Hydration, shrinkage, pore structure and fractal dimension of silica fume modified low heat Portland cement-based materials

Abstract

Low heat Portland (LHP) cement has been widely used in hydraulic projects in China, while the relatively low early strength limits its further application in engineering. In this study, the effect of silica fume (SF) content, varying between 0 and 12%, by mass of binder, on hydration heat, hydration products and pore structure of LHP cement-based materials were investigated by isothermal calorimetry, thermal analysis, and mercury intrusion porosimetry (MIP), respectively. Besides, the mechanical strength, shrinkage behavior and fractal characteristics of SF modified LHP cement-based materials were studied and compared with those of ordinary Portland cement (OPC)-based ones. The results indicate that the addition of SF effectively accelerates the hydration of LHP cement and obviously consumes the Ca(OH)2 in LHP cement paste. In addition, concrete based on LHP cement with 8 wt% SF exhibits excellent performance such as high early strength, low hydration heat and low shrinkage. It is also found that the pore structure of SF-modified LHP cement concrete becomes finer and more complex as the SF dosage increases, resulting in higher fractal dimension (Ds) values. Moreover, there exists a linear relationship between Ds and shrinkage of concrete, thus Ds may serve as a new parameter to evaluate the shrinkage behavior of concrete.