What is Good Concrete?
What is Good Concrete? |
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A good concrete is one which has workability in the fresh state and develops adequate strength. Maximum strength of concrete can only be obtained, if the concrete has adequate degree of workability in relation to the method of compaction to be used. Concrete which is to be compacted by mechanical vibrator, will need 15% less water and 15% less cement as compared to the one which has to be compacted by hand.
The principal factors which effect the workability of concrete are:
Consistency:The degree of consistency will depend on the nature of work and type of compaction i.e. by hand or vibrator. The degree of consistency can be determined by slump test.
Water/Cement Ratio or Water control of a concrete:Water/Cement ratio is the ratio of water in a mix (excluding water already absorbed by the aggregate) to the weight of cement therein. The correct quantity of water required for a mix depends on the mix proportions, type and grading of aggregate, method of compaction and the weather conditions.
Grading of aggregate:Other things being equal, the workability of concrete is greater with larger size aggregates. A smooth and rounded aggregate will produce a more workable concrete than a sharp angular one. A falky aggregate produces the hardest or most unworkable concrete.
Cement content:The higher the cement content, the greater the workability, and less the effect of grading. As such, a much greater latitude in grading can be permitted with high cement content (called rich mix), than with a mix with less cement content (a lean mix).
