INVESTIGATING THE INFLUENCE OF RECYCLED COARSE AGGREGATE ON THE COMPRESSIVE AND TENSILE STRENGTH OF SELF-COMPACTING CONCRETE

Abstract

 This paper investigates the influence of self-compacting concrete incorporating recycled coarse aggregate as a sustainable alternative to natural aggregates. The study examined how varying replacement levels of recycled coarse aggregates ( RCA) influence the compressive and tensile strength of self compacting concrete( SCC). Six concrete mixes was produced and  in each mix natural coarse aggregate was replaced by recycled coarse aggregate in the ratio of 0%, 20%, 40%, 60%, 80% and 100% by volume. A 42.5N Portland cement (PC) conforming to BS 12 (1996) and superplasticizing admixture- to maintain a nominal slump of 75mm were used throughout the work for concrete production. . The hardened concrete was tested for 3, 7, 28 and 90 days compressive strength and 28 days tensile strength as per relevant BS codes. For Compressive strength test 72 numbers of 100mm size cube specimens were cast, whereas for tensile strength test 18 cylinder specimens of 150mm diameter and 300 mm height were cast. . The result reveals that as the percentage of recycled aggregate increases the compressive strength of the SCC decreases.The strength investigation shows that, in all the mixes compressive and tensile strength has inverse relationship with percentage of recycled coarse aggregate. This is a consequence of adhered mortar attached to recycle aggregate contributing for weaker interfacial transition zone.  Findings indicate that while RCA generally reduces mechanical properties due to its higher porosity and weaker interfacial transition zone, the extent of reduction depends heavily on the replacement percentage and the inclusion of mineral admixtures. . Future applications should focus on optimized replacement levels, typically below 25%, to maintain high-performance mechanical characteristics.