Hydro-mechanical properties of fresh cement pastes containing polycarboxylate superplasticizer

• Fresh cement paste permeability is largely reduced by polycarboxylate.
• Mechanism of bleeding of paste containing polycarboxylate is highlighted.
• Polycarboxylate content has no effect on the compressibility of fresh cement paste.

A novel oedometric cell has been used to study the permeability and compressibility of freshly made cement-based pastes. This cell allows rapid tests providing an accurate estimation of compressibility, permeability and thus consolidation coefficient with no cement hydration effect. The influence of the test-induced flow on the results obtained is discussed in order to find an optimized procedure. The effects of common mix-design parameters such as W/C ratio and polycarboxylate amount are discussed. Especially, it is shown that polycarboxylate high range water reducing admixture reduces the cement paste permeability and does not influence the compressibility of the cement grain network. The effect of W/C and admixture amount on paste bleeding is also discussed.