New insights on understanding the Portland cement hydration using electrical impedance spectroscopy

•Understanding physico-chemical processes of Portland cement hydration using electrical conductivity curve from IS.•Elucidating the dissolution processes and the period after maximum conductivity value of Portland cement pastes.•Eight regions on the electrical conductivity curve were proposed.•IS is sensitive tool in identifying the hydration processes of Portland cement. This study aimed to bring new perspectives and understandings, as well as to elucidate the behavior of Portland cement hydration through electrical conductivity curves obtained by impedance spectroscopy (IS). The IS measurement was performed on Portland cement paste with w/c ratio of 0.40 up to 28 curing days. According to the results, based on the inflection points of its respective derivative, the electrical conductivity curve of Portland cement paste can be subdivided into eight different regions. A new region (region IV) in the acceleration period, characterized by the resume of dissolution reactions and microstructure formation with the paste in a semi-fluid state, was established. Moreover, a shoulder observed in region VI was attributed to the formation of AFt phases from the reduction of CaSO4, and secondary reactions of ionic release in the pore network. Hence, new insights on the electrical conductivity curve of Portland cement paste are reported confirming the IS as a sensitive and promising technique.