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What Are Post-Tension Slabs & Why Are They Used?

Posted on October 27, 2022 by a1_admin

It’s no secret why builders use post-tensioning systems in their construction; these systems are critical to strengthening concrete used in modern large-scale building projects. The same argument applies to post-tension slabs—a method used when pouring the slab foundation in commercial or residential construction. This article further explores post-tension slabs and some of the advantages and challenges of their usage in construction projects.

What are Post-Tension Slabs?

The concrete industry started experimenting with strategies and techniques to strengthen and reinforce concrete in the 1950s. The prestressing concept, now a standard in residential and commercial building construction, involves using a steel cable or tendon to squeeze and compress concrete before the concrete endures a structural load. As the construction industry continued refining its techniques to standardize prestressing, most builders eventually began using post-tensioning techniques for reinforced concrete slab foundations. The Federal Housing Administration officially endorsed the use of post-tensioned slabs in 1969, and the building method is now embraced and co-opted as the preferred method for builders.

Post-tensioned slabs contain a tendon, or steel cable, that runs crisscrossed throughout the center of the slab after the concrete has already hardened. As the poured concrete dries, the post-tensioned cables stretch and tighten, which applies a significant force to the concrete slab. This technique strengthens and compresses the concrete, which helps reduce cracking and structural instability caused by unstable soil conditions in marshes, swamps, and lake areas. The process helps residential homes and commercial buildings achieve greater load-bearing strength. Post-tension slabs are more durable and stable than traditional slabs that lack the reinforcement of steel cables.

Why Use Post-Tension Slabs?

Concrete slabs have inherent structural weaknesses; they are especially susceptible to expansion and contraction due to seasonal fluctuations and changing temperatures. Anyone that has experienced winter knows that thawing temperatures usually lead to potholes, broken water mains, and cracks in the pavement. Concrete slabs are no exception. The swelling and contraction of soils based on their contact with water is another element that adversely affects the integrity of concrete slabs. Poor and unstable soils found in Southwestern states and Mexico lead to issues with soil expansion, making it difficult for builders to lay concrete slabs.

Builders depend on post-tension slabs to reduce the risks of cracking, contraction, and soil expansion and strengthen the foundation’s structural integrity.

Post-Tension Slabs: Potential Challenges

Post-tension slabs are stronger than traditional concrete slabs; however, that does not necessarily mean a post-tension slab is without challenges. Read on to learn more about builders’ challenges when using post-tensioned slabs.

Long-Term Planning

Post-tensioned slabs are an excellent foundation for a new structure, but builders must plan accordingly for proper drainage. Gutters, downspouts, roof pitches, and balconies redirect rainfall. Builders need to be aware of the location of drainage as it can seep into the foundation and lead to cracks.

Good Things Aren’t Cheap & Cheap Things Aren’t Good

Laying the foundation of a post-tension slab requires professional workers, quality materials, and expert knowledge to understand the job’s complexity. In the building and construction industry, it’s essential to research the service provider and contractors you partner with before signing a contract.

Check the Blueprints, Again

Since post-tension slabs require the addition of steel tendons to strengthen and reinforce the concrete, the tendons must precisely align as shown on the blueprints. Improper tendon locations can cause uplifting, as the tendon applies more force than the weight of the concrete. As a result, the concrete might be physically lifting the slab.

The Advantages of Post-Tension Slabs

Aside from producing crack-free tennis courts, smooth parking garages, and a secure foundation for someone’s new home, post-tension slabs offer builders an array of advantages compared to traditional concrete slabs. Here are a few of the major benefits.

Cost Savings

Post-tensioned slabs require less concrete than traditional ones, saving builders money. Post-tensioned slabs are an investment that helps homeowners reduce the risks of concrete contraction and cracks, which inevitably costs money to repair. That’s why post-tensioned slabs are an initial investment worth it in the long run.

Shed Some Weight

A lighter yet stronger slab of concrete allows builders to design their structure with less material and overall surface space, providing more space to build supporting pillars, walls, columns, and beams. Post-tensioned slabs are also thinner, giving builders more creative freedom when designing floors.

Minimize Risks

No matter how much planning goes into a construction project, things happen, and the idea for builders is to minimize risks. Post-tensioned slabs may help prevent cracks from forming, but concrete is not immune to the elements. The good news is that if cracks form on post-tensioned slabs, they are held together and do not spread as quickly as those on traditional foundation slabs. Therefore, post-tensioned slabs are a more durable solution.

Look to the Experts when it comes to Building Repair Services

Commercial and residential structures require rational planning and maintenance. Whether your building has a traditional concrete slab or a reinforced post-tensioned slab, building owners need to maintain the structure’s integrity. That’s why across the United States, owners and property managers rely on Valcourt as their trusted partner to protect their investments. Whether it’s waterproofing, restoration, or other commercial building services, Valcourt offers over 35 years of experience protecting properties from the elements. Contact A1Orange Building Services today!

Post Tension Repair: Common Concrete Problems & Myths of Post Tensioning Debunked

Posted on October 11, 2022 by a1_admin

As early as the 1950s, a method of improving construction practices and reinforcing concrete emerged in the United States. The post-tensioning (or post-stressing) concrete method provides outstanding durability, increased design flexibility, and improved safety. This method also came the need for specialized concrete restoration and repair services.

Many modern office buildings, commercial and residential towers, parking structures, and facilities rely on post-tensioned concrete. Keeping up with commercial building repair is critical as neglected upkeep leads to catastrophic building collapses, much like the Surfside Condo collapse in Florida in 2021- an event that claimed the lives of nearly 100 people. Due to the rising demand for post-tensioning, planning repair work on post-tension slabs and components is increasingly vital for commercial building maintenance. Commercial building managers and facility maintenance teams cannot afford to overlook understanding how to spot issues quickly and handle post-tension repair needs.

What is Post Tension Repair?

Post-tensioning is a highly specialized and advanced means for reinforcing concrete, making it more suitable for commercial applications, heavy load-bearing designs, and larger building structures. According to the Federal Highway Administration, “the tensile strength of concrete is only about 10% of its compressive strength.” As a result, plain concrete members are likely to crack when loaded. However, embedding reinforced steel into the concrete members helps them accept tensile stresses that plain concrete cannot. Reinforced steel is selected assuming that the tensile zone of the concrete carries no load and that tensile stresses are resisted only by tensile forces in the reinforcing bars. The resulting reinforced concrete members may crack but can effectively maintain the design loads.

The forces within post-tensioning tendons demand that owners, designers, and contractors who maintain these structures understand the dos and don’ts of repair and maintenance to keep their structures safe.

Highly advanced design elements require specialized skills and a high level of technical knowledge to ensure the structure’s safety and that of individuals working around the structure. Properly implementing a post-tensioning system repair plan is vital to maximizing longevity and ensuring the structure remains safe and stable for as long as possible. Ultimately, post-tension repair work focuses on identifying and fixing issues involving concrete in slabs, support beams, columns, foundations, and more.

How Do You Know if Your Building Needs Post Tension Repair?

Post-tension concrete repair should begin as soon as issues become apparent. The longer the delay in repair, the more expensive the repairs will become. Concrete is popular because of its durability, but it’s also susceptible to cracks, chipping, and other issues. Routine checks and inspections are critical for building maintenance and upkeep if a commercial concrete structure utilizes post-tensioning.

Inspections of post-tensioned concrete structures should include the following regularly:

Visual inspection of facilities and critical problems areas – joints, support junctions, and large expanses
PT Corrosion Evaluation and regular moisture testing, especially in areas with high water intrusion risks
Chloride analysis of PT grout to avoid long-term exposure and corrosion of steel cables and casings
PH and chemical testing of structure to ensure no oxidation and to monitor accumulation on surfaces
Petrographic analysis, Scanning Electron Microscopy examination, and other tech-backed inspections
Cable Break Detection services to monitor tension support and durability on an ongoing basis
Regular feedback and communication between team members and staff about noted issues or concerns

While it is a valuable material and commodity for commercial construction, post-tension concrete requires a more specialized approach to maintenance and upkeep. Working with post-tension repair contractors and finding a repair management company specializing in post-tension concrete services are critical to keeping buildings in good standing. Working with industry experts makes the process easier, whether it concerns repairing a post-tension slab or maintaining building components correctly.

Common Concrete Challenges Requiring Post-Tension Repair

All buildings degrade and break down over time, but there are a few potential issues that can affect post-tension concrete more than others. Using post-tension repair services can help reduce common concrete problems and make commercial building services easier to manage. Some common issue items include:

Cracks in the concrete foundation or support structures
Uneven floors and shifting concrete in large expanse areas
Cracking grout lines or signs of separating and peeling concrete
Leaning chimneys or other structures supported by the post-tensioned system
Loose or damaged components expose the tensioning system
Chipping of concrete in critical support and expanse areas
Signs of flaking, rusting or breaking down of concrete structures
Advanced age of the structure or long periods since the last inspection or repair work

Building owners should have these areas periodically examined periodically by a qualified structural engineer for post-tension repair. The condition survey will check for potential problem areas, note any procession of damage, make recommendations for repair and maintenance, and work with your team to start the necessary steps to address issues.

What Causes Degradation in Post-Tensioned Structures?

Maintenance and upkeep are vital for a post-tensioned structure’s continued service and longevity. Structural deterioration due to exposure to moisture, corrosive elements, and the simple passage of time can lead to a loss of structural integrity, causing issues with structural safety and stability.

Most instances of repair and maintenance work on post-tensioned structures come down to one of the following concerns, all of which a post-tension repair company can assist with:

Voids and air pockets within the concrete structures create weak points
Trapped moisture between strands and between wires within the structure
Water seeping into the structure through cracks in building envelope seals
Grout segregation, deterioration, or breakdown goes unchecked
Water penetration from anchorage pockets, joints, cracks, flashing, and seals
Water penetration due to floods, roof damage, plumbing issues, or leaky windows
Chloride-contaminated grout and exposure to other corrosive chemicals
Dissimilar grouts used in the same tendon create chemical reactions
Improper installation of post-tension cables and anchors during construction
Poor maintenance and upkeep early on in the lifespan of the structure
Damages and concerns left unchecked and unaddressed for too long

Like all building materials, post-tensions concrete offers advanced benefits and features, but it is not perfect and still requires routine checks and maintenance work. Keeping up with this is vital to commercial concrete building construction and upkeep.

Debunking Myths Around Post-Tensioning and Repair

Post-tension concrete’s popularity also comes with various myths that can cloud judgments and impact maintenance protocols. The following are some of the most common myths that repair experts encounter when working with commercial maintenance teams.

MYTH: It is difficult to cut holes and add features to post-tensions slabs and structures.

REALITY: Post-tensioned structures are just as doable and can be easily customized. In this regard, there is not much difference between typical concrete structures and post-tension concrete. Tendon layouts can allow for future aesthetics or building repair needs.

MYTH: Parking garages and structures are more expensive when made with post-tensioning.

REALITY: Keeping long-term budgets in mind when comparing material and construction costs is crucial. While upfront costs for a post-tensioned system might be more, it will require less maintenance and upkeep and save management money in the long run.

MYTH: Post-tensioned buildings experience more shortening than they would otherwise.

REALITY: All concrete will experience some degree of shortening due to the nature of concrete building materials. It is inherent in the curing process as it will shrink, and there is no stopping it. Contractors control building geometry, and post-tensioning is no more prone to shrinking.

MYTH: Post-tensioning is not possible with below-grade applications.

REALITY: Below-grade applications are structures located below the main building. Post-tensioning concrete can be used in these cases quickly. Benefits of below-grade applications include less cracking, improved durability, thinner slabs, and easier excavation.

MYTH: It is always better to use more post-tensioning.

REALITY: Post-Tensioning is no compensation for sloppy design and is no cure-all. Excessive use can lead to overbalancing effects -deflection problems, cracking, shifting, bowing, or severe blowouts, all of which can be costly to fix. Too much of a good thing can be a bad thing.

Why Working with A Commercial Building Services Provider for Post Tension Repair

Ensuring commercial building repair and proper maintenance of post-tension concrete structures remains an essential part of facility management. Building owners and managers cannot afford to overlook even minor issues with structural integrity. Failure can lead to catastrophic building collapse, loss of life, and severe property damage. With post-tensioned systems showing up everywhere, repair work on the systems has become increasingly vital for commercial building maintenance. Contact The A1orange Group today to learn more and find support with a leading post-tension company.

Why Should Buildings Use Post-Tensioning Systems?

Posted on September 23, 2022 by a1_admin

Commercial concrete management, including post-tensioning systems, is critical to any residential or commercial high-rise and multi-level parking garage construction project. Post-tensioning involves placing prestressed steel “tendons” tightened once the concrete hardens. The additional stress of tightening compresses the concrete into its strongest state, ensuring it can support the external service loads (weight) once using the structure.

Failing to factor in the load-bearing capability of a structure can lead to catastrophic events, such as the collapse of the Hotel New World in Singapore in 1986. The six-story building collapsed in 60 seconds, resulting in 33 deaths. More recently, investigators are still trying to determine the cause of a partial parking garage collapse in Baltimore in July 2022.

This article looks closer at post-tensioning systems, explaining what they are, how they work, and their benefits to construction and architecture. We’ll also present some practical applications of post-tensioning concrete, criteria to consider when evaluating such systems, and where to turn for post-tensioning repairs.

What is Post-Tensioning?

Post-tensioning is a unique design technique that reinforces concrete in commercial building construction. This process helps strengthen concrete, allowing it to hold up better post-construction, keeping structures secure and stable. Post-tensioning tendons generally consist of stainless steel and reinforced cable bundles. These run inside plastic coatings or sleeves, placed inside the casings where concrete is poured before filling. Afterward, the cables are tensioned and anchored against the other concrete edges.

The post-tension acts much the same as support beams and improves the safety and stability of concrete pillars, foundations, columns, and other structures. Post-tensioning concrete is critical in the commercial building process, and proper execution gains maximum benefits.

How Does Post-Tensioning Work?

Post-tensioning works within commercial building structures as a form of prestressing. Steel is stressed and put under tension before the concrete has hardened to support the service loads and stress of the building. Most precast, prestressed concrete has this process done as well. Post-tensioned concrete means that the concrete gets poured, and then tension is applied—but there is stress before applying the loads, leaving it prestressed. It is a way of preparing the structure to support the loads and stress of large commercial systems adequately.

Reasons concrete is popular in commercial buildings and commonly seen in post-tensioning construction include:

High durability and resiliency over long periods.
Relatively low maintenance and upkeeps are required.
Affordable and easy maintenance and repairs.
Affordable for mass projects and large-scale production.
The versatility of applications allows greater design creativity.
Easy to source locally for more affordable rates.
It can be used in all climates and temperature extremes.
Highly resistant to rust and corrosion.
It is fire resistant and doesn’t burn easily.
Fewer issues with pests, mold, and other issues.

With so much in favor of concrete construction, the ability to improve the features of stability, durability, and longevity with post-tensioning only adds to the appeal of concrete usage in commercial structures.

Why Post Tensioning & What are the Benefits?

Concrete is the most popular construction material in the world, and for a good reason. It’s widespread in commercial buildings, not only for basements and foundations but also for exterior walls. And, of course, it’s used frequently for sidewalks, ramps, and parking garages. The concrete used in commercial buildings is often subject to more significant pressures and stressors than concrete for residential use. When used in massive commercial building projects, this requires additional support and design considerations.

Concrete may be among the most common construction materials, but it can still come with a high price tag. Industry estimates show that a concrete parking garage could range between $4 and $7 per square foot. This price typically includes the cost of materials and labor. A smaller structure may run $5,000 to $14,000, whereas a larger building could be as much as $174,000-$490,000. Larger commercial structures, whether office buildings or parking garages, require more structural performance, which may change how you need to utilize concrete. This is where post-tensioning makes its impact.

Considering all these features and benefits, one critical aspect of commercial concrete management and upkeep regarding degradation makes all the difference post-tensioning.

Post-tensioned concrete has a variety of benefits, including:

Allowing concrete to be used in higher and longer spans to create larger spaces
Providing increased strength and support for load-bearing areas of construction
Compensates for poor site conditions and improves structural stability
Installs and hardens faster than other conventionally reinforced concrete structures
It uses much less concrete, saving money and resources
Provides flexibility and options for primary formwork and final aesthetic touches
Increases the overall safety and durability of the structure
Provides a faster and more practical manufacturing option
Safe to use in nearly every building situation
Reliable structure strength with post-tensioning
Easily scalable for use in small, medium, and large commercial buildings

Finding the balance between affordable concrete usage and durable post-tension elements remains crucial in planning and maintaining commercial structures.

What Exactly is a Post-Tensioning System?

The post-tensioning concrete method was first developed in the early 1950s by industry specialists such as VSL in Switzerland. Post-tensioning is often a solution for addressing design and engineering issues. It enables the operational definition of the internal load path in concrete structures by superposing a favorable state for the internal stresses. This stress reduction minimizes deformations, reduces the thickness of concrete segments, reduces reinforcement congestion, joins components without relying on wet joints, and allows high-strength steel to reinforce structural components further.

The post-tensioning system is a structural support mechanism essential to many commercial concrete structures built today. Experts who specialize in concrete repair and upkeep utilize this system for three main reasons:

Structure Strength with Post-tensioning

Post-tensioning lightens the structure’s weight, reduces load-bearing packages, and helps improve the overall aesthetic appearance.

Wide Application and Usage Area

It can be used in a wide variety of structures and often occurs in a wide range of systems that vary in size and usage.

Professional Touch and Service

Post-tensioned construction offers the most suitable solution for combining production and application to create a final uniform structure.

Common Applications for Post-Tensioning

This act of prestressing has several advantages over standard rebars:

Significantly removes the risk of shrinkage cracks, so fewer joints are required. Shrinkage cracks occur naturally in poured concrete during the curing process as the concrete loses its moisture.
Cracks that do occur are held tightly together and do not grow and spread.
It allows structural concrete pieces to be thinner and lighter than they would normally.
Engineers and designers can build slabs over expansive areas or on softer soils.
Post-tensioning supports longer spans in elevated areas like floors, beans, and ceilings.

Criteria of a Post-Tensioning System to Evaluate

Building designers looking for a post-tensioning system should first consider three factors to avoid costly damages and repairs down the road.

Type of structural element – the depth of the structural component plays a key role:

Use of slab tendons with flat designs for thin structural elements such as floor flaps and ceilings.
Multi-strand tendons can be used for any other application and are common in thicker heavy construction areas.

Structural design – taking into account specific structural design requirements:

Post-tensioning can be introduced and might utilize internal or external tendons or, in some cases, a combination.
Concrete slab post-tensioning tendons are bonded or unbonded based on the location, application, and desired results.

Protection against corrosion – Protection needed to safeguard cables against corrosion:

The tendon encapsulation depends on the required protection level (PL) – PL1, PL2, PL3, typically subject to location and environmental exposures.
Corrosion protection is the application of anti-corrosion chemicals to prevent damage to equipment or facilities caused by corrosive processes.

Get Quality Building Repair and Management Services From Industry Experts Familiar With Post-Tensioning Systems

Finding the balance between affordable yet durable materials is vital in planning and maintaining commercial structures. Post-tensioning concrete systems allow the utilization of the durable and versatile nature of concrete, while the addition of steel cables and tension support add required structural stability.

The post-tensioning system is the structural support working behind the scenes to provide long-lasting strength, durability, safety, and protection. Professional building management services are integral in maintaining post-tensioning systems to guard against building collapses.

Make sure your team is ready to deal with the maintenance and upkeep of post-tensions systems. Contact A1orange Group today and work with industry experts who can keep your building in good working order.

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