BDCS_CONC

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ARCHTKBG
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246141
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BDCS_CONC
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2013-11-30 13:07:03
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CONC
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Concrete notes
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  1. Concrete History
    • BC
    • 1700: Greek Experimentation
    • 3rd Century: Romans use Pozzolan Ash from Mt. Vesuvius
    • 1st Century: Vitruvius writes de Architectura discusses "no slump" mixture and 2:1 ratio

    • AD -Process
    • 1756: John Smeaton discovers hydraulic concrete
    • 1824: Joseph Aspdin patents Portland Cement
    • 1867: Joseph Monier creates "Ferroconcrete" and reinforcent at the Paris Expedition
    • 1892: Francois Hennebrique creates "Beton Arme System" to make monolithic columns and beams using interlocking steel
    • 1918: Duff Abrams creates water-cement ratio
    • 1928: Freyssinet creates pre-stressed concrete with high strength steel wire for long span bridges
    • 1930: Air-entrained concrete is used
    • 1950: First shell structure is built.

    • AD - Buildings
    • 118: Pantheon (Rome), 142 ft dome
    • 1920: Trabeated support system (Paris), first open plan; Auguste Perret
    • 1928:Horticultural Hall (London), parabolic arch; Onderdork
    • 1930: Thin Shell Roof; Eduardo Torroja
    • 1931: Villa Savoye (open plan pillotes); Le Corbusier
    • 1937: Falling water (Pennsylvania); FLW
    • 1939: Cement Hall; Mailliart
    • 1939: Johnson Wax; FLW
    • 1948: Exhibition building (Turin); Nervi
    • 1950: Notre Dame Du Haut (Ronchamp); Le Corbusier
    • 1952: Unite de Habitation; Le Corbusier
    • 1953: Palace of Justice; Le Corbusier
    • 1957: Sports Palace; Nervi
    • 1959: Guggenheim (New York); FLW
    • 1962: TWA Terminal (New York); Eero Saarinen
    • 1988: Brazilian Sculpture Museum (Sao Paulo); Paulo Meades da Rocha
    • 2003: Auditorio de Tenerife (Canary Islands); Calatrava
  2. CONCRETE
    • A manufactured construction material composed of mixing fine aggregates (sand);
    • course aggregates (gravel or crushed rock); Portland cement; and water.
  3. Concrete Properties
    • Measured in volume (Ft3)
    • 150 pcf = normal weight concrete
  4. Concrete Mix Properties
    • Workability
    • Economical
    • Strength
    • Additional additives needed
  5. Concrete ingredients
    Inert (non-reactive): aggregates

    Active (reactive): cement and water

    Mix the aggregates and cement; then add water.
  6. Aggregate Classification
    • Fine Aggregates: 1/4" diameter or less
    • Course Aggregates: 1/4" to 1 1/2" diameter
  7. Aggregate Types
    • Irregular: provide better bonding and strength
    • Rounded: provide better workability
  8. Aggregate Size (maximum)
    • 1/3 thickness of slab
    • 3/4 of minimum space between bars
  9. HYDRATION
    A chemical reaction that causes the hardening of concrete. Cement heats up; rather than drying out.
  10. CEMENT
    Any adhesive substance capable of uniting non-adhesive materials.
  11. Portland Cement
    • Binding agent of concrete
    • Made of Lime, Silica, Iron-oxide, Alumina
  12. Type I (Portland Cement)
    • Standard concrete
    • General all-purpose
  13. Type II (Portland Cement)
    • Modified concrete
    • Slow setting and less heat
  14. Type III (Portland Cement)
    • High early strength concrete
    • Quick setting and early strength
  15. Type IV (Portland Cement)
    • Low heat concrete
    • Very slow setting (little heat)
  16. Type V (Portland Cement)
    • Sulfate resisting concrete
    • Alkaline water and soils
  17. Set time....
    • 1 hour (initial set)
    • 10 hours (final set)
  18. FLY ASH
    • A waste material obtained from coal-fired power plants.
    • Used in concrete to reduce the total greenhouse gas emissions.
  19. HVFA
    • High Volume Fly Ash
    • Needs only 2/3 the water
  20. ADMIXTURES
    Additional materials added to concrete mix to alter its characteristics and achieve a certain quality.
  21. Accelerators
    • Calcium chloride
    • Speeds up setting time
    • Manufactured as part of cement
  22. Air-entraining Agents
    • Resins, fats and oils
    • Resist freezing action
    • Manufactured as part of cement
  23. Retarders
    • Starches, sugars and acids
    • Slows down setting time
    • Manufactured as part of cement
  24. Waterproofing
    • Stearate compounds
    • Decrease permeability
    • Added to the mix
  25. Water-Reducing
    • Organic compounds
    • Reduce water content
    • Added to the mix
  26. Workability Agents (Plasticizers)
    • Powdered silicas and lime
    • Improves workability
    • Added to the mix
  27. Water-Cement Ratio
    • Expressed as gallons of water for each sack of cement
    • Controls strength and durability
    • Maximum strength is obtained by using the minimum amount of water to complete hydration but still allows workability
  28. Strength vs. Workability
    • As water is increased for workability....
    • Strength is decreased
  29. LAITANCE
    Chalky surface deposit of low strength caused by excess water.
  30. Concrete stress
    • Strong in compression
    • Weak in tension
  31. Compressive Strength
    • Compressive strength is reached 28 days after placement
    • 3,000 to 6,000 psi (4,000 most common)
    • 3,000 psi = 7:1 (7gallons of water:1 bag cement)
  32. High-Early Strength
    7-14 days to reach compressive strength
  33. READY-MIX CONCRETE
    Mix completed at a central mixing plant (1 1/2 hr from job site) and transported to the site in an agitator truck with revolving chamber.
  34. TRANSIT-MIX CONCRETE
    Dry components mixed in the truck en route to the job site and completed by adding water in the truck mixer at the job site.
  35. FORMWORK
    Molds which hold the required shape of concrete until it hardens and develops sufficient strength to hold its own weight.
  36. Formwork types
    • Wood
    • Metal
    • Fiberboard
    • Paperpulp
    • Reinforced synthetics
  37. Forms should be......
    • Practical to erect
    • Simple to strip from hardened concrete
    • Reusable
  38. TIES
    Metal devices used in formwork to prevent the spreading of the form due to wet concrete.
  39. Break Off
    • Flat Strap
    • Pull Out
  40. Screw Off
    • She-bolt
    • He-bolt
  41. Twist Off
    Wire
  42. Saw Off
    Drive-wedge
  43. REBAR
    Deformed steel used to stiffen concrete
  44. Rebar Standard Sizes
    • #3 (3/8" dia) thru #11 (11/8" or 1-3/8" dia)
    • #14 (14/8" or 1 3/4" dia)
    • #18 (18/8" or 2-1/4" dia)
  45. Rebar Specification
    ASTM#
  46. ASTM A615
    Billet steel
  47. ASTM A616
    Railsteel
  48. A617
    Axle steel
  49. ASTM A706
    Low-alloy steel
  50. Grade Designation
    • = yield strength
    • 40 (40,000 psi)
    • 50 (50,000 psi)
    • 60 (60,000 psi)
    • 75 (75,000 psi)
  51. Rebar Markings
    • Mill
    • Size
    • Type of Steel
    • Grade
  52. Most common rebar designation
    ASTM A615 Grade 60
  53. WWF 6x6 - W2.9 x W2.9
    • Welded Wire Fabric
    •           Wires @ 6" c/c each way
    •           Wires have cross sectional area of 2.9/100 or 0.029 si (6 gauge wire)
  54. Reinforcing Coverage
    • 3" @ foundation between undisturbed earth and reinforcing
    • 2" bars larger than #5
    • 1 1/2" bars #5 and smaller
    • 1 1/2" @ beams and columns
    • 3/4" @ slabs
  55. Lightweight Concrete
    90 to 115 pcf
  56. Lightweight Concrete Properties
    • Uses lightweight aggregates made from shale and clay
    • 3/4" = Maximum aggregate size
    • Air-entrainment is used
    • Handling and placing is easier
    • Modulus of elasticity is lower
    • Deflection is greater
    • Drying shrinkage is greater
    • Thermal insulation properties are better
    • Cost is greater
  57. Insulating Lightweight Concrete
    • 15-90 pcf
    • Low compressive strength
    • Uses perlite or vermiculite aggregates
    • May use "No Fines" to create air voids
    • May use foam in mix to create air voids
  58. Placing Concrete
    • Even
    • Continuous
    • Avoid segregation of aggregates
    • Place close to destination
    • 4ft = max vertical drop
    • When placing new on old, hardened should be thoroughly moistened
  59. Concrete strength is reduced by.....
    • Air bubbles
    • Vibration; hand tools; compaction reduce these
  60. Vibration
    • Greater density
    • Homogeneity
    • Durability
    • Complete contact with reinforcing
    • Stiffer mixes with reduced cement content
  61. GUNITE
    • Pneumatically applied concrete which is shot into place using compressed air.
    • Large surface areas; Thin sections
    • (swimming pools)
  62. Autoclaved Aerated Concrete (AAC)
    • A precast concrete product manufactured by adding aluminum powder to concrete; hardening it in molds; and then curing the molds in a pressurized steam chamber.
    • Manufactured in blocks (10"x25" long with 4", 8" and 10" thickness)
  63. Self-Consolidating Concrete (SCC)
    A concrete mixture that uses superplasticizer admixtures and can be placed purely by means of its own weight without the use of vibration.
  64. Carbon Fiber Concrete
    • Uses epoxy-coated carbon fiber mesh in place of standard steel mesh for secondary steel reinforcement
    • Used for precast panels, to make them thinner and lighter
    • Less concrete is required because carbon fiber is noncorrosive
  65. Concrete Testing
    Ensures required quality
  66. Slump Test
    • Measures consistency and workability
    • Performed in field with a cone
    • Allows 2-6 in of slump
  67. Cylinder Test
    • Measures compressive strength
    • Performed in lab with 6"diameter x 12" long cylinder
    • (2) cylinders (7 day & 28 day curing)
    • 2" X 4" cores from actual structure if failed
  68. Kelley Ball Test
    • Measures workability
    • 30lb 6" diameter hemisphere is dropped
    • Penetration into concrete is measured
  69. Impact Hammer Test
    • Measures compressive strength
    • Non-destructive
    • Rebound of spring loaded plunger is measured after it strikes smooth surface
  70. Calcium Chloride Test
    • (Moisture dome test)
    • Measures the moisture vapor emissions from a concrete floor.
  71. Hygrometer Test
    • (Relative humidity test)
    • Measures the moisture emissions
    • Tape a plastic sheet down for 72 hrs
    • Measure humidity under the plastic with a dew point hygrometer
  72. ALKALI-SILICA REACTION (ASR)
    A reaction between alkalies (sodium and potassium) in Portland cement and certain siliceous aggregates which cause adnormal expansion and cracking of the concrete surface.
  73. Titration Test
    Used to determine the level of alkalinity in concrete
  74. CURING
    Maintaining proper humidity and temperature of concrete for some period of time after placement to ensure satisfactory hydration of cement.
  75. Excessive Evaporation
    • Retards the hydration process
    • Reduces strength of concrete
    • Causes shrinkage and surface cracks
  76. Curing Methods
    • Supply additional moisture to the surface by ponding or sprinkling
    • Use wet covering (moist sand, burlap, or straw)
    • Cover the surface with a membrane or compound that prevents evaporation
    • Leave wood forms in place and keep them moist.
  77. Curing Criteria
    • 3 to 14 days
    • 50 and 70 degrees Farenheit
  78. Construction Joint
    • Horizontal or vertical joint between (2) successive concrete pours.
    • Keyed; Stepped; Roughened
    • Placement should be where elements are interrupted and where new is against old.
  79. Expansion Joint
    • Allows free movement of adjacent parts due to expansion or contraction.
    • Should be Weather-tight; Weatherproof; Penetrate through
    • Required in buildings more than 200 ft long; at joints of building wings; and at additions to existing buildings
  80. Control Joint
    • Tooled, sawed or premolded joints that allow for the shrinkage of large concrete areas.
    • Induces controlled cracking.
  81. Isolation Joint
    Provide a separation between a slab on grade and columns or walls so they can move independently.
  82. VAPOR BARRIER
    A thin plastic sheet material that prevents the passage of water vapor.
  83. VAPOR RETARDER
    A material that slows the rate of water vapor transmission.
  84. PRESTRESSED
    Concrete placed in compression by applying a tensile force to pre-stressed steel before external loads are applied.
  85. Pre-stressed Uses
    Exterior applications and long spans
  86. Pre-stressed properties
    5000 psi compressive strength minimum
  87. Advantages / Disadvantages of Pre-stressing Concrete
    • Advantages
    • Compression over the entire system
    • Smaller members
    • Spans are greater
    • Support loads are greater
    • Tension cracks are prevented
    • Stiffer system
    • Greater shear strength

    • Disadvantages
    • Greater material cost
    • Greater labor cost
    • Greater demand for quality control
  88. Pre-tensioning
    • Steel is stretched between abutments and tensioned with jacks before placing the concrete.
    • Once concrete is placed and achieves required strength, steel is cut.
  89. Post-tensioning
    Concrete is cast with a hollow sleeve to encase the pre-stressing steel and prevent bonding between the concrete and steel.
  90. Types of Pre-stressing Steel
    • High strength bars
    • Single wires
    • Wire strands (7 wires; 1 center; 6 spiral around)
  91. PRECAST
    Casting of concrete members at a location other than it's final position.
  92. Is Precast a right choice?
    • Check manufacturer location proximity to site
    • Size of precast elements (same or varied)
    • Trucking size
    • Highway clearance in relation to route
  93. Precast has its greatest economical advantage when....
    Identical members are cast.
  94. Advantages of Precast
    • Advantages
    • Better quality control
    • Better control over curing
    • All weather casting and erection
    • Faster actual construction time
  95. Types of Precast Systems
    Planks: floors and roofs integrated with cast structural system

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