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研究掺纳米SiO2微粉和硅溶胶对低水灰比(w/c=0.3)水泥浆体流变性能的影响及机制。结果表明,掺量不超过0.6%(质量分数,下同)时,掺纳米微粉和硅溶胶均导致水泥浆粘度随掺量增大而略有下降;掺量超过0.6%,掺纳米微粉的水泥浆粘度随掺量增大而缓慢增加,掺硅溶胶的水泥浆粘度随掺量增加则急剧增大,水泥浆流动性急剧下降,但浆体呈明显的剪切变稀行为,硅溶胶掺量分别为0.8%和1.0%,剪切速率为2.509s-1时,表观粘度分别达10和18Pa·s以上,随剪切速率增大,浆体粘度急剧下降,剪切速率为163.1s-1时,其表观粘度与硅溶胶掺量较低时相近,仅约为1.2和1.8Pa·s。沉降分析和显微观察均发现,掺加硅溶胶的水泥浆体中存在明显的团聚现象,这是由于水泥水化引起水泥浆体中离子强度迅速增大而导致硅溶胶絮凝或凝胶化所致。
The effect and mechanism of nano-doped silica powder and silica sol on the rheological properties of low water-cement ratio (w / c = 0.3) cement paste were studied. The results showed that the viscosity of cement slurry decreased slightly with the increase of the dosage when the dosage was less than 0.6% (mass fraction, the same below). When the dosage was over 0.6%, the cement with nano-micron powder The viscosity of slurry increased slowly with the increase of dosage. The viscosity of slurry with silica sol increased sharply with the increase of dosage. The fluidity of slurry decreased sharply, but the slurry showed obvious shear thinning behavior. The content of silica sol Respectively, 0.8% and 1.0%, respectively. When the shear rate was 2.509s-1, the apparent viscosities were above 10 and 18 Pa · s, respectively. With the increase of shear rate, the viscosity of slurry decreased sharply and the shear rate was 163.1s- 1, its apparent viscosity is similar to that of low silica sol, only about 1.2 and 1.8 Pa · s. Sedimentation analysis and microscopic observation showed that agglomeration was observed in the cement slurry doped with silica sol due to the rapid increase of ionic strength in the cement slurry caused by the hydration of the cement resulting in the flocculation or gelation of the silica sol To