Effect of nano silica on the workability of self-compacting concretes having untreated and surface treated lightweight aggregates

This paper presents the fresh properties of self-compacting lightweight aggregate concrete (SCLC) made with cold bonded fly ash (FA) lightweight aggregate (LWA) at a wide range of water-to-binder (w/b) ratios. For this, three concrete series including eighteen SCLCs were designed with w/b ratios of 0.25, 0.37 and 0.50, respectively. Each series have 6 different mixes in which two type of coarse LWAs (surface treated or not) and three nano silica (nS) replacement levels (0, 2.5% and 5.0%) are considered. The properties of SCLCs were observed in terms of slump flow diameter, T500 slump flow time, V-funnel flow time, and L-box height ratio. The compressive strength test was also conducted to obtain the strength level at 28 days. It is found that the fresh SCLCs have good fluidity, passing ability, uniform aggregate distribution and resistance to segregation. Incorporating treated coarse LWAs increased the workability characteristics of SCLCs. However, appreciable improvement in the consistency of SCLCs by nS addition was observed. The SCLCs made with treated LWAs and 5% nS were found to be the harder samples in this research.