Management and Reuse of Construction Wastes

Professor C.S. Poon

Dept of Civil and Structural EngineeringThe Hong Kong Polytechnic University

15

C&D Waste Generation

• Inert C&D materials (mainly sand, bricks and concrete) both suitable for land reclamation and land formation works, are disposed of at public filling areas.

• Non inert portion (bamboo, plastics, glass, wood, paper, vegetation and other organic materials) ends up at municipal solid waste landfills.

2

6

Salvageable Scraps –Reuse/Recycling

C&D Waste

C&D Waste Management in Hong Kong

Non-inert Portion -Landfills

Inert Portion – Public fills Mixed waste – Sorting facility

3

Construction Waste (source EPD)(2008)

5%

86%

10%

Sorting Facilities2,080 tpd

Public Fill Reception Facilities18,680 tpd

Landfills1,020 tpd

Total: 21,780 tpd

Figures may not add up to total due to rounding-off

93% 7%

Non-inert

68% 25%

Soft Hard

20% 5%

Recyclable Non-recyclable

Inert

Construction Waste(Approx. 15.4 M tonnes in Year 2009) (source CEDD)

88

C&D Materials Management Facilities Locations

30

The Problem

Hong Kong will soon be running out of both landfill space and public filling areas.

According to Government sources :

• Landfills will be filled up soon.

• Limited reclamation projects. Temporary fill banks will be full soon.

11

12

Delivery of Reclamation Material to Mainland

13

Designated Reclamation Site in Mainland

台山廣海灣華僑投資開發試驗區

香港特別行政區

20km

香港特別行政區

14

Construction Waste Disposal Charging Scheme

• Implemented on 1 Dec 2005

Government waste disposal facilities

Type of construction waste acceptedCharge per

tonne

Public fill reception facilitiesConsisting entirely of inert construction waste

$27

Sorting facilitiesContaining more than 50% by

weight of inert construction waste

$100

LandfillsContaining not more than 50% by

weight of inert construction waste

$125

Outlying Islands Transfer Facilities

Containing any percentage ofinert construction waste

$125

5

What can we do with the problems?

1. Avoid waste generation

2. Minimize waste generation

3. Reuse/Recycle the material

4. Proper disposal of waste

AVOID

MINIMISE

REUSE/RECYCLE

DISPOSAL

24

Form work Finish work Concrete

work

Masonry

work

Material

handling

Scaffolding

work

Hoarding

Ranking of Major Waste Producing Processeson Building Sites

Source : HK PolyU

25

Damaged during

laying

19%

Cutting Waste

39%

Damaged during

storage

11%

Over Order

15%

Damaged during

transportation

16%

Figure 6 Major Causes of Waste for Brick/Block (Source: Hong Kong PolyU [ 6 ] )

26

Over order

11%

Others

7%Cutting waste

40%

Damaged during

storage

29%

Change of design

13%

Figure 8 Major Causes of Waste for Tiles (Source: Hong Kong PolyU [ 6 ] )

Source : HK PolyU

27

Major Causes of Waste for Cement/Plaster

Improper storage

11%

Lost while

applying

19%

Left over of

mixed materials

59%

Others

11%

Source : HK PolyU

28

Percentage wastage of various trades

Trade Material Percentage wastage

Public Private

Concrete Concrete 3-5% 4-5%

Formwork Timber broad - 100%

Reinforcement Steel bars 3-5% 1-8%

Masonry Brick and block

3% 4-8%

Dry Wall Fine aggregate 3% -

Wall screeding Ready-mix cement

7% 4-20%

Floor screeding Ready-mix cement

1% 4-20%

Wall plastering Plaster 3% 4-20%

Source : HK PolyU

29

Ceiling plastering

Plaster 3% 4-20%

Wall tiling Tiles 8% 4-10%

Floor tiling Tiles 6% 4-10%

Installation of bathroom fitting

Sanitary fitting 6% 1-5%

Installation of kitchen joinery

Kitchen joinery 1% 1-5%

Percentage wastage of various trades

Source : HK PolyU

34

Design to Minimize Construction Waste

Waste arising from construction can be reduced by:

• Dimensional coordination and standardization

• Minimizing temporary works

• Avoiding late design modifications

• Detailing and simple design

35

Dimensional Coordination and Standardization

36

Minimizing Temporary Works

• In Hong Kong, most of the waste arising from temporary works is due to the use of timber formworks

37

Minimizing Temporary Works

Alternatives to be considered:

•system formworks (metal or aluminum formworks) that can be reused and/or recycled

•Prefabricated elements (facades, slabs, staircases, etc)

38

Minimizing Temporary Works

Other reusable alternatives to be considered:

• Metal temporary work• Metal platform work• Reusable safety system• Metal scaffolding or mixed

bamboo and metal scaffolding• Metal hoarding

39

0.21

0.56

0.76

1.11

1.31

1.33

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Waste reduction

Labor dependence

Developers requirement

Familiarity with the construction tecnology

Construction cost

Construction time

Fac

tors

Index

Construction Method Selection

41

On-site Construction Methods

Most waste producing work process

0

0

0

0

0.35

0.46

0.77

1.09

0 0.2 0.4 0.6 0.8 1 1.2

Hoarding

Masonry work

Concrete work

Scaffolding

Materials handling

Finish work

Packaging & protection

Formwork

Bu

ildin

g w

ork

co

mp

on

ents

index

43

On-site Low Waste Building Technologies

Formworks:

• Large panel formwork.

• Steel, aluminum and plastic forms.

• Composite steel decking.

• Pecaform.

44

Off-site: Precast and Prefabrication

• Off-site construction can reduce waste generation on-site, as waste is generated at a plant and easier to be managed and sorted.

• The use of prefabricated elements is highly applicable to high-rise construction in Hong Kong.

• Prefabrication requires experience, knowledge and also early planning and decisions at the design stage.

45

Off-site: Precast and Prefabrication

46

Modular Construction

•Modular construction approach has been demonstrated for high-rise buildings in Hong Kong by the Integer project.

Prof. C.S. PoonDept of Civil and Structural EngineeringThe Hong Kong Polytechnic UniversityTel : (852) 2766-6024Email : cecspoon@polyu.edu.hk

Thank You