Effects of Adding Neutralized Red Mud on the Hydration Properties of Cement Paste.

Sukpyo Kang,Byoungky Lee,Hyeju Kang

doi:10.3390/ma13184107

Abstract

Red mud is a highly alkaline waste by-product of the aluminum industry. Although recycling of red mud is being actively researched, a feasible technological solution has not been found yet. In this study, we propose that neutralization of red mud alkalinity could assist in its use as a construction material. Neutralized red mud (LRM + S; pH 6–8) was prepared by adding sulfuric acid to liquefied red mud (LRM; pH 10–12). After adding LRM and LRM + S to cement paste, the heat of hydration, compressive strength, and hydration products were examined. The experiments revealed that the calorific value of the cement paste with LRM was low, and its peak was delayed, when compared with that of plain cement paste (referred to as Plain), whereas the calorific value of the cement paste with LRM + S was similar to that of Plain. At the age of 28 d, the compressive strength of the cement paste with 10% LRM + S was 99% whereas that with 20% LRM was only 55% of the strength of Plain. Thus, our results help to resolve the issue of strength degradation of cementitious materials observed upon the addition of red mud and enable its reuse as a construction material.

Highlights

The development of industrial and mass-production processes has resulted in an increased generation of waste, and the disposal of such waste has been recognized as a serious environmental issue
With the intention of reducing the recycling cost of red mud, the authors of this study studied the production of liquefied red mud (LRM) by adding water to red mud with 36% moisture content such that it may be recycled as a cement concrete material
Heat of hydration of cement can be classified into heat of hydration over time and accumulated heat of hydration

Summary

Introduction

The development of industrial and mass-production processes has resulted in an increased generation of waste, and the disposal of such waste has been recognized as a serious environmental issue. The development of recycling technologies to convert large quantities of waste into natural materials may provide opportunities to mitigate the waste-management problem [1]. Red mud is a reddish-brown sludge by-product generated through the Bayer process in the aluminum industry. When producing 1.0 ton of alumina, 1.0–1.5 tons of red mud is generated as a by-product [2,3]. The chemical components of red mud are Al2 O3 (17%–20%), Fe2 O3 (48%–54%), SiO2 (4%–6%), TiO2. The disposal of red mud is becoming a major problem for industries, as it can lead to soil and water pollution owing to its high alkalinity [4]

Methods

Results

Conclusion