Effects of Water to Cement Ratio on Concrete Fracture Parameters

Abstract

This paper presents an experimental investigation of the influence of different water to cement ratios (w/c) on fracture properties of concrete. Water/cement ratio plays a vital role in governing the strength of concrete as well as the strength and thickness of interfacial transition zone (ITZ), which in turn affects the formation of fracture process zone and cracking behaviour in concrete. In this study, three-point bend tests have been performed on notched concrete beams with varying water to cement ratios between 0.35 and 0.5 to determine the fracture properties of concrete. Aggregates with a nominal maximum size of 12.5 mm have been used for this study. The size of the fracture process zone is one of the important parameters that determine the brittleness of concrete. Digital Image Correlation (DIC) has been used to obtain various fracture parameters such as crack opening displacement, length and width of the fracture process zone (FPZ). VIC-3D software has been utilized to process digital images to measure surface strains and displacements. A decrease in fracture energy has been observed with the increase in water to cement ratio from 0.35 to 0.45. This can be attributed to the modification of pore structure in ITZ with the increase in water to cement ratio. In addition, the paper also compares the variation of crack tip opening displacement at different stages of loading for the proposed water/cement ratios. Variation in characteristics of FPZ for different water to cement ratios, viz. length and width of the FPZ are also examined.