Environmental Assessment of Magnesium Oxychloride Cement Samples: A Case Study in Europe

Gediminas Kastiukas,Shuang Liang,Xiangming Zhou,Shaoqin Ruan,Cise Unluer

doi:10.3390/su11246957

Gediminas Kastiukas, Shuang Liang + Show 3 more

Open Access

https://doi.org/10.3390/su11246957

Copy DOI

Abstract

This study is the first in the literature to systematically assess the environmental impacts of magnesium oxychloride cement (MOC) samples, which are regarded as a more eco-friendly construction material than Portland cement. The environmental impacts of MOC samples prepared with various molar ratios of MgO/MgCl2∙6H2O and sources of reactive magnesia were obtained via a life cycle assessment (LCA) approach (from cradle to grave), and the obtained outcomes were further compared with the counterparts associated with the preparation of Portland cement (PC) samples. Meanwhile, a sensitivity analysis in terms of shipping reactive magnesia from China to Europe was performed. Results indicated that the preparation of MOC samples with higher molar ratios led to more severe overall environmental impacts and greater CO2 sequestration potentials due to the difference of energies required for the production of MgO and MgCl2∙6H2O as well as their various CO2 binding capacities, whereas in terms of CO2 intensities, the molar ratios in MOC samples should be carefully selected depending on the strength requirements of the applications. Furthermore, various allocation procedures and MgO production processes will greatly influence the final outcomes, and allocation by mass is more recommended. Meanwhile, the environmental impacts associated with the transportation of reactive magnesia from China to Europe can be ignored. Finally, it can be concluded that MOC concrete is no longer a type of ‘low-carbon’ binder in comparison with PC concrete in terms of CO2 emissions, and in view of the single scores and mixing triangles for weighing, MOC concrete can only be identified as a type of more sustainable binder than PC concrete when the main component MgO in MOC samples is obtained through the dry process route rather than the wet process route.

Highlights

Magnesium oxychloride (MOC) cement, which was invented not long after Portland cement (PC), is categorized as a nonhydraulic binder that forms from the reaction between magnesia (MgO) and a magnesium chloride (MgCl2) solution [1,2]
In order to obtain MgO with higher purities and reactivities, MgO may be acquired via the chemical synthesis from seawater or magnesium-bearing brine sources, accounting for about 14% of global MgO production annually [16], and the synthetic MgO obtained from seawater/brine has been proven to outperform MgO obtained from the calcination of magnesite with respect to the aforementioned properties [17], which was related to the larger specific surface area (SSA) achieved in synthetic MgO [18] in comparison with the MgO from calcination
Several key categories such as climate change, affected by CO2 emissions, were incorporated in this method, and these categories provided a comprehensive profile of the ecological impacts of magnesium oxychloride cement (MOC) and PC sample preparation

Summary

Introduction

Magnesium oxychloride (MOC) cement, which was invented not long after Portland cement (PC), is categorized as a nonhydraulic binder that forms from the reaction between magnesia (MgO) and a magnesium chloride (MgCl2) solution [1,2]. Reactive MgO, which is the key component in MOC, has been widely investigated in a series of studies in the area of construction [9,10,11,12,13,14], and can be obtained through the following two main approaches: (i) calcination of magnesia-based minerals (e.g., magnesite, dolomite or serpentine); and (ii) synthesis from brine/seawater [15]. In order to obtain MgO with higher purities and reactivities, MgO may be acquired via the chemical synthesis from seawater or magnesium-bearing brine sources, accounting for about 14% of global MgO production annually [16], and the synthetic MgO obtained from seawater/brine has been proven to outperform MgO obtained from the calcination of magnesite with respect to the aforementioned properties [17], which was related to the larger specific surface area (SSA) achieved in synthetic MgO [18] in comparison with the MgO from calcination. The overall input (i.e., raw materials and energies) and output (i.e., emissions) during the production of MgO was mainly related to the production of the base and the calcination of Mg(OH)2 [20]

Objectives

Methods

Results

Conclusion