Impedance spectra were collected in situ during the exchange of the aqueous phase with an organic solvent in young (1-28 days old) ordinary portland cement (OPC) pastes at two water-to-cement ratios (w/c = 0.35 and 0.70). The high initial values of dielectric constant (103-105) and the rapid decline upon exchange support a model of dielectric amplification where layers of calcium silicate hydrate (C-S-H) gel separate capillary pores. When the liquid in pastes of w/c = 0.35 was exchanged with isopropanol, the residual dielectric constants were typically between 102-103, indicating that C-S-H has a dielectrically amplified microstructure. After methanol exchange, however, the residual dielectric constant was much smaller, 10-100. This suggests there are two kinds of water within C-S-H gel in pastes of w/c = 0.35 - that which is exchangeable by both solvents (capillary pores) and that which is exchangeable by methanol but not isopropanol (gel pores). For pastes of w/c = 0.70, differences due to solvent types were negligible. These observations suggest that the nature of C-S-H varies with w/c ratio.
ASJC Scopus subject areas
- Industrial and Manufacturing Engineering
- Ceramics and Composites