Almost any construction project that involves large slabs of concrete is going to require some concrete reinforcement. That’s a fact. But the way you go about reinforcing the concrete may not be as clear-cut.
Ruiyi supply professional and honest service.
That’s because there is more than one way to reinforce concrete. The two most common methods of concrete reinforcement are conventional slab reinforcement and post-tensioned slab on grade reinforcement. Which method is best for your project will depend on a number of factors, which we explore in depth below.
Tendon Systems is a leading provider of concrete reinforcement, construction and restoration services. To get help with your concrete construction project, reach out to us today.
Post-Tensioned Slab on Grade
At Tendon Systems, we specialize in post-tensioned slab on grade reinforcement. That’s because we believe post-tensioned slab on grade offers undeniable advantages over traditional concrete slab reinforcement.
How Post-Tensioning Works
Post-tensioning isn’t something you can see in a slab on grade foundation with the naked eye. Instead, this term implies a process that was completed before the foundation had to bear its intended service loads.
Post-tensioning tendons are steel cables that are placed inside the foundation’s mold form before the concrete is poured. The post-tensioning of the cables happens after the foundation’s concrete is poured but before load stress is applied to the slab on grade foundation. Inside their plastic sleeves within the newly poured concrete, the cables are pulled tight and anchored to the slab on either side.
This is called “post” tensioning because it happens after the concrete is poured, but it happens before the foundation has to bear any real weight.
Pros of Post-Tensioning
Post-tensioned slab on grade offers several key advantages. Chief among them is this type of slab’s ability to withstand more pressure without cracking. This advantage comes from the fact that the interior cables are already placed under stress. That means the concrete is held tightly together, and the cables are contributing their reinforcing properties at all times.
The following are some other pros of post-tensioned slab on grade:
Cons of Post-Tensioning
Post-tensioning is considered the gold standard of concrete slab reinforcement, but there are some potential drawbacks in certain situations:
- Complex work. Post-tensioning work is complicated, so it requires highly skilled professionals to do it right.
- Possible corrosion. This issue is most often prevented by using high-quality materials, but in some cases, the tendons inside the slab can corrode through exposure to certain materials, such as salt. Higher-quality materials will resist corrosion.
Conventional Slab Reinforcement
Like post-tensioning, conventional slab reinforcement isn’t obvious when you look at a completed slab. It’s all about what’s done — or not done — to the slab in the construction process.
How Conventional Slab Reinforcement Works
The conventional slab reinforcement process is similar to the post-tensioning process. Steel cables called tendons are placed inside a concrete slab foundation to add tensile strength. But there is a key distinction between conventionally reinforced slabs and post-tensioned slab on grade: in conventional reinforcement, the cables are not stressed before the slab has to bear its load.
Ultimately, this means that the interior steel tendons will not resist a load until the concrete slab has been compressed or cracked to the point that the service load places stress on the tendons.
Pros of Conventional Slab Reinforcement
In truth, conventional slab reinforcement offers few advantages over post-tensioned slab on grade. However, there are a couple of pros of conventional slab reinforcement that could apply in some situations:
For more post tension system solutionsinformation, please contact us. We will provide professional answers.
- The construction work is relatively simple. Compared to post-tensioning, conventional concrete reinforcement is relatively simple, so less experienced and knowledgeable crews can handle it.
- It’s better than no reinforcement. If the choice is between conventional reinforcement or none at all, some reinforcement is better than none, especially when it comes to foundations.
Cons of Conventional Slab Reinforcement
Conventional slab reinforcement simply doesn’t hold its own in the post-tensioned slab on grade vs. conventional slab reinforcement fight. Here are a few of the key disadvantages:
Top-Notch Slab Reinforcement with Tendon Systems
There’s more than one way to reinforce concrete, but there is only one concrete construction services partner that does it best. At Tendon Systems, we work hard every day to provide the highest quality post-tensioned slab on grade reinforced concrete available anywhere.
We believe we accomplish that mission — just ask any one of our countless happy customers how their concrete is holding up. To discuss your concrete reinforcement needs with certified professionals, reach out to Tendon Systems today. Give us a call at (678) 835-1100 or contact us online.
First off, one could argue that post-tensioning is superior to conventionally reinforced concrete in a pure engineering sense. The reason is because post-tensioning is a method of pre-compression, which means the concrete is put into a state of compression, which allows the concrete to take on flexure without cracking. To visualize this, think of a stack of square blocks lined up together.
If you just grabbed the ‘A’ and ‘D’ and lifted up, only those two blocks will be lifted. However, if you place your palms on the outside of ‘ G’ and ‘J’ then press in, lifting up will bring the whole group of blocks together. One could press hard enough and even be able to carry some load on top of the blocks.
This concept is called “pre-compression”, or also called “pre-stressing”. The “pre” simply means stresses are present in the concrete prior to any load that has to be carried has been applied. The “post” comes from the fact that the stressing happen after the concrete is placed and has reached the required strength. Pre-stressing is the important distinction between post tension concrete and conventionally reinforced concrete.
You see, conventionally reinforced concrete simply means that there are no active stresses going on within the concrete until after the load that it is designed to resist is applied. Because of this, conventionally reinforced concrete must enter a “cracked” state before the load carrying capacity is utilized.
DRIVING FACTORS
There are 3 driving factors concerning the usage of post tension reinforcement:
- Familiarity
- Availability
- Perception or Reception
Notice engineering is not necessarily a driving factor!
In other words, since post -tensioning is simply a method of reinforcing concrete, the decision is only a matter of familiarity by the engineer designing it. Many engineers are not experienced in pre-stressed design and simply avoid it. Also, contractors not familiar with the installation requirements may simply avoid it as well.
Availability is also an important factor simply because if it is not readily available in a certain area, it may not be the best choice system. Material supply may be costlier due to transportation and travel costs. Again, engineers and contractors who are not available in a certain market or geographical area to service a post tension project may prohibit its use.
And finally, perception (or reception). In some applications, the prospect of having active compression forces existing within the concrete worries owners of buildings that may require relatively frequent modifications such as retail floor slabs. The fact that every time a tenant improvement requires saw-cutting the concrete slab it will also require an engineer and contractor with expertise in avoiding or purposefully cutting post tension cables usually deters the use. Then there are perceptions by the public that post tension is a cheap alternative to rebar and utilized at the cost of quality. However, as noted above, this is simply not true and in fact the opposite is true. As an engineering technique, it is superior.
COST: The perception by the public that post tension is a cheap alternative to rebar is 100% true! Everywhere in the US where post tension is familiar, available, and used without negative perception/reception, it results is a lower cost to construct the foundations.
Without these 3 factors in place, post-tensioning usage as a reinforcement system may encounter resistance. Now you know why!
THE MYTHS
The following are some commonly held beliefs by the public:
- Post tension foundations are what tract home and apartment builders use so therefore they are lower quality.
- Post tension foundations don’t work for our soils. Rebar works better here.
- Those post tension cables can break one day and go flying out and might kill someone.
- I have a post tension foundation with cracks in it. I think those cables didn’t get stretched enough.
- I saw a post tension foundation before they poured concrete and there was not enough reinforcement in it.
TECHNICAL INFO
The above discussion is concerning slab-on-grade foundation construction. This type of foundation is classified as a “shallow” foundation system and subject to the movements of the near surface soils. Both post tension and conventionally reinforced systems have code accepted design methodologies associated with them that structural engineers use to determine the correct design for the applicable soil movement conditions. However, there are other foundation systems that reduce the risk of near surface soil movements. These systems involve “deep” foundation elements such as piers that rely on deep soils for stability. These deep elements add substantially to the cost of the foundation. So, when debating foundation “quality” one must be talking apples-to-apples in terms of system.
If you are looking for more details, kindly visit bulk supply post tension anchor.