Effect of Aggregate on Concrete Strength under Tri-Axial Load

Strength of concrete confined by spiral reinforcement is hardly estimated because the mix proportion, properties of aggregates and so on significantly affect the strength. However, in structural designing according to the J.S.C.E standard specification, the strength is estimated from results of test carried on only conventional concrete. In recent years, high-strength concrete with extremely low water-cement ratio and self-compacting concrete with larger mortar content have been developed and practiced. Furthermore, many types of aggregates e.g. recycled aggregate and lightweight aggregate have been used for concrete. In this study, the effects of aggregate properties and concrete strength under uni-axial load on concrete strength under tri-axial load were investigated. It is clarified that in case of recycled aggregate concrete and lightweight aggregate concrete, ultimate strength of spiral reinforced concrete column estimated according to the J.S.C.E standard specification will be much higher than actual strength, and the specification will estimate the strength with too much margin for high-strength concrete and self-compacting concrete, although the specification will be proper only for conventional concrete.