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۱Laboratory Studies for Selection of a Suitable Chemical Admixture in Zirdan RCC Dam
نویسنده(ها): ،
اطلاعات انتشار: نخستین کنفرانس بین المللی تکنولوژی بتن، سال
تعداد صفحات: ۷
The use of chemical admixtures in hydraulic–cement concrete mixtures has been common in recent decades for different purposes. Zirdan dam as the 2nd reservoir RCC dam in Iran has about 220,000 m3 conventional vibrated concrete (CVC) –including mass and reinforced conventional concrete– and 280,000 m3 roller compacted concrete (RCC). Due to the hot climate of Zirdan district, suitable admixtures should be used to prolong workability and reduce the cementitious content and help prevent thermal problems. Some different kinds (brands & types) of plasticizers and super–plasticizers were tested in the dam local laboratory. Retarding effects of admixtures were tested also. The test program included normal consistency test of cement paste plus admixtures and making some trial concrete mixtures to investigate water reducing effect and compressive strength. Eventually the selected admixtures due to technical aspects had been compared economically. After the laboratory testing stage, the two top selected admixtures have been brought to dam site and used in a site test to finalize the best option. In this paper the commercial name of admixtures and their producers will not be mentioned and just be named A, B, C and etc.<\div>

۲Study the Effect of Khash Natural Pozzolan on Long–Term Strength Development of Different Types of Concrete in Zirdan RCC Dam
نویسنده(ها): ،
اطلاعات انتشار: نخستین کنفرانس بین المللی تکنولوژی بتن، سال
تعداد صفحات: ۸
The use of pozzolanic materials in concrete mixtures has been common in last decades that bring about some technical and economical benefits such as prevention of alkali aggregate reactions, reduction of permeability of concrete, reduction of the heat of hydration if used as replacement. All of these benefits are regarded to dense microstructure of concrete and chemical reaction of lime and silica when used as pozzolanic materials.In Zirdan RCC dam, due to alkali reactivity of natural aggregates and necessity of reduction of heat of hydration for mass structures, use of pozzolanic materials was a good solution. The nearest source of pozzolan is Taftan natural pozzolan that feeds Khash cement factory to produce pozzolanic blended cement and ground pozzolan. In this paper the effect of Taftan (usually named Khash natural pozzolan) as a Type N pozzolan will be discussed based on different laboratory tests and results obtained during concreting. The results show an average compressive strength development coefficient of 35%, 25% and 10% consecutively for 28\7 day, 90\28 day and 180\90 day. Eventually for attaining economical benefits and because of later ages of loading on the structures, the specified compressive strength ages from 28–days for conventional vibrated concrete (CVC) and 90–days for roller compacted concrete (RCC) could be increased to 90 and 180–days respectively.<\div>
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