A coupled water retention-mechanical constitutive model for unsaturated aggregated soils is presented here. Based on the multi-scale experimental results, the model incorporates the inter-particle bonding, fabric and partial saturation effects in a single framework. It is formulated within the framework of hardening elastoplasticity and is based on the critical state concept. Prior to model validation, we evaluate the model parameters and propose determination procedures for the main new parameters. Finally, the model is examined for its capability in simulating the experimental results of aggregated and bonded soils. Results of these simulations show that the model addresses the most features arising from the combined effects of soil structure and partial saturation.