FUNDAMENTALS OF CONCRETE

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FUNDAMENTALS OF CONCRETE

• Presented By
• Kevin J. Brigandi
• Construction Services Department Manager
• kjbrigandi_at_terracon.com
• Debra A. Nunes
• Construction Services Department Manager
• danunes_at_terracon.com

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CONCRETE BASICS

• Uses of Concrete
• Concrete can be formed in almost any color, shape
  and texture, while serving as an acoustic and
  thermal barrier
• Concrete can be placed in all environments and
  conditions
• Concrete is resistant to fire, chemical exposure
  and weather
• Concrete is environmentally safe and recyclable
• Concrete is efficient to construction and can be
  produced with a variety of durability
  characteristics and strengths

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Dams, Roads, Bridges and Parking structures
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Buildings
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Retaining Walls, Foundations and Flatwork
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Driveways and Sidewalks
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Interior Flooring Countertops
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Controlled Low Strength Material (CLSM)
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Insulated Concrete Forms (ICFs)
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What is Concrete?
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Chemical Admixtures
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Mineral Admixtures
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How Should Concrete Be Specified?

• Strength
• Water / Cement Ratio
• Air
• Minimum Cement Factor
• Slump / Durability

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Water / Cement Ratio Calculations
30 Gal 8.33 lb. 250 lb.
----------- X ------------ ----------
.44 W/C 6 Sack 94 lb. 564
lb.
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Adding Water to Concrete
Water added (gal/yd³) Approx. Slump Increase (inches) Strength Reduction (psi) Strength Reduction ()
1 1 200 7
2 2 400 13
3 3 600 20
4 4 800 27
5 5 1000 33
6 6 1200 40
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Entraining Air in Concrete
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Concrete Quality Control

• All Field Technicians should be certified
• And have a working knowledge of the following
  ASTM standards

• C31
• C1064
• C143
• C172

• C173
• C231
• C138

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ASTM C 172 Standard Method for Sampling
Freshly Mixed Concrete

• Sample from middle portion of the batch
• Sample at two or more regularly spaced intervals,
  not to exceed 15 min
• Combine and remix sample thoroughly
• Cover Sample to protect from drying

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ASTM C 143 Standard Test Method for Slump of
Portland Cement Concrete
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ASTM C 231 Standard Test Method for Air Content
of Freshly Mixed Concrete by the Pressure Method
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ASTM C 173 Standard Test method for Air
Content of Freshly Mixed Concrete by the
Volumetric Method
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Basic Techniques for Finishing Flatwork

• Strike-off
• Bull Floating
• Darbying
• Floating

• Troweling
• Brooming
• Jointing
• Edging

• Curing

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Finishing
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Curing

• Performed as soon as possible after final
  finishing is completed
• Performed to prevent the loss of moisture from
  concrete
• Helps in maintaining a favorable concrete
  temperature for a definite period of time
• Will make concrete stronger
• More impermeable
• More resistant to stress
• More resistant to abrasion
• More resistant to freezing and thawing conditions

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Curing Methods and Materials

• Ponding or immersion
• Spraying or Fogging
• Wet Coverings
• Impervious Paper
• Plastic Sheets
• Membrane-Forming Curing Compounds
• Steam
• Insulating Blankets or Covers
• discoloration can occur if not used properly

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Common Concrete Problems

• Discoloration
• Dusting
• Cracking
• Plastic shrinkage cracking
• Crazing
• Scaling
• Curling
• Blisters
• Delamination
• Pop Outs

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Discoloration
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Prevention of Discoloration

• Do not Use Calcium Chloride
• Type, kind and condition of formwork
• can influence color
• Eliminate Burning of concrete
• Proper curing - Caution with Plastic
• Uniform sub-grade moisture

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What is Dusting?
Powders under any type of traffic Easily
scratched with a nail or even by sweeping Very
weak wearing surface
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What Causes Dusting?

• Finishing operation performed while bleed water
  is on the surface or before bleeding has finished
• Insufficient curing
• Placement of non-absorptive sub grade or
  polyethylene vapor barrier
• Floating/Troweling after the condensation of
  moisture from warm humid air is on cold concrete

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Prevention of Dusting

• Do not place concrete directly on polyethylene
  vapor barriers or non-absorptive sub grades
• Proper curing
• Cold weather concrete practices
• Vent exhaust to the outside to provide
  adequate ventilation

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Cracking
The one thing I can guarantee is that your
concrete will crack!
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Crazing
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How To Prevent Crazing
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How To Prevent Scaling
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Repairing Scaled Concrete

• Clean surface thoroughly
• Resurface
• Repair mortar
• Portland Cement concrete

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What Is Curling?
Slab Curling

• The distortion of a slab into a curved shape
  due to temperature gradients throughout the depth
  of the concrete

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Why Do Slabs Curl?
Shrinkage of the top relative to the bottom of
the slab Moisture gradients in slab Temperature
gradients within the slab

• Other Factors That Cause Curling
• Bleeding / Poor curing / Joint spacing

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Minimization of Curling

• Lowest practical slump
• Largest practical aggregate size
• Largest practical aggregate content
• Avoid excessive bleeding
• Avoid vapor barriers
• Avoid higher than needed cement contents
• Proper Curing
• Adequate Joint spacing
• Increase Slab Thickness

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Blisters
An irregular hollow bump that appears on the
surface during or right after finishing operations
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Why Does Concrete Blister?

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How Do You Prevent Blisters?

• Delay final finish as long as possible
• Avoid surface drying
• Initial float done with flat blades

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Delaminations

• The top 1/8 inch of the surface is densified and
  separated from the base slab by a thin layer of
  air or water
• Forms during final troweling
• Most frequent in early spring and late fall

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What Are Pop Outs?
A Conical Fragment that breaks out of the surface
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Green Concrete Technology

• Benefits of Pervious Concrete
• Environmental Benefits
• Economic Benefits
• Structural Benefits

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Pervious Concrete Design
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Mix Designs of Pervious Concrete

• Supplementary cementitious materials (SCMs)
• Coarse Aggregates
• Water
• Admixtures

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Testing and Inspection of Pervious Concrete

• Density Testing (ASTM C29)
• No Slump
• No Air

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Self Consolidating Concrete

• The use of self-consolidating concrete (SCC) has
  grown tremendously since its inception in the
  1980s.
• Because of the material performance in its fresh
  state, the existing testing methods for
  conventional concrete are no longer suitable for
  SCC.

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Mix Designs for SCC

• SCC mixtures can be designed to provide the
  required hardened concrete properties for an
  application, similar to regular concrete.

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Benefits of Self Consolidating Concrete

• Improved constructability 
• Virtually flawless finish
• Homogenous and uniform concrete
• Better reinforcement bonding
• Flows easily into complex shapes and through
  congested reinforcement
• Superior strength and durability
• Allows for innovative architectural features

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Benefits of SCC

• Wall with Normal and SCC Concrete

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Testing Procedures for SCC
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The Industry Reference
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Contributions By
The Portland Cement Association The American
Concrete Institute The National Ready-Mix
Concrete Association Blue Circle Cement St.
Lawrence Cement Connecticut Concrete Promotion
Council