Interfacial transition zone characterization of Portland cement mortars containing relatively high dosages of polynaphthalene sulfonate superplasticizers

The microstructure and interfacial transition zone characteristics of Portland cement mortars prepared with a polynaphthalene sulfate (PNS) superplasticizer at relatively high dosages (0.8%, 1.5% by mass of cement) and varying sand-to-cement ratios (0.5, 1.0, 1.5) were investigated, using AC impedance spectroscopy, mercury intrusion porosimetry, helium pycnometry and two electrical conductance models employing the interfacial excess conductance concept and Bruggeman’s asymmetrical effective medium theories. The specimens containing superplasticizer exhibited higher electrical resistance, lower overall porosity and smaller interfacial excess conductance values compared to the corresponding control mortars. Experimental values of σm/σp, the relative conductivity (i.e. the conductivity ratio of mortar and paste) of mortars, are compared with the theoretical curve predicted by the