超细粉体对水泥净浆流变行为影响研究

采用截锥圆模法测定不同掺量超细粉体水泥复合浆液的流动度.采用ZNN-D6B型旋转黏度计研究超细玻璃粉和偏高岭土两种超细粉体对水泥净浆流变行为的影响,得到了剪切速率-剪切应力(γ-τ)曲线和剪切速率-表观粘度(γ-μa)曲线,并分别采用宾汉姆模型和赫-巴模型对γ-τ流变曲线进行拟合,得到不同掺量超细玻璃粉-水泥(GP-C)复合浆液和偏高岭土-水泥(MK-C)复合浆液的动切力、塑性粘度、稠度系数和流性指数等流变参数.结果表明:超细粉体的加入降低了复合浆液的流动度.随着掺量的增加,两种复合浆液的宾汉动切力τ0、塑性粘度η、赫-巴动切力τy均逐渐增大,MK-C复合浆液的稠度系数K和流性指数n逐渐减小,GP-C复合浆液的稠度系数K呈现增大-减小-增大的趋势,而流性指数n呈现减小-增大-减小的趋势.所有样本表观粘度μa都随着剪切速率的增大而减小,呈现剪切稀释现象.

Effect of Ultrafine Powder on Rheological Behavior of Cement Paste

Fluidity of cement paste with different dosage of ultrafine powder was determined by truncated cone method. The effect of ultrafine glass powder and metakaolin powder on the rheological behavior of cement paste was studied by a rotation viscometer with type of ZNN-D6B. The shear rate-shear stress (γ-τ)curve and shear rate-apparent viscosity (γ-μa )curve were obtained. Bingham model and Herschel-Bulkely model were used for fitting the γ-τ curve. The rheological parameters such as dynamic stress, plastic viscosity,consistency coefficient and rheological index of different dosages of ultrafine glass powder-cement (GP-C)composite paste and metakaolin-cement (MK-C)composite paste were obtained. The results show that the addition of ultrafine powder reduces the fluidity of the composite paste. The Bingham dynamic shear,plastic viscosity and Herschel-Bulkely dynamic shear of the two kinds of composite paste gradually increase with the increase of the content,and the consistency coefficient , rheological index of the MK-C composite paste gradually decrease,the consistency coefficient of the GP-C composite paste shows a tendency to increase-decrease-increase,while the rheological index tends to decrease-increase-decrease. The apparent viscosity of all samples decreases with the increase of shear rate,showing shear-thinning.