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Title: Optimization of Activator Concentration for Graphene Oxide-Based Alkali-Activated Binder

Author(s): D. F. Marbaniang, A. Kar, D. Adak, K. K. Ramagiri, D. Srinivas, and I. Ray

Publication: Materials Journal

Volume: 120

Issue: 3

Appears on pages(s): 57-72

Keywords: alkali-activated slag; alkali activator concentration; graphene oxide; layered double hydroxides; optimization

DOI: 10.14359/51738708

Date: 5/1/2023

Thermal-cured alkali-activated binders (AABs) are a potential replacement for traditional portland cement (PC) in concrete, primarily for precast applications. To avoid this energy-intensive regime and encourage wider application, this study investigates the development of ambient-cured AABs by adding graphene oxide (GO) nanoparticles. The mechanical strength and durability characteristics are determined for alkali-activated slag (AAS) mortar specimens prepared using 4, 6, and 8 molar (4, 6, and 8 M) concentrations of sodium hydroxide in the alkaline activator. The different percentages of GO by weight of slag are 0.0, 0.03, 0.06, and 0.09%. The mechanical parameters considered are compressive, flexural, and splitting tensile strengths. The durability parameters investigated are the rapid chloride permeability test (RCPT), sorptivity, and acid resistance. The performance of ambient-cured AAS mortar specimens containing GO is compared with thermalcured AAS mortar specimens (without any GO inclusions) and the control cement mortar (PC) to evaluate the effect of GO on the mortar characteristics. The strength of AAS mortar is observed to be higher both with and without GO inclusions for the molarity of sodium hydroxide greater than 4 M. The mixture containing 0.06% GO with a 4 M activator is found to exhibit optimal mechanical and durability characteristics. Mineralogical, chemical, and microstructural investigations confirm that the addition of GO to the ambient-cured AAS accelerates the rate of hydration, even at a lower concentration of the activator (4 M) due to its high specific surface area and consequent formation of a greater number of nucleation sites. Hence, ambient-cured AAS mortar prepared using 4 M sodium hydroxide and 0.06% GO is recommended for practical use.