Formwork Blog

Posts Tagged ‘Concrete Forms’

Recent Aluminium Concrete Forms Video

Video demonstrating an Aluminium Formwork System. Blokes assemble, pour and strip the concrete forms without the use of heavy lifting equipment such as cranes or forklifts.

www.WallTies.com Concrete forms and formwork manufacturer Wall-Ties and Forms.

Here is two more pedestal formwork examples. The pedestal forms will be used on typical pedestal bases (shown below). We begin by forming up the bases.

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

Here is an example of a very simple formwork box which is ready for concrete. It is held together with z-bars at the top and bottom on the corners while the centers are held together with z-bars at the top with pins and wedges at the bottom.

Pedestal Base Formwork

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

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

Location: Port Adelaide SA

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.

Location: Northern Expressway Adelaide SA

When Z-Bars become difficult to extract because concrete slurry has leaked into the conduit, it may be necessary to make a heavy duty Z-Bar extracting tool.

Z-Bar Extractor

Simply cut a notch in the plate of a Prop-Inner, Screw-Jack or similar item. The notch should be slightly bigger than the diameter of the Z-Bars being extracted.

The length of the Prop Inner tube should be cut down to a manageable length while keeping in mind that the longer the tube (handle) is, the more effective it will be for extracting stubborn Z-Bars. (The longer the handle, the heavier the tool.)

Z-Bar Extractor In Action

To use the Z-Bar Extracting tool, remove the Z-Bar plate (washer) and replace only the nut. Then simply slide it along the Z-Bar towards yourself smashing the nut.

The photo above shows us using the Z-Bar Extractor to pull out a stubborn 4 meter long, 25 mm thick Z-Bar from a poured concrete pier. The Z-Bar Extracting tool made light work from what would otherwise have been one of those crappy never-ending jobs.

Pitfalls To Avoid

Important! Don’t be a bozo and smash your fingers into something while pulling back with the Z-Bar Extracting tool! Look around before you start smashing.

Tip: The length of the handle should be determined by your surroundings. For example, you would not have a 2400mm handle if you were working from a tight scaffold. You would cut it down to say 900mm – 1500mm max.

Tip: Using the Z-Bar Extracting tool on Z-Bars that are not so stubborn is also a good idea because it will reduce the number of times the ends need to be ground-down in order for the nut to fit properly.

Smashing Z-Bars out the regular way with a hammer will burr the ends, increase servicing requirements and produce down-time when someone goes to screw a nut onto a burred Z-Bar.

Location: Bolivar Water Treatment Plant SA

While this slab formwork “may” hold the concrete, it could be done a bit more professionally by using plywood rips and a bedlog to straighten the edgeform instead of wire. I can’t believe the formworkers that did this job recon it was ready for concrete.

Dodgy Formwork

Using wire back to a single pin to pull the formwork into line is dodgy and time-consuming because the pin can flex (or the wire can break) and put a “dog leg” in the formwork.

Dodgy Formwork Braced without a Bedlog

Tip: If it is important to have nice straight formwork (it should be), always use a bedlog. A bedlog enables you to push and pull the formwork into the exact position, secure it properly and “walk away”.

Even if it is not important to have nice straight formwork because the crooked concrete will “never be seen”, it is not a good look to have dog-legs in a concrete slab. By the way – It will be seen before it is never seen. It will be seen by bosses and inspectors.

Location: Road Bridge – Port Adelaide South Australia

All the access scaffolding is now complete on this bridge column formwork. We are not quite ready for concrete yet because city council inspectors must give the okay first.

Column Formwork Almost Ready for Concrete

City Council inspectors will climb up the access scaffolding and make sure that the column forms and reinforcement steel inside the concrete forms are positioned according to the specifications on the plan. In most cases, the inspector will give it the go-ahead.

In my experience, the only times an inspector does not approve a concrete pour is when some formworker did not do what they knew had to be done. These formworkers hope that the inspector does not see that bit of steel too close to the concrete form, or that bar-chair that fell down to the bottom.

Or worse, sometimes a supervisor will instruct a formworker “not to worry about it”, then after the inspector picks it, they rush around like a freaking idiot trying to get it fixed

See the arial view of this formwork.

Location: Prominent Hill Mining Construction Site South Australia

Four concrete forms held together with Column-Clamps and held down with spaghetti nailed plywood. The 700 mm long bolts took a bit of work to cast in due to the extra reinforcement steel positioned exactly in the center of the pedestal.

Pedestal Formwork Ready For Concrete

This job was not as bad as the nightmare pedestal, but still took extra time because the formworkers had to reposition the steel in order to fit the bolts in.

Concretors Anthony and Nev Vibrating Pedestal Concrete

To ensure the correct heights, the concrete and bolt-top heights were established from a known benchmark with a Laser Level instrument and not by just measuring up from the foundation concrete.

Location: Road Bridge – Port Adelaide South Australia

Arial view of formwork for bridge columns. The concrete forms have been braced with concrete counter-weights and scaffolding has been errected in order to provide access for construction workers to complete the formwork and steelfixing and place/finish the concrete.

Braced Column Formwork with Access Scaffolding

Location: Prominent Hill Mining Construction Site South Australia

This four tread stair formwork is held together with 4 z-bar bolts, held down with pins at the front and wedges (to the structure) at the back, and braced with one timber on each side and two timbers at the back.

Four Tread Stair Formwork

Four verticle plywood cleats were also added to the back corners to prevent the rear concrete form from blowing out.