Book Description

One hundred and fifty-six exposure slabs have been constructed with and without a variety of combinations of corrosion inhibiting admixtures and topically applied inhibitors. To accelerate corrosion one hundred and thirty-six of the slabs were constructed with concrete that surrounded the top mat of reinforcement with chloride contents of 3,6, 10, and 15 Ib/yd3 (1.8,3.5,5.9, and 8.9 kg/m3). This paper presents the results from measurements made on the slabs in May 1998 after approximately 1 year of exposure. The measurements show that as the chloride ion content in the slabs increases, the macrocell current, macrocell potential, half-cell potential, and rate of corrosion increase and the resistance decreases. Macrocell currents exceed 10 uA, indicating corrosion activity, in slabs cast with chloride in the concrete except those with 3 Ib/yd3 (1.8 kg/m3 ) of chloride that were overlayed and patched or patched. Measurements taken to determine the rate of corrosion indicate high, moderate, low, and passive states of corrosion in 63,22, 12, and 3 percent, respectively, of the slabs. The measurements also show no significant difference between the slabs repaired with and without corrosion inhibitor admixtures and topical treatments. Slabs repaired with 7% silica fume showed half-cell potentials that were less negative than those repaired without silica fume.