研究了纳米TiO2(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90 d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).
This paper presents the effect of nano-TiO2 (NT)on physical and mechanical properties of cement-based materials containing 20% and 40% (by weight)fly ash (FA)as partial replacement of cement.The fluidi-ty of mortars and the setting time of pastes were tested with different NT dosage.The compressive strength of mortars is measured at 3,7,28 and 90 d.Results show that the addition of NT could accelerate initial and final setting and decrease the fluidity,while FA had the opposite effects.Introducing NT would lead to a considerable increase in early strength while it had an adverse effect on later strength.However,the positive functions of FA in later strength could offset the negative influence of NT and the optimum contents of NT and FA are 3% and 20%,respectively.Then the mechanisms of NT on properties of FA-cement materials are investigated by X-ray diffraction (XRD)and scanning electron microscope (SEM).The results of the analyses indicate that incorpora-ting NT promoted the formation and precipitation of hydration products.Furthermore,in the strength develop-ment process,NT could accelerate the consumption rate of CH and raise the pozzolanic reaction degree of FA. Also,the interfacial transition zone (ITZ)of FA mortars were improved by NT.
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