Taking performance to practice – simplified in situ approach for specifying concrete for chloride environments

Paper in proceeding, 2016

The application of conservative structural codes such as EN1992 with high factors of safety and performance based compliance measures for concrete strength means that actual structural loading rarely exceeds the capacity and therefore has negligible influence on long term load carrying capacity. Majority of structures fail due to physical and chemical changes that concrete undergoes influenced by the exposure environment and subsequent reinforcement corrosion and loss of load carrying capacity. Lack of appreciation of concrete and its interactions with exposure environments, makes Designers and Engineers adhere more closely to prescriptive standards developed for relatively less aggressive environments. The data from exposure sites and real structures prove categorically that the prescriptive specifications are in adequate, especially for chloride environments. A performance-based approach similar to that followed for strength guarantee is proposed as a way forward for bringing durability into the forefront. For marine and de-icing salt environments, a handful of measurable parameters control the flow of chloride ions into concrete and such parameters form the core of most transport models. This article shows the scope of a simplified approach to chloride transport modelling using these core parameters for one chloride exposure environment. Further, the authors put forward a strong case for in situ measurements and the benefits it can have on assessing the whole structure. Examples for predicting the remaining service life as well as forming performance-based specification are also provided.