Deformation behaviour and failure criteria of plastic concretes under compression stresses

Plastic concrete is a ductile building material, made of aggregate, cement, water and bentonite clay mixed at a high water/cement ratio. To explore its deformation behaviour and failure criteria, we tested plastic concrete samples under uniaxial, biaxial, conventional triaxial and true triaxial compression. The characteristics of the stress–strain and axial strain–volumetric strain curves of plastic concrete samples were investigated. There were three types of stress–strain curve: softening, plasticising and hardening. A deformation parameter was introduced to quantitatively evaluate the curve type and the steepness of the descending post-peak portion. Under multiaxial compression, the volume of the specimens decreased, reaching a minimum, then expanded. Failure occurred in the weakest lateral confinement direction. The octahedral shear strain and peak strain showed a linear relation at failure, and the correlation coefficient decreased with increasing bentonite content. The failure rule between the octahedral shear stress and normal stress is presented.