The influence of FeSO4 and KH2PO4 on the performance of magnesium oxychloride cement. (15th January 2016)

• Record Type: Journal Article
• Authors: Li, Ying; Li, Zongjin; Pei, Huafu; Yu, Hongfa
• Is Part Of: Construction & building materials. Volume 102:Part 1(2016)
• Page Start: 233
• Page End: 238
• Publication Date: 2016-01-15
• Subjects: Magnesium oxychloride cement -- Sulfate -- Phosphate -- Mechanical strength -- Water resistance -- Thermal stability -- Micro structure; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2015.10.186
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: Sulfate and phosphate reduce the thermal stability and mechanical strength. Sulfate and phosphate increase the water resistance and the total porosity of MOC. Sulfate and phosphate hinder the hydration of MgO in MOC. Sulfate and phosphate change the quantitative composition of crystal phase in MOC. The compressive strength of MOC firstly increases and then decreases. Abstract: As well known, sulfate and phosphate are widely used additives for MOC products. In this work, the influence of FeSO4 and KH2 PO4 on the properties of magnesium oxychloride cement (MOC) such as compressive strength, water resistance, thermal stability, composition and micro structure were studied in detail by using material testing system (MTS), X-Ray diffraction (XRD), thermogravimetry and differential scanning calorimetry (TG–DSC), scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP), respectively. The results show that both FeSO4 and KH2 PO4 incorporation can benefit the formation of gel-like 5Mg(OH)2 ·MgCl2 ·8H2 O (P5) and the water resistance of MOC. However, the FeSO4 and KH2 PO4 incorporation can downgrade the thermal stability and the mechanical strength. The influence of KH2 PO4 is more obvious than that of FeSO4 . In addition, the hindering hydration of MgO caused by sulfate and phosphate ions result in reduction of the hydration product, while the double hydrolysis reaction between Fe 2+ and MgCO3 leads to slight increase of the resultant in the slurry of MOC.