The use of geotextiles made of polypropylene (PP) in civil engineering such as tunnel requieres adequates control over their durability, and this characteristic remains poorly known due to their inaccessibility. Considering concrete environment ageing conditions (alkali medium i.e. pH = 9 to 13), the aim of this study is to complete a non-empirical kinetic model for polypropylene ageing by the determination of the extraction parameters a frequently used phenolic process stabilisers: Irganox 1010. Thin PP films containing 0.1 mol.kg-1 of stabiliser were exposed to a basic solution at 80°C, in order to accelerate extraction phenomena, and under an inert gas (nitrogen) in order to avoid any consumption of the stabiliser by ambient oxygen. The quantity of stabiliser has been followed by Fourier Transformed Infrared. Analysis has been done at various ageing times during 34 days. This study highlighted the co-existence of two phenomena: hydrolysis of Irganox 1010 and extraction to the alkali solution of the carboxylic acid compound generated by the hydrolysis reaction. A simple model with minimal number of adjustable parameters was proposed and its analytical solution simulates acceptably the experimental trends.
