Enhancing solidification in one-part geopolymer systems through alkali-thermal activation of bauxite residue and silica fume integration

Abstract

This work describes the synthesis of geopolymers, a family of amorphous alumino-silicates, employing Silica fume and bauxite waste as precursor materials in an alkali-activated polycondensation reaction and the investigation of their properties. The purpose of the study is to determine the feasibility of producing one-part alkali-activated geopolymer for use in cast-in-place construction. Following calcination of the bauxite residue at 800 °C, different amounts of solid activator Na₂O (10 %, 15 %, and 20 %) were added. Furthermore, Silica fume content ranging between 10 % and 40 % was utilised at intervals of 10 %, in lieu of alkali-thermally treated bauxite residue. The primary objective of the study is to evaluate the fresh properties throughout the first 28 days of geopolymer formation, including consistency, flowability, heat evolution, initial setting time (IST), and final setting time (FST). Scanning electron microscopy (SEM) images are used in conjunction with the 28-day average compressive strength to demonstrate the solidification of one-part geopolymers. Furthermore, these properties are affected by adding Silica fume at regular intervals between 10 % and 40 % as a replacement of the alkali-thermally treated Bauxite residue. The 28-day average compressive strength, with a maximum value of 19 MPa indicating successful geopolymer formation, supports the solidification of one-part geopolymers.