Flexural Behaviour in Prestressed Rubber Concrete Sleepers with Recycled Aggregate

This paper investigates the structural performance and mix optimisation of prestressed concrete sleepers incorporating recycled concrete aggregate (RCA) and crumb rubber (CR).Nine mix proportions of fullscale sleepers were tested in four-point bending under three regimes including centre positive, rail-seat positive, and rail-seat negative.Load-deflection responses were processed to obtain ultimate load, initial stiffness, energy absorbed to peak, and deflection at peak.Quadratic response-surface models were fitted to RCA and CR contents and combined with a multi-response desirability approach to identify compromise-optimal mixtures balancing capacity, stiffness, toughness, and sustainability.Results show that increasing RCA causes modest, smooth reductions in strength and stiffness, with no abrupt thresholds up to 50 % replacement, while peak deflection remains largely unchanged and absorbed energy follows the strength trend.CR introduces a controlled strength-ductility trade-off, enhancing toughness and peak deflection at moderate penalties to capacity and stiffness.Optimisation highlights a practical corridor centred on 25 % RCA with 4 % CR across all regimes.