混凝土预制件表面气孔影响因素的量化研究

Quantitative research on influencing factors of surface pores of precast concrete members

表面气孔是混凝土预制件最常见的外观缺陷,严重影响其美观、强度与耐久性。对混凝土表面气孔的形成原因进行了分析,使用Image-Pro-Plus图像分析软件对表面气孔进行量化表征,探究了水胶比、振捣时间和脱模剂种类对混凝土表面气孔的影响。结果表明,适当增大水胶比、降低混凝土拌合物的塑性黏度、采用适宜的振捣时间和脱模剂,可明显改善混凝土表面外观质量。在实验室试配强度等级为C50、坍落度为70 mm左右的预制管片混凝土,当水胶比为0.37、拌合物塑性黏度在3000~4000 mPa·s、振捣时间为40 s、在最佳兑水比例下使用乳液类脱模剂T4时,混凝土的表面外观质量最佳,气孔最大直径为2.2 mm,气孔面积率为0.04%。

Surface pores is the most common appearance defect of precast concrete members,which seriously affect its appearance,strength and durability.The causes of the formation of pores on concrete surface are analyzed,and the surface pores are quantitatively characterized by Image-Pro-Plus image analysis software,and the effects of water-binder ratio,vibration time and release agent on concrete surface pores are discussed.The results show that the appearance quality of concrete surface can be obviously improved by properly increasing the water-binder ratio and reducing the plastic viscosity of concrete mixture and adopting suitable vibration time and release agent.The prefabricated segment concrete with strength grade C50 and slump of about 70 mm is tested in the laboratory.When the water-binder ratio is 0.37,the plastic viscosity of the concrete mixture is in the range of 3000~4000 mPa·s,the vibration time is 40 s,and the emulsion release agent T4 is used under the optimum water ratio.The surface pore appearance quality of the concrete is the best,the maximum pore diameter is 2.2 mm,and the pore area ratio is 0.04%.