Chloride Profiling & Durability Modelling

Chloride profiling is the process of measuring chloride concentration at incremental depths within concrete to determine how far chloride ions have penetrated from the exposure surface and at what rate. This data is the primary input for durability modelling, mathematical prediction of when chloride concentration at the reinforcement depth will exceed the corrosion threshold and initiate steel corrosion.

For reinforced concrete structures in marine, coastal, or de-icing salt environments, chloride-induced corrosion is the dominant degradation mechanism. The question asset owners need answered is not "is there chloride in the concrete?", there almost always is, but "when will chloride reach a level that causes reinforcement corrosion, and what does that mean for the remaining useful life of the structure?" Chloride profiling and durability modelling answer this question quantitatively.

TRSC obtains chloride profiles by drilling powder samples at 10mm incremental depths from the exposure surface, typically to a depth of 50–80mm or to reinforcement depth, whichever is greater. Powder samples are submitted to NATA-certified laboratories for acid-soluble chloride determination to AS 1012.20. The resulting concentration-versus-depth profile is fitted to Fick's second law of diffusion to determine the apparent diffusion coefficient and surface chloride concentration, the two parameters needed to model future chloride penetration.

At 12 Creek Street, chloride profiling of the facade concrete demonstrated that chloride concentrations at reinforcement depth were well below the corrosion threshold, a finding that contradicted the conservative assumption of chloride-induced corrosion underlying the original remediation recommendation. This quantified evidence supported a significantly reduced remediation scope, directly saving the asset owner substantial unnecessary expenditure. This outcome illustrates the commercial value of measured data versus conservative assumption.