Utilization of waste from alumina industry to produce sustainable cement-based materials

Alumina industry produces a huge amount of waste (known as red mud) which contains a high content of alkali metals. This poses a serious threat to the environment. In this study, a method is proposed to use red mud to manufacture sustainable cement-based materials with low CO2 footprint. The method involves the calcination of red mud. In detail, this study investigates the effect of calcination on the physico-chemical properties of red mud. It also reports the effect of calcined red mud on the compressive strength and microstructure of hydrated cement paste. Results show that calcination at 900 and 1000 degrees C makes that cancrinite and birnessite present in red mud fully decompose to form nepheline and gehlenite minerals. This process changes the morphology of red mud particles and increases their sizes. Strength results reveal that cement pastes blended with 15% wt.% red mud calcined at 1000 degrees C possess a much higher compressive strength compared to that of pure paste. The strength of pastes containing 30% wt.% calcined red mud is almost the same as that of pure paste. To the best of our knowledge, these observations are made for the first time and they open up a promising way for the treatment and utilization of red mud wastes. (C) 2019 Elsevier Ltd. All rights reserved.