Recycling of concrete - Essay Example

Recycling Of Concrete Introduction Concrete is a manmade material that is widely used, making a significant portion of the waste that the world produces. It is extensively used as the basic material for infrastructure and construction1. Engineers and builders commonly use concrete for its durability and high strength which makes it able to withstand huge forces and loads. Global statistics on generated waste is not available. However, statistics from the World Business Council for Sustainable Development show that manufacturers worldwide produce in excess of 25 billion tons of concrete annually.

The Environmental Resource Limited in a study conducted in 1979 forecasted the rise in demolition concrete waste from about 54 million tons in 1980 to over 300 million tons in 2020 by members of the EEC (European Environmental Commission) alone. 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 presence of contaminants in concrete waste is a common phenomenon. During the recycling of airway or highway pavements, contaminants are not an issue. However, urban recycling requires extra care because of the presence of contaminants such as soil, gypsum, vinyl, rubber, plastic, asphalt, wood, and plaster. Contaminants are not a major if the recycled aggregate is to be used as the base course.

However, strict measures must be employed for the recycled concrete aggregates to make sure that the levels of contaminants are not above the permitted levels in virgin coarse aggregate. For instance, if the concrete has D-problems or problems to do with alkali-silica reactivity, the intensity of the problem may control its reuse or place limitation on its use6. The erection of reinforced concrete pavements over the recycled concrete material may at times require special attention in regard to leaching.

Sometimes, the concrete structure to be used for generating recycled concrete material can contain high levels of chloride. This is because of the exposure to high chloride concentration levels during its use. These chlorides can be exposed to the overlying concrete pavement. The movement of these chlorides from the recycled concrete material into the steel-reinforced concrete surface layer can result into corrosion of the reinforcement bars; consequently leading to the breaking of the concrete slabs7.

Conclusion Beyond doubt, concrete waste that is produced as a result of the demolition of old structures and due to natural weathering is bound to increase in quantity as shown by various studies. Without proper disposal, waste concrete can pose great threats to the environment and human health. On the other hand, leaving waste concrete in landfills is shear waste of material that may be put into good use. The use of recycled concrete for new construction is a viable endeavour considering the desirable mechanical properties of the substance.

However, before being used for new construction work, the substance needs to be properly recycled taking keen interest in the removal of contaminants and other undesirable materials. References 1. S.K. Hirokazu et al., An Advanced Concrete Recycling Technology And Its Applicability Assessment Through Input-Output Analysis’, Journal of Advanced Concrete Technology, 3/1 (2005) 53-67. 2. World Business Council for Sustainable Development, The Cement Sustainability Initiative, World Business Council for Sustainable Development, Conches-Geneva, 2009. 3. Environmental Council of Concrete Organization, Recycling Concrete Saves Resources, Eliminates Dumping.

Environmental Council of Concrete Organization, Illinois. 1997. 4. C.Y. Lo, V.W. Tam, and Kotrayothar D. A Simplified Testing Approach For Recycled Coarse Aggregate In Construction, Transactions Hong Kong Institute of Engineers, 16/4 (2009) 43-47. 5. World Business Council for Sustainable Development, The Cement Sustainability Initiative, World Business Council for Sustainable Development, Conches-Geneva, 2009. 6. Environmental Council of Concrete Organization, Recycling Concrete Saves Resources, Eliminates Dumping.

Environmental Council of Concrete Organization, Illinois. 1997. 7. B.J. Blankenagel, ‘Characterization of Recycled Concrete for Use as Pavement Base Material’, Master’s Thesis, Brigham Young University, (2005). 8. Recycling Technology Assistance Partnership, Quality Control for Recycled Concrete as a Structural Fill Material. Recycling Technology Assistance Partnership. Washington. 1998. 9. Department of Environment and Conservation, Concrete Recycling Scheme Ideal Solution for Waste, Department of Environment and Conservation, Sydney South, 2004.