الفهرس 
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Abstract
The exposure conditions for concrete in the middle east contitute one of the most aggressive climatic enviroments in the world the large fluctuation in the daily and seasonal temperature conditions causes a physical disintegration and microcracking of concrete. For, examples, the tempertaure varies as much as 20 c during a typical summer`s day.This rabid and continouos variation causes cycles of expansion/contraction and hydration/dehydration result im microcracking and damage due to thermal incompatibility of concrete.
It has been suggested that using silica fume and ground granulated blast-furnace slag for partial replacement of portland cement can minimize these concreting problems, arising from hot weather.
The current study investigated the effect of thermal cycles on various parameters of OPC mortars made with and without silica fume and ground granulated blast furnace slag with and without different types of chemical admixtures.The studied parameters included flowability of fresh mortars and water absorption,moisture loss, compressive strength, ultrasonic pulse velocity and lenght change.
It was observed from flow table test on mortars of this investigation that the flowability of OPC mortars redued with the increasing of SF content and GGBS content.The moisture loss and % absorbed water increased with the increase in pozzolomic materials content.
The use of either 5% or 10% SF in mortar increased the compressive strenght of samples exposed to cyclic heating, However, higher percentages of SF had an adverse effect on compressive strength.
The GGBS mortars exhibited a reduction in compressive stength when exposed to cyclic heating.Admixture type D, G and F are beneficial from the strength point of view under cyclic heating conditions.
The use of SF and GGBS increased the tendency to internal cracking and shrinkage, as shown from the UPV and length changes meaurements, under cyclic heating conditions.Extra care is, therefore, needed when using these materials in enviroments with fluctuating temperatures.