纳米二氧化硅团聚特性对水泥水化硬化性能的影响

Effect of Nano-Silica Agglomeration on Hydration and Hardening of Cement

以团聚粒径很大的沉淀二氧化硅(PS)和团聚粒径较小的纳米二氧化硅(NS)为原材料,研究了纳米二氧化硅团聚特性对水泥水化硬化特性的影响。结果表明:与NS相比,虽然PS团聚粒径很大,后期火山灰活性较低,其早期火山灰活性却较大,对水泥水化的促进作用也更明显。扫描电子显微镜分析表明,NS和PS的火山灰反应产物的胶结作用有限,其与水泥水化产物本体之间甚至存在明显的界面过渡区。压汞分析表明:掺PS和NS均可有效降低硬化水泥石毛细孔率;与掺PS相比,掺NS对减小20 nm～10μm的凝胶孔和毛细孔体积更有利。掺纳米二氧化硅对硬化水泥石微观结构的影响主要是由于团聚颗粒对水泥分散体系的填充效应和吸水效应所致,与晶核效应无关。

Effect of nano-silica agglomeration on the hydration and hardening of cement was investigated by using precipitated silica （PS） with much larger agglomerates and nano-silica （NS） powder with much smaller ones as additives. The results reveal that the PS exhibits a higher pozzolanic reactivity at early ages and a better accelerating effect on the cement hydration though it possesses some larger agglomerates and a little lower pozzolanic reactivity at late ages rather than NS. The observation by scanning electron micros- copy indicates that the cementitious property of the pozzolanic C-S-H gels from the agglomerates was limited. There even existed an interfacial transition zone between the reacted agglomerates and bulk hardened cement paste （HCP）. The MIP results show that the NS addition can reduce the capillary and the gel pore of the HCP in the range of 20nm-10 μm more effectively, compared to the PS addition. It is suggested that the effect of nano-silica addition on the microstmcture improvement of the HCP could be resulted fi＇om the filling and water adsorbing effects of the agglomerates in the powder rather than the seeding effect.