الفهرس 
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Abstract
In view of the increasing use of pozzolanic materials in hydraulic binders, there is a great interest in producing of blended cements; namely, pozzolanic and pozzolnic-filled cements. The use of these blended cements have increased in several countries due to economical and ecological considerations. The aim of this investigation is to study the pozzolanic activity of fly ash in cement pastes as well as in pozzolanic and pozzolanic limestone-filled cements.
The effect of replacement of cement by fly ash with amounts of 10, 20 and 30 mass% on the properties of pozzolanic cement pastes was investigated. The hydration of these pozzolanic cement pastes was studied by the determination of initial and final setting times, bulk density, total porosity and compressive strength. The degree of hydration was also followed by the determination of chemically combined water, insoluble residue and free lime contents during the hydration of the hardened cement pastes up to 90 days. The hydration products were also investigated by DTA, IR-absorption spectroscopy as well as XRD techniques.
The effect of substitution of limestone for fly ash on the hydraulic properties of pozzolanic-filled cement pastes was also investigated. It was concluded that the addition of limestone reduces the initial and final setting time as well as total porosity, whereas the free lime and combined water contents increase with limestone content. It can be concluded that limestone fills the pores between cement particles due to the formation of calcium carboaluminate hydrate as well as limestone grains act as nucleation sites for the reaction products, which may accelerate the setting of cement pastes. On the other side, fly ash has a slow pozzolanic activity.