How to Prevent Costly Concrete Failures
Up to 2,500 tonnes of cement is required to complete a kilometre of freeway. It’s a small project and yet cement usage is already immense. Imagine the amounts for completing kilometres of roads and multi-storey buildings.
As a result, the integrity of most structures depends on the integrity of concrete. From its composition up to its pouring, curing and installation, every aspect that relates to concrete is important in ensuring the integrity of a structure (e.g. roads and bridges, reservoirs, railway sleepers, residential and commercial buildings).
With this heavy dependence on concrete, engineers and developers now hire specialists to evaluate the condition of concrete in their structures. For instance, specialists perform advanced failure analysis to identify vulnerable points and areas in concrete structures. With accurate information in hand, engineers and developers can perform preventive maintenance on those vulnerabilities. Then, they can avoid costly damages and possible harm to human lives.
What causes concrete to fail?
Concrete failures can often traced back to weight (either too much weight or the structure just can’t carry the load), environmental stress, improper work and poor design. Concrete structures and sites encounter and endure various forces 24/7.
Aside from gravity, the weight of the concrete induces stress upon itself. Perhaps the load was not distributed sufficiently. Or, the structure is not sufficiently tough to support the load (e.g. might be due to size and shape of the structure or load).
Environmental and chemical agents also contribute to gradual concrete degradation. For example, erosion by fast-flowing water (e.g. concrete foundations of bridges) can slowly wear away the concrete, which weakens the structure. Temperature fluctuations can make concrete structures expand or contract. After all, there’s water content in the formation of concrete (concrete solidifies and hardens through hydration). The freezing of the water content might introduce new forces within the structure. Also, when concrete hardens and solidifies, it loses the excess water. This results to contraction or shrinkage which can compromise the structure.
Marine environments also affect concrete integrity. This is due to acceleration of the corrosion of steel reinforcement. The corrosion products can expand and introduce cracks to the concrete. For instance, the chloride ions from seawater can accelerate corrosion. In addition, potassium and magnesium sulphates can react with calcium hydroxide (present in the set cement). This reaction leads to formation of soluble magnesium hydroxide. As a result, portions of the cement dissolves. Sulphate attacks are considered severe and may quickly compromise a concrete structure exposed to marine environments.
As we’ve noticed, the integrity of a concrete structure not only depends on its proper installation and composition. It’s also about the structure’s interaction with its immediate environment. Thermal changes and chemical reactions can slowly or quickly cause concrete degradation. Compounds present with the reactant (sulphates in seawater) can accelerate degradation.
The cost of concrete problems
In a national scale, billions of dollars are lost annually due to concrete failures. That’s because compromised structures often require demolition, repair and replacement. Tonnes of cement will again be used to repair the structure. In addition, large-scale projects may take several weeks or months to repair. The labour costs and possible interruptions to transport and commercial activities should also be taken into account.
More importantly, the safety of the public is at stake. Collapsing bridges and buildings rarely happen and there’s always time to re-build. But the loss of lives is permanent.
The effects on the construction sector could also be huge and serious. This could lead to slow down or temporary halt of major infrastructure projects. Total review of construction standards will be performed including about the project designs, material quality and sourcing and project assessment and validation.
With this construction slowdown or temporary halt, the entire economy suffers because the movement of money also stops or slows down. Money won’t transfer from people to people or from a company to another company. From material purchase up to labour costs, these will all be affected by construction slowdown.
Furthermore, construction halts and delays also make assets waste time and money. For instance, if completion of a multi-storey apartment is delayed, the income to the developer and the return on investment (ROI) is also delayed. Also, potential tenants might delay their plans of moving into another suburb because of the delays and construction halts.
All of that can result from costly concrete failures. It’s possible that the statistics on financial losses about concrete failures doesn’t show the full picture. We also have to consider the effects downstream which might be more costly than we realise.
How to prevent costly concrete failures
With the upfront (cost of repair and rebuild) and downstream effects of concrete failures, engineers, developers and government agencies now prioritise ensuring the integrity of concrete structures. Government agencies are concerned because of the effects to public safety and the national economy.
The key to prevent concrete failures is by focusing on both the product (the cement and its solidification into concrete) and the process (e.g. structure design and coating application). These apply at the start and during the project.
On the other hand, continuous monitoring should also be employed after the structure was erected. That’s because concrete structures deteriorate due to the cyclic effects of the load and environment. The condition of structures changes through time and temperature fluctuations. Also, each project is unique because of the wide variety in requirements and environmental stresses.
As discussed earlier, marine environments can accelerate corrosion of steel reinforcements and the dissolving of the set cement (action of magnesium sulphate on calcium hydroxide). The concrete might pass hardness and porosity standards. But it’s an entirely different case if the structure (or portions of the structure) is exposed to harsh environments (or things where cement is vulnerable).
The end use and the immediate environment should be considered when estimating the decay or deterioration rates of concrete structures. Although there are proactive measures already in place (e.g. closely controlling water-cement ratio to minimise shrinkage), ongoing inspection and monitoring is the key to preventing costly concrete failures.
For instance, reinforcement corrosion is not immediately apparent. There might be no signs of it for several months and years. It’s especially the case when the site is submerged in water or beneath the ground. Only a prompt inspection can reveal the problem.
It’s actually a rigorous process because the structure itself and the immediate environment will be inspected and evaluated. This way, a more accurate decay rate will be established. The developer or the one in charge of the structure could then better plan for a prompt maintenance. Better assessment also results to more timely and accurate resource allocations. The expenses can be better estimated and the funds can be prepared early on.
From the beginning of the project up to during the structure’s service life, it’s important to ensure safety and integrity every step of the way. Aside from maximising your asset’s service life, this is also about protecting the end users, stakeholders and the community in general. This is also a worthwhile investment because you will maximise the service life of the structure while minimising repair costs.
A customised approach is ideal in this kind of endeavour. Each structure has a unique mix of loads, forces and environmental conditions. In addition, safety and reliability requirements vary from one project to the next. For instance, the requirements in marine environments might differ a lot compared to land-based projects.
There are several variables at play and it’s all dynamic. The interdependencies among various variables and systems make the entire concrete condition evaluation more complex. That’s why engineers and developers only work with specialists who have extensive experience in this kind of project.
Here at Corrims Consultants, we perform rigorous concrete structure inspection and assessment. We analyse all variables that affect the structure’s integrity and service life. We study the structure’s surroundings, safety and reliability requirements and the client’s desired outcomes. We also assess the seasonal influences, materials used, construction records, and techniques used.
Our concrete structure assessment services also include:
- Failure analysis
- Repair & specification
- Concrete coatings
- Resistivity, carbonation & hardness
- Porosity, ultrasound, and chlorine contamination
- Concrete field test
- Concrete moisture
- Investigation and condition assessment
The goal is to accurately assess the current condition of the concrete structure and establish its decay rate. This way, companies can better plan the maintenance and repair tasks, costs and schedules.
Contact us today and our engineers will inspect your concrete structure and its interaction with the surroundings.