EXPERIMENTAL INVESTIGATION ON THE ULTIMATE CAPACITY OF RECTANGULAR REINFORCED HYBRID CONCRETE COLUMNS UNDER AXIAL LOAD
Keywords:Rectangular concrete columns, Hybrid concrete, Conventional concrete, Concentric loading, Secondary reinforcement
An experimental investigation was conducted on five configurations of reinforced concrete short rectangular columns that were tested until failure under concentric loading. Conventional concrete (CC) and ultra-high-performance concrete (Reactive powder concrete, RPC) were used in the experiments. Two of the columns were considered control specimens, one cast from a CC mix and the other from an RPC mix. The remaining three were; cast by combining the two types of concrete into a hybrid combination having the CC at the centre of the column surrounded by a 40 mm layer of RPC. The research included studying the effect of secondary reinforcement (sizes and spacing). The reinforcement bar diameters studied were 4,6, and 8 mm and the spacings were 100, 140 and 175 mm. The columns studied had dimensions of 100×200×740 mm. The data obtained included: crack and ultimate loads as well as longitudinal and lateral strains. The test results showed that increasing the diameter of the secondary reinforcement was more significant than changing the spacings between them with respect to the CC column. The maximum recorded increase in ultimate capacity resulting from changing the diameters was 203% while that resulting from changing the spacings was 179%.