Evaluation of the effects of silica fume and air-entrainment on deicer salt scaling resistance of concrete pavements: Microstructural study and modeling

Abstract Salt scaling is recognized as one of the most critical durability concerns in concrete structures, specifically for concrete pavements in cold regions. The main objective of this study is to investigate the micro- and macro-scale effects of silica fume and air-entrainment on the mechanical strength and deicer salt scaling resistance of concrete pavements. For this purpose, an extensive set of laboratory tests was performed to determine compressive strength, electrical resistivity, and salt-scaling durability of concrete. The testing matrix comprised eight concrete mixtures including two water-to-binder ratios (0.35, 0.4) with and without silica fume and air entrainment. Further, the microstructure of specimens was investigated using mercury intrusion porosimetry (MIP) and scanning electronic microscopy (SEM). The results indicated that, the concrete containing air-entrainment and silica fume exhibited the best performance in the salt scaling test. The MIP results showed that adding silica fume reduced the volume of total pores and refined the pore size distribution. Moreover, silica fume increased the volume of pores smaller than 10 nm due to proper pozzolanic activity. The tests results were employed in a set of nonlinear regression analyses to establish empirical models to estimate the salt-scaling resistance of air-entrained and non-air-entrained concretes as a function of water to binder, fresh air content, compressive strength, electrical resistivity and characteristics of pore structures in hardened concrete. The presented models can provide a practical yet reliable means to assess the salt scaling resistance in concrete pavements.