04-05-2012, 02:19 PM
Use of RECYCLED AGGREGATES In CONCRETE
Use of RECYCLED AGGREGATES In CONCRETE.doc (Size: 168 KB / Downloads: 263)
Introduction
Any construction activity requires several materials such as concrete, steel, brick, stone, glass, clay, mud, wood, and so on. However, the cement concrete remains the main construction material used in construction industries. For its suitability and adaptability with respect to the changing environment, the concrete must be such that it can conserve resources, protect the environment, economize and lead to proper utilization of energy. To achieve this, major emphasis must be laid on the use of wastes and byproducts in cement and concrete used for new constructions. The utilization of recycled aggregate is particularly very promising as 75 per cent of concrete is made of aggregates. In that case, the aggregates considered are slag, power plant wastes, recycled concrete, mining and quarrying wastes, waste glass, incinerator residue, red mud, burnt clay, sawdust, combustor ash and foundry sand. The enormous quantities of demolished concrete are available at various construction sites, which are now posing a serious problem of disposal in urban areas. This can easily be recycled as aggregate and used in concrete. Research & Development activities have been taken up all over the world for proving its feasibility, economic viability and cost effectiveness.
International Status
The extensive research on recycled concrete aggregate and recycled aggregate concrete (RAC) as started from year 1945 in various part of the world after second world war, but in a fragmented manner. First effort has been made by Nixon in 1977 who complied all the work on recycled aggregate carried out between 1945-1977 and prepared a state-of-the-art report on it for RILEM technical committee 37-DRC. Nixon concluded that a number of researchers have examined the basic properties of concrete in which the aggregate is the product of crushing another concrete, where other concentrated on old laboratory specimens. However, a comprehensive state-of-the-artdocument on the recycled aggregate concrete has been presented by Hansen & others in 1992 in which detailed analysis of data has been made, leading towards preparation of guidelines for production and utilization of recycled aggregate concrete.
Indian Status
There is severe shortage of infrastructural facilities like houses, hospitals, roads etc. in India and large quantities of construction materials for creating these facilities are needed. The planning Commission allocated approximately 50% of capital outlay for infrastructure development in successive 10th & 11th five year plans. Rapid infrastructural development such highways, airports etc. and growing demand for housing has led to scarcity & rise in cost of construction materials. Most of waste materials produced by demolished structures disposed off by dumping them as land fill. Dumping of wastes on land is causing shortage of dumping place in urban areas. Therefore, it is necessary to start recycling and re-use of demolition concrete waste to save environment, cost and energy.