Refinement of air-borne chloride exposure classes for RC structures in the Cape Peninsula

Includes bibliography.The assessment in this study is aimed at informing and modifying the design method for RC structures that are not in direct contact with seawater but are within the marine environment. The evaluation of the severity of the exposure environment will enable an informed design of concrete structures that satisfies their desired service life and durability performance. In order to classify the severity of exposure, this study measured the concentration of airborne chlorides of select locations in the Cape Peninsula area, using the wet candle device. Five monitoring stations were exposed around the Cape Peninsula area at varying distances of 50 m, 150 m, 250 m, 2.7 km and 13.5 km from the coastline. Samples from the stations were collected twice every month over a period of 12 months and analysed for their chloride deposition rates. A site-based study which involved the collection of concrete samples from existing structures at varying distances from the sea and investigating their chloride content was also carried out. In addition, data from previous forensic investigations (chloride profiles of structures) carried out from 1996 – 2013 were also collated and analysed. Both analyses were carried out in order to further validate if the distance of a RC from the coastline influenced the chloride deposition rate and surface chloride content of the structure. The local climate and weather conditions, with a focus on the dominating wind direction, wind speed, precipitation and relative humidity were also examined