Prediction of the steel-concrete bond strength from the compressive strength of Portland cement and geopolymer concretes

• Bond models using compressive strength, for different concretes, are proposed.
• For OPC concrete, especially at early age, FIB model is non-conservative.
• A linear bond model is more appropriate when compressive strengths less than 25 MPa.
• For best bond prediction of geopolymer concretes the FIB model should be calibrated.

The oldest and simplest bond test, which is the standard concentric pull out test, is usually used as a comparative test for different concretes in order to assess the bond with deformed bars. In this paper, two types of concrete are considered: Ordinary Portland cement (OPC) concrete and a novel concrete technology, namely geopolymer concrete (GPC). Bond strength was investigated by conducting pull-out tests on ribbed bars with a nominal diameter of 10 mm and/or 12 mm. The specimens were tested at various ages ranging from 1 to 28 days. Compression tests were performed at all ages as well. The main objective of the extensive research program involving 260 pull-out tests was to develop empirical models correlating the steel-concrete bond strength to the mean compressive strength of concrete for both OPC and geopolymer concretes. The models developed are compared to the existing model adopted by FIP Committee.