BCN 5905 STRUCTURES I

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BCN 5905 STRUCTURES I

• Dr. Larry Muszynski
• RNK 327

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Theme for the Class

• Steel rusts,
• Wood rots, but
• Concrete is forever!!!!!!!!!!!
• But unfortunately, we sometimes make concrete
  forms out of Timber

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Class Structure

• 30 - 75 minute periods.
• 20 lectures, three exams, lab, two or three take
  home assignments and a Field trip?

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Course Outline

• Fundamentals and Properties of Concrete
• Concrete Construction
• Timber and Formwork

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There is No such Animal as a Cement _at_!

• Composition of Concrete
• PC Water Aggregates (FA CA) Porosity
• Heterogeneous and isotropic
• Wood is homogeneous and non-isotropic
• Steel is homogeneous and isotropic
• 1 cu.ft. weighs 94
• Properties of Fresh Concrete and Hardened Concrete

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Fresh Properties

• Slump
• Temperature
• Density Yield
• Air Content
• Time of Setting

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Hardened Properties

• Strength
• Air Content
• Density, Absorption and Voids
• Heavy 150 pcf or about 2 tons pcy
• Volume Change
• Durability
• Permeability

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How does Concrete Get Its Strength

• PC water hydration reaction gt GLUE Heat
• Cementitious material literally glues all of the
  inert (non-reactive) aggregates together to
  produce a solid load bearing mass that we call
  PCC
• Strength is inversely proportional to the
  water-to-cement ratio

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Strength vs. w/c Ratio for PCC
Strength, psi
w/c ratio
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Whats Important

• Good quality materials
• PC, water, coarse aggregate, and fine aggregate
• Proper Proportioning of the Materials
• Proper Mixing
• Placing and Finishing
• Proper Curing
• QC Testing

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How about the Costs?
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Other Types of Concrete

• Lightweight Concrete
• Structural and Non-structural (120 50 pcf)
• High Density Concrete (400 pcf)
• Mass Concrete
• Pre-placed Concrete
• No Slump Concrete
• Roller-Compacted Concrete
• Shotcrete (Wet and Dry)

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PC does NOT come from Portland Oregon

• Portland Cement
• Limestone Sand Clay Iron ore heat(1500 C)
  PC Clinker Grinding PC powder
• Dry process and wet process
• Hydraulic Cement hardens in air and under water
• Types I, II, III, IV and V
• IA and IIA blended with air-entraining agents
• White Portland Cement

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Blended Cements

• Blended Cements
• Type IP or P Portland Pozzolan Cement
• Moderate heat and moderate sulfate resistance
• Class C Fly Ash 15 to 40
• Class F Fly Ash 15 to 25 (FDOT)
• Type IS or S - Portland Blast Furnace Slag Cement
• Low Heat (FDOT)
• 25 70

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Other Cements

• Masonry Cement (mortar)
• Types N, S and M (See Table next slide)
• Expansive Cements Type K
• High Early Strength Cements - RR
• Calcium Sulfoaluminate Rapid Set
• Calcium Aluminate Cements- Cement Fondu
• Magnesium Phosphate SET-45
• Oil-Well Cements
• Acid Resistant Cements
• Silicate based
• Sulfur

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Mixing Water

• Potable
• ie. Water suitable for drinking
• Chloride lt 0.05
• Sulfate lt 0.08
• Organic salts lt 0.05
• sugar

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Aggregates

• Coarse Aggregate
• Retained on 4 Sieve
• Igneous, Sedimentary and Metamorphic rock
• Granite
• Limestone
• River gravel

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CA continued

• Maximum size from 6-in to 3/8-in
• Max size governed by ACI code
• Slab, form size and/or reinforcement
• Graded down to 4 sieve according to ASTM C136
• Common gradations, 467, 57, 67 and 89
• 1-1/2 in max, 1-in max, ¾-in max, and 3/8-in max
  respectively

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Aggregates

• Fine Aggregate
• Passing 4 Sieve ¼-in.
• Natural Siliceous and Crushed Limestone
• Graded according to ASTM C33
• See next slide
• Fineness modulus
• Indication of the average particle size (2.0 to
  3.0)

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Fine Aggregate Grading Limits
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Fine Aggregate Limits
Passing
Sieve Size
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Recycled Concrete Aggregate

• Old concrete that has been removed and crushed to
  produce aggregate.
• Coarse aggregate in new concrete
• Fine aggregate in new concrete
• Best combination is CA with natural fine
  aggregate
• Good strength
• Drying shrinkage problem
• Base-coarse replacement for natural limestone

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Mineral Admixtures

• Pozzolanic (cement replacement)
• Class C Fly ash 15 to 40 bwc
• Class F Fly ash 15 to 25 bwc
• Blast Furnace Slag (cement replacement)
• 25 to 70 bwc
• Silica Fume (cement addition)
• 6 to 12 bwc

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Chemical Admixtures

• ASTM C-494 and Table 6-1
• Water Reducing Type A
• Set Retarding Type B
• Set Accelerating Type C
• Water Reducer-Set Retarding Type D
• Water Reducer-Accelerating Type E
• High Range Water Reducers Type F
• HR Water Reducer-Set Retarding -Type G

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Air-Entraining Agents

• ASTM C260
• Admix that produces stable bubble system
• Liquid and solid
• Low dosage rates relative to other chemical
  admixtures (0.005 to 0.05 bwc).
• Increase in durability _at_freeze/thaw
• Reduces compressive strength
• 5 per percent of entrained air

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Fibers

• Steel
• Individual and bundled
• Glass alkali attack
• Synthetic 1 to 1.5 lb per cu. yd.
• polypropylene
• nylon
• Natural Egyptian pyramids
• Straw, bamboo, and wood

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Concrete Building Systems

• Beam and Girder Floor system
• Composite construction with Steel Beams
• One-way joist floor
• Flat Slabs
• Flat Plate slabs
• Two-way joist floor
• Precast and Prestressed concrete
• Connections

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