Influence Of Crack On Durabilty Of Marine Concrete

Shrinkage crack and loading crack will easily lead to daterioration of concrete stucture in marine environment. In this paper, shringkage crack and loading crack with different width in concrete was prepared by plate shrinkage, conventional triaxial compression and splitting tensile load. The carbonation of cracked concrete in simulated marine atmospheric environment was investigated, and the chloride ion penetration into cracked concrete in marine submerged zone and marine tide zone was studied. Additonally, restoration of cracked concrete with silicone water-proofing agent was evaluated. According to experiment and theoretical analysis, the following conclusions are obtained.(1) The free chloride and total chloride content in cracked concrete increase with raised width of shrinkage crack, and their relationship can be regressed to the quadratic function. When the width of shrinkage crack in concrete is less than 0.07mm, the carbonation depth in crack zone of cracked concrete is same as that of sound concrete. The chloride diffusion coefficient and crabonation depth of cracked concrete has a tiny increasement as the shringkage crack width is less than 0.1mm, and then increases with raised width of cracked concrete. Moreover, the crabonation depth in crack zone increases by 3mm in comparison with that in perimeter zone of cracked concrete.(2) When concrete with splitting crack, the critical crack width for chloride penetration into concrete increases with concrete compressive strength grade. In marine submerged zone, the critical crack width for C20^C50 concrete is 0.08⁰.12mm. And in marine tidal zone, the critical crack width for C50 concrete is 0.07mm. In simulated marine atmospheric zone, the content of CaCO₃ and carbonation depth in concrete crack zone increase with crack width.(3) The damage forms of cement mortar is compaction in the end, and Shear failure in the middle under conventional triaxial compression. The axial deformation of mortar increases with raised axial loading, and it will show the property of strain softening when unload in axial loading post-maximum. Compared to cement mortar under uniaxial compression, its compressive strength and strain increases by 1.94 times and 5.6 times when cement mortar under conventional triaxial compression. When the axial loading is less than 50% of peak axial loading, the dynamic modulus of elasticity increases with loading and the chloride content is less than that of unloaded cement mortar.(4) The relationship between chloride diffusion coefficient and axial loading, or axial deformation is related in quadratic function. When the axial deformation of mortar is higher than 0.72mm and 1.57mm, the chloride diffusion coefficient of unloaded mortar, is less than that of loading mortar in the loading bearing face area, and in the underside area, respectively.(5) When the cracked concrete is repaired by silane water-proofing agent, the chloride ion concentration in crack zone decreases markedly, and crack influeced zone in concrete reduces observably.