Sun Houchao, Shi Feiting, Wang Hui
School of Civil Engineering, Yancheng Institute of Technology, Yancheng 224051, China.
School of Civil and Environmental Engineering, Ningbo University, Ningbo 315000, China.
Materials (Basel). 2023 Feb 3;16(3):1315. doi: 10.3390/ma16031315.
Magnesium oxysulfate (MOS), mainly composed of magnesium oxide and magnesium sulfate, is a kind of gas-hardening cementing material with low energy consumption and CO emissions. In order to develop environment-friendly cement-based materials, MOS needs to be studied systematically. The paper mainly investigates the influence of citric acid (a retarder) on the working and mechanical properties of MOS paste. In this study, the setting time of fresh MOS paste is determined. The flexural and compressive strengths of hardened specimens exposed to the environment of water dry-wet (D-W) alternations, freeze-thaw (F-T) cycles, and sulfate D-W alternations are investigated. Furthermore, the drying shrinkage (D-S) rate of MOS paste is tested for 3 days and 28 days. The specimens are cured in standard or CO curing environments. A scanning electron microscope energy spectrum (SEM-EDS) is obtained to analyze the morphology of hydration products. Results show that citric acid can increase the setting time of MOS paste. The citric acid and CO curing have a positive effect on the mechanical strengths and the resistance to erosion by water, F-T cycles, and sulfate D-W alternations. The D-S rate decreased in relation to the increasing dosages of citric acid and increased with CO curing. MOS with 0.3% of the total binder material mass shows the best erosion resistance. As observed in the results of SEM-EDS, the CO curing and the citric acid can make the hydration products denser.
硫酸镁氧（MOS）主要由氧化镁和硫酸镁组成，是一种低能耗、低二氧化碳排放的气硬性胶凝材料。为了开发环境友好型水泥基材料，需要对MOS进行系统研究。本文主要研究柠檬酸（一种缓凝剂）对MOS浆体工作性能和力学性能的影响。在本研究中，测定了新鲜MOS浆体的凝结时间。研究了硬化试件在水干湿（D-W）交替、冻融（F-T）循环和硫酸盐D-W交替环境下的抗折强度和抗压强度。此外，还测试了MOS浆体3天和28天的干燥收缩（D-S）率。试件在标准或CO养护环境中养护。通过扫描电子显微镜能谱（SEM-EDS）分析水化产物的形态。结果表明，柠檬酸可以延长MOS浆体的凝结时间。柠檬酸和CO养护对力学强度以及抗水侵蚀、冻融循环和硫酸盐D-W交替侵蚀有积极作用。D-S率随柠檬酸用量的增加而降低，随CO养护而增加。占总胶凝材料质量0.3%的MOS表现出最佳的抗侵蚀性。从SEM-EDS结果可以看出，CO养护和柠檬酸可以使水化产物更致密。
