Physico-mechanical properties of self-compacting concrete containing treated cold-bonded fly ash lightweight aggregates and SiO2 nano-particles

Abstract

In this experimental study, the physico-mechanical properties of self-compacting lightweight aggregate concrete (SCLC) containing artificial lightweight aggregate (LWA) made from fly ash (FA) through cold-bonded process are investigated. Coarse LWAs were treated with a soluble solution of sodium silicates (WG) in order to enhance quality. However, the binary and ternary use of fly ash (FA) and silicon dioxide nanoparticles (nS) were considered in the production of SCLC. For this, a total of 18 SCLC mixtures were designed at three different w/b ratios of 0.25, 0.37 and 0.50, and total binder contents of 600, 550 and 450kg/m3, respectively. The physical properties were tested for water sorptivity, gas permeability and water permeability, as well as for drying shrinkage. The use of treated instead of untreated LWA reduces the negative effect of w/b ratio increment of the drying shrinkage of SCLCs. The results showed that using 5.0% nano-silica and treated aggregate decreased the drying shrinkage as much as 23%. However, a significant reduction in SCLC permeability was achieved by including nS and/or treated LWAs, specifically, a reduction of up to 70% for gas permeability at 90days. Moreover, a lower compressive strength resulted due to the use of untreated aggregate and higher w/b ratio. As a general result, it was determined that a better performance is revealed at 90days for SCLCs containing 5% nS and treated LWAs, regardless of w/b ratio.