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Concrete (Properties (Curing (Methods (Impermeable membrane - cover with…

- - - - Impermeable membrane - cover with membrane, plastic sheets, or leave formwork longer than required
      - Water - supply water to surface to keep it continuously wet
      - Temperature - keep concrete moist & raising temperature, speed strength gain, for precast
  - - - Aggregate quality - A. restrain shrinking
      - ambient conditions
      - member size - smaller shrink more
      - water content - increases shrinkage
  - - - Tranditional
        
        made of out timber & shuttering plywood
        
        easy to produce, time consuming for large
        
        most flexible, labour intensive, on-site
      - Engineered
        
        standardised components, prefabricated
        
        faster, lower life-cycle cost
        
        suitable for large application with repetition
      - Lost
        
        formwork that stays in place after cured concrete
        
        composite steel-concrete structures (structural aid)
        
        hollow polysterene blocks (acoustics improvement)
- - - - provides bulk
      - reduces cost
      - improves durability
      - affects workability
      - colour, texture of concrete
      - controls cracking (reduces shrinkage)
    - - rounded aggregates = more workable mix
      - angular aggregates make concrete stronger
    - - Chemically inactive, clean
      - Range in size to fit together, stronger and denser
      - grading = distribution of particle size
  - - - Retarders - delay set times (hot weather)
      - Accelerators - speed up set times
    - - Plasticisers - reduce water content, improve strength (same workability)
      - Slag/Fly Ash - reduce cement content, improve strength (same workability)
        
        Slag - granulated material consisitin of silicates and calcium aluminosilicate, by product of steel making in a blast furnace
        
        Fly Ash - Material extracted from flue gases of a boiler fired with pulverised coal
- - - - Lime in cement reacts with CO2, forming calcium carbonate
  - - - L ow Ductility- low bending?
      - Normal Ductility - General purpose
      - Earthquake - Earthquake resistant bars or mesh
      - Examples
        
        3-N16 - 3 Bar, Normal Ductility, 16mm diameter
        
        3-L12TM - 3 Bar, Low Ductility, 12mm diameter, Trench mesh
    - - Square - square rib mesh (100mm centres)
      - Rrectangular - rectangular rib mesh (100x200mm centres)
      - Trench Mesh - 3 or 6 Bars, 100mm centres
      - Examples
        
        SL72 - Square, Low ductility, 7mm diameter bars, 200mm CTS
        
        RL718 - Rectangular, Low Ductility, 7mm diameter bars, 100mm CTS, 8mm Bars @ 200mm crosswise
  - - - Concrete
      - Plastic
- - - - Ordinary concrete, additives up to 5%
    - - Ordinary Concrete, 5-10% additives
    - - Limestone (w/ additives) from 8-20%
    - - 3 day strength same as 7 days of GP, early formwork removal and rapid strength
    - - limit rate of heat generation, for large concrete pours
    - - use for resisitance to ground waters with sulfates
    - - does not change in volume from drying shrinkage
- - - - contamination (reactive) aggregates
      - Moisture, stress
      - Carbonation, sulphate attacks
    - - drying shrinkage
      - seasonal temperature variations