利用硬脂酸钙改善孔结构以降低碱矿渣水泥石吸水速率

Improving Pore Structure by Calcium Stearate to Reduce Water Sorptivity of Alkali-Activated Slag

碱矿渣水泥石吸水速率通常高出普通硅酸盐水泥石3~5倍,对其耐久性有严重负面影响。传统方法(如填充密实和调整配合比等)难以有效降低碱矿渣水泥石吸水速率,本工作利用硬脂酸钙(CaSt)改善碱矿渣水泥石孔结构,同时在孔隙壁上引入硬脂酸钙憎水膜,以降低碱矿渣水泥石吸水速率。通过MIP、SEM等测试手段,研究了硬脂酸钙对碱矿渣水泥石孔隙率、孔径分布、孔隙曲折度和孔形貌的改善作用,以揭示CaSt对吸水速率的改善机理。结果表明:CaSt能够在无害孔范围(100 nm内)优化AAS孔径分布,减少水化产物缺陷,增大孔隙连曲折度,并在水化产物基体壁形成CaSt憎水膜,有效降低碱矿渣水泥石吸水速率约80%左右,且低于普通硅酸盐水泥。在碱矿渣水泥体系中硬脂酸钙的特点在于兼具疏水性和孔结构改性作用,同时对力学性能影响较小,具有优越的推广潜力和研究价值。

The water sorptivity of alkali-activated slag cement is usually 3—5 times higher than that of ordinary Portland cement,which has serious negative effect on its durability.It is difficult to effectively reduce the water sorptivity of alkali-activated slag cement by traditional methods(such as increasing the compactness and adjusting the mix proportion).In this work,calcium stearate(CaSt)was used to improve the pore structure of alkali-activated slag,and calcium stearate hydrophobic film was introduced into the pore wall to reduce the water sorptivity of AAS.The effect of CaSt on the pore structure and water sorptivity of AAS was studied by means of MIP and SEM.The results show that CaSt can improve microstructure of AAS,reduce the hydration product defects,reduce the pore connectivity,and be able to form CaSt film on the surface of the hydration products,and thus the water sorptivity of AAS was reduced by about 80%.Meanwhile,it should be highlighted that in the AAS system,calcium stearate is not only a hydrophobic component,but also a pore structure modifier,making it have a good promotion potential.