Nitrite diffusivity in calcium nitrite-admixed hardened concrete

摘要

The apparent diffusivities (D_(app)) of nitrite in concrete were estimated by monitoring time-dependent concentrations of nitrite leached into water from calcium nitrite-admixed hardened concrete specimens. Experiments were conducted with five different concrete mixes and with deionized water (DI), limewater, or synthetic seawater as the leaching agents. The D_(app) in Type II Portland cement concrete for long curing times and a w/c ratio of 0.40 was approx 1.7 X 10~(-8) cm~2/s when leached at 22 deg C with limewater. The D_(app) was relatively insensitive to nitrite dosage and to DI or limewater as the leaching agent, but an increase in the w/c ratio to 0.49, or an increase in temperature by approx 14 deg C, increased D_(app) by approx 50 percent. A 20 percent Type F fly ash cement replacement reduced the apparent diffusivity by approx 60 percent. The D_(app) decreased with concrete curing time. The magnitude of the D_(app) and its dependence on concrete and exposure parameters were comparable to those observed in the transport of chloride ions in concrete.