Electrochemical impedance spectroscopy (EIS) of hydration process and drying shrinkage for cement paste with W/C of 0.25 affected by high range water reducer

The objective of this paper is to examine the hydration behaviour, fluidity and drying shrinkage of cement paste with lower water-cement ratio (W/C) of 0.25. The electrochemical technique is utilized to assess the evolution of the hydration process of fresh cement pastes with different amount of high range water reducing admixture (HRWR), as well as the fluidity measured by the mini cone method. The experimental results show that HRWR can effectively influence the hydration behaviour of paste. The parameter Rct obtained by Nyquist curves varies as the dosage of HRWR increase from 0.5% to 1.4%, indicating that HRWR indeed has obvious effect on the ability of paste transferring charge, further influence the structure of fresh cement paste. Meanwhile, the parameter of Rct is closely related to the fluidity of fresh cement paste measured by mini cone. Additionally, the drying shrinkage of cement paste increase when the dosage of HRWR changes from 0.8% to 1.4%. The cement paste with 0.8% HRWR has the highest increasement of drying shrinkage at the first 10 days. However, the drying shrinkage of cement pastes with 0.8% HRWR has the lowest value at 90 days.