06-09-2022, 11:37 AM
COMPACTION BY VIBRATION
Compaction is best done by vibration. Rodding, spading and tamping are all ways of removing air from concrete and to compact it, however the best and most efficient
method is vibration. Rodding is an age old method being used. However, this method requires very sincere manual effort, good supervision and high workability. Under
the present circumstances it is not possible to achieve this and hence compaction by mechanical means is always preferred.
On Vibration, the concrete mix gets fluidized and the internal friction between the aggregate particles reduces, resulting in entrapped air to rise to the surface. On
losing entrapped air the concrete gets denser.
Vibration helps entrapped air to escape first from between the coarse aggregate particles and later from the mortar. As the concrete subsides, large air voids between
the coarse aggregates get filled with mortar. When vibration continues some more entrapped air from the mortar is driven out. However, during this second phase,
concrete does not show any movement but it is in this phase that maximum - ~trapped air is driven out and that is the time when most of the consolidation takes
place.
For a stiff concrete mix greater effort is required for fluidisation and hence compaction has to be for a longer period. For a lean or over wet mix, compaction effort required
is less. On vibration of an over wet concrete mix the coarser aggregates settle down and a weak layer of fine materials (cement paste with finer fines of fine aggregates) will rise on the surface . With properly designed cohesive mix the formation of weak laitance layer is prevented. It is recommended that at any time if weak laitance layer (layer of cement paste and finer fines of fine aggregate) is formed it must be removed.
As long as vibrators are operated properly and not used to move concrete laterally, compaction enhances concrete performance and appearance . Compaction improves concrete density, strength, bonding with reinforcement steel, minimizes surface blemishes and also to a great extent helps in improving the durability of the structure.
The efficiency of compaction is related to the workability and characteristics of the vibrator.
For more details visit or download
![[Image: pdf.gif]](https://frontdesk.co.in/forum/images/attachtypes/pdf.gif)
concrete compaction fd.pdf
Compaction is best done by vibration. Rodding, spading and tamping are all ways of removing air from concrete and to compact it, however the best and most efficient
method is vibration. Rodding is an age old method being used. However, this method requires very sincere manual effort, good supervision and high workability. Under
the present circumstances it is not possible to achieve this and hence compaction by mechanical means is always preferred.
On Vibration, the concrete mix gets fluidized and the internal friction between the aggregate particles reduces, resulting in entrapped air to rise to the surface. On
losing entrapped air the concrete gets denser.
Vibration helps entrapped air to escape first from between the coarse aggregate particles and later from the mortar. As the concrete subsides, large air voids between
the coarse aggregates get filled with mortar. When vibration continues some more entrapped air from the mortar is driven out. However, during this second phase,
concrete does not show any movement but it is in this phase that maximum - ~trapped air is driven out and that is the time when most of the consolidation takes
place.
For a stiff concrete mix greater effort is required for fluidisation and hence compaction has to be for a longer period. For a lean or over wet mix, compaction effort required
is less. On vibration of an over wet concrete mix the coarser aggregates settle down and a weak layer of fine materials (cement paste with finer fines of fine aggregates) will rise on the surface . With properly designed cohesive mix the formation of weak laitance layer is prevented. It is recommended that at any time if weak laitance layer (layer of cement paste and finer fines of fine aggregate) is formed it must be removed.
As long as vibrators are operated properly and not used to move concrete laterally, compaction enhances concrete performance and appearance . Compaction improves concrete density, strength, bonding with reinforcement steel, minimizes surface blemishes and also to a great extent helps in improving the durability of the structure.
The efficiency of compaction is related to the workability and characteristics of the vibrator.
For more details visit or download
concrete compaction fd.pdf