粉煤灰对水泥浆体的剪切变稀和剪切增稠作用

发布时间：2018-04-03 05:26

本文选题：流变　切入点：粉煤灰　出处：《硅酸盐学报》2015年08期

【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。
[Abstract]:The effect of fly ash content on the rheological behavior of cement paste was measured by RHEOLAB QC rotary viscometer. The measured data were fitted by HERSCHEL-BULKEYYN H-Bmodel.The results show that there is an inflection point in the rheological curve of the slurry, and the rheological parameters corresponding to the inflection point are critical shear rate (纬 -critn), critical shear stress (蟿 -criterion) and minimum viscosity value (畏 _ min ~). The slurry on both sides of the inflection point can be divided into two stages: shear thinning and shear thickening.The pure cement paste still shows shearing thinning at higher shear rate.When fly ash was added into the slurry, 纬 criterion, 蟿 crit and 畏 min were lower than that of pure cement paste. When the content of fly ash was more than 40%, the slurry had shear thickening at lower critical shear rate.In the shear-thinning stage, when the content of fly ash is less than 50, the rheological index of slurry decreases significantly when the content of fly ash is increased, and when the content of fly ash is greater than 50, the rheological index of slurry increases.In the shear thickening stage, the rheological index of the slurry increases with the increase of the content of fly ash, and the degree of shear thickening of the slurry also increases.The addition of fly ash increases the degree of shear thinning of slurry in shear-thinning stage, and also increases the degree of shear thickening of slurry in shear-thickening stage.
【作者单位】：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;
【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)
【分类号】：TU528

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