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Construction and demolition are the two terms that are opposite to each other that is construction leads to formation of new structure and demolition is the tearing down of buildings and other structure. Deconstruction involves taking a building down while carefully preserving valuable elements that can be reused. Demolition and construction process also lead to wastage which contain elements that are used in building construction along with many other hazardous substances that may contain lead or other chemicals which are harmful to the environment. Many techniques are used to minimize harmful effects of deconstruction.
Demolition is the process that is just opposite to that of construction. That is deconstruction. For small buildings that are structure having two or three stories demolition is simpler than that of larger structure. There is manually or mechanical way to pulling the building by using hydraulics, bulldozers or cranes.
Wrecking ball is used to demolish the larger buildings. It is a heavy weight on a cable which is swung by the crain into side of the building. Wrecking balls are very effective, but are difficult to control and often less efficient than other methods.
Many new methods use rotational hydraulics shears and silenced rock breakers attached to excavators to cut or break through wood, steel or concrete.
1.2 Building implosion:
Large buildings, tall smoke stakes, chimneys and some smaller structures are decimated using heavy explosives substances. Imploding a building is very fast method. The fall it takes only seconds and an expert can ensure that the building falls into its own footprint and no damage is done to the neighboring structures. This is beneficial for tall structures in dense urban areas.
Any sort of error can create disaster if a demolition is failed, it can severely damage neighboring structures. The greatest danger is from flying debris from the falling building which can flew to a distance.
Partial failure of an attempted implosion is most dangerous. When any structure fails to demolish completely the structure can be unstable, it can be tilted at a dangerous angle, and could be filled with un-detonated but still primed explosives, making it dangerous for workers to approach safely.
Demolition is the new approach towards deconstruction with a single goal of minimizing the amount of waste materials going to landfills. With the rising costs of landfills this method is usually more economical than traditional demolition, and contributes to a healthier environment. This approach is implemented by extracting the materials by their type and seperating them for reuse or recycling. Wooden waste can be shredded using timber shredders and composted, or used to manufacture timber boards.
It take some time before demolition of any structure. All the valuable items are taken out from the building. Some material that is essential to remove such as glass that can have deadly projectiles must be removed. Then some parts of the building are chosen and drilled to put TNT and other explosives for detonation. Than the process of demolition takes place.
2.1 Construction and demolition wastage
Construction waste is the waste that is generated accidentally in the construction process .this wastage includes construction material such as nails, wiring, rebar. Many wastage elements are also produced during site preparation such as dredging materials and tree stumps. Most of the wastage contains materials such as bricks, concrete and wood damaged or unused material during the construction [Sherwood,1995].Certain components from the wastage material are dangerous such as Pasteboard broken into landfills and causes hydrogen sulfide which is an toxic gas.
Demolition waste is originated during process of demolition. This waste consists of insulation, nails, electric wiring, wood concrete and bricks. It may contain asbestos or lead or different hazardous substances.
Certain components from the wastage material are dangerous such as Pasteboard broken into landfills and causes hydrogen sulfide which is a toxic gas.
There are some rules by the government and the local authorities about how much waste should store before through away in landfills or other waste treatment facilities. many dangerous substances can't be moved without permissions. Among their concerns would be the proper handling and disposal of such toxic elements as lead, asbestos or radioactive materials.Â Â Â Â Â Â Â
2.1 Dealing with the Demolition & Construction wastage
The wastage produced by the construction and demolition process must be dealt as it should be removed from the site and dumped. But there are some rules by the government and the local authorities about how much waste should store before through away in landfills or other waste treatment facilities. Many dangerous substances can't be moved without permissions. Among their concerns would be the proper handling and disposal of such toxic elements as lead, asbestos or radioactive materials.
The main motive of waste management to reduce the waste produced in c&d process. This follows the philosophy of sustainable development, which requires us to use scarce natural resources more efficiently and minimize the overall environmental impacts of wastage management.
The management of handling the construction and demolition wastage depends upon the type of wastage that is produced during c&d process.
During construction, renovation and demolition activities, you may produce one or more of the
- Clean fill.
- Recovered materials.
- Regulated construction and demolition waste.
- Hazardous materials and hazardous wastes.
- Asbestos-containing materials.
- Different Management techniques differ for each of these.
3.1 Clean Fill:
Clean fill is “uncontaminated soil, rock, sand, gravel, concrete, asphaltic concrete, cinder blocks, brick, minimal amounts of wood and metal and inert (non-reactive) solids...for fill, reclamation or other beneficial use” Minimal means the smallest amount possible. For example, concrete containing wire mesh or rebar may be used as clean fill. However, exposed rebar must be removed before use. Under no circumstances are roofing shingles, sheet rock, wood waste or other construction and demolition wastes defined as clean fill[Mroueh:2002].
Concrete, cinder blocks, bricks or other clean fill materials that are painted with non-heavy metal-based paints are also considered clean fill. It is the generator's responsibility to determine if the painted materials are hazardous wastes. The most typical contaminants are lead and other heavy metals. This determination can be made by representative sampling or by applying historical knowledge of the materials in question.
If asphaltic concrete is to be used as clean fill it is recommended that it not be crushed or ground any smaller than necessary. This will help to minimize the leaching of chemicals found within the asphaltic material.
Although not regulated as waste, placement of clean fill materials may be subject to requirements of the Missouri Department of Natural Resources' Water Protection Program if it is placed in contact with surface or subsurface waters of the state, or would otherwise violate water quality standards.
3.2 Recovered Materials
Recovered Materials are those removed for reuse (lumber, doors, windows, ceramic tile and glass) and those removed to be recycled into new products. Potentially recyclable construction and demolition wastes may include scrap metals, asphalt shingles, sheet rock, lumber, glass and electrical wire[ Sherwood,1995]. However, it is important to remember that recovered waste must be used in some way.
Separating out certain wastes to be recycled into new products without having a market for them is expensive and pointless. Storing recovered materials indoors is expensive. Storing them outdoors may lower their value, since most will degrade or deteriorate when exposed to the weather. Depending on how they are stored, they may harbor rodents, provide breeding grounds for insects or be a potential fire hazard. Recyclables may not be collected and dumped on the ground while waiting for markets to develop. Therefore, before you deliver recyclable materials to a processing or recovery facility be sure the facility is legitimate.
The department's Solid Waste Management Program has information about many recycling facilities in Missouri. From construction and demolition waste, the sorting must take place at the construction or demolition site. The wastes cannot be hauled from the site and dumped for later sorting, except at a permitted processing facility or at a facility that has received a permit exemption from Solid Waste Management Program.
3.4 Regulated Construction and Demolition Wastes
Regulated construction and demolition wastes are those not classified as clean fill and not being reused or recycled. Regulated non-hazardous construction and demolition wastes must be disposed of at a permitted landfill or transfer station. To avoid violating air and solid waste laws regulated non-hazardous construction and demolition wastes:
- Cannot be burned. An open burning permit may be applied for to burn untreated wood waste.
- Cannot be buried (except at a permitted landfill).
- Cannot be hauled to private or public property and dumped, burned or buried, even with the landowner's permission.
If this happens, everyone involved, including the contractor(s), subcontractor(s), the hauler(s) and the landowner(s) can and will be held liable for the illegal disposal 260.211 and If you are a building contractor, you need to know that burying construction waste from a building anywhere on the property is illegal.
3.5 Hazardous Materials and Hazardous Wastes
Although you may find a variety of hazardous materials in old buildings, lead-based paint and asbestos are the most common items dealt with by demolition contractors.
Careful management and disposal: For many years, lead-based paint was used in residences and businesses for its stable coating properties. Although lead-based paint was virtually banned by the Consumer Product Safety Commission in 1978 for residential application, it is often encountered when buildings are renovated or demolished. Also, lead-based paint is still manufactured and sold for corrosion or rust inhibition on steel structures and for other industrial purposes. In older buildings, lead was also used for roofs, cornices, tank linings and electrical conduits. In plumbing soft solder, an alloy of lead and tin was used for soldering tinplate and copper pipe joints [Mroueh:2002].
Demolition-related waste categories typically include:
Paint Residue - Paint chips, paint scrapings and contaminated blast residue from building renovations or demolition projects.
Demolition Debris - Masonry, metal and boards that have been painted with lead-based or other heavy metal-based paint.
Scrap Metal - Metal objects that contain lead or other heavy metals. For households, the following management options apply, whether or not a contractor is doing the work for you:
Paint Residue - Paint residue may be placed in the household trash. Before disposal, wrap it tightly in a plastic bag or other container. It will be picked up by your trash hauler and taken to a sanitary landfill for disposal.
Demolition Debris - May be placed in your household trash. It may be picked up by your trash hauler and taken to a sanitary or demolition landfill for disposal.
Scrap Metal - Scrap metal should be taken to a salvage yard for recycling. If this is not possible, the metal may be placed in your household trash and picked up by your waste hauler for disposal at a sanitary or demolition landfill. For generators other than households - This category includes commercial and business enterprises, institutions and industrial buildings, and other structures not specifically identified [Sherwood,1995].
Hazardous wastes must be managed, transported and disposed of according to the Missouri Hazardous Waste Management Law and Regulations. This may require the generator to send paint residue to a permitted hazardous waste disposal facility. In some cases, a lead smelter may accept lead-based paints for use in its lead production processes. If laboratory analysis shows that the paint residue is non-hazardous, it must be disposed of at a sanitary landfill as “special waste.” Paint residue may not be disposed of in a demolition landfill.
Procedures for managing special wastes are included in the fact sheet titled Special Waste
The landfill may require you to complete a special waste disposal request form, and provide the results of testing on the paint waste to show that it is not hazardous before accepting the waste.
Demolition debris need not be tested before disposal, so long as it is not chipped, shredded, milled, ground, mulched or similarly processed. Processed demolition waste should be evaluated as described for paint residue.
Scrap metal painted with heavy metals may be sent to a salvage yard for recycling. If this is not possible, the metal may be disposed of at a sanitary or demolition landfill.
All public, institutional or commercial buildings, and in some instances, residential structures, must be inspected for asbestos before renovation or demolition activities. Before planning a demolition project, bidding a project, letting a bid or beginning the demolition, it is important to know if the building has any asbestos-containing materials and who is responsible for removing them. Buildings may contain asbestos in materials such as ceiling or floor tile, as insulation or soundproofing on ceilings, pipes, ductwork or boilers, or on the outside as transit siding or in shingles. The presence of asbestos-containing materials cannot be confirmed just by looking [Mroueh:2002].
A thorough inspection of any regulated building must be conducted by a Missouri certified asbestos inspector to determine the presence and condition of asbestos-containing materials.
Depending upon the results of the inspection, a registered asbestos abatement contractor maybe required. Contact the department's Air Pollution Control Program's Asbestos Unit If the asbestos-containing materials is to go to a landfill or transfer station, contact the facility in advance to see if they will accept materials and if they have any special handling or packaging requirements[ Javed,1994].
These are the management techniques to handle the type of wastage.
4.1 Reuse and Recycling
Recycling and reuse of the wastage produced by the construction and demolition process is the part of an green building construction. The reuse of sources is a fundamental advantage of green building construction. That means reusing and reducing most of the materials that are used in construction of any structure Recycling of the wastage is another option to use the wastage efficiently [ Sherwood,1995].
Green building construction practices can include salvaging dimensional lumber from the project, using aggregates reclaimed from crushed concrete or grinding drywall scraps for use on site as a soil amendment. After the demolition large amounts of materials can be reused or recycled, principally wood, concrete, and drywall. Rather than demolish an entire building, consider all parts of the structure are deconstructed. Deconstruction is the orderly dismantling building components for reuse or recycling. Deconstruction involves carefully taking apart portions of buildings or removing their contents with the primary goal being reuse.. This is the main features of recycle process:
- Construction reuse
- Material reuse
- Immobilization with useful application
- Useful products
- Combust with energy recovery
- Immobilization without useful application
4.2 Quantitative prevention of demolition wastes
Extending the life of buildings can reduce the volume of demolition wastes. Depending on the nature and purpose of a building the emphasis may be on extending its technical life by improving its quality and durability, or extending the functional life through flexible or multifunctional building. In both cases the measures taken in the construction stage will only have a long-term effect when the building is demolished. When a building is demolished the materials used in it will be released [Javed,1994]. At that stage quantitative prevention is limited to avoiding the disposal of more waste than is needed. Hence, from dumping of tar waste at the demolition site has to be prevented and trucks should be loaded carefully to avoid picking up excessive amounts of soil[Sherwood,1995].
4.3 Selective demolition
The objective of qualitative prevention is to improve the quality and composition of the demolition wastes to facilitate reuse. This means that buildings have to be demolished selectively. There are a number of reasons why selective demolition is not used. Firstly, the accessibility of the materials to be removed is important. The accessibility depends on the design of the structure to be demolished. Furthermore, selective demolition is only effective if wastes are also collected separately, which requires more space at the demolition site.