Chen Bin, Wang Jun, Zhao Jinyou
College of Civil Engineering, Northeast Forestry University, Harbin 150040, China.
Materials (Basel). 2020 Aug 8;13(16):3499. doi: 10.3390/ma13163499.
The shrinkage of alkali-activated slag (AAS) is obviously higher than ordinary Portland cement, which limited its application in engineering. In this study, the effects of NaAlO in mitigating drying shrinkage and autogenous shrinkage of AAS were studied. To further understand the shrinkage mechanism, the hydration products and microstructures were studied by X-ray diffraction, scanning electron microscopy and nitrogen adsorption approaches. As the partial substitution rate of NaAlO for NaSiO increased, the drying shrinkage and autogenous shrinkage reduced significantly. The addition of NaAlO could slow down the rate of hydration reaction and reduce the porosity, change the pore diameter and the composition of generated paste and cause more hydrotalcite and tetranatrolite generated-which contributed to reduced shrinkage. Additionally, raising the NaO content rate caused obvious differences in drying shrinkage and autogenous shrinkage. As the NaO content elevated, the drying shrinkage decreased and autogenous shrinkage increased. A high NaO content would cause complete hydration reactions and provoke high autogenous shrinkage. However, incomplete hydration reactions left more water in the paste, and the evaporated water dramatically influenced drying shrinkage. The results indicate that addition of NaAlO could greatly mitigate the drying shrinkage and autogenous shrinkage of AAS.
碱激发矿渣（AAS）的收缩率明显高于普通硅酸盐水泥，这限制了其在工程中的应用。本研究考察了偏铝酸钠对减轻AAS干燥收缩和自收缩的影响。为进一步了解收缩机理，采用X射线衍射、扫描电子显微镜和氮吸附法研究了水化产物和微观结构。随着偏铝酸钠对硅酸钠的部分替代率增加，干燥收缩和自收缩显著降低。添加偏铝酸钠可减缓水化反应速率，降低孔隙率，改变生成浆体的孔径和组成，并促使生成更多水滑石和四水钠沸石，这有助于减少收缩。此外，提高氧化钠含量对干燥收缩和自收缩有明显影响。随着氧化钠含量升高，干燥收缩减小，自收缩增大。高氧化钠含量会导致水化反应完全并引发高自收缩。然而，不完全水化反应会在浆体中留下更多水分，而蒸发的水分对干燥收缩有显著影响。结果表明，添加偏铝酸钠可大大减轻AAS的干燥收缩和自收缩。
