Effect of red mud proportion on the strength and microstructure of ferrosialate based geopolymer mortar

Yeddula, Bharath Simha Reddy; Somasundaram, Karthiyaini

Abstract

This paper studies the effect of various red mud proportions on the strength and microstructural changes in theferrosialate geopolymer mortar. The optimum percentage of red mud (RM) has to be found with respect to the molarity ofSodium hydroxide (NaOH) to maintain the suitable alkalinity of the mixture for maximum strength gain. This percentagehas been found to be between 20 and 30% RM proportions. From XRD micrographs, it has been found that the crystallinitypercentage increased with the increase in red mud content. For oven-cured samples, SEM images showed that, till the redmud replacement reaches 20%, any increase in the red mud leads to denser microstructure and a decrease in intensity ofunreactive particles. Beyond that, samples displayed a higher number of undissolved phases. Whereas, for ambientcuringspecimens, this limit is found to be 30%. Synergy has to be found among the red mud content, curing type and curingtemperature for optimum results. Ferrosialate geopolymer samples has shown 53.34% higher maximum compressivestrength than sialate geopolymer samples. The oxide ratios of SiO2/Al2O3 = 4.0 to 4.3, Na2O/SiO2 = 0.15 to 0.17 andFe2O3/Al2O3 = 0.27 to 0.37 have found to be limits for favouring maximum strength gain.

Keyword(s)

Geopolymer, Mortar, Red mud, Ferrosialate, Fly ash, Sialate

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