| Chloride transport process is very essentially important to the Durability and Service Life predicting of Reinforced Concrete Structures (RC) since it directly determines the initially corrosion time. However, based on the present researches, some important and necessary factors have been ignored, thus the aims in present work are to enhance the present theories of chloride ions transport, and the details are present as following:(1) To establish the model of chloride penetration into cracked concrete subjected to drying and wetting cycles. When a crack occurs, it accelerates the ingress of chloride ions and affects durability. In order to clarify the mechanism of deterioration subjected cyclic drying-wetting condition, an innovative model describing the transport of chloride ions in cracked concrete is elaborated, meanwhile the results of experimental investigation are also reported. The transporting mechanism of chloride ions in porous medium is supposed still valid for cracked concrete. The advection part is simulated by moisture transport in rough cracks, modeled as a flux based on Poiseuille law considering crack width, crack surface roughness, tortuosity and capillary pores at crack surface. Furthermore, the control equation dominating the chloride transport into anisotropic porous is established and some important factors are studies for the sensitivity. Finally, a simplified and modified Fick’s second law is proposed here to estimate the chloride ions profiles in cracked concrete.(2)To establish the computational framework of chloride transport with account of the multi-environments and external loadings. In reality, chloride ingress implies a complex interaction between physical and chemical process, in which external heat, moisture state changing, as well as the changing of concrete material because of the self-creep property, thus chloride ingress present nonlinear and time-dependent. In nature, the chloride diffusivity are influenced by creating shortcuts or modifying the microstructure of concrete regardless of the reasons for external environments or concrete properties itself, which present to be a enlarging or reducing impact. The main objects and innovation of present work are to link the changing of external environments and the responds of structures itself based on the well-known section fiber model, and to further calculate the relationship between the stress or strain and chloride diffusivity, finally based on the experimental results this euqation is obtained.(3)To analysis the chloride ingress under randomness and fuzziness and establish the framework of service-life prediction. Chloride ingress processcontain lots of uncertainty, including both the objective (fuzziness) and subjective one (randomness). A model of chloride ingress into sound and cracked concrete under fuzziness and randomness is proposedbased on the random filed theory and fuzzy theory as well as taking consideration of the impact of cracking on the durability assessment of service-life predicting. Finally then Monte Carle simulation is used for calculation of the probability of durability and service life is comparison with the stochastic method.(4)The influence of cracking on the chloride diffusivity and moisture influential depth are studied both experimentally and numerically. In reality concrete structures are not always crack-free, therefore clarifying the internal environment and relevant chloride diffusivity in cracked concrete are essential to predict chloride ingress. In present work, a detailed experimental investigation on two coefficients affecting chloride ion concentration profiles at cracked concrete were carried out, specifically chloride diffusion coefficient and convection zone of depth. For the investigation of diffusivity, Electron Probe Micro Analysis (EPMA) was used to extract the accurate chloride concentration. Furthermore, an effective chloride diffusivity coefficient of cracked concrete was calculated under the law of flux conservation, taking consideration of both crack patterns and concrete mixtures. On the other hand, for the investigation of convection zone of depth, a series of laboratory experiments with different cracking specimens were conducted to clarify the influence of external artificial weather on the relative humidity distribution in cracks, including the periodic changing of external relative humidity and temperature, fog and rainfall simulation environments, the drying phase after precipitation. |
