EnvironmentFriendly Concrete EFC for Green Highways

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Environment-Friendly Concrete (EFC) for Green
Highways

• Mohammad S. Khan, Ph.D., P.E.
• Senior Vice President
• Professional Service Industries, Inc.
• 2930 Eskridge Road, Fairfax, VA

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Outline

• Goals
• Sustainable Development
• Concrete and Environment
• The Need for EFC
• Components of the EFC Guide
• Conclusions

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Goals

• Raise the awareness of environmental concerns
  related to concrete
• Propose the development of a set of guidelines
  for the use of environment-friendly concrete
  (EFC) in transportation infrastructure
• Demonstrate that we can have concrete and
  concrete-making materials that are not only
  environment friendly but also help control
  pollution created by other industries

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Sustainable Development

• A sustainable development is an economic activity
  that is in harmony with earths ecosystem
• A sustainable development promotes the use of
  energy and raw materials resources in a way that
  assures long-term viability of human life
• This viability is threatened by depleting energy
  and raw material resources and unacceptable
  levels of environmental pollution from solid,
  liquid, and gaseous waste products

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Concrete and Environment

• Concrete industry is one of the largest consumers
  of natural resources
• Concrete industry annually utilizes 1.6 billions
  tons of cement, 10 billion tons of rock and sand,
  and 1 billion ton of water
• Each ton of cement requires 1.5 tons of limestone
  and extensive amount of fossil fuel and
  electrical energy

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Concrete and Environment

• The production of each ton of cement is
  accompanied with 1 ton of CO2 emissions
• CO2 is a greenhouse gas, one of the gases
  primarily responsible for global warming
• The contribution of cement industry to the
  worlds total CO2 emissions is about 7

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The Need for EFC

• Is the concrete industry, which comprises of
  educators, researchers, owners, architects,
  engineers, materials suppliers and constructors,
  contributing its fair share to sustainable
  development?
• The answer is no!
• There is a vast majority which even does not
  recognize that there are environmental concerns
  related to concrete

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The Need for EFC

• Transportation infrastructure accounts for
  considerable amount of concrete produced by the
  concrete industry
• There have been no concerted efforts to make
  concrete in transportation infrastructure
  environment friendly

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The Need for EFC

• Chesapeake Bay Bridge Tunnel a 17.6 mile long
  complex transportation facility connecting
  Virginia Beach and Cape Charles in Virginia
• Originally constructed in 1964 and then expanded
  in 1999
• The original construction alone utilized 550,000
  cubic yards of concrete, 110,000,000 pounds of
  steel, 4,000,000 cubic yards of sand, and 34,000
  carloads of rock
• More than 5,000 piles that are 80 to 172 ft. long
  and weigh 800 to 1000 lbs per foot of length
• Based on unusual engineering features, gigantic
  size, and utility to mankind, ASCE named CBBT as
  One of the Seven Engineering Wonders of the
  Modern World

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The Need for EFC

• The original Cooper River Bridge, connecting
  Charleston and Mount Pleasant in South Carolina,
  was constructed in 1929 and expanded with another
  structure in 1966
• Both the bridges now functionally obsolete are
  being replaced with a new 8-lane and 2.8 mile
  long structure, which is the longest cable-stayed
  main span in North America
• The main span towers are supported by 10-ft.
  diameter drilled shafts and stand 570 ft. above
  the water level

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The Need for EFC

• The new bridge has about 400 drilled shafts
• The two towers alone utilized 44,000 cubic yards
  of concrete and 7,400 tons of reinforcing steel
• The total amount of concrete in the bridge is
  estimated to be about 225,000 cubic yards

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The Need for EFC

• There is a need to develop a set of guidelines
  that facilitate the use of environment-friendly
  concrete (EFC) in transportation infrastructure
  and thus contribute to a sustainable development

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Components of the EFC Guide

• Minimize the use of portland cement and maximize
  the use of supplementary cementitious materials
• Minimize the use of natural rocks and sand as
  aggregates and maximize the use of alternate
  aggregate types
• Maximize the use of recycled concrete as
  aggregates
• Maximize the use of recycled water from
  ready-mixed concrete plants

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Components of the EFC Guide

• Maximize the use of non-potable water sources
• Maximize the use of materials that enhance the
  performance of substandard aggregates and mixing
  water
• Design concrete facilities for a service life of
  100 to 150 years
• Use concrete as a pollution control tool in
  addition to its normal function

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Components of the EFC Guide

• Minimize the Use of Portland Cement
• More cement doesnt mean better concrete
• Concrete made with high cement content is more
  susceptible to cracking
• Cracking compromises the water tightness of
  structures
• Less water tight structures are susceptible to a
  number of deterioration mechanisms

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Components of the EFC Guide

• Maximize the Use of Supplementary Cementitious
  Materials (SCM)
• These materials include fly ash, silica fume, and
  slag
• They are the produced from coal ash and
  metallurgical slag
• Disposal of coal ash and metallurgical slag is a
  serious health concern since these materials are
  toxic and can easily pollute land, air, and
  groundwater

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Components of the EFC Guide

• Maximize the Use of SCM
• These days concrete can be produced by replacing
  as much as 50 to 60 of cement with SCM
• SCM are very much underutilized
• In CBBT no SCM was used
• On Cooper River Bridge Project, 20 to 40 of fly
  ash was used as a cement replacement

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Components of the EFC Guide

• Maximize the Use of SCM
• When used in concrete most harmful metals in SCM
  are safely immobilized by the hydration reactions
  of cement
• SCM have a number of beneficial effects on the
  properties of concrete
• They reduce the permeability of concrete and thus
  improve its water tightness
• They lower the heat of hydration of concrete and
  thus reduce its cracking potential

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Components of the EFC Guide

• Minimize the Use of Natural Rocks and Sand
• Aggregates constitute about 80 of concrete by
  volume
• Sources of natural rock and sand are not
  unlimited
• We need to look at alternate sources of
  aggregates that do not consume natural resources
• Synthetic lightweight aggregates can be used in
  certain applications

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Components of the EFC Guide

• Maximize the Use of Alternate Aggregates
• Production of illuminate and titanium oxides
  results in a semi-metallic waste
• This semi-metallic waste has been used in the
  production of aggregates for high density
  concrete with a strength of about 4,000 psi
• Such concrete has application in retaining walls
• Filter cake, a by-product of calcium carbide
  production, has been used as a filler material

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Components of the EFC Guide

• Maximize the Use of Alternate Aggregates
• Glass from jars and bottles has the potential of
  being recycled as aggregates
• Researchers in Norway have explored the use of
  recycled glass as aggregate
• The use of recycled glass as lightweight
  aggregates is particularly promising
• Recycled glass as normal weight aggregate has
  been used to produce concrete with strength of
  6,000 psi

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Components of the EFC Guide

• Maximize the Use of Recycled Concrete Aggregates
  (RCA)
• Concrete industry has not kept up pace with other
  industries in recycling its constituent materials
• Recycling of abandoned or demolished concrete
  structures in the form of aggregates will help
  conserve natural resources
• Recycling of old concrete will also solve the
  disposal problems

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Components of the EFC Guide

• Maximize the Use of Recycled Concrete Aggregates
  (RCA)
• The use of RCA has more acceptance in European
  countries compared to the United States
• In Denmark more than 80 of old concrete is
  recycled as aggregates
• Within U.S. a number of States have passed
  legislation to look more closely at recycling
• FHWA and EPA are also looking at the issue

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Components of the EFC Guide

• Maximize the Use of Recycled Water from
  Ready-Mixed Concrete Plants
• Wash water from ready-mixed concrete plants is an
  environmental concern
• Wash water needs to be properly treated before it
  can be disposed off
• Recycling of wash water in concrete will help
  conserve a natural resource and also solve
  disposal problems

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Components of the EFC Guide

• Maximize the Use of Non-Potable Water Sources
• Drinking water is generally used for mixing and
  curing concrete, which utilizes extensive energy
  resources for its treatment
• Partial treatment procedures for concrete water
  need to be explored
• There are special cements that make the use of
  non-potable water, such as seawater, possible in
  concrete

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Components of the EFC Guide

• Design Concrete Facilities for a Service Life of
  100 to 150 years
• Currently a typical design life for concrete
  structures is 50 years after which it has to go
  through replacement or major rehab, which is a
  waste of natural resources initially used
• With current technology and a preventative
  maintenance program we can design structures for
  a service life of 100 to 150 years

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Components of the EFC Guide

• Use Concrete as a Pollution Control Tool
• Specially prepared concrete surfaces,
  incorporating ultra-fine TiO2 powder with
  photocatalytic properties, can covert harmful NO2
  to harmless NO3
• NO2 is an atmospheric pollutant generally present
  in urban areas and tunnels
• NO3 is easily washed away by rain

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Conclusions

• The proposed guidelines will be a major
  initiative in raising the awareness of
  environmental concerns related to concrete and
  providing a tool to transportation industry in
  selecting concrete and concrete-making materials
  that are not only environment friendly but also
  help control environmental pollution created by
  other industries