Typical plastic shrinkage cracking behaviour of concrete

Abstract

Plastic shrinkage cracking (PShC) is one of the earliest forms of cracking in concrete. Concrete structures with large exposed surfaces are especially vulnerable to PShC and the cracks formed are unsightly and can lead to premature durability issues. Although various precautionary methods exist, they are often neglected or ineffective due to the fundamental lack of knowledge regarding PShC. This paper investigates and describes the typical behaviour of PShC in conventional and low-volume synthetic fibre reinforced concrete. It is shown that PShC occurs rapidly only after the initial setting time while the crack width stabilises around the final setting time. It is further shown that the bond between synthetic fibres and fresh concrete rapidly increases between the initial and final setting times, thus playing a key role in the reduction of PShC. The insight gained into the behaviour of a typical plastic shrinkage crack serves as a sound basis for engineers and contractors first to recognise and ultimately prevent these cracks.