Efficiency of surface protection systems for concrete: water absorption, chloride migration and contact angle

The thickness of concrete cover acts as a natural protective barrier to the ingress of aggressive agents into the material, hindering the penetration of chloride ions, reducing water absorption and by limiting access of oxygen. To ensure the efficiency of this protective coat the use of surface treatments presents as a viable alternative to extend the period of protection provided by the concrete cover. The aim of this study is to evaluate the protective effect of four products available on the market to be applied on the surface protection of concrete (concrete sealers, epoxy, silicates and silane/siloxane) and compare the methods used to investigate the efficiency of protection systems. Absorption test by capillary suction, chloride penetration resistance by migration of ions and measuring the contact angle with water on the surface of protected concrete were executed. The studied products presented the ability to modify the interaction between the water and the contact surface of the concrete. With the exception of silicate, it was verified a good correlation between the results of water absorption by capillary and chloride ions migration. Among the studied products, the epoxy presents the highest resistance to chloride penetration, lower water absorption by capillarity and water repellent character. The epoxy and silicate, which showed the lowest values sorptivity, presented the highest values of contact angle, being ranked as the lowest affinity for water.