高原桥梁混凝土表面气孔形态与内部孔结构研究

Study on surface porosity and pore structure of inner for plateau bridge concrete

为解决川藏铁路某桥梁工程所面临的混凝土表面气孔和孔隙结构问题,基于工程配合比,采用三种不同等级的粉煤灰进行混凝土试验研究。采用数字图像分析方法表征混凝土表面的气孔形态,以气孔最大直径和气孔面积率为指标,研究粉煤灰种类对混凝土表面气孔特征的影响;采用压汞测孔法测试硬化混凝土内部的孔隙分布,对孔隙结构进行了分析,得出不同种类粉煤灰混凝土内部孔结构体积分布和孔结构指标。研究结果显示,粉煤灰种类对高原桥梁混凝土的表面气孔和内部孔结构有明显的影响。Ⅱ级粉煤灰混凝土表面气孔数量最多,气孔的最大直径和气孔面积率最大,Ⅰ级粉煤灰次之,磨细粉煤灰最小;磨细粉煤灰混凝土的孔隙率最小,孔隙结构较Ⅱ级、Ⅰ级粉煤灰更好。使用磨细粉煤灰可以更好地细化混凝土的孔隙结构,提高混凝土的密实度,改善混凝土的表观质量。

In order to solve the problem of concrete surface pores and pore structure for a bridge project in Sichuan-Xizang Railway,three different kind of fly ash were used for concrete test based on the engineering mix ratio.The pore morphology of concrete surface was characterized by digital image analysis method.The influence of fly ash type on the pore characteristics of concrete surface was studied by using the maximum pore diameter and pore area ratio as indexes.The mercury porosimetry was used to test the pore distribution in hardened concrete,and the pore structure was analyzed furtherly.The volume distribution and index of pore structure in different kinds of fly ash concrete were obtained.The results show that the different kind of fly ash has a significant effect on the surface porosity and internal pore structure of plateau bridge concrete.The number of pores on the surface of grade II fly ash concrete is the highest,the maximum diameter of pores and the area ratio of pores are the largest,followed by grade I fly ash,and the smallest is ground fly ash.The porosity of ground fly ash concrete is the smallest,and the pore structure is better than that of grade II and grade I fly ash.The use of ground fly ash can better refine the pore structure of concrete,improve the compactness of concrete,and improve the apparent quality of concrete.