Reinforcing steel corrosion in high-volume fly ash concrete

摘要

The corrosion of reinforcing steel in high-volume fly ash (HVFA) concrete slabs was investigated. Chloride ions were introduced into the reinforced concrete slab specimens through a natural diffusion and migration process, that is, immersion in a ponding solution of 3.4 percent sodium chloride(NaCl). Two HVFA concretes specimens with ASTM Class C and Class F fly ash were made with a water-to-cementitious materials ratio (w/cm) of 0.32; besides, three control concretes specimens with a w/c of 0.32, 0.43 and 0.55 were also investigated. The concrete cover depths to the steel reinforcing bars ranged from 13 mm to 76 mm. The corrosion of the reinforcing steel bars was evaluated by means of ha1f-eell potential, linear polarisation and AC impedance techniques. The results indicated that the concrete incorporating Class C fly ash showed the best performance with respect to chloride-induced reinforcing steel corrosion, followed by the control concrete with the w/c of 0.32-and concrete containing Class F fly ash; the control concretes with w/c of 0.43 and 0.55 showed the poorest performance.