The effect of using recycled aggregates on reinforced concrete columns exposed to an axial compressive force

At present, the need for reusing destroyed concrete products and construction wastes WHICH resulted from demolitions or wars and natural disasters has emerged because of the increase in storing cost of these wastes and also the depletion of natural building materials over time, coarse aggregate (gravel) particularly. In this research, an experimental study was conducted on /14/ reinforced concrete columns exposed to a compressive axial force, column dimensions are (250 x 250 x 1000) mm, the parameters in this research are the reinforcement ratios (1%, 1.62%) and the replacing ratios of natural coarse aggregate NA by recycled concrete coarse aggregate RA as following (0%, 10%, 20%, 30%, 40%, 50%, 60%), The values of the maximum axial load on compression for columns were measured experimentally and compared with the mathematical values according to some international codes and the Syrian Arab Code. Also, The effect of changing replacing ratios of recycled aggregate was tested on the Characteristics of concrete mixtures (Compressive strength, Splitting Strength, Tensile Strength in bending), The results showed that the water absorption ratio of recycled aggregate is higher than natural aggregate, which requires adding extra amounts of water to concrete mixtures to conserve their workability and this leads to a reduction in the resulted concrete compressive strengths, and this study shows that concrete compressive strength decreasing value reached almost around 19.8% at age 28 days for replacing ratio 60% and this value can be acceptable to use these mixtures in reinforcement concrete according to Syria Arab Code, Also the concrete compressive strength increased by 9.32% at the replacing ratio 10%, the maximum axial load on compression decreased by 6% at replacing ratios smaller or equal to 40% while the decreasing reached about 15.7% for the replacing ratio 60%