How to Stop Concrete Formwork from Failing
One of the most vital uses of concrete formwork is creating the foundations of a structure. As you may well know, weak foundations can cause a variety of problems from structural damage to collapse. Ensuring that formwork is correctly designed and used when creating concrete structures is paramount to its success.
Formwork can be defined as any temporary or permanent moulds into which concrete is poured until it hardens and is capable of supporting itself. Formwork can be used to create almost any concrete shape and is commonly used for a building’s walls, beams, columns, suspended slabs, and staircases to name only a few. In fact, formwork accounts for over 40% of the overall concrete costs of most projects.
Formwork is typically manufactured from wood, steel, aluminium, or a range of pre-fabricated modules such as glass reinforced plastics (GRP). Despite this, today’s construction industry typically employs modular formwork considering that it enhances the speed of construction and significantly reduces costs.
Formwork requirements
The success of any construction project in regard to quality, costs, speed, and worker safety requires formwork to fulfil the following requirements:
Has a secure base or foundation.
Capable of being handled safely using the available equipment.
Capable of supporting the weight of concrete during pouring and vibration as well as any other loads such as workers or equipment.
Adequately propped and braced both vertically and horizontally to ensure its shape is maintained.
Protects against any leakage through sufficiently tight joints.
Does not distort or warp when exposed to the elements.
Allows for stripping without damaging any concrete.
Most common reasons for formwork failure
There are a range of reasons which can lead to formwork failure, however most of the issues arise during the stage when the concrete is being poured. The following lists a few of the most common sources of formwork failure.
Improper inspections – Experience suggests that many formwork failures result from a lack of inspections or inspections undertaken by inexperienced personnel.
Flawed design - The majority of the failures arising from flawed design involve formwork collapse due to excessive loads. On top of that, each time formwork is reused its load capacity is lowered and this measurement is challenging for engineers to calculate.
Defective components - Where proper maintenance isn't undertaken on formwork components, they can easily become flawed after several uses. Inadequate bolts, nails or splicing, faulty wedges, and poor weld quality can jeopardise formwork integrity.
Poor foundations - Where formwork foundations are positioned on weak soil or when the foundations fail to transfer the load to the ground, formwork can easily collapse as it has a reduction in carrying capacity.
Premature removal - A common reason for formwork failure is when formwork is removed before the concrete has cured properly.
Preventative measures
In order to prevent formwork from failing and causing serious injuries, the following preventative measures should be taken.
Before concrete pour
Inspect all formwork components before use and replace or repair any flawed components.
Always assemble formwork systems according to the manufacturer's guidelines.
The formwork design should be undertaken by a qualified person with experience in the type of formwork being used.
If the formwork doesn't follow the original design, adjustments should be made with the designer examining the formwork to confirm its structural integrity.
The expected dynamic and static loads should be easily supported.
A qualified person must confirm that the formwork has been correctly erected before any concrete is poured.
During concrete pour
A boundary zone should be established during the concrete pour to prevent workers from accessing areas underneath the formwork.
During the early stages of the concrete pour, observe the formwork to identify any signs of failure. If workers require access to the area under the formwork, a risk assessment should be undertaken to ensure its safe to do so.
During the concrete pour, ensure the formwork is never overloaded.
Stripping stage
Ensure the concrete is given enough curing time (as detailed in the formwork design) before stripping.
There’s no denying that the construction industry is quite dangerous, however complying with all relevant safety measures and guidelines is the best way to minimise the associated risks and the likelihood of any injuries. If you have any inquiries about formwork or any methods used to prevent formwork failure, talk to the specialists at Uni-Span by phoning 1300 882 825.
