Water evaporation from freshly placed concrete surfaces in hot weather
✍ Scribed by G.S. Hasanain; T.A. Khallaf; K. Mahmood
- Publisher
- Elsevier Science
- Year
- 1989
- Tongue
- English
- Weight
- 589 KB
- Volume
- 19
- Category
- Article
- ISSN
- 0008-8846
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✦ Synopsis
The paper reports a study conducted in the hot weather of Jeddah, Saudi Arabia, on a number of specimens,with surface area of 0.1m 2, prepared by using the concrete produced for a construction project. This study indicates that besides weather components, the time of casting, difference of concrete and air temperatures and moisture condition of the concrete surface influence the rate of evaporation of water from freshly placed concrete surfaces. For the specimens cast in the morning, noon or early afternoon time and kept in open air, the maximum rate Qf evaporation exceeded the limiting value of 1.0 kg/mZ/hr, from view point of susceptibility to plastic shrinkage cracking. In the case of specimens cast in the noon and afternoon time the maximum rate of evaporation generally occurred in the first hour after casting when a layer of bleed water was available on the surface. However, in the case of specimens cast in the morning time, the maximum rate of evaporation occurred at noon time, 3-5 hours after casting, when the concrete had partly set and had no free moisture available on the surface. The study further shows that the shading of specimens to protect them from solar radiation lowered the rate of evaporation by 50 per cent or more of the respective rate for the specimen kept in open air. Based on the results of the study, the paper discusses the specifications for hot-weather concreting and the limitations of the graphical method used for estimating the rate of evaporation.