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This chapter is literature review on the study of recycling of construction materials in construction industry. This study was undertaking more specific subjects on the application, benefits and concept of recycling of construction materials. Therefore, it was study further on the application, benefits, procedures, barriers of recycling of construction materials, and the strategies to enhance recycling. The literature recourses were search from the reference books and journals article that getting from the internal research and library.
In the practical construction industry, majority of the construction and demolition wastes are disposing off site or on site. The ways of disposal for these wastes is landfills or burn. However, some of the construction and demolition wastes which are recyclable that will be separate on site for further processing and recycling. The recycling is the most effective and efficient method to reduce the construction and demolition wastes.
Concrete rubble from the construction and demolition wastes is also recyclable. Most of the recycled concrete rubble is use as aggregate which is to be mix with cement and sand to form the new concrete. Besides that, concrete waste also has a potential of being recycled as the road base, hardcore, sub-base, general filling, paving stone, and drainage media. Concrete waste is more suitable than the brick wastes to be form as the aggregate and supporting agent because it is stronger than the brick.
The construction and demolition works produced a large quantity of wood and timber waste for every project in the construction industry. The wood and timber waste was produced from broken and unusable timber formwork, door member and window frame. However, the wood and timber waste can be recycle and reuse in the construction industry. After the demolition works, the unbroken wood and timber can be reuse directly in other contraction project after cleaning and nail removing. The wood and timber waste can be recycle as furniture, wood bench, timber staircase, wood base panel, insulation board, and roof member. The furniture make by the wood and timber waste is recycled as chipboard first and then manufacture to be the furniture. In addition, there is an idea that the wood and timber waste maybe able to recycle as energy, such as fuel for the power generation.
For ferrous metal, it is usually almost 100 percent of the steel wastes produced in the construction industry are used to recycling to avoid material wastage. In addition, the steel is able to be recycled and reuse for more than one time. Normally, the scrap steel produced from the construction work can be reuse directly in other construction works. If it is unsuitable to reuse directly, it will be recycle the scrap steel by melting it to reproduce the steel. Recycled scrap can be use as new steel reinforcement, steel section, framing connectors, nails, structural framing, and steel formwork.
The recycling of construction waste can save the overall construction project cost. The materials cost can be decrease substantially through the recycling by the substitution from the new materials to recycled materials in the construction industry. In addition, recycling also decrease the disposal and transportation cost for the construction wastes. Since most of the construction wastes is going to be recycle, thus the amount of waste is reduce so as to save the additional disposal and transportation cost. Furthermore, recycling save the construction cost by using the construction wastes which will otherwise be lost to landfill sites.
The three main categories of collection are drop-off centres, buy-back centres and curbside collection. Drop-off centres require the construction staffs to carry the construction wastes to a central location, either an installed or mobile collection station or the reprocessing plant themselves. Buy-back centres differ in that the construction wastes are purchased by the manufacturers to recycling, thus providing a clear incentive for use and creating a stable supply. The post-processed material can then be sold on, hopefully creating a profit.
The curbside collection encompasses many subtly different systems. The main categories are mixed waste collection, commingled recyclables and source separation. The mixed waste collection is all wastes are collected mixed in with the rest of the waste, and the desired material is then sorted out and cleaned at a central sorting facility. In a Commingled system, all wastes for collection are mixed but kept separate from other waste. Source separation is where each material is cleaned and sorted prior to collection.
Once mixed construction wastes are collected and delivered to a central collection facility, the different types of materials must be sorted. This is done in a series of stages, many of which involve automated processes such that a truck-load of material can be fully sorted by using lesser time. Furthermore, some plants can now sort the materials automatically without using any manpower.
Purchasing the construction recycling product is an important part of the recycling work. It is to avoid the surplus of supply of the recycling product and cause the wastage to it. Before recycling product been manufactured, the surveying of the demand on those recycling product is important to ensure that the product is required and useful to the contractor. In this case, the construction industry is playing an important role to promote and use the recycling product to enhance the recycling.