Sustainable Construction Strategies: A Singapore Perspective K. C. G. Ong 1 , E Anggadjaja 2 , and Y Soh 2 1 National University of Singapore, 2 Building and Construction Authority, Singapore
Dec 22, 2015
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,
Amsterdam, Holland vs Singapore
Amsterdam, Holland
Metropolitan Area (A): 1,815 km2
Metropolitan Population (B): 2,158,372
Density (B/A): 1189 /km2
Singapore
Area (A): 710.2 km2
Population (B): 4,839,400
Density (B/A): 6814 /km2
Waste to Resource
Environmental Issues
Scarcity of Land
Depleting Natural Resources
Rising Cost of Raw Materials
• Island city-stateIsland city-state
• No natural resources No natural resources
• Small & densely populatedSmall & densely populated
Our Challenges
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
`
Recycling and Use of Recycled
Materials
Efficient Design to Optimize Use of Natural Materials
Singapore’s Sustainable Construction Master PlanSingapore’s Sustainable Construction Master Plan
Singapore’s Sustainable Construction Master Plan
Sustainable ConstructionMaster Plan
Strategic Thrust
1Government
Taking The Lead
Strategic Thrust
2Promoting Sustainable
Construction in the Private Sector
Strategic Thrust
3New Developments and Collaborative
Works Strategic Thrust
4Building Industry
Capabilities
Strategic Thrust
5Strategic Profiling
and RaisingAwareness
Strategic Thrust
6Minimum Standards
ThroughLegislation
Increase use of recycled & eco-friendly building materials
Encourage efficient design & use of building materials
Government Taking The Lead
Promoting SC in Private Sectors
New Developments and Collaborative Works
Building Industry Capabilities
Strategic Profiling & Raising Awareness
Government Taking The Lead
Minimum Standards through Legislation
Strategic Profiling & Raising Awareness
Building Industry Capabilities
New Developments and Collaborative Works
Promoting SC in Private Sectors
APPLICATIONS
ClientsDesigners Contractors
CollectorsProcessors
SuppliersManufacturers
Set requirementsfor sustainable construction practices
Recover more wasteRecycle to higherquality
Sustainable materialsOffer higher recycledcontent options
Business caseEnvironmentalsustainability
Key Initiatives
New Developments & Collaborative Works
Government Taking The Lead
Promoting SC in Private Sector
New Developments &
Collaborative Works
Building Industry Capabilities
Strategic Profiling &
Raising AwarenessMinimum Standards
through Legislation
Project Researcher
1 Production of Aggregates from Demolition Debris using microwave technology
National University of Singapore
2 Full scale evaluation of recycled concrete aggregates in structural application
Samwoh Corporation, BCA Academy
3 Synthetic/ Engineered Aggregates made with Dredged Material and Industrial Waste
New Earth Pte LtdBCA Academy
4 Development of Cost-Effective Wall for Sustainability in Construction
National University of SingaporeBCA Academy
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 materials
Dec 06 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
RCA Properties Compared to Virgin Aggregates
Lower strength
Higher absorption
Lower Density
Lower modulus of elasticity
Higher strength
Adhering mortar
Presence of contaminants
Removal of weaker or fissured aggregates
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
Electromagnetic waves
Frequency rage: 300MHz to 300GHz
Dielectric losses Heat generation
Low frequency microwaves Uniform heating
High frequency microwavesNon-uniform heatingNon-uniform heating
Localized fields of high Localized fields of high stressesstresses
Microwave heating as benefication to improve the quality of RCA
Benefication Using Microwave Heating
10.6GHz -1.1 MW/m2
2 seconds
Sketch of microwave decontamination system
Benefication Using Microwave HeatingCompared 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
20
xI x I e
is the initial power of microwave, and is the attenuation factor0I
Lambert’s lawMaxwell equations are generally used to describe the microwave heating which is a near-field electromagnetic problem
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
ContaminatedConcrete Specimen
Surface Decontamination
Decontaminated Concrete Specimen
Tests on
RCA
Crushing and Sieving
Tests on
RAC
Recycled
Concrete
Aggregate
Aggregate benefication using microwave
High Quality Recycled Concrete AggregateTests on
RAC
Tests on
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