الفهرس 
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Abstract
In the last two decades an increasing interest can be observed for utilizing waste tires in cementitious composites. This research aims to study the effect of implementing various types of rubber particles as additives to concrete at low volume fractions. In addition rubber particles were implemented into concrete as sand replacement by volume at high portions. Also, several methods were used to enhance the interface interaction between rubber particles and cement matrix by the use of pretreated rubber particles and the addition of silica fume.
In the first part of the study, a total of 30 mixtures were cast; three mixtures were cast as control with no additives and the other 27 mixtures were designed using fractional factorial method of experimentation to study the effect of five parameters, each at three levels, on mechanical properties of concrete; three concrete grades (C20, C25 and C30), three rubber volume fractions as an additive to concrete (0.5%, 1.5% and 2.5%), three types of additives (without, polypropylene fiber 0.2% and 10% silica fume as cement replacement by weight), three types of rubber particles (4mm granules and two types of rubber fibers with different aspect ratios) and three types of surface treatments for rubber particles (rubber treated with NaOH solution, Plain rubber and rubber treated with Polyvinyl Acetate “PVA”).
Results showed that the use of silica fume significantly eliminates the reduction in compressive strength for rubberized concrete, while the addition of polypropylene fiber enhances ductility and impact resistance. Also the intrusion of rubber particles as an elastic material to concrete improves impact resistance especially when rubber fibers are used. In addition, rubberized concrete improves flexural toughness comparing to conventional concrete.
In the second part of the study, rubber was used at high portions in concrete as sand replacement by volume. Also, the properties of rubber-cement and rubber-epoxy composites were investigated. from the test results, it can be conducted that rubber composites seem to be very promising in terms of sound and thermal insulation. Also, the rubber-epoxy composites obtain high flexibility, in spite of the low compressive strength.