Green Concrete

"Green Concrete“

Eco-friendly improvements in the concrete production

process towards a sustainable building site

[Case study on the Ras Laffan Port expansion]

The Ritz Carlton Hotel Doha, 28th March 2010

“Green Concrete” - 28th March 2010 - Nadja Ortner

� Environmental advantages on extensive use of

mass concrete on new construction

� Reuse and recycling of waste concrete and grey

water water

� Concrete cooling by means of coarse aggregate

cooling and cement cooling in comparison to

traditional cooling methods



MaterialCompressive

StrengthE-Module

Primary Energy

Consumption

N/mm² N/mm² kWh/to

PRIMARY ENERGY vs. COMPRESSIVE STRENGTH

Brick Work 5 5,000 450

Concrete 50 30,000 300

Aluminum 450 70,000 52,000

Steel 500 210,000 5,900


SUSTAINABLE

MATERIAL SUPPLY

PRODUCTIONMATERIAL REUSE &

RECYCLING

SUSTAINABLE CONCRETE

CONSTRUCTION & LOGISTICS

STAFF TRAINING & EDUCATION




Material

KG per m3

of

concrete

Percentage in the

mix design

CO2 released (kg

of CO2/ton)

Kg of CO2 per m3

of concrete

Admixture2.5 0.12 150 3.75

Coarse natural aggregate1100 45.72 2.8 2.16

Fine natural aggregate800 33.33 3.4 1.9

Fine natural aggregate800 33.33 3.4 1.9

Portland Cement320 13.34 930 139.5

Water180 7.49 0 0

TOTAL2402.5 100 147.31


Material CO2 released (kg of CO2/ton)

Admixture 150

Coarse natural aggregate 2.8

Recycled coarse aggregate 2.8

Fine natural aggregate 3.4

Fly ash 4

GGBS 52

Portland Cement 930

Water 0



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 SiloCooling 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

*) LN: Liquefied Nitrogen





� short time workability due to a

faster setting process

� extreme high concrete

temperatures caused by heat of

hydration at the setting processWithout cooling system

� uncontrollable cracking

� high costs for intensive curing

� extension of construction periods

due to a production stop caused by

high temperatures


Flake-ice cooling system

� At high temperatures further

activities are needed; such as

shading the aggregates or the

production of concrete during theproduction of concrete during the

cooler night time period

� Lower production capacity due to a

limited ice production and a long

mixing process.


Coarse aggregate

cooling system

� Achieving concrete temperatures

as low as 24 Degree Celsius.

� Reduces the risk of rejected

concrete due to temperatures out of

specification

� A coarse aggregate cooling system

does not produce ice and does not

have the capacity to freeze any

water in comparison to a flake ice

plant

� High quality concrete with a low

water/cement ratio

cooling system� No extra personnel required to run

the aggregate cooling system

� Enhanced concrete quality allows

transporting the concrete on longer

distances and provides more time

to place and finish concrete works

on site

� Uninterrupted production, even in

case of system failure thanks to

backup systems

� Reduces the admixture usage in

summer

� Cement savings


Aggregate & cement

cooling systemcooling system



CONSISTENCY OF CONCRETE

Temperature

QuantityWithout

cooling

Flake-ice

cooling

Aggregates

cooling

Aggregates

& cement

cooling

Cement 350 kg/m3 90°C 90°C 90°C 30°C

Aggregates 0/10 900 kg/m3 40°C 40°C 40°C 40°C

Aggregates 10/20 1100 kg/m3 40°C 40°C 10°C 10°C

Water 150 kg/m3 30°C -2°C 8°C 8°C

Fresh Concrete Temperature 43°C 35°C 27°C 21°C

Site Concrete Temperature 85°C 78°C 69°C 63°C


40

50

60

70

80

90

Without cooling

Flake-ice cooling

Aggregates cooling

0

10

20

30

Fresh Concrete Temperature

Site Concrete Temperature

Aggregates cooling

Aggregates & cement cooling




































Major environmental threat when batching concrete

High amount of GHG emissions released

CACO3→ CAO+CO2


CEMENT

� world cement industry accounts for 5% of global

anthro-pogenic CO2 emissions

� cement content of a standard concrete mix design � cement content of a standard concrete mix design

represents :

• ca. 85% of embodied energy

• up to 96% of GHG emissions


CEMENT SUBSTITUTES

GGBSproduced from blast furnaces

used to make iron (replacement level: up to 70%)

produced from blast furnaces used to make iron

(replacement level: up to 70%)

Fly Ashby-product of coal-combustion from coal-burning power plants by-product of coal-combustion from coal-burning power plants

OPC + GGBS 22%22%

Average Reduction of CO2 emissions for Standard Mixes :

Fly Ash from coal-burning power plants (up to 30% on buildings)

from coal-burning power plants (up to 30% on buildings)

Slag Cement (CM3 - A or B)

Blast- Furnace Cement (slag added to cement before

mixing)

Blast- Furnace Cement (slag added to cement before

mixing)

GGBS 22%22%

OPC + Fly Ash 13-15%13-15%


Reuse and Recycling of Waste materials

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

� Cement content may need to be increased


Health & Safety training

� Hazard identification

� Risk assessment and control

� Control measures

� Plant safety management plan

� Special duties as required from plant or � Special duties as required from plant or

equipment designers

� Safe driving tests and assessments for drivers

and operators


Sample Mix:

•Cement 360kg

•w/c ratio < 0.38

•humidity in sand 8% =60l

•maximum water content= 137l

•concrete temperature without cooling= 45°C•concrete temperature without cooling= 45°C

This results in:

•Maximum possible addition of water of= 77l

•Fresh concrete temperature after adding flake ice=

34°C

→ cracks


How to decrease the threat of

temperature gain on-site?


� Development Density & Community Connectivity

Concrete is a preferred building material due to its

energy efficient capabilities

� Brownfield Redevelopment→ for stabilization of

� Maximization of Open Space→ concrete can be used

to avoid retention ponds and to construct

underground garages

� Storm-Water- Quantity Reduction and Quality

SUSTAINABLE PROPERTIES OF CONCRETE IN BUILDINGS

� Heat Island Effect- Roof/Non-Roof→ concrete used to

minimize thermal differences on open spaces (shade

or surface)

� Water Efficient Landscaping- Innovative Wastewater

� Minimum Energy Performance and its Optimization

→ insulation and heat-storage properties of concrete

contribute to moderate the temperature fluctuations

→ mass properties of concrete will increase

performance when considered as a part of a whole

� Construction Waste Management→ recycling

construction waste (grey water and concrete)

� Recycled Content in Building Materials → fly ash and

slag cement (recycled); recycled concrete aggregate

� Daylight & Views →Concrete allows building large

floors with none or few columns and shallow floor

plates

� Brownfield Redevelopment→ for stabilization of

contaminated soils

� Protection or Restoration of Habitat→ used to build

underground concrete parking garages and utilities

� Storm-Water- Quantity Reduction and Quality

Control→ pervious concrete to minimize the disruption

of natural hydrologic features (also support for

vegetated roofs)

� Water Efficient Landscaping- Innovative Wastewater

Technologies- Water Use Reuse Reduction→ pervious

concrete; concrete cisterns for rain water collection

and waste/grey water management systems

performance when considered as a part of a whole

building projects simulation

� Building Reuse → longevity and durability

characteristics of concrete contribute to the

renovation of buildings through a concrete frame

and/or a concrete skin

slag cement (recycled); recycled concrete aggregate

(post-recycled)

� Usage of Regional Materials→ Concrete is always a

‘regional’ material s as produced within 40kn from site


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

Usually discharged into ponds where solids can settle out� Grey water contains:

GREY WATER

SOLUTION

Installation of close-loop systems

Inefficient procedure and environmental hazard

• Cement

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

Solution:

Reduces overall Grey water


Waste Concrete Recycling methods

� crushing concrete into recycled aggregates

� washing out the waste concrete before the hardening

begins- eco-friendly version

� recycled concrete→ use in non structural elements

such as backfills, blinding slabs, core filling,

embankments and road construction


Environmental training

� Controlling air emissions and dust

� Storage and spill prevention of hazardous liquids

� Management of process water� Management of process water

� Management of solid waste










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Green Concrete