Concrete I

1
Concrete I

• Structural Engineering Laboratory 560.208
• Spring 2000

2
Goals

• Applications of structural concrete
• Introduction to basic concrete chemistry
• Concrete constituents
• Mix design
• Admixtures

3
Applications of Structural Concrete

• Beams, columns in buildings/bridges
• Floor slabs
• Foundations
• Pavements
• Shell structures
• Dams
• Railroad ties, power poles, etc., etc., etc.!

4
Concrete Features

• Durable
• Architecturally flexible
• Relatively low cost
• Weak in tension, therefore often used in its
  well-known composite form
• classical reinforced concrete
• prestressed concrete
• Can be precast (controlled environment)

5
Concrete Constituents

• Aggregate(s)
• passive role, filler
• Portland cement
• from limestone and clay or shale
• 5 basic types
• Water
• (exothermic) chemical reaction with cement to
  form matrix
• Admixtures
• accelerators, water reducers, air-entrainers

6
Controlling Factors

• Cement type
• e.g., resistant to sulfate attack, high early
  strength, low heat of hydration
• Water-cement ratio
• weight ratio
• strong influence on strength
• lower w/c increases strength, but decreases
  workability
• Aggregate gradation
• workability, finishing characteristics

7
Additives

• Accelerators
• shorten setting time, increase early strength
• contain chlorides (corrosion problems)
• Water reducers
• enhance workability with lower w/c ratio
• superplasticizers produce flowable concretes
• Air entraining agents
• more damage resistant concretes e.g., freeze-thaw

8
Reinforced Concrete

• Concrete weak in tension
• Provide steel component to take tension

concrete
rebar
shear/confinement reinforcement
9
Prestressed Concrete

• Concrete weak in tension
• Lay prestressing bars/strand and tension
  (keep concrete in compression at all times)
• Long-span, slender, elegant members
• Precast sections
• Can be adjusted as loaded

10
Laboratory Field Trip

• Visit Genstar quarry/concrete plant
• Observe
• quarrying of aggregate
• batching/concrete mix preparation
• mix quality assurance evaluation
• transportation

11
Summary Report Requirements

• To be announced
• Make sure all group members names are indicated
  and signed off.