Degradation and life prediction model for piles due to crystallisation attack in sulfate saline area

Crystallisation attack is claimed to be a principal reason for failure of and damage to concrete structures in saline and offshore areas. A degradation mode, dividing the degradation process of concrete into four steps, is presented to describe the destruction process and mechanisms of piles subjected to crystallisation attack. A theoretical model for predicting the service life of a concrete pile is proposed, taking both the environmental factors and pile properties into consideration. Laboratory tests of fully or partially immersed concrete specimens are performed to reveal the degradation process and to validate the proposed model. Furthermore, a case study is conducted to analyse the factors that influence crystallisation attack. The results show that the proposed model exhibits good agreement with experimental results and gives a satisfactory prediction. The case study indicates that the sulfate concentration, solar radiation and depth of the groundwater are the key environmental factors that influence the service life of piles. An increase in concrete cover thickness can improve the ability to resist crystallisation attack and hence enhance the service life of concrete structures. The results of the analysis demonstrate that the proposed model is capable of predicting the service life of concrete piles under crystallisation attack.