Long-Term Flexural Behaviour of Cracked Reinforced Concrete Beams with Recycled Aggregate

This paper presents the results of an investigation into the long-term flexural behaviour of cracked reinforced recycled aggregate concrete (RAC) beams. Washed construction and demolition wastes (CDW) with a maximum size of 20 mm were used as the coarse recycled aggregate. The main variable in the research was the replacement ratio of recycled aggregate. Specimens with 0%, 50% and 100% recycled aggregate were cast and tested. The experimental results showed that samples with an increased amount of recycled aggregate had significantly reduced strength and a noticeable increase in both short-term and long-term deflection of RAC beams over equivalent normal concrete (NC) beams. Increased levels of RA resulted in greater creep and shrinkage of RAC and greater long-term loss of tension stiffening in RAC reinforced tension specimens. Prediction of long-term deflections using Eurocode 2, even after incorporating the experimental concrete properties within the Code method, underestimated the experimental deflections of the RAC beams. However, by modifying the tension stiffening factor, β used in Eurocode 2, deflections were predicted to within approximately 1%. From this investigation, it is recommended that the factor β be reduced from 0.5 (for NC) to 0.4 (for RAC @50% replacement) and 0.3 (for RAC @100% replacement).