Study on Crack Decrease Property of High-Performance Concrete Under Corrosive Environment in Subsea Metro Tunnel

摘要

The concrete performance of Subsea Metro tunnel is easily affected by construction conditions and corrosive environment, which will lead to cracks and affect the durability of concrete structure. For the problem that high-performance concrete construction in subway subsea tunnel is prone to crack, two ways of adding fiber and mixing fly ash are studied in order to improve the crack decrease property concrete. For fiber concrete test pieces, three different materials of polypropylene fiber, PVA fiber and blended composite fiber are selected for comparison; for concrete test piece mixing fly ash, the method of decreasing cement content and improving cement mark is adopted. Through large amount of laboratory test, the rule of effect of addition of fiber and mixing fly ash on concrete working performance, shrinking percentage, early crack resistance and chloride ion permeability coefficient is studied. The test results show that: outcome of crack decrease property of fiber concrete test piece is ideal. Outcome of crack decrease property of mixing complex fiber is the best with expression that concrete shrinking percentage significantly decreases which basically eliminates occurrence and development of early damaged crack, penetration depth and migration coefficient of chloride ion are obviously lower than normal concrete with promotion of durability. Shrinking percentage of concrete test piece mixing fly ash is slightly lower than normal concrete, and concrete test piece mixing fly ash has more small cracks and undesirable crack decrease outcome at early stage on the premise of existing raw material concrete.