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ABSTRACT: Use of recycled aggregate in concrete can be useful for environmental protection. Recycled
aggregates are the materials for the future. The application of recycled aggregate has been started in a large
number of construction projects of many European, American, Russian and Asian countries. Many countries are
giving infrastructural laws relaxation for increasing the use of recycled aggregate. This paper reports the basic
properties of recycled fine aggregate and recycled coarse aggregate & also compares these properties with
natural aggregates. Basic changes in all aggregate properties are determined and their effects on concreting
work are discussed at length. Similarly the properties of recycled aggregate concrete are also determined. Basic
concrete properties like compressive strength, flexural strength, workability etc. are explained here for different
combinations of recycled aggregate with natural aggregate. Codal guidelines of recycled aggregates concrete
in various countries are stated here with their effects, on concreting work. In general, present status of recycled
aggregate in India along with its future need and its successful utilization are discussed here.
1. INTRODUCTION
1.1 Prelude – Need for Recycled Aggregate:-
Urbanization growth rate in India is very high due to industrialization. Growth rate of India is reaching 9% of
GDP. Rapid infrastructure development requires a large quantity of construction materials, land requirements &
the site. For large construction, concrete is preferred as it has longer life, low maintenance cost & better
performance. For achieving GDP rate, smaller structures are demolished & new towers are constructed.
Protection of environment is a basic factor which is directly connected with the survival of the human race.
Parameters like environmental consciousness, protection of natural resources, sustainable development, play an
important role in modern requirements of construction works. Due to modernization, demolished materials are
dumped on land & not used for any purpose. Such situations affect the fertility of land. As per report of Hindu
online of March 2007, India generates 23.75 million tons demolition waste annually. As per report of Central
Pollution Control Board (CPCB) Delhi, in India, 48million tons solid waste is produced out of which 14.5
million ton waste is produced from the construction waste sector, out of which only 3% waste is used for
embankment.
Out of the total construction demolition waste, 40% is of concrete , 30% ceramic‟s, 5% plastics, 10% wood,
5%metal, & 10% other mixtures. As reported by global insight, growth in global construction sector predicts an
increase in construction spending of 4800 billion US dollars in 2013. These figures indicate a tremendous
growth in the construction sector, almost 1.5 times in 5 Years.
For production of concrete, 70-75% aggregates are required. Out of this 60-67% is of coarse aggregate & 33-
40% is of fine aggregate. As per recent research by the Fredonia group, it is forecast that the global demand for
construction aggregates may exceed 26 billion tons by 2012. Leading this demand is the maximum user China
25%, Europe 12% & USA 10%, India is also in top 10 users. From environmental point of view, for production
of natural aggregates of 1 ton, emissions of 0.0046 million ton of carbon exist where as for 1ton recycled
aggregate produced only 0.0024 million ton carbon is produced. Considering the global consumption of 10
billion tons/year of aggregate for concrete production, the carbon footprint can be determined for the natural
aggregate as well as for the recycled aggregate.
The use of recycled aggregate generally increases the drying shrinkage creep & porosity to water &
decreases the compression strength of concrete compared to that of natural aggregate concrete. It is nearly 10-
30% as per replacement of aggregate.
Recycling reduces the cost (LCC) by about 34-41% & CO2 emission (LCCO2) by about 23-28% for dumping
at public / private disposal facilities.
1.2 Advantages of recycling of construction materials:-
Used for construction of precast & cast in situ gutters &kerb‟s.
Cost saving: - There are no detrimental effects on concrete & it is expected that the increase in the cost of
cement could be offset by the lower cost of Recycled Concrete Aggregate (RCA).
20% cement replaced by fly ash is found to control alkali silica reaction (ASR).
Save environment: - There is no excavation of natural resources & less transportation. Also less land is
required.
Save time: - There is no waiting for material availability.
Less emission of carbon due to less crushing.
Up to 20% replacement of natural aggregate with RCA or recycled mixed aggregates (RMA) without a
need for additional testing for all concrete up to a characteristic strength of 65 MPa., as per Dutch standard
VBT 1995, is permitted.
1.3 Limitations or disadvantages of recycling of construction material:-
Less quality (e.g. compressive strength reduces by 10-30%).
Duration of procurement of materials may affect life cycle of project.
Land, special equipments machineries are required (more cost).
Very high water absorption (up to 6%).
It has higher drying shrinkage & creep.
1.4 Objectives of the study:-
To find out the % use feasible for construction.
To reduce the impact of waste materials on environment.
To carry out different tests on recycled aggregates & natural aggregates & compare their results.
To find out the ways of cost saving such as transportation, excavation etc.
1.5 Methodology:-
Plain cement concrete (PCC) & reinforce cement concrete is collected from sites (i.e. Sri
SavitribaiPhule Polytechnic, Pune &MangaolGrampanchyat School, Mangaol, Haveli, Pune) respectively. This
collected material is crushed by hammer to separate the aggregates & reduce their sizes in smaller fraction. On
these separated aggregates various testes are conducted in laboratory as per Indian Standard code & their results
are compared with natural aggregates. Recycled aggregate reduces the impact of waste on environment. By
using some percentage in construction sector, cost is saved, due to reduction of transportation & manufacturing
process.
1.6 Anticipated Findings:-
All the results of tests should satisfy the IS requirement of natural aggregates.
Recycled aggregate will be feasible for construction to replace natural aggregates.
Cost saving due to reduction of transportation & crushing process of natural aggregates.
During the recycling process, remanufacturing technology and the quality of recycled products would be
the barriers.
LITERATURE REVIEW
Selected international experience has been outlined here which has relevance for the Indian situation:
A) Scotland – About 63% material has been recycled in 2000, remaining 37% material being disposed in
landfill and exempt sites.
a) The Government is working out on specifications of recycling and code of practice.
b) Attempts are being made for establishing links with the planning system, computerizing transfer note system
to facilitate data analysis and facilitating dialogue between agencies for adoption of secondary aggregates by
consultants and contractors.
B) Denmark – According to the Danish Environmental Protection Agency (DEPA), in 2003, 30% of the total
waste generated was Construction & Demolition waste.
a) According to DEPA around 70-75% waste is generated from demolition activity, 20-25% from renovation
and the remaining 5-10% from new building developments.
b) Because of constraints of landfill site, recycling is a key issue for the country.
c) Statutory orders, action plan and voluntary agreements have been carried out, e.g., reuse of asphalt (1985),
sorting of Construction & Demolition waste (1995) etc.
C) Netherlands – More than 40 million Construction & Demolition waste is being generated out of which 80%
is brick and concrete.
a) A number of initiatives taken about recycling material since 1993, such as prevention of waste, stimulate
recycling, promoting building materials which have a longer life, products which can be easily disassembled,
separation at source and prohibition of Construction & Demolition waste at landfills.
D) USA – Construction & Demolition waste accounts for about 22% of the total waste generated in the USA.
a) Reuse and recycling of Construction & Demolition waste is one component of larger holistic practices called
sustainable or green building practice.
b) Green building construction practices may include salvaging dimensional number, using reclaimed
aggregates from crushed concrete, grinding drywall scraps, to use as soil amendment at the site.
c) Promoting „„deconstruction‟‟ in place of „demolition‟.
d) Deconstruction means planned breaking of a building with reuse being the main motive.
E) Japan – Much of the R&D in Japan is focused on materials which can withstand earthquake and
prefabrication
a) 85 million tons of Construction & Demolition waste has been generated in 2000, out of which 95% of
concrete is crushed and reused as road bed and backfilling material, 98% of asphalt + concrete and 35% sludge
is recycled.
F) Singapore – Construction & Demolition waste is separately collected and recycled. A private company has
built an automated facility with 3, 00,000 ton per annum capacity.
G) Hong Kong – Concrete bricks and paving blocks have been successfully produced impregnation of photo
catalyst for controlling Nox in ambient air.
H) India – Use for embankment purpose in bridges, roads etc. up to 3% to 4% of total production.
Akmal, Sami1 (2011) insist that the available resources should be used appropriately & whenever recycled it
should be done at the national level with the help of GULF COOPERATION COUNCIL (GCC) &
ENVIRONMENT PROTECTION INDUSTRIAL CO (EPIC). They observe that GCC countries produce more
than 120 million tons of waste every year out of which 18.5% is related to solid construction waste. Results
from Dubai municipality indicate that out of 75% of 10,000 tons of general waste produced, 70% is of concrete
demolition waste.
The author strongly advocates that a strong commitment & investment by government bodies as well as
private bodies make this necessary for sustainability. Some materials are reused for recycling such as plastic,
glass etc. In the same way concrete can also be used continuously as long as the specification is right. Recycling
solid waste materials for construction purposes becomes an increasingly important waste management option, as
it can lead to environmental and economic benefits. Conservation of natural resources, saving of energy in
production and transportation, and reduction of pollution are also the advantages of recycling. In particular,
concrete is a perfect construction material for recycling.
In gulf countries natural resources are imported from different locations for fulfilling the need of
construction. Small sources available in gulf countries in Arabian Peninsula are limited. For construction work,
demand of desalinated water & sand locally available exits. Conservation of natural sources, saving natural
resources, energy transportation & reduction of pollution are advantage.
Guide for Cement & Concrete Association of New Zealand (CCANZ) 8
has show that the charges applying
$10/ton on land fill dumping often make recycling concrete aggregate (RCA) a preferred option. The use of
RCA to conserves natural aggregate & the associated environmental cost of exploration & transportation waste
minimization & reducing the burden on landfills is a global issue. Extensive research has been carried out
worldwide on the use of recycled aggregate in concrete. It also shows that globally the concrete construction industry has taken a responsible attitude to ensure that its natural resources are not over exploited. Due to issues
relating to sustainability and limited natural resources, it is clear that the use of recycled and secondary
aggregates (RSA), for example, crushed concrete and asphalt and industrial byproducts such as fly ash and blast
furnace slag, will grow. However, currently, it is only in the USA, Japan, parts of Western regulations have been
sufficiently put in the place that the use of RSA exceeds 10% of the total aggregate usage. Consequently,
worldwide the use of RSA stands at approximately 750 million tones, it is less 3% out of total aggregates use in
world. They also insist that sustainability is generally recognized as a foundation for resource and energy –
saving technological developments in many fields including that of construction.
Parekh, Modhera5
(2011) discuss the issues relating to sustainability and limited natural resources. They also
suggest use of recycled and secondary aggregates (RSA), for example crushed concrete and asphalt and
industrial byproducts such as fly ash and blast furnace slag. Then products now reused in different material
production.
There are many studies that prove that concrete made with this type of coarse aggregates can have
mechanical properties similar to those of conventional concretes and even high-strength concrete is nowadays a
possible goal for this environmentally sound practice.
Mirjana Malešev4
et al insiste that the quantity of recycled aggregate varies with river aggregate by % of
0,50,100 respectively. The properties of workability (slump test) immediately after mixing and 30 minutes after
mixing, bulk density of fresh concrete, air content, bulk density of hardened concrete, water absorption (at age
of 28 days), wear resistance (at age of 28 days), compressive strength (at age of 2, 7 and 28 days), splitting
tensile strength (at age of 28 days), flexural strength (at age of 28 days), modulus of elasticity (at age of 28
days), drying shrinkage (at age of 3, 4, 7, 14, 21 and 28 days), bond between ribbed and mild reinforcement and
concrete are tested. Ninety nine specimens were made for testing of the listed properties of hardened concrete.
It has been found that workability of concrete with natural and recycled aggregate is almost the same if water
saturated surface dry recycled aggregate is used. Also, if dried recycled aggregate is used and additional water
quantity is added during mixing, the same workability can be achieved after a prescribed time. Bulk density of
fresh concrete is slightly decreased with increase in the quantity of recycled aggregate.
The authors also insist that for concrete, compressive strength mainly depends on the quality of recycled
aggregate. If good quality aggregate is used for the production of new concrete, the recycled aggregate has no
influence on the compressive strength, regardless of the replacement ratio of natural coarse aggregate with
recycled aggregate. The same findings are found for concrete tensile strength (splitting and flexural). The
modulus of elasticity of concrete also decreases with increasing recycled aggregate content as a consequence of
lower modulus of elasticity of recycled aggregate compared to natural aggregate. Shrinkage of concrete depends
on the amount of recycled concrete aggregate. Concrete with more than 50% of recycled coarse aggregate has
significantly more shrinkage compared to concrete with natural aggregate. Increased shrinkage is a result of the
attached mortar and cement paste in the recycled aggregate grains.
Brett et al2
(2010) insist that the use of recycled aggregates in concrete is both economically viable &
technically feasible. In addition to demolition waste sources, RA can also be composed of excess Concrete
materials returned to the plant.
Mirza and Saif3
have studied the effect of silica fume on recycled aggregate concrete characteristics. The
percentages of recycled aggregate replacements of natural aggregate used by weight were 0, 50, and 100%,
whereas the percentages of silica fume replacements of cement used by weight were 5, 10, and 15%. The results
show that the compressive and tensile strengths values of the recycled concrete aggregate increase as the
recycled aggregate and the silica fume contents increase. The study also indicates that in order to accommodate
50% of recycled aggregate in structural concrete, the mix needs to incorporate 5% of silica fume.
Gupta7
discusses that normally coarse aggregate is the fractured stone obtained from rocks in hills or pebbles
from river bed, and because of depletion of good conventional aggregate in certain regions, the need for
development of Recycled Aggregate technology should be taken up commercially. It is similar to fly ash, which
is available from electrostatic precipitators of various super thermal power stations which is an industrial waste
material. It is chemically reactive when, mixed with cement for use in concrete. This is also useful as partial
replacement of cement, as it gives concrete having better impermeability. Thus, it has a wider use in
construction industry. He also notifies large scale recycling of demolished waste will offer, not only the solution
of growing waste disposal problem and energy requirement, but will also help construction industry in getting
aggregates locally. Such demolition waste can be crushed to required size, depending upon the place of its
application and crushed material is screened in order to produce recycled aggregate of appropriate sizes. An
aggregate produced by demolished buildings will be called Recycled Aggregates.
Sankarnarayanan10 et al find out the scenario in India presence of Construction & Demolition waste and other
inert material (e.g. drain silt, dust and grit from road sweeping) and observes the following:
i) The potential to save natural resources (stone, river sand, soil etc.) and energy,exits in these wastes