Early-age hydration characteristics and kinetics of Portland cement pastes with super low w/c ratios using ice particles as mixing water

Abstract

The liquid water was replaced by ice particles for preparing homogenous structural Portland cement (PC) pastes at super low w/c ratios from 0.08 to 0.16. For introducing the process of PC hydration, a sophisticated conduction calorimeter was adopted to measure the early-age hydration heat evolution. The hydration kinetic parameters were determined by Krstulovic–Dabic model based on data of hydration heat evolution. The concentrations of K+ and Na+ of the pore solution were measured by ICP-OES. Experimental results showed that the acceleration period of the hydration process of PC paste was improved by increasing w/c ratio due to the improvement of space available for hydration product growth. The hydration mechanism of PC paste changed to nucleation and crystal growth (NG) - diffusion (D) when its w/c ratio below 0.16, representing a more intense hydration reaction than that of PC with a normal w/c ratio of 0.30. The concentrations of K+ and Na+ of pore solution of hydrated PC paste decreased with the increase of w/c ratios, which led to the alkalinity of that decreased with the increase of w/c ratios. In addition, the mechanical properties of hardened PC pastes were enhanced by increasing w/c ratios from 0.08 to 0.16, which could be attributed to the decrease of porosities of hardened pastes.