Assessment of concrete shear resistance of lightweight SCC beams containing scoria aggregates

Abstract

Lightweight self-consolidating concrete (LWSCC) has become a construction material that combines the benefits of lightweight concrete (LWC) and self-consolidating concrete (SCC). However, this combination may affect the shear resistance of structural members made with such concrete. This paper evaluates the shear resistance and performance of LWSCC beams. Eight full-scale beams without stirrups were fabricated and tested to failure. Seven beams were constructed using LWSCC and one was cast using normalweight self-consolidating concrete (NWSCC). Natural lightweight coarse and fine scoria aggregates were used in preparing the concrete mix. The beams were tested over a simply supported span in a two-point loading configuration. The test parameters comprised the type of aggregates, the reinforcement ratio of longitudinal steel bars, the shear span-to-depth ratio, and the depth of the beam. The experimental results showed that employing scoria aggregates in the mix resulted in beams with a reduced self-weight, where the obtained unit weight of LWSCC was 1800 kg/m3. Compared to the beam with NWSCC, the counterpart beam with LWSCC showed 25% lower shear strength. Additionally, the LWSCC beam experienced a reduction of 20% in the flexural cracking load while the beam showed a larger number of cracks at failure. The shear strength of the beams was predicted using the relevant shear design provisions of the American Concrete Institute building code ACI 318, the Canadian standard CSA-A23.3, and Eurocode 2. The ACI 318 method provided more reliable and conservative estimates for the shear capacity of the tested beams.