m.r sadri - Chief of laboratory of Zirdan RCC dam; Jahan Kowsar Construction Company
h.r araghian - Concrete technology advisor of Zirdan RCC dam; Jahan Kowsar Construction Company

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 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 Type 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.

Khash Natural Pozzolan, Compressive Strength, RCC, Zirdan Dam