Jiang Feifei, Zhou Juan, Mao Zhongyang, Chen Bi
School of Civil Engineering, Nantong Institute of Technology, Nantong 226000, China.
Suzhou Institute of Technology, Jiangsu University of Science and Technology, Zhangjiagang 215600, China.
Materials (Basel). 2023 Nov 8;16(22):7082. doi: 10.3390/ma16227082.
To reduce the mining of high-grade magnesite and solve the environmental pollution caused by magnesite tailings, magnesite tailings were used to produce MgO expansion agent (MEA), and a detailed study of its performance was carried out in this study. Firstly, the effects of different calcination times on the calcination products, the specific surface area, and the activity of MEA were analyzed. Then, the MEA produced by calcinating at 950 °C for 1 h was taken as the research object, and the effects of its content on the expansion performance, compressive strength, and flexural strength of the mortar were studied. The results showed that the decomposition of magnesite tailings after high-temperature calcination produced MEA, and the longer the calcination time, the lower the activity. The calcined tailings could compensate for the shrinkage of the mortar, and the expansion increased with the increase in curing temperature. What is more, when the content was less than 8%, the hydration of MEA filled the pores and improved the compactness, so the strength of the mortar increased with the increase in the expansion agent content. When the dosage was greater than 8%, excessive expansion increased the porosity, causing harmful expansion of the mortar and damaging its integrity, leading to a decrease in strength. Fly ash reduced the expansion of mortar, and after adding 30% fly ash, the expansion decreased by 20.0-36.1%, and the ability to suppress expansion decreased with the increase in curing temperature.
为减少高品位菱镁矿的开采并解决菱镁矿尾矿造成的环境污染问题，本研究采用菱镁矿尾矿制备氧化镁膨胀剂（MEA），并对其性能进行了详细研究。首先，分析了不同煅烧时间对煅烧产物、MEA比表面积和活性的影响。然后，以950℃煅烧1h制备的MEA为研究对象，研究了其掺量对砂浆膨胀性能、抗压强度和抗折强度的影响。结果表明，菱镁矿尾矿高温煅烧后分解生成MEA，煅烧时间越长，活性越低。煅烧尾矿可补偿砂浆的收缩，且膨胀随养护温度的升高而增大。此外，当掺量小于8%时，MEA的水化填充了孔隙，提高了密实度，因此砂浆强度随膨胀剂掺量的增加而提高。当掺量大于8%时，过度膨胀增加了孔隙率，导致砂浆产生有害膨胀并破坏其整体性，从而导致强度降低。粉煤灰降低了砂浆的膨胀，添加30%粉煤灰后，膨胀降低了20.0-36.1%，且抑制膨胀的能力随养护温度的升高而降低。
