Effect of recycled concrete coarse aggregates on service-load deflections of reinforced concrete columns

This paper describes a numerical parametric investigation for the effects of coarse recycled concrete aggregates (RCA) on the time-dependent vertical deflections of reinforced concrete columns under sustained service loads. The deflections were analyzed for interior (concentric) and exterior (eccentric) column loading conditions, with different volumetric replacement of the coarse aggregate, R, concrete strength, column width, column depth, column length, longitudinal reinforcement area, ultimate shrinkage strain, ultimate creep coefficient, and ambient relative humidity. In addition, the quality of RCA was quantified and varied through the water absorption, A(rca) (viewed as a measure of aggregate porosity), and deleterious material content, (e.g., wood, asphalt). The results show that increased R resulted in larger deflections, and increased A(rca) and D-rca resulted in larger deflections for the same R. High quality RCA with low A(rca) and D-rca resulted in deflections that were not much greater than those for natural aggregate (NA) concrete columns. The increase in deflection due to RCA was larger for columns with larger concrete strength and cross-section dimensions and smaller longitudinal steel ratios, and larger for interior columns than exterior columns with flexural cracking. RCA was also found to have larger effect on the initial column deflections than the time-dependent deflections.