Mitigating Sulphur-Induced Corrosion in RCC Structures: A Case Study of Sulphur Pit Rehabilitation

Abstract Reinforced Concrete sulphur pits in Sulphur Recovery Units are designed to store molten sulphur at around 140°C. However, exposure to aggressive sulphur compounds often leads to serious deterioration of concrete and embedded reinforcement, posing a recurring challenge across refineries globally. To address this, BPCL Mumbai Refinery undertook a comprehensive investigation and repair strategy to restore and enhance the durability of its sulphur pits. Initial inspections revealed water seepage through acid-resistant brick joints, traced to groundwater ingress through the RCC. Upon removal of insulation and acid brick linings, extensive sulphur-induced damage was observed manifested by concrete softening, cracking, and reinforcement corrosion. A detailed condition assessment was carried out using advanced Non-Destructive Testing techniques including Ultrasonic Pulse Velocity, Ground Penetrating Radar, Rebound Hammer Test, Core Sampling, Petrographic Analysis, and Half-Cell Potential. The results confirmed widespread degradation. Based on the findings, a targeted rehabilitation strategy was implemented, including sulphur attack mitigation, crack-sealing, corrosion inhibition, structural strengthening, and application of protective coatings. This initiative not only restored structural integrity of the sulphur pits but also significantly enhanced their long-term resistance to chemical attack. The case demonstrates the importance of early diagnosis and specialized repairs in extending the life of RCC structures in harsh environments.