Mechanical and Microstructural Properties of Alkali-Activated Concrete Activated By Waste-Derived Sodium Silicate from Various Synthesis Regimes

Abstract

Sodium silicate is one of the most common alkali activators for alkali-activated concrete (AAC). Production of sodium silicate has a high carbon footprint, which forms the basis for continuing research with a view to alternative synthesis methods using industrial waste materials. In this study, a low-temperature process to synthesize sodium silicate from industrial by-product silica fume is described, thus eliminating high-temperature processing. Mechanical and microstructural characteristics of AAC were studied under different synthesis regimes, including ultrasonication, heating, and combined methods. The chemical properties were analyzed with FTIR compared to sodium silicate from conventional sources, while UPV, compressive strength, flexural strength, and SEM analyses were performed to assess AAC performance. The method of ultrasonication under room temperature (SRT) appeared to provide the best performance compared to other methods with respect to compressive strength, achieving about 34 MPa by day 28 and indexing performance comparable to that of OPC concrete.

Keywords: Silica Fume-sodium silicate, Fly ash, GGBS, LKD, Sonication, FTIR