RECYCLING



TABLE OF CONTENTS





Abstract 3



Types of Construction and Demolition Wastes 4

Type I- Roadway and Site Conversion C&D Waste 4

Type II- Construction and Interior Demolition Waste 5



C&D Waste Processing Strategies 5

Type I C&D Waste Processing Strategy 6

Type II C&D Waste Processing Strategy 7



Conclusion 9

References 10













ABSTRACT





Environmental concerns about the huge landfill space that is being taken by construction and

demolition debris has brought up a new technique in salvaging construction material and recycling

demolition debris. Although one process exists for two types of waste, many have tried different strategies

in dealing with this problem. These strategies vary between "separating and sorting" then "crushing and

reducing" and "crushing and reducing" then "separating and sorting".



PROCESS OF C&D DEBRIS RECYCLING



C&D debris refers to materials generated as a result of construction and demolition projects. Metals, wood,

rocks, concrete, rubble, soil, paper, plastics and glass are among the many materials that are considered

C&D debris. Realizing that the disposal of C&D debris in landfills consumes large amount of space and is

economically and environmentally costly, the need to get acquainted with suitable recycling processes is

becoming more and more essential (1, p.18). Although, only one recycling process has been developed,

there are different strategies for implementation.



TYPES OF CONSTRUCTION AND DEMOLITION WASTES





Type I - Roadway and Site Conversion C&D Waste



C&D waste is classified as Type I if it consists mainly of rubble with a little ratio of "clean"

materials such as wood, metals, and plastics. Type I waste should be easily separable in order to be

considered as "clean". The composition by weight of a Type I C&D debris is (2, p.6.31):



Rubble

concrete, asphalt 40%

soil, rock 20%

Wood 30%

Metals, plastic 10%



Type II - Construction and Interior Demolition Waste



This type is mainly generated from urban structure such as office buildings, stores, etc.. Type II contains

mixed fractions of concrete, drywall, framing, ductwork, roofing, windows, corrugated, packaging, etc.(2,

p.6.32) . Due to its high heterogeneous composition this type is difficult to separate, it is mainly made of:



Rubble 25%

Wood 33%

Metals 20%

Corrugated 12%

other (carpet, residue, etc.) 10%



C & D WASTE PROCESSING STRATEGIES



Primary separating equipment used with type I are very efficient while with type II this procedure

along with hand sorting will take lots of time. Processing procedure is determined by the type of waste and

the possible use of the output materials (2, p.6.32). Table 1 shows the different contents of C & D waste .



Table 1 Contents of C&D Waste (2, p.6.31)

Waste type Contents

Rubble Soil, rock, concrete, asphalt, bricks

Tar-based material Shingles, tar paper

Ferrous metal Steel rebar, pipes, roofing, flashing, structural members, ductwork

Nonferrous metal Aluminum, copper, brass

Harvested wood Stumps, brush, treetops and limbs

Untreated wood Framing, scrap lumber, pallets

Treated wood Plywood, pressure-treated, laminates

Plaster Drywall, sheetrock

Glass Windows, doors

Plastic Vinyl siding, doors, windows, blinds, material packaging

White goods/bulky items Appliances, furniture, carpeting

Corrugated Material packaging, cartons, paper

Contaminants Lead paint, lead piping, asbestos, fiberglass, fuel tanks





Type I C & D Waste Processing Strategy



Clean rubble can directly be placed into a grizzly feeder where a jawcrusher and hammermiller could act on

it for reduction.





Figure 1 Debris placed into grizzly feeder



Sorting and reducing first is more practical than crushing if the debris contains material such as plastics,

paper, rags, or contaminants such as paint, lead pipes, etc.. After crushing the mix is then screened to

remove fine soil and small rocks. Any contaminants, ferrous, and non ferrous material is removed by either

manual picking or magnetic field belt. If wood is present in the rubble then the mix is guided towards a

flotation tank where the wood will float and thus the separation from rocks is achieved. Another system

instead of a flotation tank could be used and that is an air classifier. The air system is more expensive to

use, but if the recycling plant is located in a region where there is strict rules about water pollution, thus

requiring that the water from the flotation tank to be treated, then an air system might be a better option.

Crushing, reducing and then sorting and separating is much more recommended with systems made from

80% to 90% rubble, wood, a!

nd few contaminants. A general processing layout is shown in figure 2 and is available as both fixed and

portable designs(2, p.6.34).





Figure 2. Recycling plant



Type II C&D Waste Processing Strategy



It is essential that type II C&D waste be sorted and separated before being crushed and reduced

since this type of waste could have asbestos, paint, lead pipe, etc.. These contaminants could render