EFFECT OF REPLACEMENT OF AGGREGATES BY DEMOLITION WASTE ON CONCRETE PROPERTIES

摘要

Over the years there has been a change in the use of building materials. Cheap & locally available materials such as moulded earth bricks, stone, thatch, timber, steel, aluminium, plastics and fibers of various types and forms have replaced the traditional costly materials. However, all these materials have been developed to meet specific requirements of climate, availability of skilled labor and specific raw materials to affect the desired economy. Demolition of old structures to make way for new and modern ones is a common feature in metropolitan areas due to rapid urbanization. In many areas, good quality aggregates are not available locally, whereas in some others with rapid urban expansion, aggregate plants have been forced to close down because of enforcement of environmental laws. In such instances it becomes necessary to transport aggregates with the resultant disadvantages. Concrete debris was broken into pieces of about 40 to 75mm by using demolishing hammer. After wards the concrete was fed into the jaw crusher and crushed. The fraction, greater than 4.75mm was considered as coarse aggregate and less than 4.75mm was considered as fine aggregate. Thus, the waste obtained from demolition of structures could be converted into resources for new construction. The present paper makes an effort to prove that the waste from the demolition of structures is supplementary to the housing industry. Recent research indicates that the concrete obtained from the demolition waste can be used to produce aggregates, which in turn can be used for making new concrete of acceptable quality. The Coarse and fine aggregates obtained from recycling the demolition waste can be effectively used for mass concrete in foundation as well as in flooring with great economy. This will not only reduce the transportation costs of aggregates but would also provide a viable solution to the nuisance of the waste obtain from demolition of structures. Design of M_(15) and M_(20) concrete mixes using these aggregates were carried out. Four mixes of recycled concrete waste i.e. fine aggregate and coarse aggregate, were designed and tested for their compressive strength. The experimental results show that the recycled concrete waste aggregates can be effectively used to replace the natural aggregates in concrete.