Effect of Raw Material Molar Ratio on Macro-Properties of Modified Magnesium Oxysulfate Cementitious

doi:10.16552/j.cnki.issn1001-1625.2025.0735

Abstract

Abstract:

To investigate the effects of the oxygen-sulfur ratio and water-sulfur ratio on the macro-properties and mechanisms of modified magnesium oxysulfate cementitious， the influence patterns of the raw material oxygen-sulfur ratio （M=n（α-MgO）∶n（MgSO₄）） and water-sulfur ratio （H=n（H₂O）∶n（MgSO₄）） on the hydration products， mechanical properties， and water resistance of MOS were studied through XRF， hydration heat analysis， XRD， and SEM. The results indicate that： with the water-sulfur ratio fixed at 20∶1 and the oxygen-sulfur ratio fixed at 11∶1， the magnesium oxysulfate cementitious exhibits optimal mechanical properties； with the oxygen-sulfur ratio fixed at 8∶1 and the water-sulfur ratio fixed at 18∶1， the mechanical properties of magnesium oxysulfate cementitious are optimized. An increase in oxygen-sulfur ratio promotes the formation of over 80% by mass of the 5·1·7 phase， where needle-like 5·1·7 crystals interweave into a network structure. These crystals， along with unreacted MgO in the system， fill the pores in the sample， resulting in a denser structure and improved mechanical properties. Compared to the magnesium oxysulfate cementitious with an oxygen-sulfur ratio of 7∶1， the 28 d flexural strength and 28 d compressive strength of the cementitious with an oxygen-sulfur ratio of 11∶1 increase by 51.1% and 34.8%， respectively. Conversely， an increase in water-sulfur ratio leads to the hydration of MgO （which originally acts as a filler） into Mg（OH）?， causing volumetric expansion and a reduction in mechanical performance of magnesium oxysulfate cementitious.

Key words: modified magnesium oxysulfate cementitious, light-burned magnesia, 5·1·7 phase crystal, oxygen-sulfur ratio, water-sulfur ratio

CLC Number:

TU526

QIU Junfu, ZHANG Ruifeng, WANG Zhenghua, SHU Chunxue, ZHANG Jiayang, HE Xinxin, LI Yuyang. Effect of Raw Material Molar Ratio on Macro-Properties of Modified Magnesium Oxysulfate Cementitious[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2026, 45(1): 112-122.

Figures/Tables 13

Table 1 Chemical composition of raw materials

Material	Mass fraction/%
Material	MgO	SiO₂	CaO	Al₂O₃	Fe₂O₃	Other	α-MgO	Loss on ignition
MgO	87.51	6.71	3.70	0.74	0.70	0.64	62.80	6.75
T/CECS 10397—2024	≥50.00		f-CaO≤5.00				≥30.00	≤25.00

Fig.1 XRD pattern of MgO

Fig.2 Particle size distribution of MgO

Table 2 Mix proportion of modified magnesium oxysulfate cementitious with different oxygen-sulfur ratios and water-sulfur ratios

Sample	Content/g
Sample	MgO	MgSO₄·7H₂O	H₂O	Citric acid	Standard sand
M8H19	450.0	217.2	190.8	2.25	1 350
M8H18	450.0	217.2	174.9	2.25	1 350
M8H17	450.0	217.2	159.0	2.25	1 350
M11H20	450.0	158.0	150.3	2.25	1 350
M10H20	450.0	173.8	165.3	2.25	1 350
M9H20	450.0	193.1	183.7	2.25	1 350
M8H20	450.0	217.2	206.7	2.25	1 350
M7H20	450.0	248.3	236.2	2.25	1 350

Fig.3 Effect of raw material molar ratios on fluidity of magnesium oxysulfate cementitious

Fig.4 Mechanical properties of magnesium oxysulfate cementitious with different raw material molar ratios

Fig.5 Water resistance of magnesium oxysulfate cementitious with different raw material molar ratios

Fig.6 SEM images of magnesium oxysulfate cementitious paste with different oxygen-sulfur ratios

Fig.7 SEM images of magnesium oxysulfate cementitious paste with different water-sulfur ratios

Fig.8 XRD patterns of magnesium oxysulfate cementitious paste with different raw material molar ratios

Table 3 Semi-quantitative analysis of magnesium oxysulfate cementitious paste with different water-sulfur ratios

Sample	Mass fraction/%					R_wp/%
Sample	5·1·7 phase	Mg（OH）₂	MgO	SiO₂	MgCO₃	R_wp/%
M8H17	93.9	0	4.7	1.0	0.4	7.26
M8H18	91.8	0.7	4.8	1.0	1.7	5.13
M8H19	90.8	2.8	2.4	1.8	2.2	8.85
M8H20	89.9	4.9	2.4	0.8	2.0	5.86

Table 4 Semi-quantitative analysis of magnesium oxysulfate cementitious paste with different oxygen-sulfur ratios

Sample	Mass fraction/%					R_wp/%
Sample	5·1·7 phase	Mg（OH）₂	MgO	SiO₂	MgCO₃	R_wp/%
M7H20	97.2	0	1.0	0.4	1.4	8.92
M8H20	89.9	4.9	2.4	0.8	2.0	5.86
M9H20	86.8	5.6	4.8	1.2	1.6	7.18
M10H20	85.8	6.3	6.1	0.8	1.0	6.16
M11H20	81.5	7.1	8.7	1.2	1.5	5.44

Fig.9 Hydration heat of magnesium oxysulfate cementitious paste with different raw material molar ratios

References 30

[1]	QIN L， GAO X J， LI W G， et al. Modification of magnesium oxysulfate cement by incorporating weak acids［J］. Journal of Materials in Civil Engineering， 2018， 30（9）： 04018209.
[2]	韩　猛. 大掺量钢渣硫氧镁水泥性能研究［D］. 鞍山：辽宁科技大学， 2023.
	HAN M. Study on properties of magnesium oxysulfate cement with high content of steel slag［D］. Anshan： University of Science and Technology Liaoning， 2023 （in Chinese）.
[3]	WU C Y， ZHANG H F， YU H F. Preparation and properties of modified magnesium oxysulfate cement derived from waste sulfuric acid［J］. Advances in Cement Research， 2016， 28（3）： 178-188. DOI URL
[4]	WU C Y， YU H F， DONG J M， et al. Effects of material ratio， fly ash， and citric acid on magnesium oxysulfate cement［J］. ACI Materials Journal， 2014， 111（3）： 291-297.
[5]	张晓闯，陈　波，王雄锋，等. 改性剂和矿物掺合料对硫氧镁水泥耐水性的影响研究进展［J］. 水利水电技术（中英文）， 2023， 54（8）： 188-196.
	ZHANG X C， CHEN B， WANG X F， et al. Study on effect of modifier and mineral admixture on water resistance of magnesium oxysulfate cement-a short review［J］. Water Resources and Hydropower Engineering， 2023， 54（8）： 188-196 （in Chinese）.
[6]	ZHANG N， YU H F， MA H Y， et al. The phase composition of the MgO-MgSO₄-H₂O system and mechanisms of chemical additives［J］. Composites Part B： Engineering， 2022， 247： 110328.
[7]	刘冲昊，岳雪涛，翟庆振，等. 活性MgO含量对改性硫氧镁水泥强度的影响及机理分析［J］. 混凝土与水泥制品， 2023（7）： 18-22.
	LIU C H， YUE X T， ZHAI Q Z， et al. Effect and mechanism analysis of active MgO content on the strength of modified magnesium thioxide cement［J］. China Concrete and Cement Products， 2023（7）： 18-22 （in Chinese）.
[8]	LI Z G， JI Z S. Effect of molar ratios on compressive strength of modified magnesium oxysulfate cement［J］. International Journal of Hybrid Information Technology， 2015， 8（6）： 87-94. DOI URL
[9]	王爱国，楚英杰，徐海燕，等. 碱式硫酸镁水泥的研究进展及性能提升技术［J］. 材料导报， 2020， 34（13）： 13091-13099.
	WANG A G， CHU Y J， XU H Y， et al. Research progress and performance improvement technology of basic magnesium sulfate cement［J］. Materials Reports， 2020， 34（13）： 13091-13099 （in Chinese）.
[10]	吴成友，苗　梦，余红发. MgO活性和摩尔比对碱式硫酸镁水泥强度的影响机理［J］. 建筑材料学报， 2022， 25（4）： 360-366.
	WU C Y， MIAO M， YU H F. Effect of MgO activity and molar ratio on strength of basic magnesium sulfate cement and its mechanism［J］. Journal of Building Materials， 2022， 25（4）： 360-366 （in Chinese）.
[11]	中国工程建设标准化协会. 硫氧镁基胶凝材料： T/ CECS 10397—2024［S］. 北京：中国标准出版社， 2024.
	China Engineering Construction Standardization Association. Magnesium sulfate-based cementitious materials： T/ CECS 10397—2024［S］. Beijing： China Standards Press， 2024 （in Chinese）.
[12]	国家市场监督管理总局，国家标准化管理委员会. 水泥胶砂强度检验方法（ISO法）： GB/T 17671—2021［S］. 北京：中国标准出版社， 2021.
	State Administration for Market Regulation， National Standardization Administration. Strength test method of cement sand （ISO method）： GB/T 17671—2021［S］. Beijing： China Standard Press， 2021 （in Chinese）.
[13]	国家市场监督管理总局，国家标准化管理委员会. 建筑保温砂浆： GB/T 20473—2021［S］. 北京：中国标准出版社， 2021.
	State Administration for Market Regulation， Standardization Administration of the People's Republic of China. Building thermal insulation mortar： GB/T 20473—2021［S］. Beijing： China Standards Press， 2021 （in Chinese）.
[14]	吴成友. 碱式硫酸镁水泥的基本理论及其在土木工程中的应用技术研究［D］. 西宁：中国科学院研究生院（青海盐湖研究所）， 2014.
	WU C Y. Basic theory of basic magnesium sulfate cement and its application technology in civil engineering［D］. Xining： Qinghai Institute of Salt Lakes， Chinese Academy of Sciences， 2014 （in Chinese）.
[15]	郑宇浩. 硫氧镁水泥改性及耐久性的热力学机理研究［D］. 南京：东南大学， 2023.
	ZHENG Y H. Study on thermodynamic mechanism of modification and durability of magnesium oxysulfate cement［D］. Nanjing： Southeast University， 2023 （in Chinese）.
[16]	INDIA B C U， KRISHNA V， KUMAR R. Water to cement ratio： a simple and effective approach to control plastic and drying shrinkage in concrete［C］// Sustainable Construction Materials and Technologies （SCMT）. Coventry University， 2016： 1389-1396.
[17]	姜黎黎，刘江武，董文俊，等. 柠檬酸掺量对硫氧镁水泥耐水性的影响［J］. 硅酸盐通报， 2016， 35（12）： 4093-4096.
	JIANG L L， LIU J W， DONG W J， et al. Influence of citric acid addition on water resistance of magnesium oxysulfate cement［J］. Bulletin of the Chinese Ceramic Society， 2016， 35（12）： 4093-4096 （in Chinese）.
[18]	GUO T， WANG H F， YANG H J， et al. The mechanical properties of magnesium oxysulfate cement enhanced with 517 phase magnesium oxysulfate whiskers［J］. Construction and Building Materials， 2017， 150： 844-850. DOI URL
[19]	巴明芳，马哲洋，纪璐鑫，等. 不同摩尔比对改性硫氧镁水泥基材料力学性能、变形行为的影响及机理研究［J/OL］. 建筑材料学报， 1-14 （ 2024-01-16）［ 2025-08-10］. https://link.cnki.net/urlid/31.1764.TU.20240116.1349.002.
	BA M F， MA Z Y， JI L X， et al. Study on the influence of different molar ratios on mechanical properties， deformation behavior and mechanism of modified magnesium oxysulfate cement-based materials［J/OL］. Journal of Building Materials， 1-14 （ 2024-01-16）［ 2025-08-10］. https://link.cnki.net/urlid/31.1764.TU.20240116.1349.002 （in Chinese）.
[20]	DU C. A review of magnesium oxide in concrete［J］. Concrete international， 2005， 27（12）： 45-50.
[21]	郑安然，詹炳根，杨咏三. 氧硫比与水硫比对硫氧镁胶凝材料性能的影响［J］. 合肥工业大学学报（自然科学版）， 2020， 43（10）： 1378-1383.
	ZHENG A R， ZHAN B G， YANG Y S. Influence of mass ratio of MgO to MgSO₄ and H₂O to MgSO₄ on the properties of magnesium oxysulfate cementitious material［J］. Journal of Hefei University of Technology （Natural Science）， 2020， 43（10）： 1378-1383 （in Chinese）.
[22]	WANG N， YU H F， BI W L， et al. Effects of sodium citrate and citric acid on the properties of magnesium oxysulfate cement［J］. Construction and Building Materials， 2018， 169： 697-704. DOI URL
[23]	CHEN X Y， WANG S Y， ZHOU Y X， et al. Improved low-carbon magnesium oxysulfate cement pastes containing boric acid and citric acid［J］. Cement and Concrete Composites， 2022， 134： 104813. DOI URL
[24]	MIAO M， WU C Y， TAN Y S， et al. Mechanistic study of the effects of magnesia reactivity on setting and hardening of basic magnesium sulfate cement［J］. Journal of Advanced Concrete Technology， 2020， 18（11）： 678-688. DOI URL
[25]	GUAN Y， CHANG J， HU Z Q， et al. Performance of magnesium hydroxide gel at different alkali concentrations and its effect on properties of magnesium oxysulfate cement［J］. Construction and Building Materials， 2022， 348： 128669. DOI URL
[26]	吴成友，邢赛南，张吾渝，等. 碱式硫酸镁水泥水化规律研究［J］. 功能材料， 2016， 47（11）： 11120-11124+11130.
	WU C Y， XING S N， ZHANG W Y， et al. Study on hydration mechanism of basic magnesium sulfate cement［J］. Journal of Functional Materials， 2016， 47（11）： 11120-11124+11130 （in Chinese）.
[27]	马宏宇，姬仁林，马亚丽，等. 有机酸调控硫氧镁水泥的水化进程［J］. 硅酸盐学报， 2025， 53（2）： 396-405.
	MA H Y， JI R L， MA Y L， et al. Organic acids modulate the hydration process of magnesium sulphide cements［J］. Journal of the Chinese Ceramic Society， 2025， 53（2）： 396-405 （in Chinese）.
[28]	烟　卫，刘　昱，李艳苹，等. X射线衍射法钾混盐无标样定量相分析［J］. 理化检验-化学分册， 2014， 50（4）： 413-416.
	YAN W， LIU Y， LI Y P， et al. Quantitative phase analysis of potassium mixed salt by XRD without using reference standard［J］. Physical Testing and Chemical Analysis （Part B （Chemical Analysis））， 2014， 50（4）： 413-416 （in Chinese）.
[29]	WU C Y， CHEN W H， ZHANG H F， et al. The hydration mechanism and performance of Modified magnesium oxysulfate cement by tartaric acid［J］. Construction and Building Materials， 2017， 144： 516-524. DOI URL
[30]	文　静，余红发，吴成友，等. 氯氧镁水泥水化历程的影响因素及水化动力学［J］. 硅酸盐学报， 2013， 41（5）： 588-596.
	WEN J， YU H F， WU C Y， et al. Hydration kinetic and influencing parameters in hydration process of magnesium oxychloride cement［J］. Journal of the Chinese Ceramic Society， 2013， 41（5）： 588-596 （in Chinese）.