Chloride Transport in Concrete under the Frost Action – An Experimental Study
Licentiate thesis, 2009
Frost-induced ingress of chloride in concrete is one of the typical transport phenomena of aggressive substances when structures expose to severe environments such as marine tidal zone and de-icing highway in winter seasons. It is well known that Chloride ingress in concrete causes the reinforcement corrosion. So improving the knowledge and understanding of frost-induced ingress of chlorides in concrete will help for better prediction of service life of reinforced concrete structures with respect to chloride-induced corrosion.
This doctoral project has been carried out through the laboratory investigations of liquid uptake, chloride profiles, and chloride diffusion coefficient etc. Both the plain Portland cement concrete and the concrete with various mineral additions were investigated. The variables of concrete include water-binder ratio and air-entraining agent. The environmental variables include different constant temperatures in comparison with the action of freeze-thaw cycles.
The results show that the frost action is the important influencing factor, which increases the liquid uptake and chloride transport. The frost-thaw cycles cause the redistribution of water in pores inside concrete. Concrete with mineral additions had finer pore microstructure that benefited for a better resistance to frost attack within 112 cycles of freeze-thaw in this investigation.