粉煤灰对水泥浆体的剪切变稀和剪切增稠作用  

Effects of Fly Ash on Shearing Thinning and Thickening of Cement Paste

作　　者：谢友均[1] 陈小波[1] 马昆林[1] 冯金[1] 龙广成[1] 

机构地区：[1]中南大学土木工程学院,高速铁路建造技术国家工程实验室,重载铁路工程结构教育部重点实验室,长沙410075

出　　处：《硅酸盐学报》2015年第8期1040-1046,共7页Journal of The Chinese Ceramic Society

基　　金：国家973计划(2013CB036201);中国铁路总公司重点课题(2014G012);中南大学教师科学基金项目(2014JSJJ013)

摘　　要：采用RHEOLAB QC型旋转黏度计测试了粉煤灰掺量对水泥浆体流变行为的影响,采用HERSCHEL-BULKEY(H-B)流变模型对所测数据进行了拟合。结果表明:浆体流变曲线中有1个拐点,拐点所对应的流变参数为临界剪切速率(γcrit)、临界剪切应力(τcrit)和最小黏度值(ηmin),拐点左右两侧的浆体可分为剪切变稀和剪切增稠2个阶段。纯水泥浆体在较大的剪切速率下仍表现为剪切变稀。掺入粉煤灰后,浆体的γcrit、τcrit和ηmin均较纯水泥浆体降低,当粉煤灰掺量大于40%以后,浆体在较低临界剪切速率下出现了剪切增稠。在剪切变稀阶段,当粉煤灰掺量不大于50%时,增大粉煤灰掺量则浆体的流变指数显著降低,当粉煤灰掺量大于50%时,增加粉煤灰掺量,浆体流变指数增大,但均低于纯水泥浆体的流变指数;在剪切增稠阶段,随粉煤灰掺量的增加,浆体的流变指数增大,浆体剪切增稠的程度也增大。粉煤灰的掺入增大了剪切变稀阶段浆体剪切变稀的程度,也增大了剪切增稠阶段浆体剪切增稠的程度。The rheological curves of cement pastes with different fly ash （FA） contents were determined in a model RHEOLAB QC rotation viscometer. The data obtained were calculated by the Herschel-Bulkey （H-B） rheological model. The results show that there is an inflection point in rheological curve when shear rate increases. The corresponding rheological parameters of the inflection point are critical shear rate （γcrit）, critical shear stress （τcrit） and minimum viscosity （η min）, respectively. The pastes in left and right sides of the inflection point are shear thinning stage and shear thickening stage. Pure cement pastes have shear thinning even at a high shear rate. However, the addition of fly ash into cement paste decreases γcrit, τcrit and ηmin. When fly ash content is more than 40%, critical shear rate is rather low, resulting in shear thinning. At shear thinning stage, the increase of fly ash content can decrease the rheological index when fly ash content is less than 50%, and the increase of fly ash content can increase the rheological index when fly ash content is beyond 50%. At shear thickening stage, the rheological indexes increases with increasing fly ash content, leading to the development of the degree of shear thickening.

关 键 词：流变 粉煤灰 水泥 剪切变稀 剪切增稠 

分 类 号：TU528[建筑科学—建筑技术科学]