Fibre and the construction of RC swimming pool shells


Saturday, 30 July, 2011



Fibre and the construction of RC swimming pool shells

Ted Bennett of Civil & Structural Engineering Design Services Pty. Ltd. along with Rick Crambrook of Better Pools & Spas, both members of SPASA, have re-introduced the use "Fibre" concrete in the construction of RC swimming pool shells.

Ted has launched a campaign to revolutionize the way we construct concrete backyard swimming pools which will be extremely beneficial to our Pool Construction Industry.

Gone is the past poor performance of the old steel fibre pools. The newer fibres are much stronger "fibres" that will delete the use of 95% of the reinforcement bar content and considerably reduce the formwork and labour content. This will result in significant cost savings which will lead to enhanced time savings and produce economical shells, providing certain parameters are maintained and adhere too.

Ted & Rick see that there are "NO" disadvantages and from the shells cast to date they have only positive feedback.

Using this method of construction requires: excavation and temporary fence erection on day 1, inspection by the engineer for "fibre type and dosage rates" on day 2 and concrete casting on day 3. It is now possible to construct a swimming pool with three (3) week period providing all the finishes, equipment and fencing has been pre-planned to suit that schedule. Your customer will be ecstatic when you tell them that realistically you will not have to put up with the following:

  1. There should be NO waiting for a start date because the reinforcement hasn't arrived and dragged to position

  2. There should be NO excuses for the excavation collapsing due to delays caused by formwork and steel fixing crews untimely execution of their work

  3. The Xmas rush period may be achievable at last

The new "fibres" come in two(2) types and are readily available:

  1. Galvanised steel fibre named "Helix"

  2. Structural Plastic fibre named "Barchip" by Elasto Plastic Concrete Pty. Ltd. EPC and not to be confused with the "fibremesh", a completely different product

Parameters that must be maintained and adhered to are:

  • The wall and base thickness must be maintained at 150mm +/- 10mm

  • Minor vertical cog bars and 2 horizontal bars around the coping is required as additional prevention of solar movement cracking, these may be hung and chaired from simple edge formboards

  • The MIX design is critical with Western Suburbs Concrete leading the way

  • The pump should have a vibrating grate cover over the hopper to prevent "balling"

This revolutionary way is not new in "Shotcreting" or pneumatically placed concrete and what applies to a backyard swimming pools could readily apply to larger aquatic centre and resort type pools.

Some twenty years ago, "fibresteel" was used in concrete pools, however, reduced thicknesses, high dosage rates caused undesirable shrinkage cracking within a swimming pool shell which allowed the ingress of chloride ion concentrations beyond the acceptable threshold, leading to corrosion which was considered an unacceptable risk to the durability and structural capacity of the shell and finally the use of "fibresteel" deceased.

Now things have dramatically changed since the manufacture of a galvanized twisted corrosion resistant steel "fibre" named "Helix" from the USA.

We have also seen the emergence, particularly in the mining industry of the "Barchip" plastic distributed globally by EPC. This is an excellent alternative to steel fibres when considering extreme corrosive environments such as swimming pools and is the Elasto-plastic fibre known as Barchip synthetic reinforcing fibre. Barchip fibres are manufactured from minimum 550MPa high tensile strength modified polyolefin and similar to steel rebar this structural fibre has a contoured surface embossing treatment to maximize bond with the cement matrix. The base polyolefin is highly resistant to the majority of aggressive agents and will never oxidize when exposed to the conditions which cause steel to corrode in concrete. Elasto-plastic is a term used in engineering to describe a material that has the same load carrying capacity throughout the deformation process.

The future of concrete reinforcement and concrete reinforcing exists in alternatives to bar steel reinforcement that are safe-touse, and are corrosion free.

Both Helix and Bar chip are excellent alternatives to steel bar reinforcement in swimming pool construction and both should be considered, not as one versus the other, as both have the properties improve concrete ductility, toughness, crack control, and long term durability.

So why not come "On Board?"

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