50℃养护下超细粉煤灰-水泥复合材料的性能研究

Research on the properties of ultrafine fly ash and cement composites cementitious materials at high temperature of 50 ℃

摘要:

本文采用化学结合水量测试、压汞测孔法、扫描电镜观测以及力学性能测试等方法，通过与普通粉煤灰对比，系统研究50℃养护条件下超细粉煤灰-水泥复合胶凝材料的水化程度、微观结构以及力学性能。研究结果表明：超细粉煤灰在机械研磨和50℃高温养护的共同作用下活性大大提高，与普通粉煤灰相比，复合胶凝材料的水化速度更快，孔径分布更细化，抗压、抗折强度更高；超细粉煤灰掺量为25%时，复合胶凝材料在整个龄期的化学结合水量和孔结构密实度均高于纯水泥砂浆，3d时的抗压、抗折强度已高于纯水泥砂浆近一倍，并且龄期越长，对强度的提高作用越明显。超细粉煤灰掺量为50%时，体系中细集料较多造成颗粒级配分布不合理，并且缺少充足的Ca(OH)2的碱性激发，对于水泥水化程度、孔结构密实度和强度的改善作用与掺量为25%时相比有所降低，但7d时的抗折强度仍达到了纯水泥砂浆的1.67倍。

Abstract:

In this paper, non-evaporable water test, mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM) observation and mechanical properties test were used to study the hydration degree, microstructure and mechanical properties of ultrafine fly ash cement composite cementitious materials under the condition of high temperature curing at 50℃, by comparing ultrafine fly ash with ordinary fly ash. Research results show that, compared with the ordinary fly ash, under the mechanical grinding and high temperature curing at 50℃, the ultrafine fly ash and cement composite cementitious materials has faster hydration rate, finer pore size distribution and higher strength. When the content of ultrafine fly ash is 25%，the hydration degree and pore structure compactness of composite cementitious material are higher than that of pure cement mortar, and the compressive strength and flexural strength of composite cementitious material at 3d are nearly twice higher than that of pure cement mortar, the longer the age, the more obvious the effect of improving the strength. However, when the content of ultrafine fly ash is 50%, the concentration of cement in the system is greatly reduced. Because of the large amount of fine aggregate, the particle distribution is unreasonable, and the activity of ultrafine fly ash is reduced due to the lack of sufficient Ca(OH)2. Therefore, the degree of hydration, the compactness of the pore structure, the compressive strength and flexural strength of the 50% ultrafine fly ash and cement composite cementitious materials is lower than that of 25%, and the flexural strength at 7d still reached 1.67 times that of pure cement mortar.