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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
SUSTAINABLE PROPERTIES OF CONCRETE IN BUILDINGS
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)
SUSTAINABLE PROPERTIES OF CONCRETE IN BUILDINGS
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
SUSTAINABLE PROPERTIES OF CONCRETE IN BUILDINGS
40
km
SUSTAINABLE PROPERTIES OF CONCRETE IN BUILDINGS
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
SUSTAINABLE PROPERTIES OF CONCRETE IN BUILDINGS
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
SUSTAINABLE PROPERTIES OF CONCRETE IN BUILDINGS
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.
SUSTAINABLE PROPERTIES OF CONCRETE IN BUILDINGS
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
Inefficient procedure and environmental hazard
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
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.
Courtesy of: Mobil-Baustoffe
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
Courtesy of: Mobil-Baustoffe
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
Courtesy of: Mobil-Baustoffe
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)