Weather Exposure and Its Effect on Bridge Deck Curing in Alabama

Abstract

Plastic shrinkage cracking of concrete bridge decks occurs when the water evaporation rate at the surface exceeds the bleeding rate of the freshly placed concrete. Also, the rate of early drying shrinkage after the concrete hardens is related to water evaporation rate due to weather conditions over a prolonged period of time. Thus, water evaporation rate values are of great interest when placing and curing concrete bridge decks. The American Concrete Institute (ACI) has published a water evaporation chart that aids in deciding if weather conditions will cause plastic shrinkage at the time of concrete placement. The chart, although developed for plastic concrete and plastic shrinkage, could be used in conjunction with relative humidity, temperature, and wind velocity data for different locations, times during a day, and times of the year, to provide an improved guideline for indicating appropriate weather-related curing requirements for bridge decks. This study identifies typical temperature, relative humidity, and wind-weather exposure conditions in Alabama for various months/seasons of the year and times of the day; it also evaluates, via the ACI 305 Surface Evaporation Chart, concrete-surface water evaporation rates for these typical Alabama weather exposure conditions. Based on these data and results, tentative bridge-deck curing requirement categories appropriate for Alabama are identified.