| Summary: | The reuse of CDW as a coarse aggregate in the production of new concrete could potentially conserve natural resources, reduce the amount of landfill waste and reduce energy consumption; this would contribute to improved sustainability within the construction sector. The extensive scientific research conducted on this subject to date has concluded that in comparison to natural aggregate (NA), the quality of recycled aggregate (RA) is generally poorer and replacement with recycled aggregate has a negative impact on all concrete properties. The most noticeable effect is on time-dependent deformation (i.e. creep and shrinkage). This has meant that the use of recycled aggregate concrete in various construction applications has been restricted. In this study, an experimental programme has been carried out to examine the effect of incorporating recycled aggregate and steel fibres on the mechanical properties, creep, shrinkage, long-term loss of tension stiffening and long-term flexural behaviour of beams under sustained loads. The results obtained from the tests indicated that replacement with recycled aggregate reduced all concrete properties but the addition of steel fibres proved to be highly beneficial and, in fact, countered the detrimental effect of the recycled aggregate. For instance, it was found that the addition of 0.5% and 1.0% steel fibres to concrete containing 50% and 100% recycled aggregate, respectively, resulted in concrete with almost the same performance as normal concrete. An analytical investigation was also conducted to evaluate the suitability of existing code procedures for predicting the long-term deflection of concrete beams incorporating recycled aggregate and steel fibres. It was found that there were shortcomings within the existing codes when analysing these materials and modifications to the Eurocode 2 method were thus proposed. A numerical analysis program was developed using MATLAB language for predicting the long-term deflection of beams based on the proposed modifications. The program was used for validating the modifications by using the experimental results from this research and previous studies in the literature. In addition, a 3D finite element analysis was carried out using the commercial software Midas FEA which included the development of a novel approach for predicting the long-term deflection of cracked reinforced concrete beams containing recycled aggregate and steel fibres. The approach was verified by comparing the finite element analysis predictions with the experimental results from this study and data selected from previous investigations. Sensitivity and parametric studies were carried out to investigate the effect of some model and structural parameters.
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