Having chloride or exposing the concrete to the chloride environments is always generates a certain risk of corrosion in embedded steel in the concrete. Therefore, limiting values have been specified by the code of practices.

In this article, we are comparing the different British Standards issued up to the date.

BS 5324 Part 1 1997; Guide to Specify Concrete, has categorized three levels of chloride contents. The classification is based on the type of concrete such as prestress and normal concrete with steel embedments.

As indicated in the above figure the maximum allowable chloride content is specified by the mass of cement.

According to the BS EN 206:2013; Concrete- Specification, Performance, Production and Conformity, there are five chloride classes.

BS EN 206 has specified two chloride classes for prestressing concrete. In addition, a limiting value of 1% of chloride by mass of the cement has specified for the mass concrete as well.

BS 8500 specifies the factors to be considered relevant to the durability of concrete. The latest revision of BS 8500 (BS 8500-1:2015+A1:2016) has reduced the number of chloride classes to four.

Its classification of the chloride class is based on the exposure condition which is more related to the condition that the structure is exposed to. 

Further, chloride classes specified as Cl 0.2 and Cl 0.4 in BS EN 206 have been revised to Cl 0.3 and Cl0.4. One limit has specified for prestressing and post-tension concrete while maintaining the same for unreinforced concrete when compared to BS EN 206.