Simplified analytical assessment of damaged induced by the external sulphate attack in concrete piles

Underground structures and foundations, including piles, constructed with reinforced concrete may be in contact with sulphate-rich soils and water. Structural elements exposed to these conditions may be affected by an expansive process known as external sulphate attack (ESA) that generally leads to an increase in volume, hence displacements and cracking of the concrete. The most widely accepted approach to mitigate such problems is to use cement(s) with a small content of aluminates. The objective of this research was to assess the potential damage induced by ESA using a simplified analytical model that is able to consider parameters such as the cement content and size of the pile, which may also affect the risk of damage. A parametric study was performed with different pile sizes and aluminate and cement contents. The structural integrity of the elements was verified considering a life span of 50 years and three possible failure modes (tensile failure in the core, and shear or tensile failure in the interface between the damaged and undamaged regions). The results suggest that the recommendations based solely on the maximum aluminate content present in the cement are inaccurate and might lead to very different outcomes depending on the characteristics of the elements. The study indicates that other parameters should also be taken into account in order to reduce the risk of ESA in real structures, such as the size of the element or the cement content per unit volume of concrete. This work has implications for the design of pile foundations in ground conditions prone to sulphate attack.