FE2 Multiscale Modelling of Chloride Ions Transport in Recycled Aggregates Concrete
Construction and demolition waste (C&DW) is one of the heaviest and most voluminous waste streams generated in the EU (estimated at around one third of the total amount of wastes produced). The Waste Framework Directive (2008/98/EC) states that members of the EU must take appropriate actions to ensure that 70% of non-hazardous C&DW wastes must be prepared for re-use or recycling by 2020. Moreover recycling becomes an increasingly need for providing a sustainable source of aggregates for future building material production. However, the presence of remaining cement paste in the recycled aggregates (RCA) is responsible for the lower density, higher water absorption, and lower abrasion resistance. The use of RCA still raises the question of the durability aspect of recycled concrete. One of these durability issues is the chloride ions diffusion, responsible of steel rebar corrosion. The transport of chloride is a diffusion mode in the water and an advective mode in the liquid phase. Quantifying the effect of recycled aggregates on the concrete micro-structure and the consequences on the hydraulic properties and water content distribution is thus a critical issue for durability.
The objective of the PhD research is the development of a numerical multiscale flow model able to predict the impact of the RCA on both the hydraulic properties and water content distribution. Owing to the influence of the microstructure properties of the constituents on these phenomena, the model will be developed in the framework of the finite element square method (FE²) and implemented in the finite element code LAGAMINE. The model will be validated against experimental data gained through an experimental campaign realized during the project. Through the proposed innovative developments, the challenge is to better understand the influence of the RCA on the durability of concrete, in link with the chloride ions migration.