Influence of Specimen and Maximum Aggregate Size on Concrete Brittle Fracture

摘要

This paper presents an experimental investigation on the influence of specimen and maximum aggregate size on concrete brittle fracture. Approximately 250 concrete specimens with various dimensions of (width x total depth x thickness) 105 X 105 X 12.5 mm to 1680 X 1680 X 200 mm made with various maximum aggregate sizes of 4.75, 9.5, 19, 38, and 76 mm were tested. The quasi-static loading-unloading tests were performed in a closed loop displacement control mode using a servo-hydraulic Instron machine equipped with two dynamic extensometers. Fractal dimensional analysis was done on the fracture surfaces of specimens using Image analyzing technique. A significant size effect was observed. For same size specimens, as the aggregate size increased, fracture parameters, i.e., critical energy release rate, G_(1c), and fracture energy, G_F increased. For same maximum aggregate size specimens, fracture parameters increased with increase in specimen sizes. Bridging and other forms of crack face interactions that are the most probable causes of high toughness, were more pronounced in the specimens with larger maximum size aggregates. Higher values of fractal dimension were reported for the specimens with bigger aggregates.