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.

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

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

2009 Raffles place

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

A Typical RCA Production Plant

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

Japanese System – Heating and Rubbing

Source: Shima et al.

Heating and Rubbing

Source: Shima et al

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

Before microwave heating After microwave heating

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

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