Concrete Basics (PowerPoint)

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					Concrete
Objectives
   Students will learn

~ The components of concrete

~ The 3 types of concrete
FACTS

   Concrete is the most widely used
    construction material in the world
   In the U.S. almost twice as much
    concrete is used as all other
    construction materials combined
What is concrete made of?
   CEMENT

   WATER

   AGGREGATES

   ADMIXTURES
Cement
   Cement is a building material made by
    grinding calcined limestone and clay
    into a fine powder

   When mixed with water it will harden as
    it undergoes chemical changes
Cement--Chemical Composition
   Portland Cement
       Limestone, shale and clay
        WATER
   We all know what water is……
COARSE AGGREGATE
   This is an aggregate that is usually
    close to ¼ inch in diameter or larger.
     FINE AGGREGATE
   This is an aggregate that is usually very

    small/fine, such as sand.
ADMIXTURES
   Added to the mixture before or during

    mixing.

   Ingredients other than cement, water,

    or aggregates
AIR ENTRAINING AGENTS
   Produce microscopic air bubbles

    throughout the concrete
Curing of Concrete
   Over time concrete will cure, which is a
    hardening process.
   ( the amount of time it takes to be
    considered completely cured = 28 days)
Forms
   A form is the mold for setting concrete
    into a desired shape
What Is Concrete Used For?
   Construction Material



Art Work
   3 Types of Concrete

Type I

~ General purpose
~ most common type, usually used
Type II

~ releases less heat during hardening
~ more suitable for projects using large
 masses of concrete
~ heavy retaining walls, bridges
Type III

~ concrete that gains strength rapidly
~ sets rapidly – great for cold weather jobs
Why Is Concrete Used?
   Economics
       Inexpensive, readily available

   Material Properties
       Long Lasting
       Molded into a desired shape
       Great insulator
       Hard
Material Properties (cont.)

   Great Compressive Strength (up to
    8000 psi)



   Poor Tensile Strength (almost 0)
Question


   What is the difference between tension
    and compression?
Why Do We Reinforce
Concrete?


   Prevent cracking due to tension forces
How is Concrete Reinforced?
   Steel rebar
       Excellent in tension, poor in compression
   Chicken Wire
       Minimize thermal expansion
    Pictures

   Failed concrete structures due to earth
    quakes
Waste Aggregates
   Why is it important to use solid waste
    as an aggregate in concrete?
Waste Aggregates
   Environmental Preservation
   New Material Properties
       Recycled tires (crumb rubber)
            Insensitive to water
       Broken Bricks
            Fire resistant
       Plastic
            Greater resistance to freeze-thaw cycles
       Glass, PVC, Wood Chips and several others

				
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posted:11/25/2011
language:English
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