Tue use of Concrete in Green Building Construction

www.qatargbc.org

"Green Concrete“ Using the Properties of Concrete in Green Building

Construction

QGBC Villa- 28 June 2010- Doha, Qatar

©Nadja Ortner-Ortner Consulting 2010 Courtesy of: Mobil-Baustoffe GmbH

Current green building certification systems

LEED

Green Globes

California Green Building Code

CASBEE (Japan)

Green Star

BREEAM U.K. BREEAM Europe & International

DGNB

LEED, BREEAM Gulf

Source: PriceWaterhouseCooper

Indoor Environ-mental Quality

Land use

Heating & Cooling

Transportation

Lighting

Building Orientation

Material Selection

• Efficiently using energy, water land and materials • Protecting occupant health and improving employee productivity • Reducing waste and pollution

Building Materials Concrete

Development Density & Community Connectivity → Concrete is a preferred building material due to its energy efficient capabilities

Daylight & Views → Concrete allows building large floors with none or few columns and shallow floor plates

SUSTAINABLE PROPERTIES OF CONCRETE IN BUILDINGS

Brownfield Redevelopment→ for stabilization of contaminated soils

Brownfield Redevelopment

Economical Benefits

• Jobs • Income • Taxes • Business Opportunities

Social Benefits

• Quality of Life • Employment Area and

Neighbourhood Renewal

• Housing Choices

Environmental Benefits

• Mitigration/elimination of health & safety risks

• Restoration of environmental quality

• Reduction of urban sprawl

Source: City of Ottawa


REDUCE

Construction Waste Management→ recycling construction waste (grey water and waste concrete)

Recycled Content in Building Materials → fly ash and slag cement (pre-consumer recycled); recycled concrete aggregate (post-consumer recycled)


Deconstruction Material Reuse

Construction

Design for Construction

Occupancy Maintenance

Processing of Raw Materials

Extraction of Raw Materials

ENVIRONMENTAL IMPACT

LIFE CYCLE ANALYSIS

LIFE CYCLE COST

Usage of Regional Materials→ (500 miles radius) Concrete is always a ‘regional’ material as usually produced within 40km from site


40

km


Protection or Restoration of Habitat→ used to build underground concrete parking garages and utilities

Maximization of Open Space→ concrete can be used to avoid retention ponds and to construct underground garages


Source: Piedmont Triad Council of Governments.

Water Efficient Landscaping- Innovative Wastewater Technologies- Water Use Reuse Reduction→ pervious concrete; concrete cisterns for rain water collection and process/grey water management systems


Storm-Water- Quantity Reduction and Quality Control→ pervious concrete to minimize the disruption of natural hydrologic features (also support for vegetated roofs)

Source: Piedmont Triad Council of Governments.

Heat Island Effect- Roof/Non-Roof→ concrete used to minimize thermal differences on open spaces (shade or surface)

Source: Interlock Industries (Alberta) Ltd.


can reduce “embodied” energy

can contribute to energy & water savings

Conversion of waste into reusable recycled materials

reduces use of natural resources

decreases pollution related to mining &

manufacturing

Improved life-cycle costs

reduced costs for energy & water

durable materials last longer

Materials Efficiency

Sustainable Properties of Concrete

• fully recyclable

• good insulating properties (> steel; < wood)

• good energy storing properties large thermal mass

Material

Average CO2 embodied in Traditional Concrete

kg per m3 of concrete

% per m3 of concrete

kg of CO2 emitted per ton

produced

kg of CO2 emitted per m3

of concrete

Cement 320 13.34 860 275.2

Coarse aggregate

1,100 45.72 2.8 3.08

Fine aggregate 800 33.33 3.4 2.72

Admixture 2.5 0.12 150 0.38

Water 180 7.49 1.8 0.32

TOTAL 2,402.5 100 NA 281.7

Note: numbers excludes transportation- the average CO2 emission per m3 is 310 kg

Electricity

CO2 Emissions in Concrete Life-cycle

Carbon Dioxide Emissions

Diesel Fuel

One Cubic Meter of Concrete

in Structure

Placement (Pumping)

of Concrete on Site

Explosives

Unexploited Resources

Transport of

Concrete to

Construction Site

Concrete Production

Transport of Raw

Materials to

Concrete Batching

Plants

Coarse Aggregates Production

GGBFS Processing

Fly Ash Processing

Cement Production

Fine Aggregates Production

Admixtures Production

LPG Fuel

System Boundary

Major environmental threat when batching concrete

High amount of GHG emissions released

CACO3→ CAO+CO2

High amount of GHG emissions released

CACO3→ CAO+CO2

CEMENT world cement industry accounts for 5% of global

anthropogenic CO2 emissions

cement content of a standard concrete mix design represents :

• ca. 85% of embodied energy

• up to 96% of GHG emissions

CEMENT SUBSTITUTES

GGBS produced from blast furnaces

used to make iron (replacement level: up to 80%)

Fly Ash by-product of coal-combustion from coal-burning power plants (replacement level: up to 60%)

Slag Cement (CM3 - A or B)

Blast- Furnace Cement (slag added to cement before

mixing)

CEMENT SUBSTITUTES

OPC + GGBS

22% CO2→

52kg/ton

OPC + Fly Ash

15% CO2→

4kg/ton

Average Reduction of CO2 Emissions for Standard Mixes :

Concrete Application Cement

Concrete Paving 25 - 50%

Exterior Flatwork not exposed to deicer salts 25 - 50%

Exterior Flatwork exposed to deicer salts with w/cm ≤ 0.45 25 - 50%

Interior Flatwork 25 - 50%

Basement floors 25 - 50%

Footings 30 - 65%

Walls & Columns 25 - 50%

Tilt-up panels 25 - 50%

Pre-stressed Concrete 20 - 50%

Pre-cast Concrete 20 - 50%

Concrete blocks 20 - 50%

Concrete pavers 20 - 50%

High Strength 25 - 50%

ASR mitigation 25 - 70%

Sulfate resistance

Type II equivalance 25 - 50%

Type V equivalance 50 - 65%

Lower permeability 25 - 65%

Mass concrete 50 - 80%

Proposed Cement Replacement Levels

Reuse and Recycling of Waste Materials

Up to 35kg/m3 of recycled solids can be used in mix

Cement content may need to be increased

Waste Concrete Recycling Methods crushing concrete into recycled aggregates

washing out the waste concrete before the hardening

begins- eco-friendly version, if wash-out water is recycled and reused

recycled concrete→ use in non structural elements such as backfills, blinding slabs, core filling, embankments and road construction

Grey (wash-out) water from cleaning of the equipment

Usually discharged into ponds where solids can settle out

Inefficient procedure and environmental hazard

GREY WATER

Grey water contains: • Cement

• Other fines (GGBS, Fly Ash, sand < 0.1 mm)

GREY WATER


Grey (wash-out) water from cleaning of the equipment

Usually discharged into ponds where solids can settle out


GREY WATER

SOLUTION

Installation of Close-loop Systems

Reduces Overall Grey Water

Environmental Training

Controlling air emissions and dust

Storage and spill prevention of hazardous liquids

Management of process water

Management of solid waste

short time workability due to a

faster setting process

extreme high concrete

temperatures caused by heat of

hydration at the setting process

uncontrollable cracking

high costs for intensive curing

extension of construction periods

due to a production stop caused by

high temperatures

Courtesy of: Mobil-Baustoffe

Concrete without Cooling

Threats due to High Fresh Concrete Temperature

Problems with mixing, correct placing and curing

Thermal / differential thermal cracking of concrete

Decreased 28-days and later strengths

Delayed Ettringite Formation (DEF) in concrete when exceeding a temperature of about 65°C during hydration, which can cause cracking even years after installation

Threats due to High Fresh Concrete Temperature

Delayed Ettringite Formation (DEF) in concrete when exceeding a temperature of about 65°C during hydration, which can cause cracking even years after installation

Cooling of Fresh Concrete Effect Investment Running Costs Operation

PASSIVE MEASURES

FOR AGGREGATES

North Orientation of Storage low low low -

Shading low low low Easy

Spraying with Water low low low Easy

Short Process Time for Extraction high low low -

ACTIVE MEASURES

Chilled Mixing Water low medium low Easy

Crushed Ice Instead of Mixing Water medium high medium Difficult

Cooling Cement by LN in Storage Silo high low high Easy

Cooling Cement by LN in Heat Exchanger high high high Easy

Cooling Concrete by LN in Mixer Trucks medium low very high Difficult

Cooling Aggregates in Water Bath high high low Medium

Flake-Ice Cooling

At high temperatures further

activities are needed; such as

shading the aggregates or the

production of concrete during the

cooler night time period

Lower production capacity due to a

limited ice production and a long

mixing process.


SAMPLE MIX

Cement 360kg w/c ratio < 0.38

humidity in sand 8% =60l

maximum water content= 137l

concrete temperature without cooling= 45°C

cooling 1°C = 7.5kg of ice

SAMPLE MIX

Maximum possible addition of water:

77 litres

Fresh concrete temperature after adding flake ice:

34°C =

Coarse Aggregate Cooling More time to place and finish

concrete works on site

Significant energy savings

Reduced dust emissions

Reduced admixture usage

Cement savings (low w/c ratio)

Achieving concrete temperatures

as low as 25 Degree Celsius.

Reduces the risk of rejected

concrete due to temperatures out of

specification

Transportation over longer

distances possible


Aggregate & Cement Cooling

Cement cooled down by 10 °C results in a reduction of the overall concrete temperature of 1 °C

Methods:

• Air

• Nitrogen or carbon dioxide


0

10

20

30

40

50

60

70

80

90

Fresh Concrete Temperature

Site Concrete Temperature

Without cooling

Flake-ice cooling

Aggregates cooling

Aggregates & cement cooling

Cooling Method

TEMPERATURE DEVELOPMENT- COOLING METHODS Te

mp

erat

ure

in D

egre

e C

elsi

us

Conventional flake-ice cooling

Energy saving flake-ice cooling

Coarse aggregate cooling system

805 kW/h per unit 665 kW/h per unit 350kW/h per unit

2012 kW/h 1662 kW/h 350 kW/h

15456 l/day 12768 l/day 2688 l/day

10,3 l per m3 8,5 l per m3 1,8 l per m3

1kW = 0,32 l Diesel 1 ̊C= 7.5kg of ice/m3

Cooling Method Comparison: 1500 m3 of Concrete in 24h (as per mix and air temperatures from previous sample)

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www.ortner-consulting.com

Documents

Tue use of Concrete in Green Building Construction