Synergistic effects of nano and micro silica on fresh and hardened properties of self-consolidating concrete

The escalating demand for methods to diminish cement usage without compromising the strength and durability of concrete mixtures has led to an intensified exploration of alternatives. Nano silica has emerged as a prominent supplementary cementitious material, recognized for its capability to partially substitute cement. Despite this potential, there was a gap in the literature on the effects of nano silica on the concrete's fresh and hardened properties, particularly when used in conjunction with silica fume. This gap propelled the current investigation, which aims to capture and compare the effects of incrementally substituting silica fume with nano silica in self-consolidating concrete (SCC). For this purpose, four nano silica dosages—1%, 2%, 3%, and 5%— were considered as replacements for silica fume. A range of experiments, including slump flow, T50 time, and L-box tests, were conducted to assess the workability of the developed SCC mixtures. Subsequent analyses focused on key mechanical attributes, namely static modulus of elasticity, compressive strength, and tensile strength. The research further encompassed water absorption, penetration depth, and electrical resistivity evaluations to understand the durability characteristics of the developed mixtures. The scanning electron microscopy (SEM) analyses complemented these tests, offering a microstructural perspective to further explain the outcomes. This investigation's findings offer novel insights into leveraging nano silica's distinctive properties to achieve the desired SCC properties while reducing the environmental impact of this class of mixtures.