Transcript IPE SESSION # - Presentation # Presentation Name By Title

Sustainable Construction
Strategies: A Singapore
Perspective
K. C. G. Ong1, E Anggadjaja2, and Y Soh2
1National
University of Singapore,
2Building and Construction Authority, Singapore
Presentation Outline
• Background
• Strategic Thrusts
• Microwave heating to produce RCA
• Concluding Remarks
The Republic of Singapore is the smallest nation in Southeast
Asia covering a land area of approximately 700 sq. km. With
4.8 million people on an island 45 minutes drive east to west
and 35 minutes north to south,
Fig. 1 : Location Map of North Eastern Coast Phase 4 Reclamation
Amsterdam, Holland vs Singapore
Amsterdam, Holland
Singapore
Metropolitan Area (A): 1,815 km2
Area (A): 710.2 km2
Metropolitan Population (B): 2,158,372
Population (B): 4,839,400
Density (B/A): 1189 /km2
Density (B/A): 6814 /km2
2009 Raffles place
Scarcity of Land
Depleting
Natural Resources
Waste to Resource
Rising Cost
of Raw Materials
Environmental
Issues
Our Challenges
• Island city-state
• No natural resources
• Small & densely populated
Understanding
Sustainable Construction
• Adoption of environmentally friendly
building designs, construction methods
and materials
• Reduce use of natural resources
• Increase the reusability of such materials
and products
• Reduce waste
Singapore’s Sustainable
Construction Master Plan
`
Recycling and Use
of Recycled
Materials
Efficient Design to
Optimize Use of
Natural Materials
Singapore’s Sustainable Construction Master Plan
Strategic Thrust
Strategic Thrust
2
3
Promoting Sustainable
Construction in the
Private Sector
New Developments
and Collaborative
Works
Strategic Thrust
4
Building Industry
Capabilities
Strategic Thrust
1
Government
Taking The Lead
Sustainable
Construction
Master Plan
Strategic Thrust
5
Strategic Profiling
and Raising
Awareness
Strategic Thrust
6
Minimum Standards
Through
Legislation
Increase use of
recycled & ecofriendly building
materials
Encourage
efficient design &
use of building
materials
Government Taking The Lead
Promoting
SC
Private
Sectors
Promoting
SC
inin
Private
Sectors
NewDevelopments
Developmentsand
andCollaborative
CollaborativeWorks
Works
New
Building
Building Industry
Industry Capabilities
Capabilities
StrategicProfiling
Profiling&&Raising
RaisingAwareness
Awareness
Strategic
Minimum Standards through Legislation
Key Initiatives
Collectors
Processors
Suppliers
Manufacturers
Designers
Contractors
Clients
Recover more waste Sustainable materials Set requirements
Business case
Recycle to higher
Offer higher recycled for sustainable
Environmental
quality
content options
construction practices sustainability
APPLICATIONS
New Developments &
Collaborative Works
Project
Researcher
1
Production of Aggregates from
Demolition Debris using microwave
technology
National University of
Singapore
2
Samwoh Corporation,
BCA Academy
New Developments &
Collaborative Works
Full scale evaluation of recycled
concrete aggregates in structural
application
3
New Earth Pte Ltd
BCA Academy
Building Industry
Capabilities
Synthetic/ Engineered Aggregates
made with Dredged Material and
Industrial Waste
4
Development of Cost-Effective Wall for
Sustainability in Construction
National University of
Singapore
BCA Academy
Government Taking
The Lead
Promoting SC in
Private Sector
Strategic Profiling &
Raising Awareness
Minimum Standards
through Legislation
Why Recycle Aggregates?
Environmental Considerations (Singapore
context)
• Reduce the amount of and reliance on
imported natural aggregates.
• Reduce landfill space needed.
Sustainable Development
• Provide an alternative local source of
aggregates.
• Sustained demand for construction materials
Cost of Construction Materials (S$/T)
Construction Dec 06
materials
Jan 07
Feb 07
Mar 07
Aug 08
Cement
88.60
89.90
89.90
91.00
126.00
Coarse Agg
18.70
19.50
20.90
69.00
28.00
Fine Agg
16.80
16.30
27.00
60.00
37.00
Reinf Bars
744.00
752.50
767.30
786.30
1,750
Ready Mix
Concrete (per
cubic m)
77.00
78.80
103.00
186.30
130.00
Source: Singapore Department of Statistics
Recycling Facilities
• Total quantity of demolition waste ~ 1.0 to
1.5 million tons for 2007 and 2008.
• Currently 5 plants operating in Singapore
A Typical RCA Production Plant
RCA Properties Compared
to Virgin Aggregates
Adhering mortar
Presence of contaminants
Lower strength
Higher absorption
Lower Density
Lower modulus of
elasticity
Removal of weaker or
fissured aggregates
Higher strength
Two main causes of lower quality
Contaminants (chemical and physical) present in
the demolition debris that are not removed.
Mortar adhering to the RCA which is of a porous
and weak nature.
Conventional Methods to Improve RCA
Quality
Removal of physical and chemical contaminants from
the demolition debris
– Mechanical means, e.g. chiseling and hammering
– Water Jet
To separate the adhering mortar from original aggregate
(RCA Benefication)
– Pre-soaking methods
Japanese System – Heating and
Rubbing
Source: Shima et al.
Heating and Rubbing
Source: Shima et al
Microwave heating as benefication to
improve the quality of RCA
Electromagnetic waves
Frequency rage: 300MHz to 300GHz
Dielectric losses
Low frequency microwaves
High frequency microwaves
Heat generation
Uniform heating
Non-uniform heating
Localized fields of high
stresses
Benefication Using Microwave Heating
10.6GHz -1.1 MW/m2
2 seconds
Sketch of microwave
decontamination system
Benefication Using Microwave Heating
Compared to natural aggregate, the
adhering mortar has
–
–
–
–
Higher coefficient of expansion
Higher specific heat
Higher thermal conductivity
Lower Modulus of Elasticity
Microwave heating –Any detrimental effects?
Temperatures can reach 450oC, however the heating
cycle is of a very short duration (seconds) and the heating
is focused on the skin layers.
Only granite aggregates used in Singapore
Benefication Using Microwave Heating
Taking advantage of the differences in water absorption and
dielectric and thermal properties of adhering mortar and
original aggregate
The water absorption rates for RCA are between 3% to 10%,
compared to less than 1% up to 5% for natural granite
aggregates
Maxwell equations are generally
used to describe the microwave
heating which is a near-field
electromagnetic problem
I 0 is the initial power of microwave,
and  is the attenuation factor
Lambert’s law
I  x   I0e2 x
Benefication Using Microwave Heating
Temperature distribution in RCA
subjected to microwave heating
at 10.6 GHz and 1.1 MW/m2
Temperature Gradient in RCA
subjected to microwave heating at
10.6 GHz and 1.1 MW/m2
Before microwave heating
After microwave heating
Contaminated
Concrete
Specimen
Surface
Decontamination
Decontaminated
Concrete
Specimen
Crushing and
Sieving
Tests on
Recycled
Tests on
RAC
Concrete
RCA
Aggregate
Aggregate benefication using
microwave
Tests on
RAC
Tests on
High Quality Recycled Concrete Aggregate
RCA
Concluding Remarks
• A concerted and holistic approach covering the
whole construction value chain
• BCA has been working closely with the industry
to migrate towards sustainable construction.
• Increase awareness and receptiveness to
alternative construction materials and
methods
Thank You
• Small island nation (699 km2)
• Population of 4.59 million
– Chinese majority of 76.2%,
– Malays at 13.8%
– Indians at 8.3%
• Very few natural resources
• Construction spending contributes
– 3-4% of GDP
– 6-7% of total employment