دانلود رایگان مقاله انگلیسی بررسی مصالح بازیافتی در کاربردهای بتن - الزویر 2018

abstract

Solid waste has been an inevitable by-product of the operations of industrialised societies. One result of economic growth is an increase in generation of solid waste which normally was dumped in landfills and caused contamination of soil, water and air from toxic substances such as polychlorinated bi-phenyls (PCB’s), asbestos, construction chemicals, heavy metals, but the scarcity of land-filling areas, industrial growth as well as strict environmental regulations in developed and developing economies has led to the global re-assessment of the methods employed to recycle and utilise construction and demolition (C&D) waste as recycled aggregate for civil engineering projects i.e. construction and infrastructure development. Depending on their quality, recycled aggregate produced from C&D waste can be employed in various civil engineering works, which can help in a long way the economic and environmental sustainability of respective countries. With further research and development into overcoming technical as well as market barriers, considerable increase in recovery rates can be achieved with the existing technologies in developed economies. The main aim of this study is to review the literature on the production and utilisation of recycled aggregate in concrete, concrete pavements, roadway construction, and other civil engineering works and some discussion on the savings on CO2 emissions have been included. The globally published data on recycled aggregate standards (normative documents) of various countries have been systematically analysed and evaluated, and some barriers mentioned. This review may help to alleviate the concerns of consumers and encourage and further promote the use of recycled aggregate on a larger scale in civil engineering projects.

11. Conclusion

Use of recycled aggregate in concrete provides a promising solution to the problem of construction and demolishing waste. The major quantity of recycled aggregate at present is used in lower end applications, however in some developed economies; it is also used in structural concrete, due to its quality which is certified and bears Confirmite Europeenne (CE) Certificate. The standards (normative documents) regulate and maintain the quality and provide producers as well as the users, an assurance of the consistent quality of the recycled aggregate. China and India at present are the major consumers of construction aggregate and hence have high potential for recycling and re-use of C&D waste, however, despite its potential, there is huge variation in the level of recycling and material recovery in various countries around the world e.g. Brazil (6.14%), Denmark (94%), Netherland (98%). This variation is due to vast differences in construction traditions, the legislation on landfills and due to the perception and acceptance level of constructors and builders. Comparison in tabulation form of the Standards (normative documents) from various countries have been presented to provide producers, consumers as well as researchers a wider outlook on the characteristics of recycled aggregate which are desired and specified in legislation of those countries. To alleviate the concerns of consumers related to durability performance of concrete produced from recycled aggregate, it is suggested that with further research and development, improvement in legislation and by inclusion of durability factors, such as deformation (shrinkage and creep) and permeability (carbonation, air and water penetration and chloride ingress) in the legislation, will help in improving the acceptance level and usage of recycled concrete applications and assist in turning recycling as one of the important components for sustainable development.