Influence of nano silica on compressive strength, durability, and microstructure of high‐volume slag and high‐volume slag–fly ash blended concretes

Abstract

AbstractThis study investigated the influence of nano silica (NS) addition on the early‐ and later‐age compressive strengths and durability properties such as sorptivity, drying shrinkage, volume of permeable voids, and rapid chloride permeability, along with microstructural changes, of high‐volume slag (HVS) and high‐volume slag–fly ash (HVS‐FA) blended concrete. The results showed that the addition of NS improved the early‐age (3 days) compressive strength of HVS and HVS‐FA concretes significantly by 34 and 45%, respectively. In addition, the HVS concrete containing 78% blast furnace slag (BFS) gained considerable compressive strengths at later age due to the addition of 2% NS than the control HVS concrete with 80% BFS and showed comparable compressive strengths to ordinary Portland cement (OPC) concrete. On the other hand, the compressive strengths of HVS‐FA concrete containing 67% BFS‐FA blend and 3% NS surpassed OPC concrete at 28 days and exhibited superior strengths at later ages than the OPC concrete. Significant reduction in sorptivity of both HVS and HVS‐FA concretes is observed at 28 and 91 days, respectively, due to the addition of NS. Similar substantial reduction of drying shrinkage, chloride ion permeability, and volume of permeable voids are also witnessed in both HVS and HVS‐FA concretes due to the inclusion of NS than their respective control concretes without NS, and these exhibited better performance than control OPC concrete on most occasions. A denser and compacted interfacial transition zone (ITZ) is also found in the HVS and HVS‐FA concretes due to the addition of a small amount of NS.