Effect of Corrosion on Flexural Behaviour of Reinforced Concrete Beams

Abstract

In coastal environment reinforcement corrosion is an obvious cause of deterioration of concrete structures, affecting strength and durability. The present study is an attempt to quantify the effect of reinforcement corrosion on the flexural strength of reinforced concrete beams. Experimental studies as well as numerical simulations have been performed. The basic need for this study is Load-deflection behaviour and crack pattern of beams how it is affected when it is corroded with Accelerated corrosion technique. Since corrosion takes place over a considerable length of time, to achieve corrosion quickly, accelerated corrosion technique was adopted. Corrosion was measured using Applied Corrosion Monitoring (ACM) instrument. Corroded beams were tested in laboratory to evaluate their flexural behaviour. Totally 42 beams out of which, 21 made of Ordinary Portland Cement (OPC) and 21 of Portland Pozzolana Cement (PPC) were tested. The beams were tested as vertical cantilever beams; two hydraulic jacks were used one for bottom fixity and one for applying the load at the top. Strain gauges were used for measuring strains: two strain gauges on the reinforcement and the third on the surface of the concrete beam. Strains were measured by data acquisition system as well as manually. The beams were loaded till failure. The load-deflection and crack-propagation patterns were recorded for various corrosion levels. For Control beam specimen it was observed that the control beams attained the higher load carrying capacity of about 23% more compared to theoretical ultimate load. The beams were corroded to 2.5%, 5%, 7.5% and 10% corrosion rate. As the rate of corrosion increases form 2.5% to 10%, stiffness and load carrying capacity decrease rapidly while deflection, crack width and curvature increase in beam specimens. It was observed that PPC beams behaved stiffer than OPC beams.PPC beams are 15% more corrosion resistant than OPC beams as chloride migration in PPC beams is less compared to OPC beams. In the numerical study, finite element method was used. Comparative studies were done for different levels of corrosion. Results show that as rate of corrosion increases, the deflection also increases but load carrying capacities of the beams reduce, for both OPC and PPC beams. It is observed that the stiffness of the beams is reduced nonlinearly when rate of corrosion is increased. The numerical modelling results are in conformity with experimentaliv values and it is concluded that numerical modelling can be applied satisfactorily to measure load-deflection behaviour and to predict crack patterns.