Title:
Performance of Reinforcing Steel in Concrete
Containing Silica Fume and Blast-Furnace Slag
Ponded with Sodium-Chloride Solution
Author(s):
P. Gu, J. J. Beaudoin, M. H. Zhang, and V. M. Malhotra
Publication:
Materials Journal
Volume:
97
Issue:
3
Appears on pages(s):
254-262
Keywords:
blast-furnace slag; portland-cement concrete; reinforcement;
silica fume; slab; water-cement ratio
DOI:
10.14359/4620
Date:
5/1/2000
Abstract:
This paper describes the performance of steel reinforcement in concrete slabs that were ponded with a 3.4% sodium-chloride solution for a period of 6 months. The concrete slabs were cast using portland-cement concrete with and without silica fume and blast-furnace slag. The concrete cover to steel reinforcing bars ranged from 13 to 76 mm. The concrete resistance to chloride-ion penetration was determined according to ASTM C 1202. The corrosion resistance of the steel reinforcing bars was determined using half-cell potential, linear polarization, and a.c. impedance techniques. The test results showed that both the silica fume and slag concretes exhibited very low pene-trability to chloride ions, with the value of charge passed being less than 1000 coulombs. All control concretes had the value of charge passed > 1000 coulombs, regardless of the water-cement ratio (w/c). There was no significant corrosion of the reinforcing steel in the sili-ca fume, slag, and control portland cement concrete with water-cementitious materials ratio (w/cm) of 0.32 after 6 months of pond-ing with a 3.4% sodium chloride solution. Significant corrosion rates were observed for the reinforcing steel embedded in control portland cement concrete with w/c =0.43. As expected, the poorest perform-ance was of the control concrete with a w/c of 0.76, where the corro-sion of reinforcing steel was detected, even with a 51 mm concrete cover. There was a good correlation among the test results obtained using the half-cell potential, linear polarization, and a.c impedance techniques.