  The poromechanical behaviour of hardened cement paste under isotropic loading
is studied on the basis of an experimental testing program of drained,
undrained and unjacketed compression tests. The macroscopic behaviour of the
material is described in the framework of the mechanics of porous media. The
poroelastic parameters of the material are determined and the effect of stress
and pore pressure on them is evaluated. Appropriate effective stress laws which
control the evolution of total volume, pore volume, solid volume, porosity and
drained bulk modulus are discussed. A phenomenon of degradation of elastic
properties is observed in the test results. The microscopic observations showed
that this degradation is caused by the microcracking of the material under
isotropic loading. The good compatibility and the consistency of the obtained
poromechanical parameters demonstrate that the behaviour of the hardened cement
paste can be indeed described within the framework of the theory of porous
media.
