Dear reader here we will learn about compaction of no-fines concrete. We have discussed about workability requirements of no-fines concrete in previous post. Workability is important here as it defines ease of concrete compaction without producing any sort of segregation.
But in no-fines concrete, no compaction is recommended. We know about the Arching; this may occur near corners of four or around obstacles. To avoid arching in this particular location compaction can be used.
We know compaction can be applied by manual and mechanical method. The manual methods are temping or rodding or spading. The mechanical methods include power temping, vibration and shake tables etc.
Vibration may be applied in this concrete but for very small duration; otherwise cement paste can run off from coarse aggregate particles. Thus no-fines concrete has little or no tendency to segregate.
In concrete placement, dropping height of concrete has great importance. In long member, where concrete have to travel long distance, we generally cast member in different phase to avoid segregation. In many situations considerable waste of time is also reported due to this.
No fine concrete can be placed from greater dropping height, as it has inherent non-segregating property. In many case it can be placed from height as much as three storeys.
Dear reader in our next post we will learn about requirements for formwork for no-fines concrete. Please stay with us.
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