Properties of semi-lightweight self-consolidating concrete containing lightweight slag aggregate

In this research, semi-lightweight normal-vibrated concrete (NVC) and self-consolidating concrete (SCC) mixtures were developed and tested to examine their fresh properties, mechanical performance, and shear resistance. The mixtures containing fly ash (FA) and/or metakaolin (MK) were developed using lightweight slag aggregate as a coarse aggregate to obtain a density ranging from 1950 to 2050 kg/m3. Eleven mixtures with varying compressive strengths (20-55 MPa), lightweight slag aggregate-to-sand (SG/S) ratios (0.7-2.0), and total binder contents (500-600 kg/m3) were developed after extensive trial mixtures. The following fresh properties of SCC mixtures were investigated: flowability, passing ability, segregation resistance, and mixture viscosity. The mechanical properties of the eleven mixtures included compressive strength, splitting tensile strength, and flexural strength. The eleven developed mixtures were also utilized to cast eleven beams without shear reinforcement to test their shear strength and cracking behaviour in full-scale structure elements. The results indicated that a maximum SG/S ratio of 1.5 was safe to produce semi-lightweight SCC mixtures with acceptable fresh properties. The shear strength results showed that at the same SG/S ratio, SCC beams exhibited slightly higher normalized shear loads compared to NVC beams. However, the possibility of using a higher SG/S ratio in NVC mixtures not only gave these mixtures an advantage over SCC mixtures in terms of lower density, but it also allowed an increase in the shear capacity of NVC compared to SCC mixtures.