Condition Assessment and Repair Strategy for RCC Chimney of Thermal Power Station Located in Semi-Arid Region in India

Abstract

AbstractDistress caused by corrosion is generally noticed in many RCC structures in India. This distress in the form of reinforcing corrosion and cracking of cover concrete is found due to free ingress of water, oxygen and carbon dioxide through concrete cover kept to protect reinforcing bars corrosion in these structures. Due to inadequate specifications to different deteriorating influences to resist durability, many RCC structures constructed during early 80s, late 90s and even upto 1999 in India, till the revision of codal provision on strength and durability as laid down in IS 456–2000 (Reaffirmed: 2021), Plain and reinforced concrete—code of practice, are found to be in partly distressed conditions. The investigated RCC structure is 40 years old RCC Chimney with 150 m height in Thermal Power Station located in semi-arid region of India. Condition assessment study using Non Destructive Evaluation (NDE) techniques was carried out on the RCC structure for finding out the cause and extent of distress. Repair methodology was proposed based on the test results. Keeping in view the diverse nature of repair materials, the Quality Assurance (QA) & Quality Control (QC) to evaluate the performance of repair material and repair work as whole is essential for achieving the desired service life. Paper highlights various tests carried out on variety of repair materials like rust remover, anticorrosive coating, corrosion inhibitors, bond coats, grout materials, Polymer Modified Mortar (PMM), Glass Fibre Reinforced Polymer (GFRP) wrap, protective coatings, etc. The test results of repair materials were compared with available codes, manuals & manufacturers test certificate. A detailed quality inspection was carried out in order to follow the approved repair methodology and quality assurance plan. NDE techniques like rebound hammer, Ultrasonic Pulse Velocity (UPV), core extraction and pull off test, etc. were also done to verify the effectiveness of repair.KeywordsCondition assessmentRepairCorrosion inhibitorsBond coatsGrout materialsPolymer modified mortar (PMM)Glass fibre reinforced polymer (GFRP)Quality control