Fracture and Size Effect Studies on Fibre Reinforced Self Compacting Concrete Using Digital Image Correlation

Abstract

The size effect and fracture behavior of plain and fiber-reinforced concrete was investigated. Geometrically similar beam specimens of different sizes with (steel fibers and glass fibers) and without fibers were tested under three-point bending in a closed loop servo-controlled machine with crack mouth opening displacement control with a rate of opening of 0.0005 mm/sec. The fracture properties such as, fracture energy (Gf) and brittleness number were determined. Digital images were captured before loading (unreformed state) and at different instances of loading and were analyzed using correlation techniques to compute the load-point displacement, crack length, crack opening and crack tip location. It was seen that the crack mouth opening displacement (CMOD) and vertical load-point displacement computed using DIC analysis matches well with those measured experimentally. It also concluded that addition of fibers in specimens, increased energy absorption capacity tremendously in all size of specimens. It was observed that addition of fibers in concrete, brittleness number is decreased, hence the concrete becomes ductile. It was observed that the specimens follow the Bazant’s size effect law which shows that the structure becomes brittle with increase in size.