The distribution and evaluation of sulfur species in geological materials and manmade fills

Abstract

Abstract Groundwaters containing acidity and/or dissolved sulfate species are a primary factor in the attack on concrete and other construction materials. In the case of concrete, attack may be prevented by the use of suitably resistant concrete, eliminating sources of acidity and/or sulfate ions or by protecting the concrete structure from the offending solutions. Official guidelines, which have recently been modified to take account of the possible formation of sulfate and acidity after construction, are provided for the design of concrete structures to be placed in potentially aggressive situations. Limiting values for sulfates and other chemical species are also given for highway, road and bridge structures, but recent problems involving buried galvanised steel structures have highlighted the need for revised procedures to be put in place. Potential sources of aggressive solutions include the ground surrounding the structure and the construction materials, including fills, situated proximally to the structure. Unfortunately the current British Standard testing procedures are unsuitable for the purpose of assessing the potential aggressive nature of the ground and construction materials, hence risk assessments prove inadequate. This paper considers potential sources of ground acidity and sulfate rich solutions. Attention is given to suitable testing procedures for the evaluation of sulfur species in geological and construction materials. Particular attention is given to limiting values appropriate to the use of buried steel that forms part of highway, road and bridge structures.