Why does concrete crack?

Unlocking the mysteries of a critical building resource


Concrete has been the main stay of building construction for generations. Today, traditional reinforced concrete is an integral and important component of building structures. It usually takes the form of footings in ground, slabs on ground, columns and suspended slabs.


Concrete however, is not the perfect substance. As such it can suffer from defects. These defects can have a huge impact on the appearance, capital expenditure, maintenance costs, safety and effective life of the total structure.


What then are the typical forms of concrete defects? Some of the more common defects can be categorised as follows:- 


  • Structural design inadequacies – distortion, bending cracks, deflection, shear cracks, impact damage temperature change cracks, abrasion, torsion cracks and erosion.
  • Environmental causes – weathering/staining, biological growth, bacteriological attack, efflorescence (lime leaching), freeze-thaw damage and fire damage
  • Aggregate properties – aggregate swelling/shrinkage/softening, alkali-silica reaction and sulphide staining/spalling.
  • Chemical attack – sulphates, chlorides, acids and salt weathering.
  • Reinforcement corrosion – cracking, spalling and de-lamination 
  • Concrete Cancer – cracking of the concrete caused by the corrosion of steel reinforcement in concrete structures

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The shattering truth about glass

Since the 1960s, there have been numerous, high profile incidents of ‘spontaneous” failure of toughened glass in building facades. In some cases, glass has been known to simply ‘pop’ out of high-rise building windows and fall onto the streets below  Why does this happen? The cause lies within the makeup of the glass itself.


Nickel sulphide is a rare and unintended inclusion in the production of glass panels. However, the presence of nickel sulphide can be a problematic one. This is due to what is technically called, ‘delayed transformation’.


For those interested in technical detail, these follow:


Nickel sulphide crystals can take one of two forms. At high temperatures, a dense crystal is present. At lower temperatures, a less dense crystal is present. Provided the transition from high to low temperature (ie. cooling) is gradual, the crystal can move between forms without problem.


For example, in ordinary annealed glass, the crystals do not cause problems because the cooling process occurs slowly during manufacture.

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Don’t let your refurbishment get you hot under the collar

When undertaking due diligence work, we often identify instances in which owners have carried out quality refurbishments that include foyers, floors and ceilings.


While this certainly does help with the building’s maintenance and appearance, the refurbishment often overlooks a critical part of the equation: the air conditioning unit.


Air conditioners are a critical resource for buildings everywhere.  Why is it then that they are so often overlooked? Many building owners do not consider the air conditioning unit to be particularly important in terms of refurbishment. Some owners do not even consider that air conditioning units would ever need to be refurbished.  This however, is certainly not the case.


For most buildings, the air conditioning units were installed when the building was constructed. In some cases, this is as many as thirty years ago. As such, these air conditioning systems were designed to suit conditions relevant to the times when the building was originally constructed. For older buildings, this means that the air conditioning was designed to cater for factors that we consider common today such as computers, longer working hours and work station clusters.


Why is this a problem? Computers and body temperature each affect the general air flow required within a building. Consider a 10 storey building with a central air conditioning unit. It is likely that over a period of years, the number of employees within the building would have increased; the required electricity would have significantly increased; and the hours of work would most likely also be significantly greater.

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Don’t overlook the value of proactive maintenance

For many years, building owners have subscribed exclusively to the theory, if it aint broke, don’t fix it. This however can be an expensive mistake.


It is important to acknowledge that a building is an asset. As such, it needs to be protected and maintained to ensure that its value is not eroded.


To retain and attract tenants, your asset must be presented in the best possible condition, which in turn will maintain or increase its value.


Napier & Blakeley Building Consulting Manager, Nigel Towse says that if building maintenance is ignored, it can have significant consequences.


“There is a common misconception that buildings have long lives and only deteriorate gradually. This may be true for the more robust forms of structure. However even these can deteriorate rapidly with structural failure, environmental issues, chemical attack or the ingress of moisture.”


The health and well being of tenants is paramount in any leased asset and is heavily linked to how the building is maintained. There are basic, statutory obligations that require regular maintenance to be carried out to this end. In particular, cleaning, testing, and checking etc, of fire systems, boilers, lifts and hoists.


“By planning and carrying out your maintenance efficiently, you can minimise your capital expenditure. This will ensure that your asset is safe, economical, efficient, environmentally friendly, and retains its value,” says Towse.