Rapid evaporation from freshly cast concrete and the Gulf environment

In hot dry climates, such as exist in the Arabian Gulf region, plastic shrinkage cracking can develop when the rate of evaporation exceeds the rate at which bleed water rises to the concrete surface. Furthermore, with or without plastic shrinkage cracking, surface drying can still lead to a reduction in abrasion resistance and an increase in porosity and permeability at the critical near surface, or 'cure affected zone'. This paper discusses evaporation and surface drying in hot, dry environments, as in the Arabian Gulf region, based on experimental measurements of the rates of both evaporation and bleeding. Measured rates of evaporation are compared to predicted values obtained from the Menzel equation, the most commonly used formula for this purpose. The paper concludes by pointing out the precautions to be taken in order to prevent exposing recently placed concrete to excessive drying. (C) 2001 Elsevier Science Ltd. All rights reserved.