خلاصة:
In recent decades, manufacturing of tires have been rocketed. The main cause of this process is development of automobile industry in worldwide, so the high volume of scrap tires has been created massive stockpiles zones. Furthermore, environmental threat related to waste tires, and disposing them properly has come to a world crisis, due to the requirement more spacious storage than other wastes and the massive volume and their fixed shape. Therefore, there is immediate and effective need of recovering and reusing waste tires.
Waste tires have efficient applications in engineering, especially mortars and concrete. The results of various investigations have demonstrated that rubberized self-compacting concretes show lower compressive strength, modulus of elasticity, stiffness, rheological properties, fracture energy, durability, flexural strength, ultrasonic pulse velocity etc. and higher deformability before failure, saving in cement and aggregate usage, dynamic properties, strain capacity, fatigue strength etc. Therefore, adding waste rubber into self-compacting concretes leaves a numerous positive and negative impacts on its properties.
In this paper, authors present an overview of literature investigating of waste rubber used as an additive or fine and/or coarse aggregate replacement in self-compacting concrete with special attention on positive and negative influences on fresh and hardened self-compacting concrete properties.
ملخص الجهاز:
The results of various investigations have demonstrated that rubberized self-compacting concretes show lower compressive strength, modulus of elasticity, stiffness, rheological properties, fracture energy, durability, flexural strength, ultrasonic pulse velocity etc.
C. Bignozzi and co-workers [12] prepared rubberized self-compacting concrete(SCC) containing different amounts of untreated tire waste and their mechanical and microstructural behavior were investigated.
(به تصوير صفحه مراجعه شود)Fig2- Compressive relative strength as function of tire rubber volume in concrete [12] They published their results as below: - SCRC (self-compacting rubberized concrete) requires slightly higher amount of superplasticizer than SCC to reach self-compacting properties, keeping constant water/cement and water/powder weight ratios.
(به تصوير صفحه مراجعه شود)Fig11- Relationship between chloride ion permeability and water absorption [19] SholihinAs’ad and his collogues [21] held an experiment with the aim of getting the fresh state behavior of self-compacting concrete containing waste material fibers such as, plastic bottle, rubber tire and alloy cans.
(به تصوير صفحه مراجعه شود)Fig16- Compressive strength for SCRC [23] - When 5% waste tire rubber powder was added the 28 days ultrasonic pulse velocity was 4000 m/s and that of the other samples were more than 4000 m/s.
(Fig. 23) (به تصوير صفحه مراجعه شود)Figure23-Variation in the compressive strength with respect to rubber replacement level [26] Saeid Hesami and his co- workers [27] studied on the mechanical behavior of self-compacting concrete pavements incorporating recycled tire rubber crumb and reinforced with polypropylene fiber.