Bearing capacity of steel fiber reinforced reactive powder concrete confined by spirals

Based on two basic considerations, (1) the enhancement of bearing capacity by the inclusion of confining spirals and (2) the crack-bridging and energy-absorbing improvements gained by adding steel fibers to the mixture, steel fiber-reinforced reactive powder concrete (SFR-RPC) reinforced by steel spirals can be applied to post-tensioned anchorage zones. Twelve SFR-RPC prisms containing steel spirals and a longitudinal duct hole were loaded at high concentration over a limited circular area. The tests indicated that all specimens retained integrity at failure and exhibited no less than four radial cracks, the entire depression occurred on the loading-end surface, and the splitting tendency generally developed below the first turn of the spiral if the wedge cone formed ahead of the bearing plate. Three major factors related to the geometry of the zone directly influence the bearing capacity: (1) the local aspect ratio of the net area of the concrete supporting the plate to the area of the bearing plate, (2) the core aspect ratio of the area of the bearing plate to the area of the core surrounded by the steel spirals, and (3) the steel ratio of the spirals. An expression of the bearing load capacity is proposed on the basis of the testing results.