Failure Behavior of Concrete Cylinders under Different End Conditions

Uniaxial compression tests were performed on plain concrete cylinders to evaluate the strength performance and cracking behavior under different end conditions. Ground concrete surfaces were tested with regular bearing plates and compared to graphite-coated concrete surfaces that were tested with tungsten disulfide and regular steel plates. High-speed video technology was used to study the propagation of macrocracks. The frictional restraint was proven to influence the compressive strength, crack initiation, crack propagation, and fracture pattern. Compared to the concrete cylinder tested with standard end conditions, the compressive strength decreased 17% for reduced surface friction. High surface friction caused crack initiation at the center of the sample with inclined crack propagation toward the ends, while reduced confinement caused cracks to start from the top or bottom and propagate parallel to the applied compression toward the other end of the specimen, resulting in different fracture patterns.