الفهرس 
ABSTRACT
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Abstract
Most of R.C. constructions, especially underground, are always subjected to aggressive environmental conditions during their exploitation. These conditions are represented by sulfate attack from surrounding soil or underground water. When cement-based materials are exposed to sodium sulfate attack, gypsum and ettringite are produced by chemical reactions of sulfate and Ca(OH)2, and C3A. Formation of gypsum plays an important role on the damage of materials. According to that, the actual compressive strength of R.C. elements decreases and consequently is accompanied with large deformations. Finally, a higher reduction of the construction durability occurs. So, the need for using as effective and economic admixtures for the protection of concrete elements against sulfate attack or any other decayed environmental conditions is required.