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Fundamentals of Construction and Demolition (C&D) Waste Recycling

Mohan Ramanathan, B.Tech., M.S. (USA)

Managing Director
Advanced Construction Technologies Pvt Ltd.,

No.16, Cenotaph Road, Teynampet, Chennai 600 018.

 

Synopsis:

Construction activities generate over million tones of construction and demolition (C&D) materials each year.  These materials contain a lot of reusable materials.  If not properly managed, they will become wastes, a burden to the society, which will be extremely expensive to handle and will occupy precious landfill space.  This paper contains an overview of the concept on waste management and how proper waste management plan at the life cycle of construction can reduce its generation, maximize its direct reuse, increase the opportunity for recycling and reduce the need and hence the cost for its disposal as waste. Recycling can turn the otherwise waste materials into usable products.

Mohan Ramanathan MD, Advanced Construction Technologies Pvt Ltd

Which can help conserve our natural resources for our next generations and for the sustainable development of the society.owever, success on recycling takes time and requires a proper waste management plan at global level and the general acceptance of the recycled products.  This paper will cover some overseas experience and the experience in India.

 INTRODUCTION

Construction activities generate huge amount of construction and demolition (C&D) materials each year.  The activities include site formation, tunneling works, demolition of building and structures, decoration and reconstruction works, new construction and maintenance works.  Most of these materials are inert materials such as earth, rocks and concrete, which can be reused or recycled.  Even timbers and wooden materials can be reused or recycled if properly handled.  In the old days, when the materials were scare and expensive in comparison to labour costs, lots of these C&D materials had been salvaged and reused through balance cut and fill, rehabilitation, reclamation, reuse of brick and masonry, reuse of timber and wood to its maximum potential.  With the prosperity and rapid development of a society, the society has become more and more extravagant and less concern on conservation of natural resources.  Factors contribute to this situation are.

1. Lower cost in quarrying of natural resources due to modern machines.
2. Low import cost of aggregates from neighbouring developing regions.
3. Demolition of buildings and structures long before the end of its designed or useful life.
4. Base "use and throw way"  habit.
5. Tight development programme for quick financial return.
6. Improper or lack of waste management.

As a result, lots of natural resources were drained away as waste and required extra expense and resource to handle and accommodate.  Worst still, it will not only create environmental and social problems, the society will consume the remaining natural resources at a much faster rate than is necessary.  There is therefore a need for proper waste management for the sustainable development.

STRATEGY.

In order to minimize the adverse impact, both social and environmental, most developed countries have formulated their own strategies on management of waste at national level.  Such measures include.

1. Mandating adoption of waste management plan at national level, such as in Germany, Denmark and Hong Kong.
2. Setting target on achievement on recycling by stages.
3. Imposing heavy tax on waste disposal.
4. Imposing aggregates tax to encourage use of recycled aggregates
5. Increasing effort in education and information on waste reduction and recycling to identify and exploit the opportunities of recycling and overcome the barriers and obstacles due to conservatism.

Generally speaking, the following strategy in hierarchical orders are adopted by most countries.

1. Minimizing the generation of waste in the first instance.
2. Reusing the C&D materials in its original from as far as possible.
3. Recycling with minimal input of energy.
4. Disposing of the waste environmentally, with waste to landfills.

 

WASTE MANAGEMENT PLAN

For successful implementation of the waste management strategy, it is required to formulate, implement, monitor and review of a Waste Management Plan during the whole life cycle of the projects. In advance countries, such as Germany and Denmark, Waste Management Plan has not only established at corporation level and project level, it has been extended to state level or even high to show the determination and commitment on waste management.

In general, the waste management plan should cover activities at all stages, from conceptual and planning stages, through design and construction stages, and to maintenance and reconstruction stages.  Waste minimization, reuse, recycling and disposal should be well planned and implemented, monitored and reviewed at all stages, with life cycle cost on waste disposal taken into consideration.

In Hong Kong, the Government has issued technical circular requiring the implementation of waste management in public works projects.  The Government is also encouraging the private sector to adopt the same.  In addition, there is also drive to motivate financial incentive on management and reduction of waste by implementation of construction disposal charging scheme.

WASTE MINIMIZATION

Systematic and proper maintenance can slow down deterioration and prolong the useful life of building and structures to delay the process needed for reconstruction.

REUSE

In the old days, people had every endeavour to make the best use materials available and had every incentive to maximize the use of natural resources.  In underdeveloped countries, people treat every piece of masonry, brick or tile, rock and crushed concrete as valuable.  During the demolition, they will take down the bricks and good tiles carefully. striping out the mortar and properly stacked aside for reuse later.  Even in advance countries, wooden doors can be carefully salvaged by adopting selection demolition, with the salvaged doors for reuse or resale in the 2^nd hand market or 3^rd or 4^th world markets.  Wooden planks or timbers can also be trimmed to size for appropriate reuse.  Topsoil can be saved for gardening or landscaping use, while earth or rubble can be reused in site formation or reclamation if feasible.

RECYCLING

Apart from those valuable metals such as steel rebars and aluminum window frames, which have high scrape value, rubbles and demolished concrete can be processed into recycled rockfill or aggregates for use in construction.  To avoid unnecessary waste of energy resources, only those materials with marketable value should be recycled.  In most countries, 90% of the demolition construction materials consist of concrete and masonry, which are recyclable.  Depending on the types of construction, some buildings were made of mostly masonry while some others were made mostly with concrete.  To avoid mixing recyclable materials with non-recyclable one, it is recommended to separate them at source by selective demolition and on-site sorting, as sorting highly mixed materials at the receiving ends is extremely expensive and not environmental friendly.

RECYCLING PRACTICE

Although different countries adopt different practices to suit their own situations, the recycling practices can be broadly classified in the following categories.

Adopting on site recycling and reuse with minimal import and export of construction materials for large reconstruction projects.

Examples:

During the reconstruction of super highways (outbound) in Germany, old concrete pavements were broken up and processed at a pre-planned nearby recycling site, with recycled aggregates used in producing concrete Grade 45 in an adjacent batching plant for use in new pavement construction.  The advantages of this arrangement are:

1. Minimal export of waste and minimal import of raw materials
2. Minimal addition of traffic loading on existing busy road networks.
3. Energy saving due to reduction on fuel consumption by lorries.
4. Reduced noise and air pollution due to least generation of traffics and fuel consumption.
5. Maximization on the recycling potentials and values due to no mixing of high quality demolished materials. 
6. Adopting on site crushing with recycled products used in other projects or for re-sales.
7. Collecting and stockpiling recyclable materials, then hiring mobile crushers for processing.
8. Establishing centralized recycling facilities.
9. Establishing recycling facilities within landfill site, with truck delivering C&D materials into the landfill site and collecting recycled products at exit (e.g. Denmark)

APPLICATIONS

Based on overseas experience and the experience in Hong Kong, recycled aggregates have lots of applications, running from high value applications such as use in concrete production and manufacture of concrete paving blocks and kerbs, to low end use as road sub-base materials, rockfill, filters, pipe bedding, in-fill to stone columns. However, the acceptance in high value application is slow in most parts of the world due to barriers and obstacles arising from conservatism and lack of confidence in using new construction materials. Fortunately, the American Concrete Institution (ACI) and the European Union in the frame of RILEM" have been far-sighted enough to establish ground works on sustainable concrete with use of recycled aggregates. In Hong Kong at least 4 ready mixed concrete producers have experienced in producing recycled concrete up to Grade 40 for use in public works projects despite a slow start of using recycled aggregates in concrete production.

PROMOTION

Acceptance on using recycled materials takes time and promotion is required. Some overseas countries have taken 10 to 15 to develop the markets on recycling. In order to overcome the barriers and obstacles arising from conservatism and lack of confidence, education and information are the most important means to identify and exploit the opportunity on promoting recycling. It is necessary that the message and understanding of recycling be discussed at universities, technical institutes, amongst enterprises and public servants. Information centre should be set up for the transparent sharing of information and know-how on the development and use of recycled aggregates. In Hong Kong, the Government has taken the lead to liaise with the key players including concrete producers, contractors, academics and government department to collect information such as test data and research results for disseminating via the web connection

CONCLUSION

Natural resources are not unlimited and will be depleted with time. Unnecessary wasting of natural resources should be restricted and regulated. Formulating and implementing proper waste management plan throughout the life cycle of the projects can minimize waste. With an integrated resource management, most of the construction and demolition material can be recycled and more natural resources can be conserved for our next generations. The success on recycling and using recycled materials in high value applications required promotion by means of education and information, in addition to statutory mean.

Mohan Ramanathan, B.Tech., M.S. (USA)

Managing Director
Advanced Construction Technologies Pvt Ltd.

No.16, Cenotaph Road, Teynampet, Chennai 600 018.

Acknowledgements

Mr. Winston F.K, Fong

Reference:

1. Chan, S.Y. and Fong F.K., "Management of Construction and Demolition Materials and Development of Recycling Facility in Hong Kong " Proceeding of International Conference on Innovation and Sustainable Development of Civil Engineering in the 21^st Century, Beijing HKIE, July 2002.
2. Cheng, N.T., Technical Note 2/2000: Investigation of Opportunities for Recycling Inert Construction and Demolition Material in Hong Kong. Civil Engineering Department, HKSAR Government, June 2000. Civil Engineering and Development Department, Guidelines for selective Demolition & On Site Sorting,  Government, July2004.HKSAR
3. ETWB Technical Circular Works No. 15/2003 - Waste Management on Construction Site, Environmental, Transport and works Bureau, HKSAR Government, 15 May 2003.
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