CHLORIDE-INDUCED STEEL CORROSION IN CONCRETE - PART 1 - CORROSION RATES, CORROSION ACTIVITY, AND ATTACK AREAS

This paper presents results from a major long-term study on chloride-i nduced steel corrosion in concrete. The performance of a set of 50 rei nforced concrete slabs made with a range of portland and blended cemen t binders was evaluated, Two portland cements, a high C(3)A and a low C(3)A, a blended fly ash cement, and a blended blast furnace slag ceme nt were used. All reinforced concrete slabs were exposed to high chlor ide conditions by partial immersion in a three percent NaCl solution m odeling seawater conditions. The reinforcement was cleaned and weighed prior to inclusion into the concrete slabs. Periodic nondestructive m easurements of concrete performance included half cell potential monit oring, concrete resistivity and electrochemical measurements of rates of corrosion of steel in concrete using potentiodynamic anodic procedu res. Individual slabs were broken for reinforcement recovery at predet ermined times during the study. Measurements were made of the area of corrosion and the weight loss of steel through corrosion. This informa tion was related to the nondestructive data acquired on the slabs. Bec ause of the large amounts of information acquired in this study, infor mation has been published in two parts. In Part I, estimated corrosion current (I-c) data and areas under the I, versus time envelope (Acr) for reinforcement within concrete slabs is presented. These data were obtained using potentiodynamic anodic polarization techniques. Measure ments of the reinforcement corroded area in concrete are also presente d and related to the electrochemical measurements taken. It was found that concrete water:binder ratio significantly influenced the corrosio n rate of steel in concrete. Relationships were established between co rrosion activity and the area of chloride-induced steel corrosion. Obs erved relationships were different for reinforcement within portland c ement concretes and blended cement concretes considered. Work describe d in Part 2 focuses on relationships between electrochemical data on c hloride-induced reinforcement corrosion and gravimetric weight losses of steel in the concrete slabs. In addition, the relative performance of the portland and blended cement concretes is evaluated.