Investigating the two-dimensional diffusion-reaction behaviour of sulphate ions in cement-based systems

This paper describes experimental approaches to evaluate two-dimensional sulphate attack behaviour inside cement-based systems. First, the sulphate content at various depths was measured using titration. This was followed by mechanical evaluation on cylindrical samples to establish the associated stress-strain response. Three types of binder namely, Portland cement conforming to CSA Types GU and HS and, a 30:70 blend of fly ash and Portland cement Type GU, were employed. The specimens were immersed in a sulphate rich solution for up to 12 weeks. The results show that all specimens suffered more from two-dimensional sulphate attack as compared to that seen with exposure in one dimension. Also, the positive role played by an embedded aggregate emerged in that it was seen to impede the transport of sulphate ions inside the cement-based system. As well, self-healing under prolonged exposure was observed, which was more significant with both binders that contained Portland cement Type GU.