Bond behaviour of bars embedded in ecological high-ductility cementitious composites

Ecological high-ductility cementitious composites (eco-HDCC) are cost-effective high-ductility materials that have promising applications in structural engineering. With an important role in structural design, the bond-slip behaviour of steel bars and basalt-fibre-reinforced polymer (BFRP) bars embedded in an eco-HDCC were investigated using pull-out tests. Factors such as bar type, bar diameter and embedment length were considered, and all these factors were found to have an effect on the failure mode. The bond stress-slip curves of the steel bars and BFRP bars in the eco-HDCC displayed four distinct stages: linear, non-linear, descending and residual stages. Residual bond stress was found to exist at the interface between the BFRP bar and the eco-HDCC. Moreover, the bond stress showed a decreasing tendency for a larger bar diameter or longer embedment length, while the slip displayed the opposite trend. Analytical models were developed to predict bond stress-slip curves based on the experimental data. As a general consideration for structural design, the BFRP bars proved to be a good alternative for structures, showing excellent bond properties at the pull-out stage. A reasonable bar diameter and embedment length need to be selected to prevent specimen splitting and to ensure a certain bond stress or slip.