Pore structure characterization of early-age cement pastes blended with high-volume fly ash

High-volume fly ash is normally used as a partial replacement for cement to improve the workability, durability, and economic properties of concrete. The pore structure is an important factor affecting the performance of concrete. In this study, the influence of water-binder ratio (w/b) and fly ash content on the pore structure of early-age cement paste was determined using low-field nuclear magnetic resonance spectroscopy. Experimental results show that the most probable pore diameter increases with fly ash content and w/b and decreases with age. The porosity increases with w/b and decreases with age. A modified pore structure model, which is based on the existing models and the Weiball distribution, is proposed for high-volume fly ash cement-based materials.