砂浆塑性粘度对自密实清水混凝土表观性能的影响

The Effect of the Mortar Viscosity on the Surface Properties of Self-Compacting Fair-Faced Concrete

摘要: 本文研究了自密实清水混凝土的砂浆流变性能和表面性能，采用Image-Pro Plus软件进行了表面图像的定量分析，并分析了表面性能与流变性的相关性。结果表明，自密实混凝土中的砂浆流变性能符合宾汉姆体的流变方程，砂浆塑性粘度是影响自密实混凝土表观性能的重要因素，而与屈服剪切应力的相关性较低，与宏观工作性的表征指标流动速度和扩展度的相关性也不明显。增加用水量或掺加引气剂，均可降低塑性粘度和屈服剪切应力，但采用轻砂等体积替代黄砂只能降低塑性粘度，但屈服剪切应力提高。随着塑性粘度的增大，自密实混凝土表面气孔面积百分数逐渐增大，孔洞尺寸分布变宽，直径大于2 mm气孔增多且孔径变大。塑性粘度低于9.37 Pa∙s的自密实混凝土表面清水效果较好，表面气孔面积小于0.2%，最大孔径小于5 mm。

Abstract: This paper studies the mortar plastic viscosity and the surface properties of self-compacting fair-faced concrete, and the software Image-Pro Plus is used to quantificationally analyze the surface properties. The mortar rheological properties are described by applying Bingham fluid. The results indicate that the viscosity properties of mortar in the self-compacting fair-faced concrete are in line with the rheological equation of Bingham fluid, which shows that the mortar plastic viscosity is a significant factor for the surface properties of self-compacting concrete, but the correlation between surface properties and the yield shear stress or the flow velocity is low. The increase of water content or adding air entraining agent, can reduce the plastic viscosity and shear yield stress, but the equal volume replacement of river sand with light sand can only reduce the plastic viscosity, but the yield shear stress will increase. With the increase of plastic viscosity, the percentage of surface pore areas gradually increases, the pore size distribution becomes wider, and the number of pore with the diameter more than 2 mm increases; furthermore, the diameter of the biggest pore becomes larger. The self-compacting concrete with the plastic viscosity less than 9.37 Pa∙s has a better fair-faced surface. In this condition, the percentage of the surface pore areas is less than 0.2%, and the diameter of the biggest pore is less than 5 mm.