干旱区生态环境知识资源中心

Concrete structures in service deteriorate slowly either due to ageing or due to durability problems caused by exposure conditions. The deterioration of structures generally appears in the form of cracking. Freeze thaw, alkali-silica reaction, abrasion, carbonation and chloride diffusion into the cover concrete leading to corrosion of reinforcing bars in RC structures are well known and globally recognized causes of cracking & spalling of concrete in service structures. Large amounts of energy and materials, in addition to financial resources, are wasted when structures deteriorate. To determine the cause of damage and to carry out repair & restoration to enhance the service life, NDT and related diagnostic study are carried out.

This paper highlights the NDT and diagnostic studies of a distressed 37-year-old service building located in a semi-arid region and another service structure located near the sea shore in India. This paper highlights the field and laboratory studies carried out using non-destructive and partially destructive testing techniques. The investigation included visual survey, compressive strength, ultrasonic pulse velocity testing, carbonation and chloride measurement. Estimation of corrosion using half-cell potential testing was also done. The study reported was done on selected RC members of each structure. Data interpretation of the test results and service life of the structure is briefly given.

Based on the visual inspection and analysis of the test data, the indigenously available repair and strengthening measures to restore the service life of the structure are described, covering application of anti-corrosive treatment, epoxy grouting, bond coat, polymer modified mortar as per ACI Committee Report, an anti-carbonation protective coating, unidirectional Glass Fibre Reinforcement Polymer (GFRP) wrapping technique using epoxy saturant is summarized in this paper.