Ahmad Jan

Ageing and increasing traffic demands, combined with aggressive environmental exposure, can significantly deteriorate reinforced concrete bridges. In coastal regions, chloride ingress is a major threat due to its role in initiating reinforcement corrosion. This study was carried out to evaluate the existing condition of the Mumbai Monorail. The visual inspection with non-destructive tests, including ultrasonic pulse velocity, rebound hammer test and natural-frequency measurement, was utilised, while the chloride-ion penetrability was assessed using the rapid chloride permeability test (RCPT). The RCPT results were used to characterise chloride-ion penetrability at the tested locations. However, due to cracks in pier 2A-70, the measured reduction in natural frequency corresponds to an effective global stiffness reduction of approximately 25%, based on the assumption of comparable mass distribution and boundary conditions between the reference and distressed piers. The strengthening was carried out by near-surface mounted (NSM) bars and carbon fibre reinforced polymer sheets (CFRP), and the results demonstrate reductions in concrete stress of 62.12% and 68.77% in the compression and tension zones, respectively, while the corresponding reductions in steel reinforcement stress are 56.90% and 65.89%. These reductions indicate an improved serviceability response of the strengthened pier within the adopted numerical assessment framework, which employs an experimentally informed equivalent-stiffness model for the comparative evaluation of the strengthening schemes. The study provides an integrated approach for evaluating the condition and durability of existing reinforced concrete infrastructure by combining visual assessment, non-destructive testing, and chloride-ion penetrability measurements. The findings can assist in identifying vulnerable locations, interpreting durability-related risks, and supporting condition-based maintenance and rehabilitation decisions. The methodology provides a useful framework for durability assessment of similar ageing reinforced concrete infrastructure under variable environmental exposure.

In this study, the incorporation of glass fibers in concrete bridge decks has been studied for improving its mechanical properties as well as energy absorption capacity and toughness indices. The mix proportion of 1:3:2 (cement:sand:aggregate) was selected having water-cement ratio of 0.71. For the manufacturing of glass fiber reinforced concrete (GFRC), the glass fibers (2-inch) were incorporated at a percentage level of 1%, 2%, 3% and 4% by weight of cement in concrete mixes. The findings reveal that the split-tensile and flexural strength of GFRC increases at all the percentage levels, however, the compressive strength of the blended mixes get reduced by increasing the dosage of glass fibers in the concrete. Besides, the energy absorption and toughness indices are also studied for different types of loadings (i.e. compressive, splitting-tensile and flexural loadings) up to a percentage level of 4%. The findings reveal that the split-tensile and flexural energy absorption was increased with the increase in the dosage of glass fibers in comparison with the conventional concrete mixes, however, the compressive energy absorption of the blended mixes get reduced by increasing the dosage of glass fibers in the concrete. Whereas, the toughness indices for compressive, spilt-tensile and flexure was increased while increasing the percentage of glass fibers as compared to the conventional concrete. Among the different percentages of glass fibers, its 4% addition gives better results as compared to 1%, 2% and 3%. Hence, the 4% of GF can be suggested to be the optimum percentage of the fibers for the selected mix-design in controlling the resistance of concrete in the bridge decks. Although, the energy absorption of GFRC is lesser in comparison with the toughness indices, GFRC are appropriate for enhancing ductility and resistance against loadings in concrete bridge decks.