Solution properties of solids in the ettringite—thaumasite solid solution series

Abstract

The thaumasite form of sulfate attack (TSA) has received considerable research attention since its discovery in several motorway bridge foundations in the UK in 1998. Its significance as a deterioration mechanism in concrete, leading to the fluidisation of the matrix in extreme cases, is now acknowledged. Despite the continuing uncertainties that exist with regard to mechanisms for thaumasite formation, there is now reasonable agreement on conditions that favour TSA, and, as with all deleterious reactions affecting concrete structures, there is a desire to be able to anticipate the likelihood of occurrence so that such problems can be ‘designed out’ in the formulation stage. Inevitably, this points to the development of suitable models and the generation of reliable data. It is towards this latter goal that this paper is focused. Building on our previous studies, which reported on the means of fixing intermediate compositions in the ettringite–thaumasite solid solution series, this paper describes the treatment of solubility data, which can be utilised in phase development and solubility models involving this system.