Sep 2018 CONCRETE COMPACTION EXPLAINED
A critical process in the successful placement of cement, concrete compaction influences the overall strength of cured concrete, enhancing the chemical bond and reinforcing the density of the concrete by packing the aggregate particles together. Careful attention should always be paid to recently place concrete and the method used to adequately compact the concrete.
Why is Concrete Compaction an important process in placing cement?
It is as a result of the densely compacted and equispaced particles of cured concrete that ensures its strength and durability which will ultimately be compromised if spacing is interrupted by air pockets and bubbles. By expelling air particles and pockets from recently placed concrete ensures that the matrix of cured concrete is able to take shape without setting around cavities or hollow spaces.
Through the process of Concrete Compaction the overall durability of set concrete is improved as a result of;
- Concrete compaction improves a concrete installation’s abrasion resistance
- By ensuring aggregate and particles are more densely packed decreases the permeability of a typical porous material
- Effective compaction reduces concrete shrinkage that occurs as moisture in the concrete evaporates
The rule of thumb is for every 1% air in concrete it reduces the strength by 5%
Concrete compaction can be a manual or a mechanical process either by hand or by using a specialised equipment and machinery.
Selecting the ideal method to expel unwanted air bubbles before concrete is set will depend on a number of factors including;
- The required reinforcement quality for the project
- The depth at which the concrete has been placed and accessibility to the required processes
- Positioning and properties of the concrete structure
- Availability of expertise and necessary equipment required
Manual / Hand Concrete Compaction
Performed manually and by hand through a number of different methods, hand compaction can be performed by way of Roding, Ramming or Tamping. Ideally used for DIY concrete projects and structures that are not load bearing or exposed to extreme conditions, hand compaction expels air out of concrete by the following methods;
- Roding makes use of a 2 metre long rod that is no more than 16mm in diameter and equipped with a fairly rounded point. By poking the concrete with the rods air pockets are “popped” allowing the concrete to slump back into the space that was occupied by the air pocket.
- Typically utilised for the compaction of ground floors Ramming is no longer a commonly practiced method in concrete compaction
- Tamping concrete compaction involves the use of a 10cm by 10cm wooden beam which is used to “beat” or bat the surface of the concrete. Not only effective in removing air bubbles and pockets from concrete but it also assists in levelling the surface of poured concrete and is commonly utilised in paving and sidewalks as well as concrete roofing.
Mechanical Concrete Compaction
Making using of vibration technology, mechanical concrete compaction employs specialised equipment to remove air pockets in concrete. Through a process that sees the temporary liquefication of concrete that ultimately eliminates air between the aggregate, mechanical compaction can be done by way of;
- Internal Vibration
- External Vibration
- Table Vibration
- Platform Vibration
- Surface Vibration
Keep a look out for more from Sephaku Cement on the various methods of concrete compaction and which option is ideally utilised on various construction projects.