چكيده به لاتين
In the railway industry, sleepers, which are responsible for maintaining the width of the line, distributing and transferring the loads from the rail to the ballast and providing longitudinal and lateral strength, are produced in different types of timber, metal, concrete and composite. Today, concrete sleeper has found a special place in the railway industry, due to its high strength and cost-effectiveness of production. On the other hand, one of the disadvantages of this type of sleepers is its high hardness and low damping ratio compared to timber sleepers. Therefore, it can be said that the production of high strength sleepers such as concrete sleepers with high damping ratio such as timber sleepers can be very suitable and reduce vibrations and increase the life of other components in railway lines. In this thesis, with the aim of increasing the damping ratio and decreasing the compressive strength of concrete, the effect of crumb rubber on some of the dynamic and mechanical properties of concrete and the effect of EAF slag aggregates on the compressive strength of concrete in three stages were investigated. In the first stage, the effect of replacing concrete’s limestone aggregate with slag aggregate on the compressive strength of concrete in 4 mix designs, in the second stage, the effect of replacing powdered EAF slag with cement on the compressive strength of cement mortar in 4 mix designs and in the third stage, the effect of replacing crumb rubber with slag aggregate on some of the mechanical and dynamic properties of concrete were investigated. The results showed that replacing powdered slag with 10%, 25% and 40% of cement, caused 4%, 46% and 48% decrease in 28-day compressive strength of cement mortar. Also, by replacing the limestone aggregates used in the construction of B70 concrete sleepere in Karaj Sleeper Prodoction Factory by EAF slag aggregates, 13% increase in 1-day accelerated curing of compressive strength was observed. And by replacing 5%, 10% and 15% by volume of rubber with fine-aggregate slag materials, resulted in 8%, 21% and 30% decrease in 28-day compressive strength, increase in ultrasonic pulse velocity, decrease of slump and also 5%, 23% and 35% increase of concrete damping ratio. It was found from this dissertation that replacing limestone aggregates with Electric Arc Furnaces slag increases the compressive strength of concrete and replacing rubber powder with this aggregates reduces the compressive strength and increases the damping of concrete specimens.
