By: Briejsh Parekh / Clarissa Aguiar / Leandro Arcuri

 

FIRST, ONE QUESTION: WHAT IS CDW?

Construction and demolition waste (CDW) is one of the heaviest and most voluminous waste streams generated In North America. It accounts for approximately 20% – 25% (Figure 1) of all waste generated and consists of numerous materials, including concrete, bricks, gypsum, wood, glass, metals, plastic, solvents, asbestos and excavated soil, many of which can be recycled. CDW arises from activities such as construction of buildings and development of civil infrastructure, total or partial demolition of buildings and civil infrastructure, road planning and maintenance. In some countries, even materials from land levelling are regarded as construction and demolition waste.

 

CDW SOURCES & DISPOSING

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REDUCING CDW

The traditional handling of CDW represents a lost opportunity. Most of this material is not waste, but a valuable resource. As the cost of construction materials escalates due to dwindling virgin resource availability, many of the materials that we throw away are becoming increasingly valuable. Almost everything – from concrete and lumber, to electrical wiring and plumbing fixtures – can be reused or recycled. The purpose of separating CDW is that there will often be markets for certain items, but once mixed or contaminated, these materials have lost their value.

REUSING CDW

Materials can be reused in a number of ways. Proper planning before beginning of the project will help to implementation an effective waste reduction program.

In construction related projects, the design phase allows for the use of materials that have been deconstructed elsewhere. Materials may be reused on or off-site, or for a similar or different application of its original function.

RECYCLE CDW

In some situations materials cannot be reused. When this occurs, waste reduction can still be achieved by recycling. The waste reduction work plan should also identify materials for which recycling opportunity exist. The work plan should contain a list of potential recyclers.

 

CDW MATERIALS & SOLUTIONS

 

AN EXAMPLE OF SUCCESS

This case of study presents a case of building a shopping centre in Recife of 255,500 m².

The excavation residues of 4,000 helical foundation piles and the demolishion residues from old existing warehouses were transformed into recycled aggregates with a mobile plant installed at a worksite. Recycled aggregate was used in the layers of the paving work (regularization of the terrain and sub-base).

A total waste (soil deriving from piling + demolition) of 66.082 tons. If all this material was taken to a licensed landfill, the cost of provision would be of US$28.00/ton, or a total of US$1.9 million, besides environmental costs.

The Figure 1 shows the gravimetric composition of CDW. It is observed that it was predominantly concrete. The Figure 2 shows excavated soil composition. It was observed that sandy soils is 85% of total soil composition.

In order to use excavation and demolition waste in the paving stage of the project, the following actions were established:

  • Processing of waste from demolition (CDW) of the warehouses through a mobile unit installed at the construction site (Figure 3).
  • Separation and storage of excavated soil in the implementation of continuous helical piles; (Figures 4 and 5)
  • Conduction of laboratory tests to characterize the CDW and the excavated soil (Figure 6).

 

To study economic feasibility of reusing CDW in paving stage of the project, detailed estimate was created, values are shown in Table 1.

Table 2 shows costs for the disposal at two sites, both licensed by environmental agencies. Both are located in the Metropolitan area of Recife.

 

Therefore, for the calculation of the financial impact from use of the investigated materials in paving project, two scenarios for reuse of waste were considered:

Scenario 1: all the CDW is taken to the processing mill for recycling, and the pile soil is deposited in the inert landfill. The layers of paving are executed with natural aggregates;

US$2,2million

Scenario 2: use mixture of pile soil with CDW in the regularization of the terrain and the sub-base layer. The base layer is performed with the remaining available CDW and another portion of natural aggregate (SGG).

US$ 320,498.21

In conclusion, the sustainable work was US$ 1.9 million cheaper than conventional construction, showing the potential of the “green economy”.

To sum up:

  • Reduces the production of greenhouse gas emissions and other pollutants by reducing the need to extract raw materials and ship new materials long distances;
  • Conserves landfill space, reduces the need for new landfills and their associated cost;
  • Saves energy and reduces the environmental impact of producing new materials through avoided extraction and manufacturing processes;
  • Creates employment opportunities and economic activities in recycling industries;
  • Saves money by reducing project disposal costs, transportation costs, and the cost of some new construction materials by recycling old materials onsite.

REFERENCES

Arcelor Mittal – Meet the sustainable construction challenge: ArcelorMittal steel solution benefits Retrieved from: http://ds.arcelormittal.com/construction/germany/download_service/sustainable_construction_with_steel/language/EN

Christowam, F. (October 2015) Instituto de Engenharia – A utilização do aço na construção civil. Retrieved from http://www.insti tutodeengenharia.org.br/site/noticias/exibe/id_sessao/4/id_noticia/9566/A-utilização-do-aço-na-construção-civil

Farias, A. (2013). Technical and Economic Analysis of Construction and Demolition Waste Used in Paving Project. Paris:18th International Conference on Soil Mechanics and Geotechnical Engineering

Ferrara, I. (June 2008). Illegal Disposal of Commercial Solid Waste: A Dynamic Analysis., Vol. 36, No. 2. USA: Atlantic Economic Journal

Freeman, J. (2007). Moving to Markets in Environmental Regulation: Lessons from Twenty Years of Experience. USA: Oxford University Press.

Gusmão, A. D. (2008). Manual de Gestão dos Resíduos da Construção Civil. 1a Edição. Brazil: Editora Camaragibe.

Vaughn, J. (2009). Waste Management: A Reference Handbook (Contemporary World Issues). Santa Barbara: ABC-CLIO.