Concrete Flashcards
Mixture of fine and coarse aggregates with cement and water
Concrete
Combination of water and cement
Paste
Combination of paste & fine aggregates
Mortar
Concrete used for superstructures and heavily reinforced substructures
Class A concrete
Concrete used for unreinforced or with small reinforcement footings, pedestals, massive pier shafts
Class B concrete
Thin reinforced sections
Class C concrete
Prestressed concrete structures
Class P concrete
Concrete deposited in water
Seal
Stages of Concrete formation
Mixing Dormancy Hardening Cooling Densification
The reaction between C3A and CAH (tricalcium aluminate & aluminate hydrate)
Mixing
The mixture remains plastic with no heat generation.
Dormancy
The mix starts to stiffen, stage dominated by silicate reactions
Hardening
Concrete shrinks: Shrinkage is restrained by friction from underlying layers
Cooling
Hydration continues if cement and water are still present in the mixture
Densification
Materials added to concrete mixtures to modify their properties
Admixtures
Concrete properties commonly modified by admixtures
Rate of Hydration
Workability
Dispersion
Air-entrainment
Used to speed up the initial set of concrete by increasing the rate of hydration to shorten the setting time
Accelerators
Used to slow down the setting of concrete and delay initial setting time up to 4 hours
Retarders
Obtain higher strength by decreasing the water-cement ratio at the same workability as an ordinary mix
Water reducer or plasticizer
For normal workability but with extremely high strength due to a very low water-cement ratio
Superplasticizer
Admixtures help incorporate a controlled amount of air in form of minute bubbles (0.01-0.25 mm dia.)
Air-entraining admixtures
Materials used for preventing or delaying drying up of intrinsic moisture inside the capillaries of the concrete
Curing materials
Physical properties of concrete
Workability
Durability
Strength
Impermeability
Empirical test that measures the workability of fresh concrete
Slump test
A curing method is where concrete is continuously wet by the application of water for a minimum period of 7 days after the concrete has been placed.
Water method
Curing method where the application of an impervious membrane and shall be practically colorless liquid
Curing compound
A Curing method is where water is sprayed using a nozzle that atomizes the flow into a mist.
Waterproof membrane method
Pre-cast concrete members are steamed for a minimum of 4 hours
Steaming curing method
