中文摘要：

为研究粉煤灰掺量和水胶比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40%载荷水平下粉煤灰等量取代水泥量为0（质量分数,下同）、12.5%、25%、40%和60%,水胶比分别为0.31、0.35和0.4时高性能混凝土的徐变度。试验结果表明：粉煤灰掺量不变时,混凝土的徐变度随水胶比的减小而显著下降。水胶比固定时,混凝土抵抗徐变的能力与粉煤灰掺量密切相关。对于不同的水胶比,粉煤灰掺量对混凝土徐变的影响规律明显不同,水胶比为0.31时,粉煤灰掺量越大,其抑制混凝土徐变的能力越强;但是当水胶比为0.4时,混凝土的徐变度随粉煤灰掺量的增加先减小而后增大。为了阐明其中的内在机理,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,并结合纳米压痕技术比较粉煤灰与水泥颗粒的弹性模量。可以看出,粉煤灰颗粒的弹性模量明显高于水泥颗粒,故能通过＂微集料效应＂抑制混凝土的徐变。但是,这种＂微集料效应＂受粉煤灰与基体界面结合情况的影响较大,当水胶比为0.31时,界面结合很强,＂微集料效应＂的发挥程度随粉煤灰掺量的增大而提高;而当水胶比为0.4时,由于高粉煤灰掺量下的界面结合明显变弱,＂微集料效应＂不能正常发挥,而且界面的弱结合也降低了混凝土抑制徐变作用。提出粉煤灰抑制混凝土徐变效能系数的概念来表征粉煤灰掺量和水胶比对高性能混凝土徐变的影响。该系数随水胶比的减小而增大,从而,降低水胶比是减小大掺量粉煤灰高性能混凝土徐变度的有效途径。

英文摘要：

The creep behaviors of high-performance concrete （HPC） incorporated with 12.5%,25%,40%,60% of fly ash and without,respectively,were tested under a stress strength ratio of 40%,in order to clarify the effects of fly ash proportion and water-binder ratio on specific creep characteristics. The water-binder ratios are 0.31,0.35 and 0.4,respectively,and the tests were conducted under controlled temperature （20±1）℃ and humidity （60±5）% conditions. The results show that specific creep of concrete decreases with the decreasing water-binder ratio at constant fly ash content,and the capability of fly ash in hindering creep of concrete is related to the fly ash content at constant water-binder ratio. The capability of hindering creep of concrete increases with the fly ash percentage at a water-binder ratio of 0.31,and decreases with the fly ash content of higher percentage at a water-binder ratio of 0.4. Based on the elasticity modulus of cement and fly ash particles tested by nano-indentation and SEM morphology of interface between fly ash and matrix in different fly ash contents,the creep mechanism of HPC with different fly ash proportions and water-binder ratios is analyzed. The analysis revealed that the fly ash particles can reduce the creep of HPC though ‘micro-aggregate effect’ for its higher elasticity modulus. The ‘micro-aggregate effect’ is affected by the interface bonding between FA and cement paste. Compact interface bonding can be observed when the water binder ratio is 0.31,and the micro-aggregate effect of FA plays a positive role. The more the micro-aggregate,the less the creep of HPC. The combination between fly ash and matrix plays an adverse role with high content of FA when the water binder ratio is 0.4,and fly ash cannot reduce the creep of HPC through the micro-aggregate effect,with the interface bonding exerting much more negative influence. To clarify the effect of the interaction between fly ash proportion and water-binder ratio on creep of HPC,the efficiency coefficient of