Model for cover cracking of RC beams due to partial surface steel corrosion

Cracking of the cover concrete due to steel corrosion is considered by many researchers to indicate the end-of-service life of corrosion-affected reinforced concrete (RC) structures. Numerous models have been developed to predict the time from corrosion initiation to cracking of the cover concrete. In the previous models, concrete with corroding steel bars was assumed to behave like a thick-walled cylinder under uniform internal pressure. Recent research publications have however, shown that steel corrosion is often concentrated on the surface of the steel that faces the direction of ingress of corrosion agents. This paper presents a model that relates the level of partial surface steel corrosion with the transverse and vertical strains measured on the exterior faces of corrosion-affected RC beams. The model assumes that the remaining section of the steel after corrosion is elliptical shaped. Finally, the model is calibrated with experimental data in the literature and it is shown that assuming uniform steel corrosion underestimates the internal pressure applied by the expansive corrosion products.