INFLUENCE OF LONGITUDINAL REINFORCEMENT RATIO ON SHEAR CAPACITY OF NO COARSE-AGGREGATE CONCRETE

The study investigated the effect of longitudinal reinforcement ratio on the shear capacity of concrete beams without transverse steel. The concrete mixture did not include coarse aggregate. The Joint ACI-ASCE Committee 426 (1973) has shown that the shear is transferred across the surface where there is slip and it is called the aggregate interlock. To study the effect of longitudinal reinforcement ratio on the shear capacity of concrete without coarse aggregate, six beam specimens with the size of 110 x 7 x 12.5 cm and a/d ratio of 45/10.5 were investigated. The longitudinal reinforcement ratios were set from the minimum to the maximum, i.e. 0.0077, 0.0137, 0.0214, 0.0308, 0.0547, and 0.0772. The ratios of the ultimate shear to the shear capacity of concrete (Vu/Vc) were found between 1.0705 and 2.8748. When the longitudinal reinforcement ratio increases particularly from the minimum ratio, the value of Vu/Vc also significantly increases. The values of Vu/Vc were found less than 2, thus Vs is required. When the longitudinal reinforcement ratio approaches maximum, Vu/Vc becomes relatively constant and was found more than 2. This concludes that the ratio of Vu/Vc of the concrete without coarse aggregate is lower than normal concrete. The existing ACI's formula for computing the shear capacity contributed by concrete, which has not been changed for decades, is only applicable for normal concrete (with coarse aggregate). This research proposes a theory to develop a new shear capacity formula specifically for concrete without coarse aggregate.