Experimental study of the effects of water-binder ratio, silica fume and air-entrainment on the microstructure and salt scaling resistance of concrete pavements

Salt scaling of concrete pavements is known as a serious problem in cold regions. In the present study the effect of water-binder (W/B) ratio, silica fume and air entraining on the salt scaling resistance, compressive strength and electrical resistance were investigated. Microstructure of the concretes was assessed by mercury intrusion porosimetry and scanning electron microscope. Water-binder ratios were 0.35, 0.40 and 0.45. Silica fume was used, by 8% weight of cement, in the predetermined mixtures. The results showed that the best salt scaling resistance was correspondent to the air entrained silica fume specimens. By reducing the water-binder ratio, the amount of surface scaling was decreased. The MIP results declared that silica fume refined the microstructure and also decreased the total porosity and critical pore radius compared with those for the reference specimens. Furthermore, the MIP results of the silica fume specimens declared that the pores smaller than 10 nano were increased, due to the effective pozzolanic reaction. The scanning electron microscope images showed that the concrete containing silica fume had a denser gel compared with those for the reference ones. Introducing silica fume into the specimens had remarkable effect on the later age electrical resistance of the concrete. It was concluded that the highest electrical resistance belonged to the durable specimens. The results of the present study clarify how the micro structure may influence the salt scaling resistance of concrete pavement, this achievement will surely reduce the cost of rehabilitation of concrete pavements in the cold regions.