Two reasons may explain this behavior: The shaping pressure and the samples sizes.
In Ref.[31] the test pieces were pressed under 54.5 MPa with a mixingwater between 7% and 10% and parallelepiped of 30 × 10 × 60 mmwere formed.
Mohammed et al. [57] showed how the CS decreaseswith the size of test specimens and Pérez and Romero [58] reportedhow CS it is increased with the increasing of forming pressure.
Despite these slight differences, trends are in accordance in bothcases