Definition Of Construction And Demolition Waste Construction Essay

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Construction waste originates from the construction, repair, and remodel of residential and nonresidential structures. The waste generated is relatively clean, and can be readily separated at the jobsite. On residential construction and renovation projects, wood, drywall, and cardboard make up 60 - 80% of jobsite waste (NAHB). Metal, brick, block, vinyl, and asphalt waste are generated in relatively smaller quantities. Commercial construction waste volume varies based upon the size and type of construction.

Demolition waste is generated during the removal of existing structures; structures that were built over a range of time periods using a variety of materials and construction methods-some of which are no longer appropriate. Demolition materials include: aggregate, concrete, wood, paper, metal, insulation, and glass.

Demolition waste is often contaminated with paints, adhesives, and insulation and the recyclability of wood may be hindered by nails and other fasteners. Large pieces of wood and dimensional lumber can be recovered through de-nailing and re-planning and, because of the availability of local outlets; many demolition projects have been able to recycle as much as 80% of mixed debris.

[Houston-Galveston Area Council (H-GAC)]

http://www.recyclecddebris.com/rCDd/Resources/Documents/GuideWhatsInBuilding.pdf

C&D waste is material produced during the construction, renovation, demolition, or deconstruction of residential and commercial buildings and their infrastructure. C&D waste typically includes concrete, wood, metals, gypsum wallboard, asphalt and roofing material. For the purpose of the Guide and pocket version, materials are C&D waste if they would normally be hauled away for disposal. [C&D Waste Management Pocket Guide]

The definition of recycling is to pass a substance through a system that enables that substance to be reused. Waste recycling involves the collection of waste materials and the separation and clean-up of those materials. Recycling waste means that fewer new products and consumables need to be produced, saving raw materials and reducing energy consumption. [Atmospheric Environment]

http://www.ace.mmu.ac.uk/eae/sustainability/Older/Waste_Recycling.html

Reuse is using the existing materials instead of throwing it away. That does not include only building materials. Pipes, ceiling fixtures, bath fixtures, lamps, electrical sockets, even furnishings like vanities, bath tubs, shelves, cabinets all these can be used to some extent. Reusing does not mean YOU have to use it. Donating it to nonprofit organizations is one noble option of construction waste management. Some government institutions even take a cut of your tax per value of your donated materials.

http://www.streetdirectory.com/travel_guide/21929/corporate_matters/construction_waste_management.html

Types of C&D waste can be recycled

There are a large number of materials widely used in the construction industry. For this reason, there are also a large number of wastes produced when the construction and demolition works are carry out. The C&D waste measure is differ in the nature of the construction project.

Brick

Brick is a pure and natural product. It is made by loam or clay mixing with water and is kiln-fired. Because of the natural raw material used for production, bricks contain no pollutants or allergens. Bricks are also resistant to noxious insects as well.

Bricks are widely use in the construction field. It is one of the major resources for construct a building. In addition, it had been the ideal building and construction material and continual use for more or less 5000 years. Bricks are the most common walling materials. It is widely used for the building wall, retaining wall and monuments. It is normally laid or joint by using mortar whereas some bricks such as compressed earth blocks can be dry stacked.

Bricks are really useful in construction field because it has multiple of benefits. The selection of the bricks will give the impact to the external appearance of a building. It is also more durable and last longer compare to others materials such as wood, vinyl siding or aluminum. Besides, it has better sound resistance and fire resistance which classified as non flammable materials. Moreover, it has a good load-bearing properties and potential low energy impact.

While modern methods of brick construction have a much lower sustainability index, the UK brick industry has developed a strategy to minimize its environmental impact and increase its energy efficiency and use of renewable energies. The bricks wastage may reduce by improve the durability and strength of the bricks.

Overall, bricks are one of the selections for a sustainable building practice and it is currently achieve its popularity around the world. In brief, bricks produce little waste or no waste because it requires minimal energy use and can be turned back into its original at the end of their life.

Concrete

Concrete is originally from cement mix with stone aggregate. In the manufacture of cement, limestone, sand, clay and iron ore are blended, ground and heated to 1400 -1550 Celsius in a rotating kiln. The resulting material called clinker is cooled, pulverized and mixed with gypsum to create what is known as Portland cement, a hydraulic material primarily made up of calcium silicates.

Concrete is most used material in the construction field. Concrete is commonly apply for the foundations all kind of structures and filling in the spandrils or arches or the hearting and backs of walls. With the materials has improved, it has been employed for many other purposes such as walls built in concrete. There are several types of cement to form concrete; usually the construction will use Portland cement. Concrete is form by a mixture of cement and stone aggregates. Cement mix with the water to create the paste so as to bind the aggregate together to form concrete.

The quality of the concrete has the interrelationship with the amount of water and stone added. The quality of the concrete is depends on the quantity of the mixing ratio. A suitable cement, sand and water mixing ratio is use in order to form a strong concrete. The higher amount of the water contain will dilute the cement paste. Thus, the properties of the concrete are influenced by the property of the cement. Reinforcement bar added to form reinforced concrete will have better strength.

According to Deputy Works Minister Datuk Yap Khoon Seng, at least 5% of the construction of new roads under the 10th Malaysia plan would use the cement concrete paving method. This is because concrete has longer lifespan and better quality if compare to asphalt for new road construction. Hence this will reduce the expenditure in terms of maintenance in long run.

http://www.cement.org/tech/

http://www.cement.org/tech/cct_cement_characteristics.asp

Wood

Wood is obtained from a falling tree or deforestation. Wood is unique and versatile. Wood has been used throughout the history of mankind. Wood has provided to the construction industry with a wide range of building products and materials for construction from many years ago.

Wood can be use in many parts in a building. It can be apply in the floor including flooring, framing and footing. It is also can install for wall which include framing, internal lining and insulation. Besides, it also can act as a plasterboard and gutters for roof part. In short, wood can be the only material to building up a whole building.

Wood is often considered to be the cheapest and best materials for the construction. Besides, the manufactured of wood has the lowest amount of carbon released if compare to others building materials such as steel and aluminum. Moreover, it continues to store carbon dioxide for the remainder of its life as a wood product or even in a part of a building whereas others materials will not store the carbon dioxide.

However, regular maintenance is required to maintain the life cycle of the wood to resist fungus attack. Furthermore, timber is insufficient in the fire resistance. Hence, it will be the main consideration to construct a building.

Wood is one of the materials that can be repaired and re-used. It can be re-used or re-machined into other products, such as railway sleepers as a garden design material or re-machined into floor boards and wood profile. Many wood-producing companies use wood and wood waste to provide power and heating in their factories. Wood processing waste is also used in chipboard production or for animal bedding. In fact, wood is renewable.

Asphalt

Asphalt is sticky and black which is derived from the same crude oil which produces kerosene, gasoline and vinyl. It is primarily used in road construction such as surface for roads, airport runways, parking lots and playgrounds. Asphalt is used to bind or glue with the aggregates particles. It is also mainly used as a sealant for rooftops.

Construction field will rather to select asphalt than concrete for road construction because its initial cost and maintenance is cheaper. Asphalt provide good quality road and can continually to lay at the same point when there has damages on the road.

Asphalt waste is produced when it lose their plasticity and therefore harden and therefore crack or crumble. The stress of heavy traffic is also one reason which causes the asphalt loses their strength.

Asphalt can be recycled back into new asphalt by crushing it. Markets for recycled asphalt paving include aggregate for new asphalt hot mixes and it can be used sub-base for paved road.

Steel/Metal

Metal is commonly used as structural framework or as an external surface covering for roof. There are many types of metals used in constructing a building such as steel and aluminum. Steel has become a worldwide building material because its offers better strength, durability, versatility and economic value. Steel has a long life cycle, require little or no maintenance and it also provide a beauty aesthetic appearance.

However, corrosion is one of the biggest weaknesses of the metal. Moreover, the reason of why it is not fully equipped in a building is because its heat conductivity.

Metal is the most profitable and recyclable material. Steel can be completely recycled at the end of its useful life and it is permissible to repeating recycled. it can be melted down and reform into other metal product. This will reduce both the cost and environmental impact of making new steel as it conserves energy.

Gypsum Wallboard/Drywall

Gypsum board is one of the common wallboard uses in building construction. It is also known as drywall. Gypsum is a natural mineral in crystalline form, is a hydrous sulfate of calcium. It is generally has two layer of special papers and the gypsum rock core sandwiched between. Different types of gypsum wallboard will use to fit the different types of purpose. Basically, gypsum wallboard is used to cover interior walls of a home or other structures. Gypsum wallboard carries an advantage which is noncombustible.

The unused gypsum wallboard can be removing and recycle. The wallboard which has not been treated with surface chemicals such as water resistant and fire retardant can be used in agriculture as a fertilizer and as a soil amendment. It is also can be returned to the supplier or else donate or sell it.

Glass

Glass is made from mixtures of sand and silicates. Glass occupies a special place in construction field with its unique characteristic. Uses of glass in previously is quite limited because it is thought to be an easily break building material. Hence, this is the main reason to take into account for a construction project and many will select others materials than it because of its weakness.

Modern glass has improved and not only can look through, it is also stronger, safer and energy efficient. Glass has therefore widely demand for the architectural and decorative finishes. It is utilized in the construction of several elements of exterior and interior of architecture.

By using the glass cladding in a building, it fulfill the functional requirements of lighting, heat retention and cost saving. It is an outstanding material for thermal insulation, water proofing and chemical resistance.

Glass is also relatively inexpensive and it is same as metal which can be fully recyclable. Recycling the glass can help in reducing the C&D waste, lower the construction cost and reduce the environment problems. Usually the glass will be crushed to pebble size and remove the sharp edges hence it will not harm the workers when use it as aggregate instead of sand. It can be use as decoration in concrete plaster or use as bedding in place of sand.

Ways to recycling and reuse Bricks

Bricks recycling are still new at the construction industry. Bricks arising from C&D may be contaminated with mortar, plaster or others materials such as timber and concrete. This may lead the bricks may vary in quality. It is therefore difficult to assess the strength and load-bearing capacity of the recycled bricks.

One of the brick recycling method is using the impact crusher to crush the bricks into small pieces. Impact crusher is tends to remove the mortar from the bricks or else the contractor may need to carry out wash screen or finishing screen to remove the mortar.

The impact crusher is suitable to crush mid-hard and above rocks. With an impact crusher, the bricks can be crushed from the machine is more cubical and the amount of fine-to-aggregate ratio can be adjusting. When processing the bricks recycling, the contractor need to aware is that any difference in density between bricks and the concrete and asphalt material because this may affect the output of the crusher.

Even the unused bricks also can be recycled through crushing process and reground it to manufacture new quality brick.

If the bricks are merge with other aggregate material it can be used for the foundation by processed with the impact crusher. The crushed bricks are usually used to form filling materials. It can be used either in drain layer or as part of the vegetation layer in the drain layer material.

As recycled bricks may not be ideal for use as backfill for buildings or roads, several contractor may use the recycled bricks in others way, primarily use in landscape application.

While contaminated bricks may not suitable for use in recycling activity, it is still allows to use in others purpose. In the easiest way to recycle the bricks, it can be reused as the bedding material in road construction, for sound insulation wall or as tennis court material. Besides, recycled bricks can be used for the pavement, parking lots, rooftop application, and driveways or even as an alternative to mulch.

Used bricks are being much sought in the market due to its unique and aged look. The popularity of the old bricks is becoming a fashionable alternative in residential construction.

It is an opportunity for the contractor to recycling the brick into a saleable end products and resale it to have boost revenue due to the recycling bricks has the opportunities in the market.

Ways to recycling and reuse Concrete

There are several types of machine plants use to crush the concrete, rocks and stones. The types of the crusher are as below:

Jaw Crusher

Jaw crusher is ideally suitable for primary and secondary crushing. The jaw crusher is primarily reduces the large size rocks by placing the rocks into compression. By placing the concrete into a jaw crusher, the movable jaw plate exerts force on the concrete by forcing it against the fixed jaw plate. The space at the bottom of the "V" will align the jaw plate to crush the concrete into the size by adjusting the movable jaw board.

Impact Crusher

Impact crusher crushes the materials in the crushing cavity with high impact which generate by using a plate hammer on the rapidly rotating rotor. The materials are cast along tangential direction to impact plate at the other end of the crushing cavity. The materials are repeatedly crushed again and return to the plate hammer by undergoes the process above. The materials are bumping with each other at plate hammer and the impact plate in the process. Then the materials will crack, loose then comminuted and grain into size smaller than the gap between impact plate and plate hammer will be discharged.

Cone Crusher

Cone crusher is suitable used in primary or secondary crushing. The crushing actions is done by the closing of the gap between the mantle line (movable) mounted on the central vertical spindle and the concave liners (fixed) mounted on the main frame of the crusher. The gap is open and close by an eccentric on the bottom of the spindle the central vertical spindle to spin.

Process of recycling concrete into aggregates:

Figure: Process of recycling concrete into aggregates.

Concrete crushing can be start with primary jaw crusher, cone and/or large impact crusher with the rubble from 30 inches to 4 feet coming with the primary screening. A secondary cone or impact crusher may or may not need to be run depending upon the final product desired as the secondary screens is same.

A scalping screen is to remove dirt and foreign particles. A fine harp deck screen will helps in removing the fine material from coarse aggregate.

Water floatation, hand picking, air separators and electromagnetic separators carry out to ensure the recycled concrete product is free of dirt, clay, wood, plastic and organic materials.

With the more care that put into the quality, a better quality aggregate will produce by recycling the concrete. Sound quality control and screening may add into the process to produce the aggregates without having to wash it as virgin aggregate which may be ladened with clay and silt.

Figure: Process of recycling concrete pavement into aggregates

First, remove the concrete pavement from site and remove the steel, soil and other contaminant material from the concrete.

Then, the demolished concrete is crushed by the jaw crusher and sized by screening operation to the specified requirements.

Fine impurities such as soil and loose cement mortar should be removed by special crushing operations, washing, dry or wet screening or hydraulic sizing. Impact crusher is more suitable to operate the secondary crusher because impact crusher tends to remove more mortar from bricks than a jaw crusher.

Lightweight contaminates, such as wood or porous chert, may require the use of other aggregate beneficiation methods, such as hydraulic separation. Except for removing steel, impurities, and contaminates, this process is identical to the process used to produce aggregate from virgin stone materials.

Recycle to separate it back into its component part: sand, aggregate and rebar

To be revised…

The three main types of crushers are jaw, impact, and rolling. Jaw crushers are best suited for quickly reducing large or odd shaped debris from. C/D projects to a manageable size, typically less than 15 cm in diameter. High speed rotary impact crushers use a lot of energy and may pose a safety hazard from flying debris. However, an impact crusher would outperform a jaw crusher in freeing rebar encased in the rubble [Vollmer, 19921. A roller crusher is composed of two he: cylindrical rollers separated by the desired particle diameter. It is used for secondary crushing.

Dust control at a concrete crushing plant is critical, especially if the plant located near residential or other sensitive areas. At Wheaton Asphalt (Wheaton,

IL), the crusher operator uses a hose to spray water directly on the rubble as it passes through a jaw crusher. The main markets for processed concrete are asphalt and concrete pavement road base, and as a fill material.

A dry process for quality recycled concrete aggregate

There is a new dry process for recycled concrete into aggregate establish by the aggregate equipment manufacturers, Kotobuki Engineering & Manufacturing Co. Ltd. (Kemco) of Hiroshima, already well known for their innovative dry sand manufacturing process. The manufacturer has set the target to recycle the concrete into coarse and fine aggregate with the quality as close as possible to the original constituents.

The plant is constructed in the form of two adjacent towers. One of the towers carrying the crusher and air screen, fed by a bucket elevator and the other is to support the bag filter and skimmer assembly. With this arrangement, the footprint can be minimizing which is very compact, and to enable the dust emission is near as near to zero as to be insignificant to be achieved. The feed material of crusher dust must be dry which has around 2% water content can usually be expected direct from a crushing process. The finished sand will place in a small drum mixer to prevent segregation and maintain consistency. The concrete sands recycled by RC7 system have been found suitable as up to 100% replacement for natural sand, with cement saving.

Reuse

Crushed concrete may be reused as an aggregate in new Portland cement concrete or any other structural layer. Generally it is combined with a virgin aggregate when used in new concrete. However, recycled concrete is more often used as aggregate in a sub-base layer.

They can use the recycled product as gravel base for roads or as dry aggregate for new concrete.

Most concrete in urban areas is recycled as fill or road base and not placed in landfills. Concrete pieces from demolished structures can also be reused to protect shorelines, for example in gabion walls or as rip rap.

Recycled concrete can be used as aggregate in new concrete, particularly the coarse portion.

Benefits of Recycling and Reuse

With the awareness of wastes from construction and demolition works towards the environment problems, waste management in construction activities has been increasingly promoted in order to protect the environment.

Environmental

Previously, disposal of C&D waste is commonly use landfill method. This will occupy a large space for the landfill activity. While put into practice with C&D recycling will conserves the landfill space, this will reduces the need for new landfills and associated cost such as transportation cost to dispose the C&D waste from site. Indeed, this will help that less chance of ground water contamination.More to the point, this will give another benefit to the wild life which their habitat place is protected.

Besides, recycling of C&D waste can reduce the emission of greenhouse gas and other pollutants by reducing the need to remove raw materials and ship new materials from long distances. With recycling and reuse of C&D waste, this will achieve environmental friendly.

Economy

Through implementation of recycling of C&D waste into the construction industry, this will creates an employment opportunities to the people. For example, a company will need a lot of skilled labour to operate the recycling activities. Above and beyond, the country may increase the public image concerning the environment through implementing the recycling activities.

Cost Efficient

Recycling and reuse of C&D wastes can saves the money by reducing disposal costs, transportation costs and the cost of some new construction materials by recycling old materials on site. More to the point, recycling and reuse C&D waste on site will give a hand directly to assist to achieve environment friendly.

By recycling the C&D waste and reuse it may saves a large amount of money. Besides, the price of using recycling materials is lower if compare to using the brand new materials. Overall, recycling and reuse will helps in save the construction cost.

Energy conservation

To produce a brand new material, it requires the raw material and manufacturing in the factory. This may lead to the emission of the greenhouse gas and also energy consumption during production of the material.

Recycling C&D waste requires less energy than manufacturing the new product. With this reason, this will save the energy and reduce the environmental impact of producing new materials through avoided extraction and manufacturing process.

Apart of it, recycling the C&D waste may also save the energy for transporting the new materials to the site.

Barriers of Recycling and Reuse

Malaysia contractors are lack of awareness of the importance to the recycling and reuse of the C&D waste. Malaysia is still fall behind in the practice of recycling and reuse of C&D waste if compare to others country like Japan, United State and United Kingdom. Unless the industry can overcome the barriers, otherwise the recycling will always abandoned before tried.

Time

The construction industry will always have a perception that recycling the waste on site will slow down the progress. This is because the labours need to separate the waste while the labours also need to carry on the work. Due to the time is the key for a project, hence most of the contractor will not practice the recycling activity.

Collection, Sorting and Transportation

The C&D waste usually is collect in a single container at site. Contamination can be a significant problem so the C&D waste should be handling in a proper way. Hence, it is difficult to separate the materials which are mixing with contaminated waste and uncontaminated waste unless the separation is done by hand or specialized machinery.

Besides, to carry out the recycling activities need a large space to store all the collected C&D waste. The usage of transport to collect the C&D waste will increase due to the location of the site to collect the waste.

Cost

Besides, some of the C&D wastes will be costly in the way of recycling. For example, timber is a major problem to contractor recycling C&D waste. It cannot be burned and it must be disposed to landfill. Moreover, separation from concrete and bricks is costly. Hence, most of the contractor will select the cheapest way which is disposed to landfill. Besides, the cost of the equipment and plant will be the obstacle for recycling activity. This is because some of the equipment is not available at Malaysia hence it needs to import from foreign country. Even though the construction industry has private contractor recycling the C&D waste, but not every contractor willing to pay for the waste management services. In many cases, solid wastes are either burnt or disposed illegally, mainly to avoid the disposal cost to a legal dump site.

Standard

On the other hand, some of the contractor might believe that the recycling C&D waste will have lower quality if compare to the brand new materials. Moreover, the specification of the recycling material is most concern by the contractor whether it is officially certified by the authorities in the building and construction industry. There is a risk to carry out the recycling C&D waste because not every contractor will to make use of the recycled materials recycling from C&D waste. Hence, it is doubt that the recycling of C&D waste will have the demand in the market.

Knowledge

Lack of knowledge in recycling and reuse C&D waste was an important barrier. This is because the contractors do not familiar with the technical contained and also the ways and method to recycling and reuse the C&D waste. An important barrier is the lack of communication among the design team (architect/engineer) and the contractors and waste haulers. There are many issues that must be addressed and each party must be very clear with their role and responsibilities on the C&D waste management. The contractor might need to provide training to the labour in order to achieve the recycling of C&D waste and reuse it again. Most waste normally is handle by sub-contractors because the responsibility of waste handling on site is not clear.

Technology

Technology is the key point in recycling and reuse of C&D waste. The recycling activities need to be carrying by the specialized machinery. In fact, Malaysia is lack of construction waste recycling facilities and appropriate technology. Recycling of C&D waste is still poorly developed, there are limited types of waste presorting in the industry. Thus, Malaysia is still need to improve the technology of the recycling equipments or plants in order to achieve the C&D waste recycling. In addition, the construction industry also lack of necessary expertise and capabilities to monitoring and operating the equipment.

http://www.3rkh.net/3rkh/files/3RKH_CHYPERLINK "http://www.3rkh.net/3rkh/files/3RKH_C&D_waste_FinalReport.pdf"&HYPERLINK "http://www.3rkh.net/3rkh/files/3RKH_C&D_waste_FinalReport.pdf"D_waste_FinalReport.pdf

Regulation

Recycling and reuse the C&D waste is categorize under a special fraction of solid waste under regulation. Malaysia construction industry does not have a proper waste registration but only have an informal permit somehow not every states have recycling activities. Most of the Asian countries do not have regulation and laws on C&D waste management. A formal national regulation of C&D waste in Malaysia is still in process.

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