EXTENSION OF SERVICE LIFE OF REINFORCED CONCRETE STRUCTURES BY SURFACE IMPREGNATION WITH SILANE

Service-life of steel reinforced concrete structures is often limited by penetration of aggressive compounds into the porous structure of the cement-based material and subsequent deteriorating chemical reactions. Moisture content and water migration play an important role in almost all damage mechanisms in concrete. Capillary suction of water is a most efficient mechanism for transport of dissolved salts into the porous structure of concrete. Capillary suction can be significantly reduced if not totally prevented by surface impregnation with liquid silane. Then ingress of aggressive ions such as sulphates, chlorides and ammonium compounds dissolved in water is minimized. In this contribution results of three research projects will be presented and discussed: (1) determination of the depth of penetration of silane in concrete and silicon resin profiles in surface treated concrete, (2) relation between the silicon resin profile and effectiveness of water repellent treatment as a chloride barrier, and (3) the effectiveness of surface impregnation of chloride-contaminated concrete. It has been found that surface impregnation of concrete with liquid silane reduces the ingress of chlorides substantially. An efficient, reliable and durable chloride barrier can be established by deep impregnation (7 mm to 10 mm). When concrete is already chloride contaminated the effectiveness of surface impregnation is to be tested before application of a protective measure.