Flashcards
civil222 week 1
Cards in this deck (29)
- 1why concrete?fluid
make any desirable shape with wood, steel, cardboard, fabric
easy to obtain materials ( gravel, water, cement)
fire resistant
durability
different surface finishes & colours
resists abrasion
low permeability
corrosion resistant
sound resistant
creates local jobs & utilize local materials
quick construction - 2Structural Properties of concretestrong in compression
weak in tension - 3Aggregatesclean- paste can bound well
well graded - efficient use of paste
60%-70% of total volume
1/5 space btw forms - 4well graded
- 5fine aggregatesnatural or manufactured sand
less than 5 mm - 6coarse aggregatesgravel or crushed stone
5 mm ~ 28 mm - 7cementPortland cement
most expensive materials - 8supplementary cementing materialsfly ash
silica fume - 94 principal ingredientsaggregates( fine&coarse)
Portland cement
water
air - 10what kind of chemical reaction for making cementexothermic chemical reaction btw cement and water
- 11exothermic reactionchemical reaction that release energy by
lights or heat - 12water-cement ratiokilograms of water / kilograms of cement
or
liters of water / kilograms of cement - 13what w/c ratio is required for hydration0.25 ( min)
w/c can range from 0.35 - 0.60 - 14lowering w/chigher compression strength
lower permeability ( water tightness)
Increase wear resistance
sulphate resistance
Increase durability - 15two types of air in concreteentrapped & entrained air
- 16how to measure air content of concretevolume
- 17entrapped airwhen mixing materials, it occurs naturally
bubbles > 1mm - 18entrained airadmixture suspends air bubbles
bubbles < 1 mm
decrease lengthened mixing time - 19adding air entrainment for freezing & thawingair bubbles (10 - 100 micro meters) trapped in concrete
ice will expand into bubbles
prevent cracking
measured by volume - 20three kinds of tests for air contentspressure method ( Boyle's law)
Volumetric method ( for lightweight concrete)
Gravimetric method - 211 MPa1 N / mm2
- 22compressive strengthForce / Area
increase rapidly after mixing
slows down over time - 23ideal conditions for curing to achieve 28 days strength sooner100 % relative humidity
21 Celsius
wet and warm
practical curing time 7 days - 24workabilitythe ease of placing and finishing
the plastic ( fluid) concrete - 25finishabilitythe ease of finishing the surface of
the concrete - 26CSA standard Practices for concrete Methods of testingCSA A23.1-09 /
CSA A23.2-09 /
CSA A23.3-09 / - 27SegregationSeparation of the aggregates from the paste
- 28Bleedingthe formation of water on the surface of
the fresh concrete - 29—
Information
- Description
- Flashcards on civil222 week 1, created by jin86 on 19/01/2016.
- Created by
- jin86
- Views
- 0
- Rating