SHEAR CAPACITY OF REINFORCED CONCRETE BEAMS USING RECYCLED COARSE AGGREGATES

An investigation into the shear capacity of reinforced concrete beams using recycled coarse aggregate from crushed graded inorganic particles processed from used construction materials and demolition debris is reported. Eighty (80) beams 150 x 150mm cross-sectional area and 1000mm length and twelve (12) cubes were cast. The concrete mix adopted was 1: 2: 4 (cement: sand: granite/recycled aggregate) with w/c ratio of 0.55 by weight. The percentage replacement of normal coarse aggregate by recycled aggregate was 0% for forty (40) beams and 30% for the remaining forty (40) beams. Six (6) cubes for each mix were cast. The specimens are subjected to line loads to determine their failure behaviour, deflection, crack patterns and post-crack performance. The results showed that the average density and strength of recycled aggregate concrete were slightly lower than that of normal aggregate concrete as the recycled aggregate concrete cubes densities and strengths averaged 97.8% and 88.7% of that of normal aggregate concrete. Each test beam specimen exhibited initial flexural failure at mid span. Diagonal cracks also propagated from each of the supports to the point of the application of load, indicating shear failure. The failure mode of me test specimens varied with the shear span - effective depth ratio as well as the concrete mix type.