Experimental study of early-age bond behavior between high strength concrete and steel bars using a pull-out test

• Early-age bond behavior between steel bars and HSC was investigated.
• A model for early-age bond strength was proposed considering concrete age.
• A model for early-age slip corresponding to bond strength was proposed.
• A model for early-age bond behavior between steel bars and HSC was proposed.

High strength concrete (HSC) is used extensively in practice. However, HSC is prone to cracking at early age, which can be the first step in a construction’s deterioration and its malfunction. Reinforcement is one possible way to prevent the negative effect of early-age cracks in HSC structures. The early-age bond behavior is necessary to determine the cracking width of structures. Although the bond behavior between steel bars and normal strength concrete has been studied, study on early-age bond behavior between steel bars and HSC is still lacking. This paper presents an experimental investigation on the bond behavior between steel bars and HSC of different ages using a pull-out test. Test results showed that: (1) the early-age bond strength between steel bars and HSC increased with the increase of age; (2) the bond strength between steel bars and HSC increased with the increase of concrete strength and a model for the early-age bond strength between steel bars and HSC was proposed; (3) the slip corresponding to bond strength decreased with the increase of concrete compressive strength and a model for the early-age slip corresponding to bond strength was proposed; (4) a prediction model for early-age bond stress–slip relationship between steel bars and HSC was proposed based on BPE model, which showed good agreement with test results.