Concrete Cover Cracking with Localized Corrosion of Reinforcing Steel

Abstract

The work estimated experimentally the critical amount of steel corrosion needed for concrete cover cracking of a reinforced concrete element where only a fraction of the steel bar length is corroding. The amount of corrosion needed to crack the concrete cover was ~ 49 micrometers to ~ 137 micrometers in specimens with localized corrosion, in comparison to ~ 15 micrometers to 75 micrometers for uniform corrosion reported for the other investigations in comparable systems. An empirical equation is proposed for the critical amount of steel corrosion as a function of specimen dimensions (concrete clear cover, C; rebar diameter, theta; and anodic length, L). In this equation the critical amount of steel corrosion is proportional to the first power of C/theta and to a higher power of [C/L+1]. Quantitative determinations of the development and magnitude of stresses produced by corroding steel in concrete have been obtained. Estimated pressures at the steel/concrete interface for C/theta >= 3 reached values comparable to the concrete compressive strength. The potential use of a fracture-energy-based model to predict the critical amount of steel corrosion needed for concrete cover cracking of a reinforced concrete element was supported by indications of approximate agreement between estimates of the work of corrosion expansion and the energy required to crack the concrete.