (ITZ) around the corner of the aggregates. The cracks then propagate and spread to the mortar which then reduce the stiffness of the specimens.