Abstract
Aluminosilicate gels form geopolymers and nanocrystalline zeolites which have comparable strength properties, making them a potential replacement for ordinary Portland cement. The study explores the use of two untreated industrial wastes, Class-F fly ash and red mud, for synthesizing geopolymeric material at ambient synthesis conditions. The high alkalinity present in the red mud was exploited for the dissolution of silica in the fly ash and red mud. The mechanical, mineralogical, microstructural, and pore characteristics were analyzed and the contributions of curing period, Si/Al, Na/Al, and liquid-to-solid (L/S) ratios on the compressive strength of the end products were also investigated. The alkalinity of the system due to the red mud was adequate for the dissolution of raw fly ash and the subsequent formation of aluminosilicate gels. The strength of the end product was directly proportional to the initial Si/Al ratio and the specimens with highest fly ash content exhibited highest compressive strength values after 28 days of curing. Furthermore, fly ash contributed to the formation and distribution of interstitial and capillary pores in the aluminosilicate matrix. The lowest L/S ratio of the initial mix resulted in the end product with the highest unconfined compressive strength.
Highlights
With the rise in global environmental pollution, energy crisis, and depletion of mineral resources, there is a need for the reuse of industrial wastes such as fly ash and red mud [1,2].Globally, around 780 million tons of fly ash and 150 million tons of red mud are annually generated, needing urgent utilization [2,3]
The chemical composition of the fly ash and red mud are shown in Table 1 and the fly ash was
This study examined the feasibility of synthesizing geopolymers from coal fly ash and red mud at ambient laboratory conditions
Summary
With the rise in global environmental pollution, energy crisis, and depletion of mineral resources, there is a need for the reuse of industrial wastes such as fly ash and red mud [1,2].Globally, around 780 million tons of fly ash and 150 million tons of red mud are annually generated, needing urgent utilization [2,3]. With the rise in global environmental pollution, energy crisis, and depletion of mineral resources, there is a need for the reuse of industrial wastes such as fly ash and red mud [1,2]. A coal combustion byproduct, contains significant amounts of. Aluminosilicate gels form geopolymers and nanocrystalline zeolites which have comparable strength properties, making them a potential replacement for ordinary Portland cement [7]. They have been synthesized using aluminosilicates and an alkali activator solution such as Na2 SiO3 , NaOH, Crystals 2019, 9, 572; doi:10.3390/cryst9110572 www.mdpi.com/journal/crystals
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