Dear reader we all know consolidation is an essential element of concrete placement. Here we will discuss about manual consolidation. Concrete inherently have some flowability and due to gravity some consolidation of concrete is achieved while deposition of it in form.
But how much consolidation is occurred naturally without external effort? In stiff mix, the consolidation is negligible and in well proportioned mixture designed for flowing behavior less external consolidation attempt is required.
The techniques that we know are rodding and spading. Considerably flowable or plastic mixtures are consolidated with rodding techniques.
Spading is also sometimes applied at surface of forms. Now what is spading? Near from insertion of flat tools and subsequent withdrawn is done in this techniques. Repeated insertion and withdrawn reduce air pockets near surface of member.
In spading coarse aggregates are moved away from form which facilitates movement of water and air to top surface of member but bugholes near concrete surface is reduced both in quantity and size.
Hand tamping can be used for stiff mixer. Here concrete is initially placed in a thin layer and tamped or rammed carefully, then subsequent layers are provided and each layer is worked carefully by tamping. The quality of consolidation is not bad but the effectiveness is reaped at the cost of many labors.
Whatever the effectiveness, manual methods of consolidation, now-a-days, are only used in non-structural and small concreting operation.