The artificial super lightweight aggregate (SLA) with isolated void has recently been developed in Japan, which is characterized as the water absorption of about 3% and a density ranged from 850 to 1200kg/m3. Concrete mixed with SLA exhibits excellent performances compared to that with conventional lightweight aggregates. Therefore, SLA concrete has high potential for use in various infrastructures including marine structures.
　It is well known that the low crushing load and the spherical shape of artificial lightweight aggregates may cause deficiencies in load carrying capacities agahst shear or tensile forces. For example in the current JSCE standard specification, the shear capacity of a lightweight concrete beam is reduced to be 70% as that of general normal-weight concrete. This value for reduction was based on experimental studies on conventional lightweight aggregate concrete beams. Therefore, the applicability of this reduction to SLA concrete beams has to be confirmed.
　Reinforced SLA concrete beams with the controlled density of concrete were experimentally load-tested. The test results showed that the shear capacity becomes low as the density of concrete is decreased. The conversion term from general normal-weight concrete to SLA concrete for calculating the ultimate shear strength was proposed based on the test results, which is a function of the density of concrete. The shear resisting mechanism of SLA concrete beams was discussed with the shear span to effective depth ratio.