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

These defects are a significant worldwide problem and cause multi-billion dollar losses to infrastructure and building owners annually.

Reasons for the rectification of concrete defects can range from purely subjective (the aesthetics); to preventive (to prevent additional damage); to structural (preventing partial or complete failure); to safety (avoiding impact from falling debris).

As evidenced by the recent traffic disruption caused by structural cracking on the Riverside Expressway in Brisbane, one of Australia’s busiest stretches of road, the consequences (time, distraction and expense) of cracking concrete can be severe.

What then is the solution to problems caused by cracking concrete? The type of concrete defect rectification varies with respect to a number of factors: budgetary constraints, time limitations, weather conditions, and the requirement for specialised techniques.

In the specific case of concrete cancer, cracked concrete is removed followed by cleaning, treating and replacing any rust affected steel. The area is then repaired to the original concrete profile using cement mortar, epoxy mortar or concrete. This depends on the size of the damage and the structural requirement. Cracks are repaired using suitable epoxies, special mortars and injection techniques

While the rectification processes are usually expensive and time consuming, they are nevertheless an important step to take. Cracked concrete can have severe consequences, and if remain unchecked, associated costs can escalate significantly from both a repair, and damage control perspective.

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.

However, during the production of glass for use in high rise buildings, a very fast cooling process is used. This process in necessary to create the toughened glass that is capable of withstanding exposure to strong winds.

The problem begins when the glass is cooled rapidly during the toughening process. This rapid cooling process often fails to cool the nickel sulphide crystals. So the nickel sulphide remains trapped in its high temperature form. However, the story doesn’t necessarily stop there. Sometimes, years later, the crystals may spontaneously start to transform and result in the glass breaking, causing the windows to shatter onto the streets below.

This problem still presents itself in glass manufactured today. If a significant amount of toughened glass is used, there is likely to be nickel sulphide inclusions. Statistically speaking, around two out of every 1000 toughened glass panels that are produced are likely to contain nickel sulphide inclusions.

The solution is not particularly feasible at this point in time. Existing detection methods are expensive and time consuming. The only way to detect and remove the potential for nickel sulphide is to examine each pane of glass individually. Each image must then be analysed for the detection of inclusions. Once these inclusions are detected the panes of glass are removed and the process of heat soaking begins. Heat soaking is a process first used in 1982 which heats up the glass pane enough to cause the inclusions to change phase altogether, thereby removing them. At this stage there is a 95% conversion rate for removing the inclusions via heat soaking. 

However, this is not the same as a 100% success rate, and it is indeed a time consuming and expensive process. While there are new developments within the industry that one day may overcome this problem, the shattering truth remains that when toughened glass is used, nickel sulphide inclusions are more likely than not to present themselves.

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.

In this instance, the air conditioning unit will have to work significantly harder than it did when it was first installed.

This can lead to several problems due to the increased workload, including increased maintenance due to, or to prevent failure, and increased running costs.

Effective, efficient air conditioning systems are a major consideration for employees and therefore benefits. So, a building owner must consider this issue when allocating funds for refurbishment, in order to achieve an optimal return on investment.

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.