The Construction And Demolition Construction Essay

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Construction and Demolition (C&D) waste is a significant and growing part of the disposed waste stream in our country; it makes up approximately 28% of the disposed waste. C&D materials are generated in the construction and demolition of residential and commercial buildings, roads, tenant improvements and remodels, landscaping and site clearing activities. These wastes are heavy, having high density, often bulky and occupy considerable storage space either on the road or communal waste bin/container. It is not uncommon to see huge piles of such waste, which is heavy as well, stacked on roads especially in large projects, resulting in traffic congestion and disruption. Waste from small generators like individual house construction or demolition, find its way into the nearby municipal bin/vat/waste storage depots, making the municipal waste heavy and degrading its quality for further treatment like composting or energy recovery.

Construction and demolition (C&D) waste is produced during new construction, renovation, and demolition of buildings and structures. C&D wastes includes bricks, concrete, masonry, soil, rocks, lumber, paving materials, shingles, glass, plastics, aluminum, steel, drywall, insulation, roofing materials, electrical materials, plumbing fixtures, corrugated cardboard, and tree stumps.

C&D materials can be recovered through reuse and recycling. In order for materials to be reusable, contractors generally must remove them intact (windows and frames, plumbing fixtures, floor and ceiling tiles) or in large pieces (drywall, lumber). Some materials may require additional labor before they can be reused. For example, lumber may need to be denailed and window frames may need some new panes. In order to be recyclable, materials must be separated from contaminants (e.g., trash, nails, and broken glass). This can be accomplished if contractors require workers to sort materials as they remove items from buildings or as debris is produced. Many contractors simply use labeled roll-off bins for storage of source-separated materials. For projects where on-site source separation is not possible, contractors often use C&D materials processing firms.

Many materials can be salvaged from demolition and renovation sites and sold, donated, stored for later use, or reused on the current project. More than 200 used building materials stores around the country buy and/or accept donations of used building materials. Contractors can avoid the cost of removal by allowing private companies to salvage materials from the site. Organizations that have space may want to consider storing high-value materials for later projects. Many building materials may be reusable during renovation projects and projects where a new building is built following the demolition of another. Planners can increase reuse potential by making efforts to use the same size and types of materials as in the old construction. Inadequate storage space for materials during the interim from removal to reinstallation may limit reuse as a materials recovery option. Typical materials suitable for reuse include plumbing fixtures, doors, cabinets, windows, carpeting, bricks, light fixtures, ceiling and floor tiles, wood, HVAC equipment, and decorative items (including fireplaces and stonework).

1.2 Aim

Study into reduce construction waste by recycling

1.3 Objective

Identify the concept of waste management

Investigate the types and percentage of construction waste

Investigate the method to reduce or recycle the construction waste

1.4 Hypothesis

Reduction in construction waste can reduce the cost of the construction

1.5 Scope of work

My scope of work in this research is to identify the concept of waste management. Secondly, I will also investigate about the types and percentage of construction waste. For example, reinforcement bar, timber board, concrete and bricks. Lastly, I will investigate about the method to reduce the construction waste. The area that I want to investigate is general construction wastes that produce during construction, demolition and renovation.

1.6 Problem statement

The reason that I want to do a research for my title, which is reduce or recycle the waste of demolition, renovation and construction in construction industry is because I want to introduce to people an interesting type of method the save our environment in construction industry. Since, construction industries are well known as one of the worst environmental polluters .The method is recycle or reduce the waste generate by the construction industry. First, we recycle the waste like bricks, concrete, masonry, soils, rocks, lumber, paving materials as more as possible to reduce the waste quantity. So that, the land needed to burrow the waste is reduce and save land in our earth. Not only that, through this method we also can reduce the use of raw material to produce construction product. This can save material in our earth. Besides that, in this waste recycle or reduction process can generate more jobs for people. Through this recycle and reduction process involved a lot of sector in the country. Construction industry is a very important and very huge issue in the whole world. I believe that my research title is a very important and is a must in application of recycle or reduction of construction waste materials in the world's construction industry nowadays.

1.7 Research methodology

Stage 1: Literature review

A systematic literature review is to be conducted which cover textbooks, institutional, journals, seminar and conference paper. This study will review the relevant literature on the reduction and recycling of building construction waste in Malaysia.

Stage 2: Case study

In order to have more depth information for the reduction and recycling of building construction waste. I will conducting a case study in Malaysia by searching the construction site. Then, interview will also be conducted to the contractor who applying the concept of reduction and recycling of building construction waste.

Stage 3: Evaluation of case study

After conducting a case study, I will review and analyse the information and photos collected in the site that I have searched. It is to identify whether the site is using concept of reduction and recycling of building construction waste.

Stage 4: Writing up

After doing all the research, understanding and getting enough information, it enable me to writing up the content following the dissertation that I proposed in this stage.

Conceptualisation Objectives : -

Identify the concept of waste management

Investigate the types and percentage of construction waste

Investigate the method to reduce or recycle the construction waste

Identification of Scope

Literature Review

Case study-Data/information collection


Sufficient Data ???


Evaluation case study

Writing up

Chart 1.1 Research Methodology Flow Chart

1.8 Proposed Contents

Chapter 1 - Introduction

It is introduction about the reduce or recycle waste of construction materials, introduced some cases of waste construction material that really happened in construction industry whether in local or oversea.

Chapter 2 - Literature review

It is the analysis data from cases found or resource from internet regarding the type of the waste of demolition of building can be reduced or recycled. Identify the means and method of construction waste management and provided some method to reduce or recycle the construction waste in the case study or search the best solutions method.

Chapter 3 - Research design and methodology

This part will be include the method on how to get the information (eg. By using interview, questionaire or case study etc.), where to get the information and what information to get.

Chapter 4 - Analysis of result and discussion

This is the part of analysis and discussion to obtain the final result or recommendations from the research methodology.

Chapter 5 - Conclusion

This chapter will be the result from chapter 5 which is the conclusion after analysis.

Chapter 6 - Suggestion for further research

The suggestion of further research related to title of research proposal. The following will be the references which is recording the location or place to get the resource of articles, books or magazine etc.

Chapter 2 Literature Review

2.1 Introduction

Construction waste becoming a serious environmental issue in most of the country in the world. Governments of the countries encouraging the contractor to reduce the construction waste by recycling and reuse and other methods. Besides that, the contractor are not active in that manner of construction waste reduction because of profit maximization. Successful construction and demolition (C&D) waste management requires the efforts from varied parties using their area of expertise. The construction industry are generating a significant quantity of waste, most will end up in landfills.

In 1998, the U.S. estimated that 136 million tons of construction waste is generated in the U.S. annually, which is equal to 25 percent to 40 percent of the national solid waste stream. A 2003 update shows an increase to 164,000 million tons annually, of which 9 percent is construction waste, 38 percent is renovation waste, and 53 percent is demolition debris.

C&D waste disposal causes a sequence of adverse effects that are not always apparent to building professionals. These include the loss of useful property, wasted materials and embodied energy, greenhouse gas generation, and environmental stressors associated with producing new materials instead of using existing materials. The number of C&D landfills is declining, which means fewer disposal options, greater hauling distances, and increased fuel consumption and vehicle emissions. Capping, closing, and monitoring landfills, and cleaning up leaking or contaminated landfill sites drain public funds. There is only 20 percent of C&D waste is being recycled in U.S.

Figure 2.1- Use of materials and C&D waste generation in the life cycle of building

Operating waste







Construction waste

Source : (Patrick, 1999)

In Malaysia, the waste from construction industry is the highest waste which cause significant damage to our environment. Construction and demolition waste in Malaysia normally discharge in landfills. Our government spend RM400 million per year on waste disposal. Nowadays, the issue of construction waste minimization is an important issue. Reduction of construction waste by recycling and reuse becoming famous, it is because the cost of landfills is higher while the land for construction waste discharged is lesser, land for landfills becoming more expensive and there is a lot of rules, regulations and restrictions by the local authorities which stop the contractor from disposing construction waste in landfills gradually.

2.2 Definition of construction waste

Construction waste is defined as waste or debris resulting solely from construction, remodeling, repair, or demolition operations on pavement, buildings, or other structures. The waste from the construction include bricks, concrete, masonry, soil, rocks, lumber, paving materials, shingles, glass, plastics, aluminum (including siding), steel, drywall, insulation, asphalt roofing materials, electrical materials, plumbing fixtures, vinyl siding, corrugated cardboard, and tree stumps.

 Estate Management, University of Cambridge (2010) defined construction waste as any substance or object that you discard, intend to discard or are required to discard is waste and as such is subject to a number of regulatory requirements. Even if material is sent for recycling or undergoes treatment in-house, it can still be waste.

Dolan (1999) defined construction waste as composed primarily of a mixture of unused or damaged raw materials. Normally construction wastes are wastage such timber from fabricated formwork, steel when steel bars cutting, tiles when cut to size and the others. Even prefabricated assemblies such as doors and windows, which are packaged in large quantities of cardboard, metal or plastic strapping and wood tend to produce a significant amount of waste.

Peter Yost (1997) defined construction waste as discarded material (such as blocks, bricks, concrete, glass, plastics, steel, wood) and soil generated by new building construction, refurbishment, or demolition of existing structures, and which is neither biodegradable nor toxic. It also called construction waste.

Tom Napier (2010) defined construction waste as waste materials generated by construction activities, such as scrap, damaged or spoiled materials, temporary and expendable construction materials, and aids that are not included in the finished project, packaging materials, and waste generated by the workforce.

Hong Kong, a country have high level of construction activity defined construction waste as anything generated as a result of construction and then abandoned, regardless of whether it has been processed or stockpiled. It comprises surplus materials from site clearance, excavation, construction, refurbishment, renovation, demolition and road works.

However, in England, the Environmental Protection Act 1990 (EPA 90) Section 75 defined waste as :

Any substance which constitutes a scrap material or an effluent, or other unwanted surplus substance arising from the application of any process

Any substance or article which requires to be disposed of as being broken, worn out, contaminated or otherwise spoiled, but does not include a substance which is an explosive within the meaning of the Explosive Act 1875; or anything which is discarded, shall be presumed to be waste unless the contrary is proved. (Henry Hurrel Clay,1999)

2.3 Concept of waste management

How waste management, or diversion, is accomplished, and to what extent, depends on specific project requirements and conditions. Several issues contribute to an overall waste diversion strategy. A good waste management concept is very important for construction waste reduction. There is several stages of waste management for reduction of the construction waste below:

2.3.1 Waste Management Planning

Waste management should be an integral part of a development project. Each of the principal project participants, Architectural and Engineering (A/E) services (or Construction Management consultant), the Contractor, and Subcontractors will engage in waste management to some degree throughout the project. Firstly, the employer or the project owner and their A/E must create waste reduction goals. The Contractor is responsible for the means, methods, techniques, sequences, and procedures of construction, which include waste disposal methods.

2.3.2 Facility Design

The design team where design multiple functions with one material rather than requiring multiple materials to perform one function. Design to optimize systems and components use.

Be efficient in area and volume. If there is less material required by the design, then less waste is generated at the site.

Observe standard material and product dimensions. Avoid to perform cutting, jointing and special fitting, which creates scrap of materials.

Where possible, choose a construction systems that do not require temporary support, shoring, construction aids, or other materials that will be disposed as debris during and after the construction period.

Where possible, select materials that do not rely on adhesives, which require containers and packaging waste and create residue. Then, adhesives inhibit recycling and salvage at the end of the component's or building's life.

Where possible, reduce the requirements for coatings, laminates, finishes, adhesives, and the associated scrap, packaging, and waste application. Select materials with integral finishes.

Where possible, avoid to use materials which are contamination, environmental exposure, sensitive to damage, or spoilage on-site, which increase the potential for jobsite waste.

2.3.3 Construction Contract Requirements

The project owner and their A/E (or CM consultant) must determine how their waste management requirements will be represented in the contract documents and incorporated into the project. Several provisions are relevant to the project's overall waste reduction performance.

1) To represent waste reduction requirements in the contract documents, there are essentially three ways:

Describe the waste reduction goals and depend on the Contractor's own initiative to achieve them. This may be more effective if the project owner and Contractor have a good working relationship, and encouraging the Contractor is sufficient for them to "do the right thing."

Specify definitive debris diversion criteria and minimum waste. This is commonly incorporated into the demolition specification as a numerical criterion, such as "divert from landfill disposal a minimum of 70 percent of the non-hazardous construction waste generated at the site."

Develop incentives to reward the Contractor. This may be implemented as an award-type incentive based on the diversion rate, or by including options in the bid schedule for each of several ranges of diversion rates.

2) Requirement for the Contractor to submit a C&D waste management plan. Normally, the Plan includes the following:

Individual's name who is responsible for waste prevention and management.

Actions that will be taken for solid waste reduction.

Description of the regular meetings to address waste management.

Description of the specific approaches to be used in recycling/reuse.

Waste characterization, which estimated material types and quantities.

Name of landfill and the estimated costs, assuming no salvage or recycling.

Identification reuse programs in local and regional.

List of specific waste materials to be salvaged and recycled.

Estimated percentage of waste diverted by this Plan.

Recycling equipment to be used.

Identification of materials that cannot be recycled or reused.

Description of the means by which any materials to be recycled or salvaged will be protected from contamination.

Description of the means of collection and transportation of the recycled and salvaged materials.

3) Require the Contractor to document their actual practice in waste diversion throughout the project. The Waste Management Plan, and also include progress reporting procedures to record actual diversion and cost corresponding to each diversion and cost estimate.

4) As the accepted waste management plan is a part of the contract document, it should be incorporated into the owner's quality assurance and contractor's quality control processes. Some public owners will not approved the progress payments until updated actual diversion performance reports are submitted.

5) Vest title to debris and waste materials to the Contractor, and allow the Contractor to get the economic benefits. These include cost avoidance through reduced debris tipping expenses, revenues from salvaged and recycled materials, and cost avoidance by using materials taken from the site back into the project. (Tom Napier,2010)

2.3.4 Jobsite Waste Reduction

There are variety methods a contractor can divert construction waste or demolition debris at the site. The following general practices are common:

1) While protecting new materials is necessary, the Contractor can direct their subcontractors and suppliers for extraneous packing and packing reduction.

where possible purchase materials in bulk. Avoid individual packaging for volume purchases.

Use containers and packing materials that can be returned.

Reuse non-returnable containers on the jobsite to the maximum extent possible.

Give away non-returnable containers. Contact local and community organizations (schools, community service groups, youth groups, Habitat for Humanity, others similar).

2) Use scrap in cutting full new materials. Contractor can direct subcontractors and trades to collect and keep scrap at cutting and fabricating locations. Collect paints and liquids from almost-empty containers to avoid disposing of useable materials because there is not enough for one container to finish a job.

3) For materials that are mixed, heated, exposed to environmental conditions, or otherwise subject to spoilage, limit preparation of these materials to quantities which can be installed within their expiration times. To throw out expired or spoiled materials can be reduced by working in smaller batches. Ensure volatile materials, and materials that degrade when exposed to heat, cold, or moisture are protected from spoilage and are not wasted.

4) Recycle damaged components, products, and materials, or separate them into their constituent materials for recycling.

5) Establish a return or buy-back relationship with suppliers. Alternatively, unused, or used but serviceable materials and products can be sold to architectural salvage or used materials retail outlets.

6) The Contractor may contract with a C&D recycling firm who accepts commingled debris. At the recycling site, concrete and masonry rubble are separated out of the debris for crushing into aggregate products. The remaining debris is then crushed and conveyed along a pick line for sorting and recycling.

7) The waste diversion potential in a demolition scenario is considerable. The project schedule and the building's construction type are the two primary factors in determining what and how salvage, reuse, and recycling can be accomplished. Develop the project schedule to accommodate salvage, reuse, or recycling. The quality and quantity of materials salvaged is a direct function to the time available for salvage.

8) Prior to demolition, salvage as much useable material and components as the schedule will allow. Windows and doors, wood flooring, cabinetry, architectural millwork, electrical fixtures, plumbing fixtures, mechanical equipment and anything that can be detached and removed can be usually be salvaged and reused (Tom Napier,2010).

2.4 Cause of Construction Waste

According to Nezech (2008) stated that the cause of construction waste can be divide into 6 group as follow :

Manpower, caused by unskilled labours, lack of supervisions, sub-standard subcontractor personnel, and inexperience field supervisors.

Professional management, caused by poor planning, poor information distribution, lack of coordination among construction stakeholders.

Design and documentation, caused by site documentation system that not integrated well, unclear specification, low quality drawings, delay in revision and redistribution of construction drawings, design changes, and low quality design.

Materials, caused by low quality materials, delivery of materials that not according to schedule, material handling on site, and inappropriate use of materials.

Work execution, caused by incorrect construction method, lack of construction equipment, unsuitable equipment, incorrect selection of equipment, and poor site layout.

External factors, caused by among others site condition, weather, and damage caused by a third party.

Table 2.1- Main cause of construction waste in each group based on frequency analysis.

Group of causes

The main causes of waste

Work execution

Lack of construction equipment


Material handling and storage on site & delivery of materials that not according to schedule


Unskilled labours

Design and documentation

Design changes

External factors

Weather, site condition & damage caused by third parties

Professional management

Poor planning, coordination & information distribution

Source: Adapted from Nezech, (2008)

Work execution has been proved that it is the most important group of causes of the construction waste in construction industry. Inadequate proper construction equipment suggestion as the main contributor to construction waste. Other contributor factors are poor site layout and incorrect or ineffective construction method. Project size influences work execution which can lead to production of construction waste. The bigger the size of the project the more likely that the waste would be produced due to incorrect construction method and inadequate construction equipment. Project duration has a relationship with work execution and external factors. The longer the project duration the more likely that the waste would be produced due to poor site layout and damages caused by third parties. (Nezech, 2008)

Material is the second important group causes of construction waste, which resulted from poor material handling in the site and delivery of materials that not according to schedule. Example for poor material handling is the cause of material defect like broken and brittle while shifting the material from one place to another place. Example for delivery of materials that not according to schedule is the materials send to the site early than the schedule, this may cause defect to the materials because of long period of storage in the site.

Third is manpower, majority of manpower who are working in the construction project, including road construction, are unskilled. This condition has lead to inefficiency and rework, which produce construction waste. Fourth is design changes frequently during the building construction process. The waste produces when there is a change to demolition certain part of completed work to comply the new design.

Fifth is external factor, which including weather, site condition and damage caused by third parties. Example for weather causes construction waste is heavy rain in the construction site during the waiting time for the concrete to cure. This cause the concrete falling down and need to replace with fresh concrete. Concrete which fall down is the waste produce during the heavy rain. Sixth is poor planning, planning normally executed by project manager to ensure smooth construction sequence and waste minimization. Example for poor planning like the concrete is ready in the site but the formwork has not done in the part going to receive concrete.

Table 2.2- Rank of the cause of construction waste in each source

Group of activities


Group of causes of construction waste

Construction process


Work execution






Professional management


Design and documentation


External factors

Structural works


Work execution






External factors




Design & documentation

Material management


Work execution






External factors




Design & documentation

Source: Adapted from Nezech, Elkhobar and Zaldi (2008)

However, Ofori. G (2000) declared that there are six categories of construction waste generation at site, which is design, procurement, handling of materials, operation, residual related and others. In this research, the factors which cause waste on site were only four factors, which is design, operational, material handling and procurement. Table below showed the sources and causes of construction waste.

Table 2.3- Sources and causes of construction waste


-Lack of attention paid to dimensional coordination of products

-Changes made to the design while construction is in progress

-Designer's inexperience in method and sequence of construction

-Lack of attention paid to standard sizes available on the market

-Designer's unfamiliarity with alternative products

-Complexity of detailing in the drawings

-Lack of information in the drawings

-Errors in contract documents

-Incomplete contract documents at commencement of the project

-Selection of low quality products


-Ordering errors( example: order significantly more or less)

- Lack of possibilities to order small quantities

-Purchased products that do not comply with specification


-Errors by tradepersons or labourers

-Accidents due to negligence

-Damage to work done cause by subsequent trades

-Use of incorrect material, thus requiring replacement

-Required quantity unclear due to improper planning

-Delay in passing of information to the contractor on types and sizes of products to be used

Equipment breakdown

-Inclement weather

Material handling

-Damages during transportation

-Inappropriate storage leading to damage or deterioration

-Material supplier in loose form

-Use of whatever material which are close to working place

-Unfriendly attitudes of project team and labourers


Source : Adapted from and Ofori. G (2000)

2.5 Characteristic of construction waste

Table 2.4- Common components of construction and demolition activities

Road work

Asphalt; concrete; soil; reinforcing metal

Site work

Soil; wood, including trees and brush; organic matter; sand; stone; concrete; pipe


Mixed rubble, including wood, concrete, masonry, and steel; fixtures; mechanical equipment, etc


Scrap wood; roofing; wall board; insulation; flooring; ducts; pipe; packaging; fasteners; concrete; steel


Scrap wood; roofing wall board; insulation; flooring; ducts; pipe; fixtures; mechanical equipment; packaging; fasteners; concrete; steel

Source : (Patrick, 1999)

Table above described the most common construction waste produce by certain building's work. Most contractor consider the waste produced during construction or demolition as a homogenous by-product of the construction process. All cut-off material, packaging, and spend container are placed into the same refuse container even though the nature of the waste may vary across each type of activity. Major renovation projects, for example, create significantly more amounts of C & D waste than new construction projects, particularly if the renovation involves substantial demolition of the existing structures. There are two component to the characterization of construction and demolition waste, it is composition and quantity. The composition of the waste is defined by the type of included constituent components. The quantity of C&D waste is based either on the volume or weight of the debris depending on the requirement of the processor.

Composition of waste

Waste from constructing a new building does not have the same characteristics as demolition waste. A builder will typically order excess sizes or quantities of materials to ensure that there will be enough materials on hand to construction the building. By weight or by volume, wood, drywall and cardboard combined make up between 60 and 80 percent of jobsite waste in construction projects ( Yost and Lund 1997) even prefabricated assemblies, such as doors and windows, which are packaged in large quantities of cardboard, metal or plastic strapping, and wood tend to produce a significant amount of waste at construction sites. In new construction, concrete will not have much waste.

Demolition produces a significantly different waste than construction or renovation. Demolition debris is more likely to contribute materials contaminated by undesirable components and potential toxic substances such as lead paints, stains and constituent. The biggest problem with demolition debris is that the various types of debris are mixed together during the course of the demolition. Even with careful manual disassembly of the structure, different types of materials mixed together are still possible. For example, the removal of exterior walls in a load-bearing masonry system will result in a combination of masonry units, such as concrete block or brick, mild steel reinforcing metal and grout. The composition of C&D waste varies according to the type of project and the method of construction and demolition. There are sixteen categories of materials that make up C&D waste in general. Table 4 lists these categories and their sources. Several waste such as concrete, masonry and ceramics are considered inert by solid waste authorities, because they will not be degraded by bacterial activity once landfilled. Besides that, wood is the best example of a material that will degraded by the bacterial activity once landfilled. (Patrick.J et. Al, 1999)

Quantifying waste

The amount of C&D waste produced depend on several variables. Donovan,(1991) suggests that the amount of C&D waste generated at the national level depend on:

The extent of growth and overall economic development that drives the level of construction, renovation and demolition.

Periodic special projects, such as urban renewal, road construction and bridge repair, and unplanned events, such as natural disasters.

Availability and cost of hauling and disposal options.

Local, state and federal regulations concerning separation, reuse and recycling of C&D

Availability of recycling facilities and the extent of end-use markets

The difficulty in quantifying the amount of waste being landfilled is due to the difficulty of measuring specific quantity of the waste. The C&D debris is handled by contractors, waste haulers and landfill operators. Another difficulty in quantifying the waste is its highly variable and heterogenous nature. The amount of waste produced by a contractor may differ significantly that produced by another, due to level of expertise or training of employees. (Patrick.J et. Al, 1999)

Table 2.5- C&D waste material categories and sources

Waste material

Demolition source

Construction source


Roads, bridges, parking lots, roofing materials, flooring materials



Masonry building equipment white goods, appliances installed equipment



Plumbing fixtures, tiles



Foundation, reinforced concrete frame, sidewalks, parking lots, driveways



Lead-based paint, asbestos insulation, fiberglass, fuel tanks

Paints, finishes


Ceiling systems material, insulation



Windows, doors



Wall board, interior partitions


Metals, ferrous

Structural steel, pipes roofing, flashing, iron, stainless steel


Metals, nonferrous

Aluminum, copper, brass, lead

Same, but no lead



Corrugated cardboard, packaging


Vinyl siding, doors, windows, signage, plumbing



Site clearance

Same, add packaging

Wood, treated

Plywood: pressure- or creosote-treated, laminates


Wood, untreated

Framing, scraps, stumps, tops, limbs


Source : (Patrick.J, 1999)

2.6 Techniques for Reduction of Construction Waste

2.6.1 Source Reduction

Source reduction or waste prevention includes the design, manufacture, purchase, or use of materials such as products and packaging, in a manner that reduces their amount or toxicity before they enter the waste management system (Pichtel, 2005). In other words, by not producing the waste, there is no longer a concern over storage, collection, disposal costs and liability. Reduction is the best and most efficient manner of minimizing the generation of waste and eliminating many of the waste disposal problems. Conventionally, hazardous materials in most industries are the leading target for reduction and as the costs of handling the toxic wastes are rising, the effort to reduce them are stimulated as well. In view of that, the increasing costs will start acting as a strong encouragement to reduce non-hazardous wastes as well. The best way to reduce impact upon landfill is to fully utilizes waste reduction practices in design phase and as well as in construction stage. This can be implemented by on-site sorting of construction wastes before disposal which will eventually leading to recycling

(Cheung, 2004)

2.6.2 Reuse Technique

Reuse technique is defined as re-employment of materials to be reuse in the same application or to be used in lower grade application. The contractor has the major responsibility for adopting the reuse technique in the project. Materials such as wood, earthworks, steel, concrete, masonry, tiles, plasterboard, insulation materials, paints, solvent and carpets can be profitably reused on the construction site.

2.6.3 Recycle Technique

Recycle technique is defined as utilizing wastes as raw materials in other application. Recycle endeavors can be successfully utilized during the construction phase. The party responsible at this stage is the contractor. The responsibility allocated to the contractor could be as follows:

The contractor can apply on-site/off site waste recycling for waste materials such as earthworks, wood, concrete, masonry, asphalt, tiles, metals, non-ferrous metal, packing, plastic, glass, cardboards and plasterboard.

When recycled materials are used, the contractor should ensure that all recycled materials should be in accordance with all the quality tests of the national specifications.

2.6.4 Recovery Technique

A recovery technique is a process of generating energy from waste materials that cannot be reduced, reused or recycled. The party responsible at this stage is the contractor who can apply various waste recovery technique such as briquetting, incinerating, pyrolysis, gasification and biodigestion. This recovery technique is a waste-to-energy recovery technique which is recommended universally. The best recovery technique is the waste-to-material recovery technique for conservation of natural resources.

2.7 Recycling Methods

2.7.1 Plastic Recycling

There are various type of plastic recycling process to recycle the used plastic into new products, which is plastic process scrap recycling, mechanical recycling and chemical or feedstock recycling. Plastic Process Scrap Recycling

Currently most plastic recycling in the UK is of 'process scrap' from industry, example polymers left over from the production of plastics. This is relatively simple and economical to recycle, as there is a regular and reliable source and the material is relatively uncontaminated. Process scrap represents some 250,000 tonnes of the plastic waste arising in the UK and approximately 95 percent of this is recycled. This is usually described as reprocessing rather than recycling. Mechanical Recycling

Mechanical recycling of plastics refers to processes which involve the melting, shredding or granulation of waste plastics. Plastics must be sorted prior to mechanical recycling. At the moment in the UK most sorting for mechanical recycling is done by trained staff who manually sort the plastics into polymer type and colour. Technology is being introduced to sort plastics automatically, using various techniques such as X-ray fluorescence, infrared and near infrared spectroscopy, electrostatics and flotation. Following sorting, the plastic is either melted down directly and moulded into a new shape, or melted down after being shredded into flakes and then processed into granules called regranulate. Chemical or Feedstock Recycling

Feedstock recycling describes a range of plastic recovery techniques to make plastics, which break down polymers into their constituent monomers, which in turn can be used again in refineries, or petrochemical and chemical production. A range of feedstock recycling technologies is currently being explored. These include pyrolysis, hydrogenation, gasification and thermal cracking. Feedstock recycling has a greater flexibility over composition and is more tolerant to impurities than mechanical recycling, although it is capital intensive and requires very large quantities of used plastic for reprocessing to be economically viable. (Industry Council for Electronic Equipment Recycling,2005)

2.7.2 Concrete Recycling

Concrete recycling are importance because it protects natural resources and eliminates the need for disposal by using the available concrete as an aggregate source for new concrete or other applications. According to a FHWA study (2004), 38 states recycle concrete as an aggregate base, 11 recycle it into new portland cement concrete. The states that do use recycled concrete aggregate (RCA) in new concrete report that concrete with RCA performs equal to concrete with natural aggregates. Most agencies specify using the material directly in the project that is being reconstructed.

Recycling of concrete is a simple process. It involves breaking, removing, and crushing existing concrete into a material with a specified size and quality. The quality of concrete with RCA is very dependent on the quality of the recycled material used. Reinforcing steel and other embedded items, if any, must be removed, and care must be taken to prevent contamination by other materials that can be troublesome, such as asphalt, soil and clay balls, chlorides, glass, gypsum board, sealants, paper, plaster, wood, and roofing materials.

In general, applications without any processing include:

Many types of general bulk fills

Bank protection

Base or fill for drainage structures

Road construction

Noise barriers and embankments

Most of the unprocessed crushed concrete aggregate is sold as 37.5 mm (1½ in.) or 50 mm (2 in.).

After removal of contaminants through selective demolition, screening and air separation and size reduction in a crusher to aggregate sizes, crushed concrete can be used as:

New concrete for pavements, shoulders, median barriers, sidewalks, curbs and gutters, and bridge foundations

Structural grade concrete

Soil-cement pavement bases

Lean-concrete bases

Bituminous concrete (Portland Cement Association,2010) 

2.7.3 Paper Recycling

The used paper collected and send to the paper recycling plant to perform the several process below to produce new paper.

i . Re-pulping and Screening

The paper moves by conveyor to a big vat called a pulper, which contains water and chemicals. The pulper chaps the recovered paper into small pieces. Heating the mixture breaks the paper down more quickly into tiny strands of cellulose called fibers. Then the old paper turns into a mushy mixture called pulp. This pulp is forced through screens containing holes and slots of various shapes and sizes. The screens remove small contaminants such as bits of plastic and globs of glue. This process called screening.

ii. Cleaning

Mills also clean pulp by spinning it around in large cone-shaped cylinders. Heavy contaminants like staples are thrown to the outside of the cone and fall through the bottom of the cylinder. Lighter contaminants collect in the center of the cone and are removed. This process is called cleaning.

iii.. Deinking

Operation to remove printing ink and "stickies"(sticky materials like glue residue and adhesives). Papermakers often use a combination of two deinking processes. Small particles of ink are rinsed from the pulp with water in a process called washing.

iv) Flotation

Larger particles and stickies are removed with air bubbles. The surfactants cause ink and stickies to loosen from the pulp and stick to the air bubbles as they float to the top of the mixture. The inky air bubbles create foam or froth which is removed from the top, leaving the clean pulp behind.

v) Refining, bleaching and color stripping

The pulp is beaten to make the recycled fibers swell, making them ideal for papermaking. If the pulp contains any large bundles of fibers, refining separates them into individual fibers. If the recovered paper is colored, color stripping chemicals remove the dyes from the paper. Then, if white recycled paper is being made, the pulp may need to be bleached with hydrogen peroxide, chlorine dioxide, or oxygen to make it whiter and brighter. If brown recycled paper is being made, such as the used for industrial paper towels, the pulp does not need to be bleached.

(The Leading Technical Association for the Worldwide Pulp, Paper and Converting Industry,2001)

2.7.4 Masonry Recycling

Masonry is normally crushed as recycled masonry aggregate. A special application of recycled masonry aggregate is use it as thermal insulating concrete containing polystyrene beads (Hendriks and Pietersen, 2000), which provides a lightweight type of concrete and with high thermal insulation. Another potential application for recycled masonry aggregate is to use it as aggregate in traditional clay bricks as well as in sodium silicate brick (Hendriks and Pietersen, 2000):

i. A little portion of recycled masonry aggregate is used as a replacement for clay in

brick and as a sand replacement in sodium silicate brick.

ii. For use in traditional clay brick, this fraction should not contain any lime to prevent

adverse effects on strength, shrinkage, durability and colour.

iii. When used in sodium silicate brick, this fraction may contain lime, but the sodium

silicate brick should be produced at a pressure of 15 bar and at lower temperatures than

clay brick.

When the recycled masonry aggregate is used for sodium silicate brick, adhering cement has to be removed by a mechanical or thermal process. Interfacial stress is created when cement covered brick is heated to 900 â-¦C and the cement can then be removed as fines (Hendriks and Pietersen, 2000). This material can be heated to produce clinker. The volume of carbon dioxide (CO2) produced by this process is lower than that when natural material is used. Lime mortar can be reused after heating; but the adhesive has to be removed mechanically when processing sodium silicate brick.

2.7.5 Metal Recycling

i. Process one- Collection

The most commonly recycled metals are steel and aluminum. The benefit of scrap metal recycling is that it has an indefinite reuse life; metal can be recycled over and over without losing strength or losing its material compound. The recycling process starts with scrap metals are collected from disposed vehicles, consumers items (such as cans), and industrial products. The metals are sent to sorting agents who separate the metals by type and composition, to keep like metals together. The sorting agents then send the scrap metals to a metal recycling plant.

ii. Process two- Melting

The metal recycling plant performs a quality inspection on the scrap metal it receives to make sure that the sorting agent has correctly separated the types of metals. After the inspection, the metal is heated by a smelter, a device capable of melting large objects at very high temperatures. The different types of metals go through different smelters, because each metal has a different melting point (for example, aluminum melts at 1,200 degrees Fahrenheit, steel melts at 2,800 degrees Fahrenheit). Once the metals are fully molten, they are molded into small bars called ingots and are allowed to cool.

iii. Process three- Uses

The ingots are distributed to manufacturers and re-melted to become made into different products. Some popular uses for recycled metals are aluminum cans (for soft drinks), office products (filing cabinets, storage racks), and household products (canned foods, metal furnishing). In recent years, steel from old automobiles has even been used in conjunction with new steel to manufacture new automobiles. (Edward Jenkins,2008)

2.7.6 Timber Recycling

Timber waste from C&D works is produced in large quantity all over the world. It

is estimated that more than 2.5 million tonnes of timber wastes generated in the United

Kingdom each year (Coventry, 1999; Masters, 2001). Timber waste has a potential of being recycled as:

i) Whole timber arising from C&D activities can be utilized easily and directly for reused in other construction projects after cleaning, de-nailing and sizing. Undamaged wood can be reused as plank, beam, door, floorboard, rafter, panel, balcony parapet and pile (Hendriks and Pietersen, 2000). In 2004, Japan developed a new technology in turning timber waste into furniture, shoring wooden pile for relocated pine trees, wood bench and timber stair.

ii) A special lightweight concrete can be produced from aggregate made from recycled

small wood chunk.

iii) Timber waste can be recycled as energy, such as fuel, charcoal for power generation in Japan. In the Netherlands, 400,000 tonnes of wood from C&D activities are generated (Hendriks and Pietersen, 2000) most of this wood is landfilled or incinerated as a by-product in either coal-fired power plant or cement kiln; prior to incineration the

wood will have be reduced in size drastically. Blast furnace deoxidization is also

adopted in recycling timber.