毕业论文---改性粉煤灰对水泥基材料干燥收缩的影响.doc

2011年6月 10日摘 要 用超细石灰石通过煅烧对粉煤灰进行活化改性，使粉煤灰玻璃体表面腐蚀并生成具有活性的硅酸盐矿物，改善粉煤灰颗粒和环境的接触界面，增加掺入改性粉煤灰的水泥基体早期胶凝材料的量，从而提高粉煤灰的活性指数。采用扫描电子显微镜（SEM）和X射线衍射（XRD）分析手段对改性粉煤灰进行表征微观结构形态和化学组成，并测量掺改性粉煤灰水泥浆体积变形、水分蒸发和水化程度以及不同龄期强度。 结果表明：改性粉煤灰表面生成钙黄长石等钙铝硅酸盐；改性粉煤灰能有效的抑制浆体的干燥收缩，收缩随石灰石掺量增大而增大，随保温时间的延长而降低，影响复合水泥浆体干燥收缩的因素除水分蒸发外，还有辅助混合材本身活性及表面结构形态；改性粉煤灰复合水泥浆体7d和28d强度随石灰石掺量增大而增大，随保温时间的延长而增大。 改性粉煤灰可以有效提高复合水泥浆体的力学性能。在满足强度的基础上加大掺量还可能有效抑制水泥浆体干燥收缩，为大掺量粉煤灰在水泥基材料中应用研究打下基础。 关键词：粉煤灰；改性；强度；干燥收缩 Abstract The purpose of the paper is to activate and modify the properties of fly ash and to corrode the surface of fly ash vitreous to generate silicate minerals with activity, also, we aim to improve the contact interface between fly ash particles and the environment and to increase the volume of cement matrix early cementations materials which are used to modify the fly ash, thus enhancing the activity index of fly ash through the calcimine of superfine limestone. We use methods like SEM and XRD to analysis the microstructure and chemical composition of modified fly ash. Still we measure the volume deformation, evaporation of water, extent of hydration and strengths at different ages of cement paste with adulteration of modified fly ash. The results show that modified fly ash can generate such aluminum silicates as gelignite and effectively restrain the dry shrinkage of paste. We can see that the shrinkage rate rises as the volume of limestone increases and goes down as the extending of heating preservation time. Other than water evaporation as a factor that can affect the dry shrinkage of composite cement paste, there are activities of auxiliary admixture and the structure form on the surface. The compressive strength of 7d and 28d of modified fly ash composite cement paste rises as the volume of limestone increases and decreases as the prolonging of heating preservation time. Modified fly ash can greatly improve the mechanical properties of composite cement paste. On the basis of satisfying the requirements of compr