In this paper, the mechanical constitutive law of fresh mortar, which can be applied to mortar from dry state to high flowing state, is proposed on the assumption that fresh mortar is a kind of particle assembly consisited of time-dependent particles (cement) with friction resistance and cohesive resistance, and time-independent particles (aggregates) with friction resistance between relative moving particles. The stress state of fresh mortar changes in order of visco-elastic state, visco-elasto-plastic state and failure state as shear stress increases. After the behavior of particles in each stress state is investigated, the relational formulas between shear strain and shear stress are induced on the basis of expanded Eyring's viscosity and Murayama's theory for the mechanical behavior of rigid particle assembly, and are verified by shear experiment using fresh mortar. Moreover, the relation between the constitutive law proposed in this paper and Bingham model is investigated theoretically, and its verification is carried out.
