Chloride de-icing salts are used for winter maintenance on highway bridges, and are known to penetrate concrete and cause corrosion of the reinforcement. Cracks, which provide easy routes for chlorides to reach the steel may be sealed with reactive resins or with liquid silicate solution. The object of this work was to assess the effectiveness of various crack injection systems for protecting the reinforcing steel from the ingress of de-icing salts. Concrete slabs were cracked, held under a constant load and repaired using various injection techniques. The slabs were ponded with sodium chloride solution and after various periods of exposure were broken up to assess the effectiveness of the repair methods. An earlier report described the injection methods and slab assessment after repair; this report discusses durability. There was little corrosion away from the cracks on either repaired or unrepaired slabs. Carbonation caused light corrosion at intersections of the reinforcement with unrepaired cracks on the slab exposed to water only. Corrosion had occurred at about half the intersections of the unrepaired cracks on the salted slabs; repair reduced this number by about half. It was observed that corrosion could occur even in fully filled cracks. Conditioning and exposure increased the flexural stiffness of the slabs. (Author/publisher)
Abstract