Post on 21-Aug-2014
description
Durability of Reinforced
Concrete – A major
player in Environmental
SustainabilityBY
OLUKAYODE ALAO
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Presentation Outline 2
(Con)Fusing Sustainability & Durability of Concrete Structures
Why concrete?
Unsustainable aspects of concrete production
Deterioration Mechanisms
Making Concrete Structures Durable & Sustainable
Research Objectives
Benefits of Durable Concrete Structures
Summary
The new paradigm for engineers is ‘sustainability’
Sustainability: it infers actions which meets the needs of the present
without compromising the ability of future generations to meet their own
needs (WCED, 1992)
Typically 𝑪𝒆𝒎𝒆𝒏𝒕 + 𝑨𝒈𝒈𝒓𝒆𝒈𝒂𝒕𝒆𝒔(𝑭𝒊𝒏𝒆 𝒂𝒏𝒅 𝑪𝒐𝒂𝒓𝒔𝒆) +𝑾𝒂𝒕𝒆𝒓 = 𝑪𝒐𝒏𝒄𝒓𝒆𝒕𝒆
....Reinforced Concrete (RC) structures are the most commonly used building material in since the 19th Century.....
Durability of RC (Service life) is the space of time where it fulfils its functional requirements.
(Con)Fusing Sustainability & Durability of RC Structures
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The new paradigm for engineers is ‘sustainability’
Sustainability: it infers actions which meets the needs of the present
without compromising the ability of future generations to meet their own
needs (WCED, 1992)
Typically 𝑪𝒆𝒎𝒆𝒏𝒕 + 𝑨𝒈𝒈𝒓𝒆𝒈𝒂𝒕𝒆𝒔(𝑭𝒊𝒏𝒆 𝒂𝒏𝒅 𝑪𝒐𝒂𝒓𝒔𝒆) +𝑾𝒂𝒕𝒆𝒓 = 𝑪𝒐𝒏𝒄𝒓𝒆𝒕𝒆
....Reinforced Concrete (RC) structures are the most commonly used building material in since the 19th Century.....
Durability of RC (Service life) is the space of time where it fulfils its functional requirements.
(Con)Fusing Sustainability & Durability of RC Structures
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Why concrete?
Its a democratic material
Its low cost →compared to
steel/aluminium
Availability of raw materials →limestone
and aggregates are naturally available
Versatility
Adequate engineering properties
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Why concrete?
Its a democratic material
Its low cost →compared to
steel/aluminium
Availability of raw materials →limestone
and aggregates are naturally available
Versatility
Adequate engineering properties
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strength
mouldablity
Unsustainable aspects of concrete
production
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Unsustainable aspects of concrete
production
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Growing World Population
Industrialization UrbanizationIncrease in
Cement Production
Unsustainable aspects of concrete
production
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Growing World Population
Industrialization UrbanizationIncrease in
Cement Production
Source: The Cement Sustainability Initiative - http://www.wbcsdcement.org/
Unsustainable aspects of concrete
production
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Growing World Population
Industrialization UrbanizationIncrease in
Cement Production
Source: The Cement Sustainability Initiative - http://www.wbcsdcement.org/
Cement production contributes 5-7% of global CO2 emissions
Problem!
11Unsustainable aspects of concrete
production
Current World demand/year
•11.5 billion tons of concrete
•1.5 billion tons of cement
•1 billion tons of water
•9 billion tons of aggregate
Depletion of natural resources
Deterioration Mechanisms
RC used in industrial, residential, marine environments
Alkali-Aggregate reaction
Freeze/thaw action
Delayed Ettringite formation
External Sulphate attack
Acid attack
Chloride-induced Corrosion
Carbonation
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Steel
Concrete
Failure
Deterioration Mechanisms
Chloride-induced Corrosion
Carbonation
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Steel
MARINE
EXPOSURE
CATEGORY
TIDAL AND
SPLASH ZONES
SPRAY ZONE
Extreme Exposed to
seawater, heavy
wave action
Not applicable
Very severe Exposed to
seawater,
sheltered
location
Within 500 m of shore in
an exposed location
Severe Coastal Near shore (1 – 15 km) in
an exposed location
Moderate Inland Anywhere else > 15 km
from the coast
DURABLE
Design Appropriately Performance requirements
Environmental conditions
Major deterioration mechanism
Quality concrete Construction site practice
Structural Health Monitoring Damage detection
Structural Assessment
Making Concrete
Structures Durable & Sustainable14
DURABLE
Design Appropriately Performance requirements
Environmental conditions
Major deterioration mechanism
Quality concrete Construction site practice
Structural Health Monitoring Damage detection
Structural Assessment
Making Concrete
Structures Durable & Sustainable15
DURABLE
Design Appropriately Performance requirements
Environmental conditions
Major deterioration mechanism
Quality concrete Construction site practice
Structural Health Monitoring Damage detection
Structural Assessment
Making Concrete
Structures Durable & Sustainable16
MARINE
EXPOSURE
CATEGORY
TIDAL AND
SPLASH ZONES
SPRAY ZONE
Extreme Exposed to
seawater, heavy
wave action
Not applicable
Very severe Exposed to
seawater,
sheltered
location
Within 500 m of shore in
an exposed location
Severe Coastal Near shore (1 – 15 km) in
an exposed location
Moderate Inland Anywhere else > 15 km
from the coast
SUSTAINABLE
Removal or substituting of
Portland cement Supplementary cementitious materials
(SCMs) such as fly ash, slag and silica
fume (7-50%)
Geopolymer concrete (0%)
Microclimate condition and the
severity
Recycle and Reuse Recycled concrete aggregates (RCA)
Recycled aggregates (RA)
Making Concrete
Structures Durable & Sustainable17
MARINE
EXPOSURE
CATEGORY
TIDAL AND
SPLASH ZONES
SPRAY ZONE
Extreme Exposed to
seawater, heavy
wave action
Not applicable
Very severe Exposed to
seawater,
sheltered
location
Within 500 m of shore in
an exposed location
Severe Coastal Near shore (1 – 15 km) in
an exposed location
Moderate Inland Anywhere else > 15 km
from the coast
SUSTAINABLE
Removal or substituting of
Portland cement Supplementary cementitious materials
(SCMs) such as fly ash, slag and silica
fume (7-50%)
Geopolymer concrete (0%)
Microclimate condition and the
severity
Recycle and Reuse Recycled concrete aggregates (RCA)
Recycled aggregates (RA)
DURABLE
Design Appropriately Performance requirements
Environmental conditions
Major deterioration mechanism
Quality concrete Construction site practice
Structural Health Monitoring Damage detection
Structural Assessment
Making Concrete
Structures Durable & Sustainable18
Research Objectives 19
ENVIRONMENTAL EXPOSURE CLASSIFICATION
INVESTIGATE THE RELATIONSHIP
AND INTERACTIONS
WITH RC
ENVIRONMENTAL PARAMETERS
MEASURE THE CONC. OF AIRBORNE
CHLORIDES IN CAPE PENNISULA
AREA
DURABLE, HENCE SUSTAINABLE
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Benefits of Durable RC Structures
Economic benefits
Savings on Maintenance expenditure
Use of SCM’s
Environmental sustainability
Reduce cement use→ Reduces CO2
emission
Reduce concrete production → Reduce heat production
Reabsorption of 5% CO2
Aesthetic benefits
Defaces beauty of structure
Safety of Users
Collapse or Failure of structures
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Benefits of Durable RC Structures
Economic benefits
Savings on Maintenance expenditure
Use of SCM’s
Environmental sustainability
Reduce cement use→ Reduces CO2
emission
Reduce concrete production → Reduce heat production
Reabsorption of 5% CO2
Aesthetic benefits
Defaces beauty of structure
Safety of Users
Collapse or Failure of structures
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Benefits of Durable RC Structures
Economic benefits
Savings on Maintenance expenditure
Use of SCM’s
Environmental sustainability
Reduce cement use→ Reduces CO2
emission
Reduce concrete production → Reduce heat production
Reabsorption of 5% CO2
Aesthetic benefits
Defaces beauty of structure
Safety of Users
Collapse or Failure of structures
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Failure
Spalling
Summary
Concrete is greener than you think but its production unsustainable
Design and construction processes need to become sustainable
Efforts to reduce CO2 emissions from cement production continues…
Important for structural engineers to understand environmental loading
Environmental factors such as wind, precipitation, RH and temperature affect rate of deterioration
RC structures with longer service life will reduce or eliminate cement use
South Africa has to promote the use of RCA and RA because its cuts
down on natural resource exploitation
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