An improved understanding on the influence of water-cement ratio and ITZ on fracture mechanisms in concrete

Interfacial transition zone (ITZ) is significantly influenced by Water to Cementitious material ratio and governs the overall strength and fracture properties of concrete. Even though an ample number of studies on this line are available in the literature, there is a lack of unified conclusions pertaining to the influence of water-cement ratios on various fracture characteristics and the underlying mechanisms. In this study, an attempt has been made to investigate fracture characteristics such as,size of fracture process zone (FPZ) , fracture energy, traction free crack, toughening mechanisms, etc. in view of varying interfacial transition zone properties and water-cement ratio. Plain concrete beams of size 700x150x80 mm (LxDxB) with varying water-cement ratios have been considered and tested under centre point loading by controlling the crack mouth opening displacement. Acoustic emission (AE) technique has been used for understanding the internal damage parameters. A novel method has been proposed for identifying the traction free-crack tip and the FPZ size using AE event location data at different stages of loading. The role of ITZ on fracture mechanisms in different types of concrete has been critically discussed.Evaluation of fracture energy reveals that its relation with water-cement ratio is affected by the type of concrete.