Experiment on the Anti-permeating and Anti-cracking C50 Concrete of Thin-walled StructureCHEN You-zhi~1,ZOU Qi-ling~2,LI Fang-xian~1,SUN Tao~1,XU Bing-bo~1(1.School of Materials Science and Engineering ,Wuhan University of Technology, Wuhan 430070,China;2.The Office of Bridge Maintains of Wuhan City ,Wuhan 430015,China)According to the features of concrete of thin-walled structure, C50 anti-permeating and anti-cracking concrete was designed by utilizing moderate-heat Portland cement. The results indicated that the strength of 28 days reached 56 MPa and impermeability reached P12 by adding polypropylene fiber or steel fiber or mixed polypropylene fiber and steel fiber in the concrete. The concrete adding polypropylene fiber was better in permeability and crack resistance. From the SEM, gauged mortar microstructure of concrete with expansion admixture was density and a large number of ettringite generates can compensate the shrinkage of gauged mortar and help the permeability and crack resistance.anti-permeating and anti-cracking concrete; polypropylene fiber; steel fiber