Associate Professor/Honorary Scientist of Shanghai Pujiang Scholars, School of Naval Architecture, Shanghai Jiao Tong University, China.

Speech Title: Multi-Phase Modelling of Multi-Component Ionic Transport in Composite Materials: In case of Recycled Aggregate Concrete
Abstract: Concrete is always treated as inhomogeneous composite material and inorganic non-metallic materials, whose response of inclusion structures and ionic transport mechanism in internal are crucial to the service life of concrete-based infrastructure and buildings. To facilitate understanding on mechanism of chloride-induced durability problems in reinforced concrete structure, one has to consider not only the multiple meso/micro phases (i.e., aggregates, cementitious materials, interfacial transition zone (ITZ), cracks, etc.), but also the multiple ionic species (K+, Na+, Ca+, Cl-, OH-, SO42-, etc.). Taking account of above critical factors, a series of “double-multi” models have been developed to exactly link to this particular theme. The proposed “double-multi” model is very suitable in further investigating a set of research areas, e.g., diffusivity prediction, binding effect, EDL effect, cracking effect, ITZs, aggregate morphology, etc. In this paper, a five-phase composite model of recycled aggregate concrete (RAC), which includes three continuous phases (new mortar, adhesive old mortar and original natural coarse aggregates) and two interphases (new ITZs and old ITZs), is proposed to predict the effective diffusion coefficient of chlorides in RAC. Interestingly, based on parametric studies with a series of critical factors, the present numerical model reveals some important features of RAC, which has previously not been properly investigated.
Keywords: Cementitious Materials; Composite Material; Concrete; Inorganic Non-Metallic Materials; Diffusion; Multi-phase, Multi- species; Recycled aggregate concrete (RAC)