Identification of the percolation threshold in cementitious pastes by monitoring the E-modulus evolution

The determination of the fluid-to-solid transition in cement-based materials is fundamental to understanding the evolution of early-age mechanical properties and to detect the time after which the material may withstand stresses. The transition is gradual, and non-destructive methods are needed for clear identification. This paper presents a study using a recent method for continuously monitoring the E-modulus of cement-based materials since casting, based on evaluating the first resonant frequency of a composite beam containing the material under test. It is intended to demonstrate the capability of this method to detect the percolation threshold and to check eventual correlations with the released heat of hydration. Five sets of mix compositions are tested, with w/c ratios ranging from 0.30 to 0.50, with the addition of limestone filler, or with partial replacement of cement by fly ash, silica fume or metakaolin.