ORIGINS OF CHLORIDE LIMITS FOR REINFORCED CONCRETE

The subject of chloride limits in concrete is currntly being debated within the concrete industry. The purpose of chloride limits is control of steel corrosion in reinforced and prestressed concrete. The origins of these limits provide an appreciation of the need for limits, and the potential need for changes. A distinction should be made betwen the limit, which refers to the amount of chloride permittd in new concrete code authorities ( a criterion set by man) and the so-called limit for corrosion under, which is the actuasl amount of chloride nede to initiate corrosion under a given set of conditions (determined by nature). The two are not necessarily equal. The limit must be set; the threshold must be investigated. Rational limits should reflect thresholds. Significant research into the threshold for chloride-induced corrosion has been carried our over the past few decades. Throughout this document, the commonly accepted reference for chloride limits, percent of chloride ion by mass of cement, will be used unless noted otherwise.