Dr. Qingfeng Liu, Associate Professor in Civil Engineering, Honorary Scientist of Shanghai Pujiang Scholars, School of Naval Architecture, Ocean & Civil Engineering, Shanghai Jiao Tong University, China

Title: A "double-multi" model for carbonation and its multi-factors on chloride binding in concrete composites

Abstract: Under complex marine and industrial-polluted environment, the concrete structures are exposed to chloride and carbon dioxide. Both chloride diffusion penetration and carbonation penetration are dominant causes of the deterioration concrete and steel reinforcement, and the circumstances become worse when these two factors are combined. Chloride binding effect is one of the most significant phenomena during chloride transportation. However, carbonation effect may influence the chloride binding effect by decomposing Friedel’s salt and C-S-H gel, thus releases chloride ions into the pore solution. To further explore the influence mechanism of carbonation on chloride binding, this process is simulated as a numerical model under the position of chloride-contaminated first and then carbonated. By using the proposed “double-multi” model (multi-phase modeling of multi-species transport), this work adopts the concept of carbonation rate to elaborate the synergetic effect of different environmental factors, including temperature, relative humidity and carbon dioxide concentration. It is proved that the binding effect is observably influenced by the multi-factors influenced index carbonation rate. The comparisons of the influence degree of various factors are also elaborated.

Keywords: Cementitious Materials; Composite Material; Concrete; Inorganic Non-Metallic Materials; Durability; Multi-phase, Multi-species; Chloride binding; Carbonation; Synergetic effect