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研究了纳米TiO_2(NT)对粉煤灰(FA)水泥基材料(粉煤灰20%,40%等量取代水泥)物理力学性能的影响。首先测试了不同NT含量的FA水泥砂浆的流动度和净浆的凝结时间,然后测试了3,7,28和90d水泥砂浆的抗压强度。研究结果显示,NT的掺入可以加速初凝和终凝,降低流动度,FA具有相反的作用。NT可显著提高砂浆的早期抗压强度而对后期强度发展不利。然而,FA对后期强度发展的积极作用可以弥补NT的不利影响,最佳NT和FA掺量分别为3%和20%。接着通过XRD和SEM研究了NT对FA水泥基材料性能改善的机理。结果表明,掺入NT有助于水化产物的生成和沉淀。此外,在强度发展的过程中,NT可加速CH的消耗并提高FA的火山灰反应程度,形成更多的C-S-H,并且NT还可改善FA水泥砂浆的界面过渡区(ITZ)。
The effect of nano-TiO_2 (NT) on the physical and mechanical properties of fly ash (FA) cement-based materials (fly ash 20%, 40% Firstly, the fluidity of FA cement mortar with different NT content and the setting time of the paste were tested. Then the compressive strength of cement mortar was tested at 3, 7, 28 and 90 days. The results show that NT incorporation can accelerate the initial setting and final setting, reduce the fluidity, FA has the opposite effect. NT can significantly improve the early compressive strength of mortar, which is detrimental to the late strength development. However, the positive effect of FA on the late strength development can make up for the adverse effects of NT, with the best contents of NT and FA being 3% and 20% respectively. Then, the mechanism of NT on the properties of FA cement based materials was studied by XRD and SEM. The results show that incorporation of NT contributes to the formation and precipitation of hydration products. In addition, NT accelerates the depletion of CH and increases the volcanic ash reactivity of FA, resulting in more C-S-H and also improves the interfacial transition zone (ITZ) of FA cement mortars during strength development.