Farqad Yousuf¹, Wei Xiaosheng^1,

The effect of the water-to-cement ratio on cement paste microstructural development was investigated using electrical resistivity measurements and computer modelling. Three cement pastes with 0.3, 0.35, and 0.4 w/c ratios were used in this study. The electrical resistivity measurements curve as a function of time for the three pastes shows that the lower the w/c ratio the higher the electrical resistivity through the whole time. The effect of overall porosity and initial distances between particles significantly influence the measurements. Although low w/c ratio paste has low liquid electrical resistivity comparing to other samples, still has high bulk electrical at all ages. The influence of particles proximity due to lower water amount was interpreted through monitoring the electrical resistivity development and computer illustration. The demonstration provides more explanation about the importance of water-to-cement ratio. Through the conducted experiments, empirical correlations were developed regard predicting compressive strength and autogenous shrinkage of cement pastes when all parameters are related to porosity. Setting time was also predicted by monitoring the critical points on the electrical resistivity curve. Scanning electron microscopy (SEM) was employed to elucidate the effect of the w/c ratio on the morphology of hydration products, and it was observed that high w/c ratio paste has more fibers per unite area comparing to lower w/c ratio pastes due to the long distances between hydrates for expanding.

water-to-cement ratio, electrical resistivity, computer illustration, cement hydration, cement strength, cement setting