Effects of Water-to-Cement Ratios on the Properties of Magnesium Potassium Phosphate Cement Prepared with Lithium-Extracted Magnesium Residue

Weixin Zheng,Chenggong Chang,Xueying Xiao,Jinmei Dong,Jing Wen

doi:10.3390/app11094193

Abstract

Salt lake magnesium phosphate cement (SLMKPC) was prepared by mixing potassium dihydrogen phosphate (KH2PO4) with lithium-extracted magnesium residue (MR). The hydration-hardening process and the variation in the phase composition and microstructure of hydration products with the change of the water-cement-ratio (W/C) were studied by measuring the setting time, hydration exothermic temperature, and compressive strength of the hardened slurry. It was found that W/C ratios had significant effects on the setting time, hydration exothermal temperature curve, and compressive strength of SLMKPC. With the increase of W/C, the setting time was prolonged significantly. The exothermic hydration peak temperature first increased and then decreased, and the number of exothermic peaks gradually changed from one to two. The optimal compressive strength was obtained when W/C = 0.2–0.3. Hydration products changed significantly with the increase of W/C, the MgKPO4·6H2O (MKP) in the matrix was more stable when W/C = 0.2 and 0.3 than when W/C = 0.25, 0.35, and 0.4. When W/C = 0.3, SLMKPC had a compact structure with a certain operating space and better mechanical properties.

Highlights

It is noticeable that W/C ratios had a great influence on setting time
The increment of setting time became slow after W/C = 0.3, and the setting time increased by 15% and 8%, respectively, as compared to those with
The SLMKPC slurry was very dry at W/C < 0.2 (Figure 8c) and could not achieve operational capability due to excessive moisture loss

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. As an energy material, plays an important role in mitigation problems caused by fossil fuels. The application of lithium-ion batteries in electric vehicles can reduce environmental pollution caused by traditional vehicles [1,2]. Lithium is abundantly found in salt lake brine [3]. Lithium is mainly extracted from salt lake brine by chemical precipitation for industrial applications [4,5]. In order to remove high Mg2+ concentration, hydroxide or carbonate are generally added, producing a large amount of magnesium residue (MR) [6]

Methods

Results

Conclusion