"Admixed Chlorides in Concrete: History, Impacts, and Standardization"

Abstract

The presence of chlorides in cementitious materials results in corrosion of the embedded metallic materials. Early construction practices (pre 1960s) relied on admixed calcium chloride to accelerate the early strength gain of concrete. Until the 1950s, few publications focused on the effects of chlorides in concrete on corrosion and the use of chlorides was well established. However, in the 1960s significant publications reported on the effects of chlorides on the corrosion of prestressed wires and strands – these publications were the result of several failures of prestressed systems. Later, significant research was performed on the corrosion of steels in cementitious materials―a significant portion of this work attributable to the researchers being recognized in this symposium: Brian Hope and Morris Schupack. Their considerable efforts led to new knowledge regarding corrosion durability of reinforced and prestressed systems. Recently, ACI Committees 201 and 222 standardized limits on allowable admixed chlorides in the constituent materials. However, more standardization is needed―ACI Committees 318 and 349 report different admixed chloride limit requirements than Committees 201 and 222. This paper provides an overview of past research, analyzes the effects of chlorides on service life and economy and provides data from a research project. Using this information, the authors propose a standardized limit for chlorides in concrete.