Management and Reuse of Construction Wastes

Transcription

1 Management and Reuse of Construction Wastes Professor C.S. Poon Dept of Civil and Structural Engineering The Hong Kong Polytechnic University 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. 15

2 2 C&D Waste Management in Hong Kong Salvageable Scraps Reuse/Recycling C&D Waste Non-inert Portion - Landfills 6 Inert Portion Public fills Mixed waste Sorting facility

3 Construction Waste (source EPD) (2008) Sorting Facilities 2,080 tpd 10% 5% Landfills 1,020 tpd 86% Public Fill Reception Facilities 18,680 tpd Total: 21,780 tpd 3 Figures may not add up to total due to rounding-off Construction Waste (Approx M tonnes in Year 2009) (source CEDD) 93% 7% Inert Non-inert 68% 25% Soft Hard 20% 5% Recyclable Non-recyclable

4 C&D Materials Management Facilities Locations 8 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. 30

5 11 Delivery of Reclamation Material to Mainland 12

6 Designated Reclamation Site in Mainland 香港特別行政區 台山廣海灣華僑投資開發試驗區 20km 13 Construction Waste Disposal Charging Scheme Implemented on 1 Dec Government waste disposal facilities Public fill reception facilities Sorting facilities Landfills Outlying Islands Transfer Facilities Type of construction waste accepted Consisting entirely of inert construction waste Containing more than 50% by weight of inert construction waste Containing not more than 50% by weight of inert construction waste Containing any percentage of inert construction waste Charge per tonne $27 $100 $125 $125

7 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 5 Ranking of Major Waste Producing Processes on Building Sites Form work Finish work Concrete work Masonry work Material handling Scaffolding work Hoarding 24 Source : HK PolyU

8 Figure 6 Major Causes of Waste for Brick/Block (Source: Hong Kong PolyU [ 6 ] ) Damaged during transportation 16% Over Order 15% Damaged during storage 11% Damaged during laying 19% Cutting Waste 39% 25 Figure 8 Major Causes of Waste for Tiles (Source: Hong Kong PolyU [ 6 ] ) Over order 11% Change of design 13% Others 7% Cutting waste 40% Damaged during storage 29% 26 Source : HK PolyU

9 Major Causes of Waste for Cement/Plaster Improper storage 11% Others 11% Lost while applying 19% Left over of mixed materials 59% 27 Source : HK PolyU Percentage wastage of various trades Source : HK PolyU Trade Material Percentage wastage Public Private Concrete Concrete 3-5% 4-5% Formwork Timber broad - 100% 28 Reinforcement Steel bars 3-5% 1-8% Masonry Brick and 3% 4-8% block Dry Wall Fine aggregate 3% - Wall screeding Ready-mix 7% 4-20% cement Floor screeding Ready-mix 1% 4-20% cement Wall plastering Plaster 3% 4-20%

10 Percentage wastage of various trades Ceiling Plaster 3% 4-20% plastering Wall tiling Tiles 8% 4-10% Floor tiling Tiles 6% 4-10% Installation of bathroom fitting Installation of kitchen joinery Sanitary fitting 6% 1-5% Kitchen joinery 1% 1-5% 29 Source : HK PolyU 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 34

11 Dimensional Coordination and Standardization 35 Minimizing Temporary Works In Hong Kong, most of the waste arising from temporary works is due to the use of timber formworks 36

12 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) 37 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 38

13 Construction Method Selection Construction time Construction cost Factors Familiarity with the construction tecnology Developers requirement Labor dependence 0.56 Waste reduction Index 39 On-site Construction Methods Building work components Formwork Packaging & protection Finish work Materials handling Scaffolding Concrete work Masonry work Hoarding index Most waste producing work process 41

14 On-site Low Waste Building Technologies Formworks: Large panel formwork. Steel, aluminum and plastic forms. Composite steel decking. Pecaform. 43 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. 44

15 Off-site: Precast and Prefabrication 45 Modular Construction Modular construction approach has been demonstrated for high-rise buildings in Hong Kong by the Integer project. 46

16 Thank You Prof. C.S. Poon Dept of Civil and Structural Engineering The Hong Kong Polytechnic University Tel : (852) cecspoon@polyu.edu.hk