Red Mud-Blast Furnace Slag-Based Alkali-Activated Materials

Alessio Occhicone,Ivana Bosković,Claudio Ferone,Mira Vukčević

doi:10.3390/su132011298

Alessio Occhicone, Ivana Bosković + Show 2 more

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https://doi.org/10.3390/su132011298

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Abstract

The aluminum Bayer production process is widespread all over the world. One of the waste products of the Bayer process is a basic aluminosilicate bauxite residue called red mud. The aluminosilicate nature of red mud makes it suitable as a precursor for alkali-activated materials. In this work, red mud was mixed with different percentages of blast furnace slag and then activated by sodium silicate solution at different SiO2/Na2O ratios. Obtained samples were characterized by chemical–physical analyses and compressive strength determination. Very high values of compressive strength, up to 50 MPa, even for high percentage of red mud in the raw mixture (70 wt.% of RM in powder mixture), were obtained. In particular, the higher compressive strength was measured for cubic samples containing 50 wt.% of RM, which showed a value above 70 MPa. The obtained mixtures were characterized by no or scarce environmental impact and could be used in the construction industry as an alternative to cementitious and ceramic materials.

Highlights

Aluminum is one of the most used materials in the world
The most commonly used ore for aluminum production is bauxite, where aluminum is present as oxides and hydroxides (AlO(OH), Al(OH)3 ) [2]
The Bayer process is industrially adopted all over the world where aluminum is obtained from the electrolysis of molten aluminum salts

Summary

Introduction

Aluminum is one of the most used materials in the world. More than 120 billion tons are produced every year [1]. The most commonly used ore for aluminum production is bauxite, where aluminum is present as oxides and hydroxides (AlO(OH), Al(OH)3 ) [2]. The composition of the bauxite varies according to the place where the deposit is located, and from the deposit itself. The most economically convenient minerals are those containing more than 45 wt.% of aluminum oxide, about 12 wt.% of iron oxide, and less than 8 wt.% of SiO2 [2,3]. The Bayer process is industrially adopted all over the world where aluminum is obtained from the electrolysis of molten aluminum salts.

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