Kinetics parameters of cement hydration by electrical resistivity measurement and calorimetry

Abstract

The electrical resistivity method was used to detect bulk resistivity development (ρ(t) − t) and a calorimeter was used to measure the heat evolution (Q(t) − t) in cement pastes with and without fly ash at a fixed water to binder ratio of 0·4 during the first 24 h. The logarithmic equation ρ(t)=Kmln (Dt) is proposed to show electrical resistivity development over time during the deceleration period of hydration. A similar logarithmic equation, [Formula: see text], can be obtained from the heat evolution results. The parameters Km and [Formula: see text] respectively represent the rate of densification of the cementitious matrix per unit volume and the heat release rate per unit weight of binder. The paste with a lower replacement content of fly ash was found to have higher Km and [Formula: see text] values. There is a positive linear relationship between Km and [Formula: see text], so [Formula: see text] can be determined by Km. The parameters D and D′ represent the hydration rate for a cement particle in the hydration system: D slightly increases with fly ash replacement content using the electrical resistivity method and D′ from the heat results is close to the D value from the electrical resistivity method for the same fly ash content. A logarithmic relationship is established between the hydration heat at 24 h and the resistivity at 24 h. Based on this idea, the kinetics of hydration heat can be predicted using electrical resistivity measurement as an alternative method.