Melbourne’s Leading Concrete Pouring Specialists
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Post-tensioned slabs are built tough, but they’re not bulletproof. Around 40% of structural repairs in Australia involve concrete slabs, and many are post-tensioned ones!
When cracks appear, tendons corrode, or tension drops, your building’s safety and performance are on the line. Leave it too long, and the damage (and repair bill) can skyrocket.
In this guide, we’ll break down the most common post-tensioned slab issues and show how the pros fix them to restore strength and keep your structure safe for years.
Post-tensioned slabs are a type of reinforced concrete system designed to handle heavier loads and span longer distances than traditional concrete slabs. They are created by placing high-strength steel tendons inside ducts within the concrete.
Once the concrete has cured, these tendons are tensioned using hydraulic jacks, then anchored securely at each end. This process places the concrete into compression, which significantly improves its performance and reduces the likelihood of cracking.
These slabs are commonly used in multi-storey buildings, bridges, car parks, and large residential homes where strength, durability, and flexibility in design are priorities. Importantly, post-tensioned slabs can offer benefits such as reduced slab thickness compared to conventional designs, lowering the overall weight of a structure and leading to savings in foundation requirements.
While the construction process is more specialised, post-tensioned slabs offer long-term advantages in structural efficiency and maintenance. By understanding how they work, property owners and builders can make informed decisions about their suitability for specific projects.
Post-tensioned slabs are strong and reliable, but like any structural system, they can face challenges if not maintained or installed correctly. Below are some of the most frequent issues that arise and why addressing them promptly is critical for maintaining structural integrity and safety:
Moisture entering the slab can cause the steel tendons to corrode, weakening their structural capacity. This often results from inadequate sealing, damaged ducts, or poor waterproofing.
Corrosion can progress unnoticed until serious structural problems emerge, making regular inspections vital. Professional repair involves cleaning, replacing, or protecting affected tendons to restore strength and prevent future damage from environmental exposure.
High stress, construction mishandling, or anchor head failures can lead to cables breaking or slipping within the slab. This reduces tension and compromises load-bearing capacity.
Detecting the problem early with specialised testing allows for targeted repairs, which may involve re-tensioning or replacing cables. Leaving the issue unaddressed can lead to progressive structural failure over time.
Cracks can appear due to shrinkage, settlement, or structural overloading. While small cracks may be cosmetic, larger ones can indicate serious issues affecting slab integrity.
Professionals assess crack size, depth, and pattern before deciding on repairs, which may include sealing or reinforcement. Timely action ensures cracks do not worsen or allow moisture to damage the tendons inside.
Water entering the slab through unsealed joints, surface wear, or poor drainage can weaken concrete and corrode embedded steel tendons. Persistent moisture leads to long-term deterioration and costly repairs.
Solutions include waterproof coatings, sealing cracks, and improving drainage systems. Preventive measures are key to extending the slab’s lifespan and preserving its load-bearing performance in various environmental conditions.
Anchor heads can be damaged during construction or over time from environmental exposure. This compromises the effectiveness of the post-tensioning system. Damage may also expose tendons to moisture, accelerating corrosion.
Repairing or replacing anchor heads promptly ensures the slab retains its designed strength. Protective coatings and regular inspections help prevent further issues and maintain structural performance.
Repairing post-tensioned slab problems requires skill, precision, and the right equipment. Below are the key repair techniques used by specialists to address common post-tensioned slab issues effectively:
When tendons are corroded or broken, professionals carefully expose and replace them without damaging the surrounding concrete. This involves removing damaged sections, installing new tendons, and re-tensioning them to the correct specifications.
Protective measures such as grease coating or plastic sheathing are applied to prevent future corrosion. This method restores the slab’s load-bearing capacity and extends its service life significantly.
Structural cracks are repaired by injecting epoxy or polyurethane materials into the damaged area. This bonds the concrete back together and prevents moisture from entering.
For wider cracks, surface sealing may be combined with reinforcement to improve strength. These repairs not only restore the slab’s appearance but also protect internal tendons from corrosion, ensuring the structure remains safe and durable.
Waterproofing is essential when slabs suffer from moisture ingress. Professionals apply high-quality sealants, membranes, or coatings to create a protective barrier. In some cases, drainage systems are improved to redirect water away from the slab.
These measures prevent further deterioration, protect steel tendons, and maintain the slab’s structural performance in all weather conditions, especially in areas prone to heavy rainfall or high humidity.
Damaged anchor heads are removed and replaced with new components that meet current engineering standards. Protective coatings are then applied to resist corrosion.
Where possible, professionals also address the root cause of the damage, such as inadequate sealing or environmental exposure. This ensures the post-tensioning system operates effectively, maintaining the intended strength and performance of the slab over time.
For slabs with significant load-bearing concerns, additional reinforcement is added. This can involve installing external post-tensioning systems or applying fibre-reinforced polymer (FRP) wraps for extra support.
These strengthening methods are designed to handle increased loads while preventing future cracking or deflection. Structural upgrades like these not only resolve current issues but also enhance the slab’s overall resilience and long-term durability.
Ongoing maintenance protects structural performance and minimises costly repairs. Here are the preventive maintenance tasks to follow:
Urban Pour brings extensive experience and technical expertise to every post-tensioned slab project. Our team understands the complexities of these advanced concrete systems and uses industry-leading diagnostic tools to identify issues accurately.
We bring deep technical expertise to every project, ensuring slabs are designed, installed, and maintained for maximum strength and performance. From minor cracks to major tendon repairs, we apply proven techniques that restore strength, stability, and safety to your structure.
We follow strict Australian building codes, ensuring all work meets the highest standards of quality and compliance. Our specialists are trained to handle repairs in both residential and commercial environments, delivering solutions tailored to the specific needs of each project.
We prioritise clear communication, so clients know exactly what to expect at every stage, from inspection to final sign-off. With a focus on durability, our repairs are designed to stand the test of time while minimising disruption to your property.
Choosing Urban Pour means partnering with a reliable team committed to delivering long-lasting results and exceptional service at competitive rates.
Post-tensioned slabs deliver strength and performance, but timely repairs keep them at their best. From cracks to corrosion, expert solutions restore safety and extend lifespan. Do not wait for problems to worsen.
Contact Urban Pour today for professional slab construction, precise repairs, and maintenance strategies that protect your investment and keep your structure performing at its peak. Your slab’s long-term strength starts with the right team, and we are ready to help.
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