Synthesis of structural binder based on red mud and fly ash activated using Ca(OH)2 and Na2CO3

Abstract

This paper explored the effectiveness of red mud and fly ash as precursor materials to produce an environment-friendly high strength brick product using a Ca(OH)2 and Na2CO3 activation. Overall, despite the inclusion of up to ~ 81% of red mud and fly ash, 7-day strengths were developed ~ 17-34MPa; this was high enough to be used as a structural binder for brick production. In particular, the use of NaOH was very effective in increasing flowability, and, more importantly, early strength in the red mud-CNF blended system, despite the red mud inclusion, because NaOH greatly improved the degree of reaction of the system, resulting in more C-S-H formation as well as significant pore size refinement at early days of curing. Trial bricks were also prepared to examine possible toxicity due to the inclusion of red mud and fly ash using the toxicity characteristic leaching procedure (TCLP) test.