Preparation of magnesium oxysulfate cement with semidry carbonation high calcium content light-burned magnesium (Ca-LBM)

• Published in: Construction & building materials Vol. 408; p. 133664
• Main Authors: Hu, Zhiqi, Chang, Jun, Chen, Xiaoyang, Guan, Yan, Bi, Wanli
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 08.12.2023
• Subjects: Carbonation treatment; Chloride erosion; Magnesium oxysulfate cement; Chloride erosion; Carbonation treatment; Magnesium oxysulfate cement
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2023.133664

[Display omitted] •Carbonation treatment of semidry high calcium content light-burned magnesium.•A carbonated-517 phase was found to have better stability.•The carbonated products exhibited better mechanical properties. With the large amount of high-quality magnesite mining, low-grade magnesite is discarded, which not only pollutes the environment but also wastes resources. Therefore, to utilize high-calcium magnesite tailings, carbonated light-burned magnesium with a high calcium content was used to prepare magnesium oxysulfate (MOS) cement. Characterization was performed by FT-IR, SEM, TEM, TG-DTG, TG-MS, MIP, XRD, and zeta potential measurements. The following conclusions are drawn: a porous shell layer was formed on the surface of the carbonated powder particles; thus, the hydration reactivity was reduced, but a better dispersibility was obtained. The setting time of the samples increased with increasing carbonation treatment time, and the early strength was lower than that of the control, but it increased significantly with the curing period. The 28 d compressive strength of the samples treated with carbonation for 2 min was 12.1 % higher than that of the control, and the volume density was 3.7 % lower than that of the control. In addition, a carbon-containing 517 phase (C- 517) structure was found. This C-517 phase exhibited better stability and resistance to sodium chloride erosion. After immersion in sodium chloride solution for 28 d, the softening coefficient was 0.84, which was 385 % of the control, so the carbonated samples had better durability than the ordinary MOS cement. The semidry method is used to carbonate light-burned magnesium with high calcium content, which avoids the negative effect of calcium oxide on the hydration process of MOS cement and provides a method to solve the discarding of high-calcium magnesite tailings.