In as much as concrete is useful for various construction activities, it makes a huge percentage of the clutter found in landfills. In other words, most of countries generate construction and demolition waste (C&DW) and a bigger proportion of the waste are concrete. There is considerable regional difference because of the construction traditions, thus, the amount of concrete in C&DW ranges between 20 and 80 percent2. Concrete takes a long time to breakdown and is usually an eyesore when left in the open or when not properly disposed. Options for Dealing with Waste Concrete When old buildings are demolished, they always produce large quantities of debris and concrete waste. Most of the waste concrete is recycled due to various reasons such as the increase in the tipping fees by the local governments in attempt to reduce the dumping of waste into the landfills3. Before being recycled, the concrete waste must be sorted and items such as rebar and others made of steel removed. The final product of recycling process of concrete waste is referred to as the recycled aggregate. Recycled aggregate constitutes a large portion of construction and demolition waste (C&D waste)4. The properties of concrete are relatively unique and its recovery revolves around standard definitions such as recycle and reuse. Reuse of concrete is practically impossible because it lacks its original properties. Recycling entails breaking down the concrete into aggregate or smaller blocks which can be used in a new form.
Recycling of concrete is a common phenomenon in many countries and these countries possess well-established concrete recycling industries. Most of the concrete is crushed and used as aggregate5. Uses and Benefits of Recycled Concrete The aggregate is always used as fill material, for structural paving or as a substitute for gravel or natural aggregate. Recycled concrete can also be used to fill plant beds, provide protective beds for laying pipes on large scale for water and sewerage systems. The cost of recycled concrete in some regions is relatively cheap compared to the natural aggregate (the cost is 20 to 30 percent less) 8. The recycling of concrete is especially made easy considering its low toxicity. Recycled concrete has an advantage over virgin concrete in that it weighs between ten and 15 percent less but maintains similar performance levels in both cases. The reduced weight of recycled concrete is an advantage considering the hauling fees, reduced strain on surrounding structures and building equipments. Furthermore, a foundation built of the recycled material is smaller and less complex. A case study done by Pumpdump Pty Ltd indicates that recycled concrete has environmental gains; pollution incidents were absent, there was significant reduction in the labour costs and the time wasted in cleaning up was minimized9. Thus, recycling of concrete is worthwhile since it benefits the construction industry and it keeps the environment clean. Considering the facts above, there seem to be a great potential in using recycled concrete for new constructions. This is especially the case considering that most of the product is basically aggregate. Contaminants and Other Problems The