Last edited 09 Mar 2020

Concrete compaction

Contents

[edit] Introduction

Compaction is a process of expelling entrapped air. If we don’t expel this air, it will result into honeycombing and reduced strength. It has been found from the experimental studies that 1% air in concrete reduces the strength by approximately 6%.

There are two methods of compaction:

  • Hand compaction.
  • Mechanical compaction.

[edit] Hand compaction

Hand compaction is used for simple, small structures. Workability should be decided in such a way that the chances of honeycombing is minimised.

Methods of hand compaction include:

  • Rodding: 'Poking' with a 2m long, 16 mm dia rod at sharp corners and edges. The thickness of layers for rodding should be 15 to 20 cm.
  • Ramming: Generally used for compaction on ground in plain concrete. It is not used either in RCC or on upper floors.
  • Tamping: The top surface is beaten by a wooden cross beam of cross section 10 cm x 10 cm. Both compaction and levelling are achieved simultaneously. It is mainly used for roof slabs and road pavements.

[edit] Mechanical compation

Vibration is imparted to the concrete by mechanical means. This causes temporary liquefaction so that air bubbles come to the top and are expelled.

Mechanical vibration techniques include:

[edit] Related articles on Designing Buildings Wiki.