The mitigation of the external sulfate attack from the standpoint of the design of concrete structures is usually based on the use of cement with limited content of aluminates. Nevertheless, other parameters may affect the final durability, such as the cement content, the geometry and size of the structure. The consideration of these factors is highly complex. Few straightforward methods are available to verify the durability of structures subjected to sulfate ingress. The objective of this paper is to present a simplified model for the verification of the durability, considering variables related with the composition, the exposure and the geometry of the structure. First, a model to simulate the chemical-physical- mechanical phenomenon is proposed and validated. Then, this model is simplified to make it easy to apply. Finally, a parametric study is performed to evaluate the influence of the shape and size of the element on the durability