The letterbox is the opening which allows self leveling concrete grouting compounds such as Renderoc LA55 to flow into a hole in the side of a concrete structure which needs to be filled. The forms are fixed to the concrete structure and sealed with silicone sealer to prevent the grout from leaking out.

Tip: Before cutting the services pipes into the formwork, use a laser level to check the RL of the pipe trench. If the pipes are in a trench which is too low or too high, it can be difficult or even impossible to cast the pipes into the formwork at the correct RL.

If the pipes are in fact at the wrong RL, and engineers are unable to approve a new depth, then the trench will have to be fixed.

There is no need however to check the RL of the pipe trench if the pipes are not already in the trench and all you have to do is cast some short pipes which will be joined up later.

These Fibreglass “Location” Pins are made from 10mm Fibreglass Rod. Simply cut the rod into lengths of about 100mm. You should drill a 10mm round hole which will ensure a snug fit after you bash them in. Make sure the drill does not slip over the line or the concrete line will not be straight.

Grout will leak from even the most tiny holes, so silicon sealer is used to secure the Grouting Formwork into position which prevents all leaks.

The Rail Track was removed and the Slab demolished after the crane passed through. There is 6 Ball Mills so this process was done several times.

Click the images for a larger more detailed picture.

Bolt Template

The bolt template is made from steel in order to support the weight of the bolts. The template must have the Center Lines scribed into it in order to place it into the correct position.

The template is clamped onto aluminium formwork beams. The beams are secured onto the formwork shutter with a timber and Z-Bar holding-down assembly.

The center of the bolts was marked onto each side of the forms and a string line was stretched across.

Then we used either a plumb bob, or spirit level to align the string line with the scribed centers on the template.

Doing this positions the bolts pretty close, but not close enough for a mining job. Later surveyors will come and check the bolt centers and each bolt position.

The total weight of the bolts is 480 kg. It is essential to get the assembly positioned as close as possible so that it makes it easier to lever into a spot-on position with the surveyer.

The Bolts

For safety reasons, we found it necessary to lift these bolts in one at a time with a crane.

Tolerance Tubes

After the bolts are in, polystyrene Tolerance Tubes must be added to the bottom of the bolts at the correct height. The height was established and scribed onto the formwork shutter, then transferred onto the bolts with a spirit level.

Adding the Shear Key and Bottom Template

The Shear Key was added next. After that the bottom template made from form ply was added.

A hanging assembly made with timber and z-Bars was used. The Z-Bars were used to wind the Shear Key up until it buts up tightly into the Spreader Bar timber holding it firmly in position.

The Z-Bars are also used to “Crack’ the Shear Key after the concrete is poured. Crack the Shear Key while the concrete is soft (Don’t wait till the next day).

Concrete Finished

One down, 7582 to go Personally, I’d rather be fishing.

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Obviously you would not cut these down to size from a brand new length, but because cutting Z-Bars to size is common, there will always be lots of Off-Cuts which can be used for this.

Z-Bar Pin And Wedge

To use the pin and wedge system, you must first have location pins on the inside of the formwork. This will prevent the formwork going over the line when the wedge is hammered in. These location pins are usually some thin steel around 10mm, but some projects do not allow steel so fiberglass pins are used.

Next, drill a hole larger than the Z-Bar to allow for a pretty loose fit. You’ll know the hole is too small if you have to use a hammer to drive them in.

Ensure there is a nice gap for the wedge to fit in. I often use a piece of plywood as a packer between the forwmwork and the drill bit. This leaves a gap of around 20mm which is heaps for a wedge.

After the hole is drilled, tap the wedge in until the formwork hits the location pin on the other side. Then secure the wedge with a nail wrapped around the pin to ensure the wedge stays in while the concrete is being vibrated.

Z-Bar Pin And Wedge

Using Z-Bar pins and wedges ensures that the formwork stays in the correct position while the concrete is being poured, plus, it’s fast and is easy to strip.

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Pedestal Base Formwork

After the base concrete is poured, the formwork is stripped leaving the pedestal steel starters exposed. After the steelfixers fix the remaining steel to the starters, it is time to assemble the pedestal formwork.

Typical Pedestal Base

On this job there are many pedestals this particular size (1200mm H x 1100mm x 1100mm) so we are using conventional timber and plywood formwork along with prefabricated steel forms.

Example #1 – Conventional Pedestal Formwork

One box composed of four small formwork shutters held together with z-bars and strong-backs.

Conventional Pedestal Formwork

Example #2 – Prefabricated Steel Pedestal Formwork

One box composed of two steel forms held together with nuts and bolts.

Prefabricated Steel Pedestal Formwork

There is several of these steel forms on this job because there are lots of these typical (exactly the same) pedestals.

Prefabricated Steel Pedestal Formwork

A closer look at the bolt template, bolts, tolerance tubes and shear key.

Pedestal Bolt Template and Shear Key Formwork

Here is the finished pedestal. If you look closely, you will notice that the shear key formwork is yet to be stripped.

Finished Pedestal

The pedestal formwork will be assembled after the concrete base is poured and set.

Dimensions: 2000mm x 2000mm wide x 1200mm high.

Precasting six cone shaped concrete structures 2 at a time for the Adelaide Aqua Port Stanvac Desalination project.

Scaffolding

The 400 mm thick bases for the concrete units was poured first and the 2600 mm cone shaped section will be added on top. After the bases are poured, the scaffolding is added to enable steel fixing, formwork erection and pouring of concrete.

Tube and Fitting Scaffold

Internal Formwork

The internal formwork is 1800 mm diameter (not cone shaped) which includes 2 x 6mm plywood layers bent into shape and screwed into the vertical timbers one layer at a time.

Cone Formwork Internal

External Formwork

The external formwork below is cone shaped. It will also be skinned with 2 x 6mm plywood layers. It will take a bit longer to screw the ply to the external formwork because of all the extra cutting into the cone shape.

Cone Formwork External

Below we see the skinned external formwork being added to the structure in 2 parts. There is no way this formwork would fit around the steel in one piece, so we split it in half, lifted it in two crane lifts and joined it all up in position.

Cone Formwork

Finished Precast Concrete Unit

Below we see the finished 30 tonne pre-casted concrete unit. It will later be placed on a barge with the other 5 units and floated out to Port Stanvac Desalination Project.

Cone Shaped Pre Cast Concrete

Plain old circular formwork is a bit easier than cone shaped formwork.