Investigation on multi-cracks initiation and propagation of fiber reinforced concrete in restrained shrinkage ring tests

Abstract

To explore the application of ring tests on assessing the cracking potential of the fiber reinforced concrete (FRC) at early age, restrained shrinkage ring tests were conducted for FRC with three steel fiber volume fractions, i.e. 0.5%, 1.0% and 1.5%. A fracture mechanics-based numerical method was developed by combining thermal and structural analyses. The whole fracture process, including multi-cracks initiation, propagation and final through-going cracking, in the FRC rings with different fiber volume fractions can be obtained. In addition, cracks initiation positions, strain variations of inner steel ring and crack width variations of the concrete rings were investigated. The results indicated that the fiber volume fraction essentially determined the fracture behavior of FRC under restrained shrinkage. For a low fiber volume fraction, e.g. 0.5%, only one crack initiated and propagated throughout the cross-section of the FRC wall. For a high fiber volume fraction, e.g. 1.5%, there was no cracking observed in the tests. For a medium volume fraction, e.g. 1.0%, three or four cracks initiated and propagated in sequence, and several strain drops of the inner steel ring were observed in the tests. The final strain drop represented that one crack propagated throughout the FRC wall and the previous drops indicated the new cracks initiation and propagation.