Determination of fracture mechanic data using pressure in internal cracks

A new test method to determine caharacteristic fracture mechanic data of concrete, especially mass concrete, is investigated. Large cylindrical specimens (diameter 60 to 110 cm, hight 40 to 60 cm) with an internal penny shaped crack are used. Pressure is slowly applied in the crack using an open or closed (flat jack) hydraulic system and the critical pressure causing instable crack growth is determined to calculate KIc values. Efforts are made to allow the determination of the fracture energy values. The aim of this project is to develop and optimize a new test method for mass concrete, giving engineeers a practical tool to quantitatively evaluate the stability of cracked unreinforced concrete structures. Expected advantages of the method are the relatively simple test set up, the long circular crack-process-zone and the easy production and testing of large specimens.