ABSTRACT
Interaction of sulfate ions with cement paste matrix causes sulfate attack which threatens integrity and durability of concrete by expansion of cement matrix and progressive loss of strength. This paper discusses the devastating effects of sulfate attack in a tunnel which is located in the South west of Iran. During tunnel excavation, a vast volume of groundwater and H2S gas entered into the tunnel that leaded to the failure in the concrete segments At severely damaged parts of the tunnel, surface layers of concrete segment were liquefied and accumulated (Figure 1).
