Note: The rate of pour affects the load on the formwork. The chart is for the safe height of column that can be poured in an hour.

 

Two finishes are available:

 

Structural; which will show a spiral line on the finished column.

 

   Architectural; columns lined with a rigid plastic sheet, providing a smooth finish to the concrete column.

 

Storage

Column formwork should not be stored in direct sunlight for long periods; where possible columns should be stored vertically.

 

Where columns can be stored horizontally:

 

The ground must be flat, even and clear of debris

 

Formwork stacks should not exceed 1.5 meters high

 

Formwork made from heavy profile should not be stored on top of formwork made from light profile

 

Fixing

The top and bottom of the column must be fixed in their designated positions.

 

At the bottom; typically the column is held by 4 equally spaced blocks of wood fixed to the floor slab

 

At the top: The top of the column is usually held in place by the soffit formwork

 

Where there is no soffit formwork (such as a final floor to a roof) props should be placed on the vertical bracing to position the column.

 

 

 

A hole cut in a piece of plywood to suit the O.D. of the column and to the vertical bracing will help resist damage from equipment used during pouring.

 

Note: Forms should be placed with the arrow facing upwards.

 

Bracing

 

Bracing is recommended for columns:

 

3.5 meters and longer with diameters larger than 450mm

 

3.0 meters and longer with diameters less than 450mm

 

Plastube columns are generally braced according to accepted industry practice. Bracing ensures the column remains straight and reduces the chances of bowing during pouring. It is especially important with tall, small diameter columns.

 

Cross bracing is typically placed at intervals of between 4 and 6 times the column diameter.

 

Vertical bracing assists in ensuring the column remains plumb and in the correct position.

 

Commonly 4 timbers (100mm x 75mm) for diameters below 600mm or 6 timbers (for larger diameters) are equally spaced around the circumference of the column, running the full height of the column.

 

Props should not be placed directly onto the Plastube column formwork.

 

Stripping

Two methods of stripping Plastube columns are commonly used;

 

Unwinding: Use a strong knife and pliers to break the spiral lock at the top of the column and unwind it, pulling it away from the concrete column. Once started, the unwinding process can be continued by hand.

 

Slab Stripping: Using an angle grinder or similar, the plastic column may be cut from top to bottom and sprung free from the concrete.

 

This method is typically quicker than unwinding, but may leave score marks on the finished column.

 

This publication aims to give general guidance to experienced form-workers in the use of Plastube circular column formwork.

 

It should be read in conjunction with relevant Standards, Specifications and Codes of Practice.

 

For further information contact either David or Terry.

PLASTUBE TECHNICAL GUIDE

 

Plastube circular column formwork is made by spirally winding a continuous strip of plastic profile, locking the edges together to form a tube. It’s a fast and effective process that results in the most convenient formwork available.

 

Ordering

Plastube circular column formwork is custom made to the sizes ordered. There are no standard lengths or diameters.

 

Plastube columns are ordered by specifying the diameter and length required. Two thicknesses of plastic profile are available, depending on the height of the concrete pour – as per the chart below.