粉煤灰掺量对高性能混凝土徐变性能的影响及其机理  

INFLUNCE OF FLY ASH PROPORTION ON CREEP CHARACTERISTICS OF HIGH-PERFORMANCE CONCRETE AND ITS MECHANISM

作　　者：赵庆新[1] 孙伟[1] 郑克仁[1] 陈惠苏[1] 秦鸿根[1] 刘建忠[1] 

机构地区：[1]东南大学材料科学与工程系

出　　处：《硅酸盐学报》2006年第4期446-451,共6页Journal of The Chinese Ceramic Society

基　　金：国家自然科学基金重点(59938170);国家自然科学基金(50278018)资助项目。

摘　　要：为研究粉煤灰对高性能混凝土徐变性能的影响,在(20±1)℃、相对湿度为(60±5)%的条件下测试了33%载荷水平下粉煤灰等量取代水泥量(质量分数,下同)为0,12%,30%和50%时高性能混凝土的徐变度。试验结果表明:粉煤灰掺量为12%和30%时,混凝土抵抗徐变的能力随其掺量增加而增强,其365d的徐变度分别为不掺粉煤灰混凝土的76%和46.5%。粉煤灰掺量为50%时,混凝土抵抗徐变的能力没有得到改善,其365d的徐变度为不掺粉煤灰的混凝土的102%。应用扫描电镜二次电子成像观测不同掺量下的粉煤灰颗粒与基体的结合情况,并结合水泥–粉煤灰体系中非蒸发水量的研究,试分析了粉煤灰掺量对高性能混凝土徐变的影响机理。结果表明:粉煤灰掺量对于其“微集料效应”的发挥存在一临界值,当粉煤灰掺量小于该临界值时,粉煤灰与基体结合良好,“微集料效应”得以正常发挥。混凝土的徐变度受到体系的非蒸发水量和“微集料效应”发挥程度的影响。粉煤灰掺量越大,体系的非蒸发水量越小,“微集料效应”发挥程度越高,徐变度减小越明显,并且混凝土的徐变度减小率与体系的非蒸发水量减小率和微集料数量正相关。当粉煤灰掺量超过临界值时,混凝土的徐变性能受到体系水化产物数量、“微集料效应”和粉煤灰与基体结合情况这3个因素的共同作用,并且随着粉煤灰掺量的继续增加,其与基体结合情况对混凝土徐变性能的负面影响显著增强。The specific creep of high-performance concrete （HPC） incorporated with mass fraction（the same below） of 12%, 30%, 50% and without fly ash were tested under stress strength ratios of 33% in order to clarify the effect of fly ash on creep behavior. The tests were made under controlled temperature （20± 1） ℃ and humidity （60±5）% conditions. The results show that the fly ash has a great positive effect on the creep characteristics of HPC with 12% and 30% fly ash. The specific creep after one year are 0.76 and 0.465 times of HPC without fly ash respectively. It has slight effect on the specific creep of HPC when the proportion of fly ash incorporated reaches 50%. The specific creep after one year is 1.02 times that of HPC without fly ash. Based on the amount of non-evaporable water and scanning electron microscope morphology of the interface between the fly ash and matrix at different fly ash proportions, the creep mechanism of HPC with different fly ash proportions was analyzed. The analysis reveals that the most important factors, which affect the creep characteristics of HPC, are the ＂micro-aggregate effect＂ and the amount of hydration products. There is a critical value for fly ash proportion that affects the ＂micro-aggregate effect＂. The combination of interface between fly ash and matrix is fine. The ＂micro-aggregate effect＂ has a great effect on the creep behavior of HPC when the fly ash proportion is under the critical value. The more micro-aggregate, the less specific creep of HPC in this instance. The combination between fly ash and matrix worsens and exhibits a negative influence on the ＂micro-aggregate effect＂ when the fly ash proportion is over the critical value. The combination of interface around fly ash plays an important role in the creep behavior of HPC as well as the amount of hydration products and micro-aggregate when the fly ash proportion exceeds the critical value.

关 键 词：高性能混凝土 徐变机理 粉煤灰 掺量 微集料效应 非蒸发水 

分 类 号：TU528.01[建筑科学—建筑技术科学]