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.
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