-
Construction and Demolition Waste, its Variability and Recycling
in Brazil
Srgio Cirelli Angulo, MEng.1
Leonardo Fagundes Rosemback Miranda, MEng 1 Vanderley M. John,
Dr. Eng. 2
1 Ph.D. candidates. Escola Politcnica da Universidade de So
Paulo. Av. Prof. Almeida Prado, trav 2. 05508-900. So Paulo.
Brazil. Phone: +55 11 3091-5459. Fax: +55 11 3091-
5544. E-mail: [email protected] ;
[email protected] 2. Escola Politcnica da Universidade
de So Paulo. Dept. of Civil Construction Eng. Av Prof. Almeida
Prado, trav 2. 05508-900. So Paulo Brazil. Phones: +55 11
3091-5794; Fax: +55 11
3901-5544. E-mail: [email protected] 1 CDW GENERATION RATE IN
BRAZIL
There are few consistent studies on construction and demolition
waste (CDW) generation rates in Brazil. However, the available data
does allow suggesting that the amount of CDW is probably higher
than the amount (w/w) of Municipal Solid Waste (MSW). A typical
Brazilian
per capita CDW generation rate for some cities is above 500
kg/year (Table 1).
Table 1 CDW Quantity, population and some generation rates in
Brazil (Pinto, 1999).
City State Population
(Inhab.)
CDW Quantity (ton/year)
CDW per capita
(kg/year)
Data from year
Santo Andr So Paulo 625,564 369,745 591 1997
Vitria da Conquista Bahia 242,155 113,150 467 1998
Ribeiro Preto So Paulo 456,252 380,695 834 1995
So Jos do Rio Preto So Paulo 323,627 250,755 775 1997
These values are consistent with reported international
generation rates. The reported CDW
participation in the total MSW varies from 13% (Bossink;
Brouwers, 1996) to 67% (Lauritzen, 1994). A study conducted by the
European Union reports a variation of the per capita generation
from 136 kg/year up to 3359 kg/year (EU, 1999). A significant
portion of
the variation in CDW generation rates is a direct result of CDW
definition. Other sources of variation are the differences in the
industrial structure and the degree of development as well as the
characteristics of the building technologies used in each country,
etc.
2 ORIGIN OF CDW
Like most developing countries, Brazil is still under
construction. The construction related
business is about 15% of the Brazilian GNP. Because of the
relatively high production of construction waste at building sites,
CW represents approximately 50% of the total CDW generated (Pinto,
1999). In more developed countries, like those of Europe and the
USA, the
construction activity is responsible for about 1/3 of the total
CDW produced (Lauritzen, 1994; Peng et al, 1997)
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In Brazil, construction waste quantities are increased due to
high rates of material wastage at
building sites. Table 2 presents selected wastage rates measured
at about 63 new building sites in Brazil (Souza et al., 1999). This
data is valid only for the formal construction industry. Until now,
there has been no data about material wastage for the informal
(do-it-yourself)
construction sector, which produces most of the low-cost houses
in Brazil.
Table 2 Material wastage in new building sites and estimations
of construction waste
(Souza et al, 1999; Andrade, 2001).
Wastage (%) Waste (%) Materials
Median Minimum Maximum 2.1.1 Median
Concrete 9 2 23 1.3
Steel 11 4 16 7.7
Blocks and bricks 13 3 48 13
Ceramic tiles 13 5 19 13
Mortar (screed) 42 8 288 2.1
3 CDW TRADITIONAL MANAGEMENT IN BRAZIL
As a rule, municipal policy towards CDW residues has been to
ignore them. The only strategy towards CDW traditionally adopted by
local authorities has been to repeatedly clean fly
tipping areas and, sometimes, operate a CDW landfill or accept
CDW dumping in the municipal solid waste landfill. Nevertheless,
the landfill never succeeds in attracting more than a fraction of
the total CDW generated and fly tipping is the most common
private
solution adopted for disposing of CDW. The landfill operated by
the city of So Paulo attracts only 15% of the total CDW generated
in that area (Schneider, 2002).
Fly tipping areas can be streets (Figure 1), parks, private
areas and creek banks. The environmental impact associated with
this kind of dumping is important. The proliferation of pests (rats
and poisonous insects, among others), traffic hazards and landscape
destruction are
part of this issue. The city of So Paulo estimates that illegal
dumping in public areas is as high as 20% of the total CDW
(Schneider, 2002).
Removing this illegally dumped CDW is also very expensive. In
city of So Paulo, the local authorities report spending about R$45
million a year (about US $19 million) removing illegally dumped CDW
(Schneider, 2002) from the one official CDW landfill.
(a) (b)
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Figure 1 Illegal dumping sites in city of So Paulo. (a) Street
used as dumping area just
after being cleaned by the local authorities (2002-08-30) (b)
the same area after two months (2002-11-04).
Most middle-sized and big cities do have private CDW landfills.
Most of these landfills operate without a license. Environmental
licensing is very difficult because there are no consolidated
regulations. Also, private dumping sites do not have any design
that ensures
stability and there is no practical control over the waste
dumped, leading to great risk of environmental contamination. It is
known that one illegal C&D landfill collapsed about 10 years
ago in So Paulo, killing 13 persons.
As a consequence, CDW management is a profitable business, with
revenues estimated to be higher than US $40 million/year in the
city of So Paulo alone (John; Agopyan, 2000). Most
CDW in Brazilian middle-sized and big cities is collected and
transported by specialized private companies, using open containers
(chain lift skips).
In big cities like So Paulo, there are no longer so many places
suited to be landfills. So the landfill prices are increasing. Also
a significant part of the CDW generated in So Paulo is, at present,
being exported to other municipalities within the metropolitan area
and illegally
dumped there. This additional distance adds to the cost of
transport and disposal. The price for removing and dumping a 4m3
container (including the renting fee for up to a week) can be as
high as US $30,001 in So Paulo.
There are some companies that recycle CDW as rendering mortar
using a small rotating mill installed at the building site
(Miranda, 2000). Grigoli (2000) reports other uses of CDW in-
site. 4 TRENDS ON CDW MANAGEMENT IN BRAZIL
Management of CDW is changing very fast. In the next few years
most municipalities are expected to develop specific policies
towards CDW.
Some municipalities, such as Belo Horizonte, have already
implemented successful systems to manage CDW and others are in the
process of doing the same. This system includes registration of
companies that transport CDW, a well-located network of CDW deposit
sites
which attract most of the CDW and a recycling plant, which
produces aggregates and gives proper destination to the metallic
and organic fraction. Education is an important component of the
system as well as an effective structure to prevent and punish fly
tipping. In big cities,
like So Paulo, stations sort the waste and transfer it to bigger
trucks, making the system cheaper and reducing the impact of
transporting the CDW in urban area.
The CDW recycling plant belongs to the municipality, which
consumes most of the aggregates as road base. Very frequently,
political changes halt the entire system. So Paulo, Londrina and So
Jos dos Campos are examples.
The National Council for the Environment (CONAMA) is in the
process of approving a directive on CDW management that will
require all municipalities and building contractors to
set up management schemes. This directive has been negotiated
with the community. Additionally, the CDW Task Group of the
Environmental Chamber of the Construction
1 Exchange rate US $1 = R$2.4
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Industry of the State of So Paulo is drafting drafts of
technical standards related to the use of
recycled aggregates as well as proposals of regulations for
licensing CDW landfills and transfer stations.
As a result of these efforts, recycling construction demolition
waste is expected to become an important business in Brazil in the
near future.
5 RECYCLING PLANTS TECHNOLOGY
Brazilian CDW recycling plants are simple and stationary. As in
Europe, most of plants are derived from mining engineering but do
not apply any better technological equipment or new
ways of more elaborate separation and concentration (Hendriks,
2000). As a rule, these plants consist only of manual pre-sorting
system, crushers, manual sorting that removes contamination,
conveyor belts and screenings (Figure 2). A magnetic separator is
used in
some plants such as the ones in So Paulo and Belo Horizonte.
There is no systematic control of the arriving material although
there is visual inspection. Likewise, there is no systematic
quality control of the delivered aggregates.
Figure 2 Typical Brazilian CDW recycling plant (City
Municipality Vinhedo So
Paulo state) aggregates for road base. Most of the aggregates
produced by the recycling plants are used as road base in urban
paving
activities. Some tentative applications of selected recycled
aggregates for concrete component production (concrete blocks and
paving blocks) have been made, in the cities of Vinhedo, Belo
Horizonte and Santo Andr. However, in at least one case, the cement
consumption rate
was at least 30% higher that the required for natural
aggregates. 6 CDW, ITS VARIABILITY AND RECYCLING POSSIBILITIES
6.1 Sources of composition variability
CDW is a mixture of the materials used in the building (Figure 3
and Figure 4) and the
composition is highly variable. In Brazil, the typical building
waste is a mixture of ceramic or concrete blocks, mortar,
reinforced concrete, steel, plastic, asbestos cement and wood. The
use of gypsum as plasterboard or plaster is on the rise and is
expected to become a significant
part of the waste in a few years time.
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Figure 3 Contamination of a CDW container in downtown So Paulo,
by litter. In addition to the litter, there is mixture of waste
from masonry, concrete, wood
and rubber.
Construction waste, which is about 50% of the Brazilian CDW, is
considered to be more
mixed and variable because there is less discipline in waste
discharge. This is due to the wide variety of contractors, the high
cost of waste separation, insufficient areas for waste discharge
and different waste period production in building sites (Hendriks,
2000). In Brazil, demolition
waste also tends to be a mixture of all phases, because
sophisticated selective demolition techniques are only applied to
very old residential buildings, where the bricks, windows, etc have
a high market value.
As most of the CDW containers are parked in the streets or in
front of the building site, neighbours often place additional
litter in the containers, further increasing the contamination
(Figure 3). So, without changes in CDW management at both
construction and demolition sites, it will be very difficult to
classify the arriving waste as predominantly concrete or masonry,
as specified
by European countries (Rilem Recommendation, 1994; Hendriks,
2000).
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Figure 4 Brazilian CDW in containers typically contains a
mixture of masonry, mortar
and concrete.
6.2 Composition variability
As can be seen in Table 3, the composition of Brazilian CDW
recycled aggregates is highly
variable. Angulo (2000) presents results of the most
comprehensive investigation about the variability and quality of
CDW aggregate produced in Brazil. While studying the operation of
an experimental recycling plant in Santo Andre (So Paulo
Metropolitan Area), the author
took hourly samples during 12 working days. Zordan (1997)
results are after three random samples.
Table 3 Reported composition and its variability for some
Brazilian CDW aggregate recycling plants.
Angulo (2000) Zordan (1997) Composition
(%) Min Av Max Brito (1999)
Carneiro et
al. (2001) Min Av Max
Concrete 23 44 62 20 21 22
Gravel 3 23 50 10 19 28
Mortar 10 28 61
32 53
35 37 39
Ceramic 0 4 13 33 15 16 23 30
Soils - - - 30 21 - - -
Wood & Organic - - - 1 4 - - -
Others 0.0 1.2 4.6 4 7 - - -
City Santo Andr So Paulo Salvador Ribeiro Preto
6.3 Variability and recycling
The high variability of the composition is in itself a major
problem when recycling, even when considering its use as road base
aggregate.
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Angulo and John (2002) compared the aggregates characteristics
(mortar + ceramic
maximum content, maximum water absorption, density, maximum
content of contaminants and filler content) with those specified in
the RILEM recommendations and the Dutch Standard (Rilem
Recommendation, 1994; Hendriks, 2000). None of the 36 samples
studied
complied with the standards for use in structural concrete. And
only 10 samples did comply with the Dutch rules for demolished
masonry aggregate, suitable for use in non-structural concrete
applications. The major reasons for non-compliance with
non-structural applications
were filler content and the presence of contaminants as well as
mortar plus ceramic maximum content. The contaminants most
frequently detected were asphalt, glass and wood. No evaluation for
sulphate control was made.
Zordan (1997) investigated the effect of the variation of the
composition of the CDW in concrete. It was found that compressive
strength is reduced 30% for 1:3 (cement/aggregates
proportion) and w/c (water/cement) relation of 0.5 when the
composition varies (see Table 3). Miranda (2000) studied the
influence of CDW composition variability on performance
rendering mortar. Laboratory produced waste was analysed to
determine what influence the content of concrete blocks, ceramic
blocks and mortars have in the properties of fresh and hardened
mortar samples. An increase in mortar content generated a higher
incidence of
cracking on rendering caused by higher water/cement relation.
So, at present, road base aggregate seems to be the only market for
recycled CDW aggregates.
However, in most cities, the municipal consumption of road base
aggregate is not enough to consume the total available waste
(Pinto, 1999).
Consequently, long-term development of a market big enough to
recycle all CDW will demand new and more valuable applications. To
achieve this goal it will be necessary to (a) introduce changes in
CDW management for construction, demolition and transportation,
(b)
to significantly improve the recycling plants. 6.4 Improving
Brazilian recycling plants
One possibility for improving CDW recycling plants is the
adoption of equipment to classify the waste based on its specific
gravity, like jig (Jungmann; Quindt, 1999; Ancia et al., 1999).
This kind of technology allows separating the densest aggregates
that can be, potentially,
recycled in more valuable applications, like concrete
production. Results from Angulo (2000) confirm that this technology
can be very useful in the Brazilian market (Figure 5).
-
y = -9,81x + 26,89
R2 = 0,55
y = -15,63x + 40,74
R2 = 0,85
y = -24,50x + 61,36
R2 = 0,66
0
5
10
15
20
25
30
0,5 1,0 1,5 2,0 2,5 3,0
Specific gravity (kg/dm?)
Wa
ter
ab
so
rpti
on
- 2
4 h
(%
)
ceramic
rock
concrete_mortar
Figure 5 Water absorption x specific gravity of different CDW
aggregate phases
(Angulo, 2000) Another option is the adoption of homogenisation
piles, especially when combined with jigs,
because they drastically reduce the variability of composition,
density and water absorption. Simulations with the data from Angulo
et al (2001) show that piles , which were accumulated during 3 or
more weeks of production presented stable compositions, water
absorption and
specific gravity. Considering the typical production of a
recycling plant to be above 300 ton/day, the homogenisation pile
would require a relatively large storage area, which would reduce
the recycling site options and increase the site cost. Combining
the homogenisation
technique with jig classification can reduce the time necessary
to get a stable composition Developing a fast and cheap methodology
to control the quality of recycled aggregates is also
vital to the development of more sophisticated markets for the
aggregates. Such techniques must be precise enough to allow
certification of the composition and other quality relevant
requirements of the generated aggregate.
7 CONCLUSIONS
C&D Waste is a relevant problem in Brazilian society. The
generation rate is high, being
around 500 kg/year per capita. Illegal dumping is a current
practice, with considerable social and environmental impact.
Nevertheless, CDW management is a prosperous business in most
cities.
At present, the amount of recycled waste is very small and the
resulting product is used as road base. The technology of the
recycling plants is very simple. There is no systematic
quality control of the resulting product. It results in
aggregates with high variable compositions and with a high content
of ceramic and mortar materials. A small fraction of the resulting
aggregate is suitable for more valuable applications like producing
concrete and
concrete components. The ongoing changes within the
institutional framework, especially the national regulation on
CDW, technical standards and the development of municipal
policies will greatly increase the demand for recycling in the near
future.
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In order to increase recyclability and attract private
investments to the recycling market, both
waste management practices and recycling technology must be
improved. Homogenisation piles combined with density based
classification systems (jig) are interesting options for the
technical improvement of recycling plants.
8 ACKNOWLEDGEMENTS
This research is supported by FINEP (Fundo Verde e Amarelo),
CNPQ (doctoral scholarship)
e FAPESP (doctoral scholarship). 9 REFERENCES
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