| 摘要: |
| 利用Mg（OH）2煅烧分解的不同活性MgO制备了不同摩尔比（n（MgO）/n（MgSO4））的碱式硫酸镁水泥（BMSC），分析了其抗压强度发展规律；结合水化放热、液相电导率、X射线衍射（XRD）、扫描电镜（SEM）和压汞仪（MIP）等测试手段，分析了其影响机理.结果表明：当摩尔比为5时，随着MgO活性的升高，BMSC早期1 d抗压强度呈现先增后减趋势，原因是MgO活性越高，水化越快，但MgO活性过高不利于水化强度相（5·1·7相）的形成； BMSC后期抗压强度随着MgO活性的降低而增大，原因是低活性MgO制备的BMSC中5·1·7相结晶程度较高.当摩尔比为7时，BMSC水化过程中出现Mg（OH）2成核和生长的第3放热峰，导致水泥抗压强度出现倒缩.高强度BMSC中孔的类型主要为晶间孔，且水化产物结晶程度越高，孔径越大. |
| 关键词: 碱式硫酸镁水泥 氧化镁 活性 抗压强度 水化 |
| DOI：10.3969/j.issn.1007-9629.2022.04.005 |
| 分类号:TU528.01 |
| 基金项目:国家自然科学基金资助项目（52002202，51662035）；青海省应用基础研究项目（2019-ZJ-7005）；青海省科技基础条件平台（2018-ZJ-T01）；中国科学院西部之光项目 |
|
| Effect of MgO Activity and Molar Ratio on Strength of Basic Magnesium Sulfate Cement and Its Mechanism |
|
WU Chengyou1,2, MIAO Meng1, YU Hongfa1,3
|
|
1.School of Civil Engineering，Qinghai University，Xining 810016，China;2.Qinghai Provincial Key Laboratory of Building Energy-Saving Materials and Engineering Safety，Qinghai University， Xining 810016，China;3.Department of Civil Engineering，Nanjing University of Aeronautics and Astronautics，Nanjing 210016，China
|
| Abstract: |
| Basic magnesium sulfate cement （BMSC） with different molar ratios was prepared from different active MgO decomposed by calcination of magnesium hydroxide. The development law of compressive strength was analyzed. The influence mechanism was analyzed by hydration exothermic， liquid conductivity， X-ray diffraction （XRD），scanning electron microscope （SEM） and mercury intrusion porosimetry （MIP）. The results show that when molar ratio （n（MgO）/n（MgSO4）） is 5， the strength increases first and then decreases with the increase of MgO activity in the first day， resulting from the fact that the higher MgO activity yields the faster hydration， on the contrary， too high MgO activity is not conducive to the formation of hydration strength phase （5·1·7 phase）. With the complete hydration of MgO， the strength increases with the decrease of MgO activity in the later days due to the 5·1·7 phase in BMSC prepared with low MgO activity The degree of crystallization is high. When the molar ratio is 7， the third exothermic peak of Mg（OH）2 nucleation and growth appeared in the hydration process of BMSC， which led to the strength of BMSC to shrink. The main pores in high strength BMSC are intergranular pores， and the higher the crystallinity of hydration products， the larger the pore size. |
| Key words: basic magnesium sulfate cement （BMSC） magnesia reactivity compressive strength hydration |
