基于不同流变模型下粉煤灰对水泥净浆流变性能的影响

Influence of fly ash on rheological properties of cement paste under different rheological models

采用Rheology QC旋转黏度计研究粉煤灰掺量对水泥净浆流变性能的影响,并分别采用Bingham流体模型和Herschel-Bulkey(H-B)模型对浆体的流变曲线进行拟合,分析不同粉煤灰掺量对浆体屈服应力、塑性黏度、触变环面积、临界剪切速率以及流变指数的影响。研究结果表明:采用Bingham流体模型拟合得到水泥-粉煤灰复合浆体的屈服应力、塑性黏度以及触变环面积等流变参数均随粉煤灰掺量的增加先降低后升高,当粉煤灰掺量为50%时,各流变参数降为最低。采用H-B模型拟合得到水泥-粉煤灰浆体的流变行为则为浆体先呈现剪切变稀后出现剪切增稠,浆体剪切变稀或剪切增稠的程度均随粉煤灰掺量的增加而增加,浆体的临界剪切速率随粉煤灰掺量的增加出现先降低后升高,当粉煤灰掺量为40%左右时,浆体的临界剪切速率最低。

Rheological properties of cement -fly ash paste were determined by a rotation viscometer with type of Rheology QC.Bingham model and Herschel -Bulkey（H -B）model were used for fitting rheology curves .Influ-ence of fly ash content on yield stress,plastic viscosity,thixotropy,critical shear rate and rheological index of the cement paste were investigated.Results show that yield stress,plastic viscosity and thixotropy decrease ini-tially with the increase of fly ash content up to 50% and then increase according to Bingham model.Cement -fly ash pastes take on shear -thinning effect first and then shear -thickening effect according to H -B model.Shear-thinning and shear -thickening increase with addition of fly ash.The critical shear rate descends initially and then rises with the increase of fly ash content.The lowest critical shear rate can be obtained when the fly ash content is about 40%.