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