Main Properties of Concrete
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1.3Main properties of concrete
Main properties of concrete must be understood. Wet concrete is known as fresh concrete while concrete that has been solidified is known as hardened concrete. The main property of fresh concrete is workability, whilst the main properties of the hardened concrete are strength, durabality, expansion and shrinkage.
Workability
It implies the ease with which a concrete mix can be handled from batching stage to compacting stage.
Strength
Concrete undergoes hardening process as soon as it is placed in the mould. High concrete strength can be achieve by using high quality materials, correct mix proportion and method of preparation as well as proper process of curing.
Expansion and shrinkage
It may occur in concrete during hydration process. However, if the concrete is wet, it expands and the maximum expansion and shrinkage are from 0.09% to 0.13%. continuous expansion and shrinkage can cause cracks in concrete.
Durability
Durability of concrete to weather change, chemical attack, cold and fire depends on the quality and its mix proportion. Concrete that absorbs water will reduces its durability. (civil engineering form 4, 2007)
1.4Proportioning Concrete Mixtures
For successful concrete performance the mixture must be properly proportioned.Detailed treatment of concrete proportioning is beyond the scope of this text, but some practical considerations include:
Although it takes water to initiate the hydraulic reaction, as a general rule, the higher the water cement ratio, the lower the resulting strength and durability of the concrete.
The more water that is used (which is not to be confused with the water-cement ratio), the higher will be the slump.
The more aggregates that is used, the lower will be the cost of the concrete.
The larger the maximum size of course aggregate, the less the amount of cement paste that will needed to coat all the particles and to provide necessary workability.
Adequate consolidation process stronger and more durable concrete.
The used of the properly entrained air enhances almost all concrete properties with little or no decrease in strength if the mix proportion are adjusted for the air.
The surface abration resistance of the concrete is almost entirely a function of the properties of the fine aggregates.
(Peurifoy Schexnayder Shapira, (7th edition),2006)