Qatar: Green Concrete Technologies - Towards a Sustainable Concrete Industry in Qatar
All the water added in the mixing process can be replaced by ice. To decrease concrete temperature for 10 Kelvin about 7.5 kg of ice are needed. *EXHIBIT A* shows an example of the typical overall concrete temperature profile of concrete produced during the hot summer season in a desert environment.
SUSTAINABLE COOLING OF READY-MIXED CONCRETE Producers in Central Europe have developed an effective, economic and reliable system to regulate the concrete temperature of large concrete quantities. The system was initially used in Qatar, where it continues to be operated successfully. In the process the aggregates are cooled by using cold (4째C) water flowing through the storing silos. The system can be used for aggregates with a grain size over 4mm. For each fraction of aggregate two silos must be used. In one silo the hot aggregates are cooled while the other silo is used for the concrete production. The time needed to cool the aggregates is dependent on the water chiller output and the available cold water volume. It is necessary that the silos are waterproof. A crucial point is therefore the metering valves of the silos dosing the aggregates. In the first installation of the aggregate cooling system prototype in Qatar 200 tons of aggregates per hour can be cooled down by 35 K. Using the cooled aggregate and cool water for the concrete production the concrete temperature can be reduced by 20 K. For high quality concrete using a low water/cement ratio it must be taken into consideration that the use of flaked ice in the concrete mixture is very limited. Using 70kg of ice the concrete temperature can be reduced by about 10 K. Using flaked ice will cool mainly the cement mortar while the aggregates in the mixture will still have a higher temperature. Due to the temperature adjustments between
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