Bio-cementation is a process to improve structures and soils which appears to be more environmentally friendly and to need less energy than classical techniques. Previous studies have shown its potential for a broad spectrum of applications: internal erosion, soil liquefaction, landslides... One of its interest is to increase the mechanical properties, while keeping a high permeability. Indeed, only a tiny volume fraction of calcite, essentially localised at the contact between grains, is needed to increase dramatically the macroscopic properties. Thus, this project aims to characterise the mechanical properties of the bio-cemented contacts designing original micro-mechanical experiments coupled to high resolution 3D imagery. The contact properties will be then used to predict macroscopic laws and effective properties using DEM (Discrete Element Modelling) simulations. Moreover, one work package of this project will be dedicated to the study of the improvement durability by measuring the evolution of the mechanical properties with the exposure time to acid conditions, representative of an acid rain.