Effect of varying surface ageing on frost-salt scaling

Surface scaling of bridge structures, caused by a moist and saline environment with frost attack, should be minimized to guarantee a long service life. For frost-salt scaling, near surface material properties are critical. Thus it is also essential to know how ageing resulting from carbonation, drying and hydration will change the durability performance of concrete. Laboratory studies on the effect of surface ageing on frost scaling were included in the Finnish DuraInt project (Effect of Interacted Deterioration Parameters on Service Life of Concrete Structures in Cold Environments, 2008 - 2011). The effect of five different ageing conditions on the freeze-thaw scaling performance of concrete was analysed, using natural or accelerated ageing methods. Concrete specimens were subject to one or two rounds of combined ageing - degradation mechanisms. The effect of binder type, w/b ratio, air content and air pore structure is discussed. The results showed that ageing with carbonation typically increased scaling. Binding material type and air entrainment quality were also decisive.