Time of Wetness and HR-T Complex as Tools for Corrosion Risk Evaluation in a Concrete Block Exposed to a Humid Tropical Environment

Abstract

Material surface time of wetness (TOW) and temperature (T) are critical variables that influence the corrosion behavior of reinforced steel bars in concrete, and concrete durability. In concrete structures, both variables are indirectly dependent on the atmospheric relative humidity/ temperature complex, and specific structural characteristics: concrete composition, water/cement ratio, curing time, geometry and orientation in the environment. Concrete internal TOW and T distribution data were collected using Cu/Au electronic sensors arranged at 15, 40, 65 and 75 mm depths in a concrete block (300 x 300 x 150 mm; w/c 0.5) exposed for one year in a rural-urban humid tropical climate in southeast Mexico. Concrete internal TOW allows structure designers to define concrete cover thickness over steel reinforcement bars. The results indicate that under the tested exposure conditions, the side of the block with the highest TOW values (west) would require a thicker concrete cover than that with lower values (east). Longer TOW can increase the possible permeation of gases such as CO2, and consequent concrete carbonation, as well as lead to loss of the passive state in steel reinforcement and initiation of the corrosion process.