CoFeMgAl-LDHs/CNTs复合材料对水泥水化及微观结构的影响

通过进行水化热测试、非蒸发水含量测试、X射线衍射分析、扫描电镜分析、压汞测试及强度试验,研究了钴铁镁铝水滑石-碳纳米管复合材料(CoFeMgAl-LDHs/CNTs)对水泥水化过程、硬化水泥净浆孔结构及强度的影响。结果表明,CoFeMgAl- LDHs/CNTs复合材料通过成核作用显著提升了水泥3 d内的水化程度,从而显著提高了水泥净浆3 d内的抗压强度,3 d后强度提高效果逐渐减小,7 d后复合材料对硬化水泥浆体强度没有明显的提高作用。掺入CoFeMgAl-LDHs/CNTs复合材料的水泥净浆与空白净浆相比,胶凝孔和毛细孔含量明显增多,大孔含量有所降低,同时复合材料的桥联作用进一步优化了水泥净浆的微观结构,从而提高了水泥基体薄弱部位的应力承载能力。因此在同一龄期,复合材料掺入后硬化水泥净浆的强度有所增大。由于复合材料掺量的变化对孔径分布没有明显的影响,改变复合材料的掺量对同龄期硬化水泥净浆强度提升影响较小。

Effect of CoFeMgAl-LDHs/CNTs Composite Material on Hydration and Microstructure of Cement

Heat of hydration test,non-evaporating water content test,X-ray diffraction analysis,scanning electron microscope analysis,mercury intrusion test and compressive strength tests were used to investigate the effect of the Co-Fe-Mg-Al hydrotalcite carbon nanotubes(CoFeMgAl-LDHs/CNTs)composite material on the hydration process,pore structure and strength of hardened cement paste.The results show that CoFeMgAl-LDHs/CNTs composite material significantly improves the hydration degree of cement within 3 d through nucleation,and thereby significantly enhances the compressive strength of the cement paste in the age of 3 d,the effect of improving the strength gradually reduces after 3 d and become unobvious after 7 d.Compare with blank cement paste,the content of gel pore and capillary pore in hardened cement paste increase obviously,while the macro pore decreases.At the same time,bridging effect of composite material optimizes microstructure of cement paste,and increase the stress bearing capacity of weak parts of cement matrix.Therefore,at the same age,the strength of hardened cement paste is increased.Because the change of composite content has no obvious effect on the change of pore size distribution,the change of composite content has little effect on the strength improvement of hardened cement paste at the same age.