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Durability of Reinforced Concrete – A major player in Environmental Sustainability BY OLUKAYODE ALAO 1

Durability of Reinforced Concrete – A major player in Environmental Sustainability

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Page 1: Durability of Reinforced Concrete – A major player in Environmental Sustainability

Durability of Reinforced

Concrete – A major

player in Environmental

SustainabilityBY

OLUKAYODE ALAO

1

Page 2: Durability of Reinforced Concrete – A major player in Environmental Sustainability

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

Page 3: Durability of Reinforced Concrete – A major player in Environmental Sustainability

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

3

Page 4: Durability of Reinforced Concrete – A major player in Environmental Sustainability

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

4

Page 5: Durability of Reinforced Concrete – A major player in Environmental Sustainability

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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Page 6: Durability of Reinforced Concrete – A major player in Environmental Sustainability

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

6

strength

mouldablity

Page 7: Durability of Reinforced Concrete – A major player in Environmental Sustainability

Unsustainable aspects of concrete

production

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Page 8: Durability of Reinforced Concrete – A major player in Environmental Sustainability

Unsustainable aspects of concrete

production

8

Growing World Population

Industrialization UrbanizationIncrease in

Cement Production

Page 9: Durability of Reinforced Concrete – A major player in Environmental Sustainability

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/

Page 10: Durability of Reinforced Concrete – A major player in Environmental Sustainability

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!

Page 11: Durability of Reinforced Concrete – A major player in Environmental Sustainability

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

Page 12: Durability of Reinforced Concrete – A major player in Environmental Sustainability

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

Page 13: Durability of Reinforced Concrete – A major player in Environmental Sustainability

Deterioration Mechanisms

Chloride-induced Corrosion

Carbonation

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Steel

Page 14: Durability of Reinforced Concrete – A major player in Environmental Sustainability

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

Page 15: Durability of Reinforced Concrete – A major player in Environmental Sustainability

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

Page 16: Durability of Reinforced Concrete – A major player in Environmental Sustainability

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

Page 17: Durability of Reinforced Concrete – A major player in Environmental Sustainability

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

Page 18: Durability of Reinforced Concrete – A major player in Environmental Sustainability

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

Page 19: Durability of Reinforced Concrete – A major player in Environmental Sustainability

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

1

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Page 20: Durability of Reinforced Concrete – A major player in Environmental Sustainability

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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Page 21: Durability of Reinforced Concrete – A major player in Environmental Sustainability

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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Page 22: Durability of Reinforced Concrete – A major player in Environmental Sustainability

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

Page 23: Durability of Reinforced Concrete – A major player in Environmental Sustainability

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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Page 24: Durability of Reinforced Concrete – A major player in Environmental Sustainability

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