Compaction of Concrete


EFFECT ON HARDENED PROPERTIES
as may be seen from Figure , the effect of compaction on compressive strength is dramatic. For example, the strength of concrete containing 10% of entrapped air (air voids) may be as little as 50% that of the concrete when fully compacted.





Permeability may be similarly affected since compaction, in addition to expelling entrapped air, promotes a more even distribution of pores within the concrete, causing them to become discontinuous. This reduces the permeability of the concrete and hence improves its durability.
The abrasion resistance of concrete surfaces is normally improved by adequate compaction. However, excessive vibration, or excessive working of the surface, can cause an excessive amount of mortar (and moisture) to collect at the surface, thereby reducing its potential abrasion resistance. In flatwork therefore, a careful balance is required to expel entrapped air without bringing excessive amounts of mortar to the surface of the concrete.


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