Bcn 5905 Concrete

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BCN 5905STRUCTURES 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 aCement @$&!*^#%

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 ItsStrength

PC + water = hydration reaction > GLUE + Heat

Cementitious material literally glues all of the

inert (non-reactive) aggregates together toproduce 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?

Item % of Total Cost

Concrete Materials 24%

Labor & Equipment 8%

Reinforcing Steel 12%


Formwork Materials 10%



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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 ConcreteRoller-Compacted Concrete

Shotcrete (Wet and Dry)


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PC does NOT come from PortlandOregon

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 SulfoaluminateRapid Set

Calcium Aluminate Cements- Cement Fondu

Magnesium PhosphateSET-45 Oil-Well Cements

Acid Resistant CementsSilicate based

Sulfur


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Mixing Water

Potable

ie. Water suitable for drinking

Chloride < 0.05%

Sulfate < 0.08%

Organic salts < 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, -in max, and 3/8-in max respectively


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Aggregates

Fine Aggregate

Passing #4 Sieve ~ -in.

Natural Siliceous and Crushed LimestoneGraded 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

Sieve size % Passing

No. 4 95-100

No. 8 80-100

No. 16 50-85

No. 30 25-60

No. 50 5-30

No. 100 0-10


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Fine Aggregate Limits

Sieve Size

% Passing


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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 ash15 to 40% bwc

Class F Fly ash 15 to 25% bwcBlast 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 solidLow dosage rates relative to other chemical

admixtures (0.005 to 0.05% bwc).

Increase in durability @freeze/thawReduces compressive strength

5% per percent of entrained air


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Fibers

Steel

Individual and bundled

Glassalkali attackSynthetic 1 to 1.5 lb per cu. yd.

polypropylene

nylonNaturalEgyptian 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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