Sometimes a heavy live load comes on the structure when heavy stress passes through its concrete slab. Having them in the right place is important. Tendons can be easily routed around obstructions. From cast-in-place parking garages and podiums to multistory flat plate designs, Post-Tension Services of Texas is prepared to take any elevated Post-Tension Slab project to the next level. Many of todayshigh performance slabs contain Post Tension Cables. Afterwards, once the concrete has gained strength but before the service loads are applied, the cables are pulled tight, or tensioned, and anchored against the outer edges of the concrete. When the strands are stressed, the wires will stretchabout 4 inches for a 50 foot strandto apply 33,000 pounds of load. 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. A post-tension slab is a concrete slab that has steel cables running through it that have been placed under 33,000 +/- pounds of tension. When the proper tensioning force reaches the tendon, it is fixed by the anchor. Post tension cables are helpful for many . With that being said, tendons in floor slabs can be as far apart as five feet and as close together as a few inches. When the post-tensioning slab is stressed, the concrete is squeezed. For a 100,000 ft2 post-tensioned slab, this would result in an estimated 900 lineal ft of cracks. What we learned is that they are virtually the same price at about $4.50-5.00 per square foot when the cast in place slab has rebar at 18 centers. This value comes from D = sL/AE where s = 189 ksi, L = 12 inches, A = 0.153 in 2, and E = 28,000 ksi. This is achieved by laying out high-strength steel cables in a crisscrossed grid pattern throughout the foundation prior to pouring the concrete. Since PT is simply reinforcement, there really aren't any specific decorative applications related to post tensioning. These circles are usually about 2 to 4 feet apart. With decades of experience in repair and stressing operations, there arent any Post-Tension Slab Problems our crew leaders have not seen. This hybridisation helps achieve the formation of a much thinner slab with a longer span devoid of any column-free spaces. A post-tensioned foundation is a concrete slab foundation that is reinforced with stranded steel cables that are tensioned after the. The alignment of the tendons is observed during concreting of the slab. Post-tension cables are steel wires inserted into plastic sheathing laid in place while pouring the concrete slab. Alameda, CA 94502 The steel expands during the tensioning process. Initially, there were problems with corrosion of the cables used in this method. Digital Concrete locates all types of reinforcing steel, while post tension cables are probably the most common. post. Tendon (cable) tails after tensioning. But is very weak in tension. Settlement may cause damage to a house, but some settlement can be prevented or reduced. D uring concrete slab edge spall repairs on post tensioned (PT) buildings, the typical procedure is to replace rusted PT anchors along the slab edge. Like all construction methods, the . In some of our articles we provide links to products that may be beneficial given the subject matter of the content. Post-tensioning now is used extensively in bridges, elevated slabs (parking structures and residential or commercial buildings), residential foundations, walls, and columns. For a 100,000 ft2 post-tensioned slab, this would result in an estimated 900 lineal ft of cracks. Boerne, TX 78006, COPYRIGHT 2020 - POST-TENSION SERVICES OF TEXAS|ALL RIGHTS RESERVED. Worth a look. Stepping down to a welded wire fabric brings the cost of the slab down to about $4.00/sf. Some examples are apartment buildings, office buildings, slabs-on-ground, water tanks, and bridges. If these cables are cut, nicked or in any way compromised, they can rip through the concrete and render the slab useless, or seriously injure someone. Therefore, if a slab is prepared using this compound, the load-bearing capacity of the slab is increased. It is a concrete slab that has steel cables running through it that have been put under lots of stress to reduce cracking of the concrete and increases the strength of the slab. Mar 14, 2010. From fabricated rebar to curing compounds, Post-Tension Services of Texas has you covered. These groups of steel cables are incredibly important for increasing structural support as well as allowing for greater spans between supporting columns or beams . A post-tensioned foundation is a concrete slab foundation reinforced with stranded steel cables. Also Read :Difference Between One Way Slab and Two Way Slab | What Is Slab? Post tensioning is of two main types - unbonded and bonded. Commercial foundations will have much more steel. Since the early 1950's, post tension tendons have been used in the design of concrete structures. Which usually resists the deflection of the slab. Monostrand tendons are the most commonly used unbonded post-tension tendons. The steel tendon in the PT slab is mostly kept in compression. This method enables the designer to take advantage of reinforcing concrete similar to prestressed concrete. What Are the Disadvantages of Post-Tensioning? But, nowadays tendons are provided in concrete slabs. Steel tendons are prestressing steel cables inside plastic protective ducts or sleeves, each one with anchors on each end to transmit the forces into the structure. There is no reason, with the current technological testing methods in place, to hit rebar let alone post tension cables. The released tension will find the path of least resistance. If your foundation has a crack or cracks know what to look for to determine if they are major or minor. And the concrete is shrinking. Post-tensioned slabs contain a tendon, or steel cable, that runs crisscrossed throughout the center of the slab after the concrete has already hardened. Commercial foundations will have much more steel. A post tensioned slab can be identified by the grouting of the live stressing end of the cables. Post tensioned concrete is an improved version of reinforced concrete. Therefore, reinforcement is provided in the tension zone of the slab to strengthen the concrete in tension and to prevent the sudden collapse of the concrete structure of the building. Additionally, we assist both residential and commercial . In post tension slab systems, cables are spaced approximately 30 to 36 inches apart. As Southern Arizona's leading supplier of unbounded post-tension materials, Arizona Post-Tension specializes in all aspects of posts tensioning, involved in slab-on-grade. concrete hardens. | Components of Space Frame System | Types of Space Frame | Space Frame Structures Examples | Advantages & Disadvantages of Space Frame Structure, What Is Folded Plate? Concrete is reinforced with threaded steel cables that are tensioned after curing. It is a method of increasing strength with conventional slab reinforcement. What Is Monolithic Slab? We can quickly diagnose and properly repair any slab. In this article [] 10501 Sparkman Rd. These tendons cable is held in plastic or steel tubes. Tendon elongation during stressing (D) is typically considered to be 0.081 inches per foot of concrete. As a leading Post-Tension Foundation Company, we provide Post-Tension products, services, and concrete reinforcing materials to national builders, custom builders, and turnkey concrete contractors. Now that being said, you still need to take precautions, but post tension slabs are usually 10"+ thick. Anchors are used to anchor in the concrete. | What Is Grid Slab? We are a full-service Post-Tension Foundation Company based in Dallas, and we specialize in residential and commercial slab-on-ground and elevated Post-Tension Concrete new construction projects. Our dedicated commercial team specializes in estimating and drafting elevated post-tension projects, allowing for quick and precise estimates. Once 75% strength of the concrete slab is achieved, or after about 27 days, stress is applied using stressing jacks. Structural engineers design concrete slabs with post-tension cables to obtain greater span lengths between supporting columns and to allow thinner slabs. What is post tensioned concrete used for? Location. The people that install them claim that the post tensioned slab is cheaper when you compare it to the much thicker traditional slab you would need to do the same job on very expansive soils. Why does the sign sayDo not cut or core? Benefits of Post Tension Cables. Post-Tension Services of Texas employs multiple repair crews specializing in both slab-on-ground and elevated applications. Post-tensioning slabs are usually the flat slab and the thinnest slab. Post-tensioning tendons are made up of more than one group of prestressing steel. The post-tension cables are put down on the inside of the concrete . 1 - 3 2 - 6 3 - 10 4 - 12. | Difference Between Floating Slab and Monolithic Slab, What Is Brick Masonry ? Avoid Cutting Cables. The use of post-tension concrete has become increasingly prevalent in the construction industry. Life Expectancy Of A House: Will It Last 50, 100 or 200 Years? . According to this, standard sizes 0.50 and 0.60 mm are kept. A post-tensioned concrete slab on grade will typically be 8 inches thick and use 3000 psi concrete. | Types of Brick Work Construction | Classification of Brick Work | Application of Brickwork | Advantage & Disadvantage of Brick Work, Type of Heavy Construction Equipment | Earth Moving Equipment | Material Handling Equipment. The strand cables level usually reached the highest level in the form over the positions of the supports and lowest level between the supports so the tension force on the cables pulls pressing up the slab in the middle of the spans. From residential new construction, multifamily Post-Tension Projects, commercial multistory flat plate designs, parking garages, and podiums to Post-Tension Materials, stud rails, barrier cable, and Post-Tension Repair, Post-Tension Services of Texas would enjoy the opportunity to add strength to your next project. When a concrete slab is stressed by the post-tensioning method, it means the steel is being tensioned and the concrete is being compressed. There was an error trying to send your message. Post tensioned slabs are stronger and more resistant to cracking than a traditionally reinforced slab of the same thickness. 129 Industrial Dr. While there are many different types of PT cables, above can be seen the stressing zone for a 40 cable Post Tension bundle. Another source of information may be the builder or local building department. They are usually applied to single strands or braided through the slab. Therefore, the builder puts up the do not cut or core warning signs for safety to the homeowner and potential contractors working on the building later on. (510) 523-7226 The stranded cables are slid inside of plastic-sheathing, which prevents the stranded steel tendons from touching the concrete. With structural members the duct is often grouted full following stressing to bond the strand to the concrete along its entire lengththese are called bonded tendons. This is accomplished by pre-stressing cables which run throughout the slab and by compressing the concrete. Post tensioning slab is a method of providing strength and stability to the long-span slabs in building construction. These are often placed next to a door that goes from the garage into the house. Other benefits are that fewer control joints may be required to help control shrinkage cracks. Of course, when it's time to actually do the post-tension slab coring, everyone gets (understandably) nervous because hitting a PT cable could be a matter of life or death. STRUCTURAL TECHNOLOGIES has an array of specialized products and systems used to repair, strengthen and protect post-tensioned structures. As a result, even though post-tensioning is meant to help prevent a slab from cracking, the slab can still crack if the tensioning process is done incorrectly. Tendons used in the post-tension slabs are groups of steel wire. 2257 Harbor Parkway For concrete imaging applications, it all starts with our field markings, which come in the form of paint, marker, crayon, and any other method as directed by the client. heidi@digitalconcretescanning.com Post Tensioned Concrete is a commonly used method of concrete construction where multiple strands of steel cables are placed throughout a concrete slab to reinforce the structure. For a 270 stard with a standard 3-inch grade, the strand is given a tensile strength of 33,000 pounds. When cutting or drilling into the concrete slab a post tension steel cable may get cut or damaged. 20 - When installing post tension cables, you are allowed to have 1 inch of the cable exposed in the concrete at the . I am a Degree Holder in Civil Engineering. Articles and Resources On Common Structural Issues In Homes, The Painted Ladies Are Over 100 Years Old and Still Beautiful, Avoid a Money Pit Ask These Questions, An Empty House Can Kill the Homeowners Insurance Policy, 10 Questions To Ask About Homeowners Insurance, Dog Bite Lawsuits can be Costly for Homeowners, Post tension slabs - Answers To Questions, Foundation Cracks: Causes, Seriousness and When To Worry. Cables are arranged as indicated by the engineer and chaired to run through the center of the slab. "}},{"@type":"Question","name":"Post Tension Cables","acceptedAnswer":{"@type":"Answer","text":"Post-tensioning cables are used in construction. With decades of experience in repair and stressing operations, there aren't any Post-Tension Slab Problems our crew leaders have not seen. Post-tensioned concrete slabs are typically expected to crack less than other slabs because post-tensioning produces a compressive stress that must be exceeded before enough tensile stress develops to cause cracking. On typical houses I mostly see 5 to 6 tension cables, if they are run. The process is very similar to that used for slabs, except on a bigger scale. Post tensioned slabs should be stressed when the concrete strength designated by the engineer's plan is reached. Post tension slab is also known as pt slab. These devices are often used to locate reinforcing steel members such as rebar, post-tensioning cables and steel mesh in concrete floors, walls and bridge decks, utility conduits laid beneath or within a building slab, significant air voids, and similar potential obstacles. Fill out the form below to request pricing. I started this site to spread knowledge about Civil Engineering. Post tension slabs are used in some common applications as follows: Also Read :What Is Monolithic Slab? | Types of Stone Masonry | Specification of Stone Masonry | Advantages & Disadvantages of Stone Masonry, What Is Brick Work Construction? The tubes are connected to each other by an external screw coupling and the outer face is sealed with PE tape. People are surprised about beds in igloos and how they are made. This paper presents a new method for optimizing the layout of post-tensioned cables in concrete slabs. Copyright 2022. Post-tensioning now is used extensively in bridges, elevated slabs (parking structures and residential or commercial buildings), residential foundations, walls, and columns. Since there are a number of tendons and wires spread inside the post-tension slab, it can result in corrosion. As a result, cracks and deformation occur in the concrete slab. We then used Hilti KB-TZ Anchors to secure the Unistrut to the concrete. These steel strands have a tensile strength of 270,000 pounds per square inch and are stressed to about 33,000 pounds - making them about twice as strong as a typical slab on grade foundation. And that doesnt include the cost of other concrete repairs. www.avalonstructural.com. The post-tensioning method is then widely used in bridges, elevated slabs (parking structures and residential or commercial buildings), residential foundations, walls. Sometimes these circles are not visible because of landscaping or because the patching of the cone-shaped voids blends in. Once inside I observed a hole in the ceiling about 5 inches in diameter and 1 inch deep. PT slabs on ground can be placed and stamped just like with any other concrete slab. As a result, the strength of the concrete increases. 1. Post-Tensioning Repair Products. Stressing should only be done by qualified workers. Because it is brittle in tension properties, it can break suddenly after failure. Post-tensioning or PT slabs have become an increasingly popular use over the last 30 years. Compared to conventional rebar foundation, the installation of post . | What Is One-Way Slab? These are often used as components of concrete slabs where extra forces are needed to achieve structural integrity without having to thicken the entire slab. Post Tensioned Concrete Slab is a method of providing strength and stability to long-span slabs in building construction. document.getElementById("ak_js_1").setAttribute("value",(new Date()).getTime()); You can find him on Facebook,Twitter, Tumblr, Instagram, and Google News, Twitch.tv, YouTube, Linkdin, Pinterest , Telegram. Drywall Cracks - What causes cracking, when is it structural? Post-tension slabis increasingly heard in the construction industry. ABOUT US. Many of today's high performance slabs contain Post Tension Cables. Also Read :What Is Space Frame? And that doesn't include the cost of other concrete repairs. Less concrete or thinner slabs may also be possible for certain expansive soils. The normal steel tendon used for post-tensioning should have a minimum yield of 243,000 psi. | Components of Space Frame System | Types of Space Frame | Space Frame Structures Examples | Advantages & Disadvantages of Space Frame Structure. As the poured concrete dries, the post-tensioned cables stretch and tighten, which applies a significant force to the concrete slab. One cable by itself has a breaking tension of about 41,000 pounds. Post tension slab is a combination of conventional slab reinforcement and additional high-strength steel tendon. The cables are pulled to 33,000 pounds, resulting in 8 inches of elongation in a 100-foot cable. . The post-tensioning process works as follows: First, you must install steel tendons into the formwork and position them before the concrete is placed. Can a post tension slab be repaired? External post . They indicate the end of the post tension cables. The results can be dangerous and structurally hazardous to the structure. What are they a sign of and what can be done? There may be times when there are no visible signs on the wall and no stamped sign on the concrete floor. What Is Space Frame? Post tension slab is also known as pt slab. It helps in reducing the quantity of concrete required for construction. Your email address will not be published. When errors are made on-site during the post-tensioning process, the ability of the reinforcement to prevent cracking is decreased. Concrete is reinforced with threaded steel cables that are tensioned after curing. Post Tension Cables (PT Cables) are drawn tight with thousands of pounds of pressure. The loads help support the interior areas of the building. Construction of post-tensioned slabs on grade is very similar to using reinforcing steel, except for the tensioning step. This approach alleviates the need to reinforce the area below the slab which can be more expensive for the homeowner. And we keep a (long and growing) list of the mistakes we've encountered along the way. "}},{"@type":"Question","name":"Post Tensioned Concrete Slab","acceptedAnswer":{"@type":"Answer","text":"Post Tensioned Concrete Slab is a method of providing strength and stability to long-span slabs in building construction. | What Is Grid Slab? All Rights Reserved Watertight, abrasion-free, and fatigue-resistant plastic tubes are also available in the market. Since the thickness in the post tension slabs is reduced, the amount of concrete and reinforcement is also reduced by 20% - 30% compared to the conventional concrete slab. Seldom does a homeowner cut or drill into their slab, but when remodeling or especially while fixing sewer problems, there may be a need to cut or drill the slab. No Post-Tensioner is better prepared to serve the multifamily construction industry than Post-Tension Services of Texas. Headquarters Fax: . It has been sent. The cables are modeled using three-dimensional B-splines so that the prestressing forces are . In addition to providing Post-Tension Cable materials, we can also provide stud rails, Barrier Cable materials, accessories, drawings, and installation services. Control Joints, Expansion Joints and Cold Joints in Concrete, Causes of Houses Settling: When Serious And What To Look For, Cracks In a Concrete Garage Floor: When Are They Serious. Nonshrink type grouting is used in place of anchoring. When these post-tensioned steel tendons are stressed, the concrete is squeezed, in other terms, the concrete is compacted which increases the compressive strength of the concrete, and at the same time the steel tendons that are pulled increase the tensile strength. But there was no need to fret. For projects that require modifications to post tensioned structures such as new slab openings, we are capable of modifying post tension cables to suit the project needs. Digital Concrete can use ground penetrating radar to determine the location of all reinforcing steel in a 2x2 area in about 10 minutes. Post-Tension Foundation slabs . For residential construction, tendons at 48 inches on center are common. Knowing the ways and the extent to which problems can occur helps us . Digital Concrete Scanning which goes into tension after the concrete hardens. Errors that lead to cracks in post-tensioned slabs. Which can be used in the post-tension slabs. There are a few times that cracks in a garage floor are a warning sign of foundation or other problems; can you recognize them? This tension makes the concrete slab and foundation much stronger than concrete without reinforcement and helps reduce cracking. We have given detailed information about Post Tension Slab in this article. Conventional concrete & rebar foundations last about 20-30 years before failure begins to occur. Please try again later. #18. ohmhead said: Well there is no electrical formula its set by the structual engineer in your specs for the last 35 years of construction most PT decks you must space 2 inches apart conduits and your largest conduit in a slab is min 2 inches from top 2 inches from bottom covered . The Post Tensioning workers use many sized bar chairs that locate the strand cables at there correct profiles. The foundation in question was a post-tension cable reinforced foundation as opposed to a foundation which is reinforced with steel rebar (See the typical photograph in this article). Post-tension slabs are created with concrete trenches around the perimeter of the house where the external walls will be placed. The problem is that the PT anchors are holding very high PT cable loads. PT slab gives a very effective structure in building construction. As a building material, concrete is very strong in compression but relatively weak in tension. | What Is Floating Slab? The basic element used in post-tensioning systems is called tendons. Concrete has a high strength property in compression. The big advantage to a post tensioned slab is the additional resistance to cracking and vertical movement. BuyersAsk is owned by an Engineer, Doctor and Home Inspector/Contractor. Experienced in post-tension slab work. Save my name, email, and website in this browser for the next time I comment. We look forward to the opportunity to provide you with a quote. Disadvantages Of The Post Tension Cable System. Post-tensioning slabs are usually the flat slab and the thinnest slab. The slab will "usually" contain steel in the form of mesh or rebar. To overcome this problem, post-tensioning steel tendons are placed in the slab before concreting. It allows structures and features such as fewer beams, longer clear spans, thinner elements, and thinner slabs. Insurance: Cracked and Damaged Foundations, Are You Covered? Reading time: 1 minute Post tension slab is a combination of conventional slab reinforcement and additional protruding high-strength steel tendons, which are consequently subjected to tension after the concrete has set. Once the cables are tensioned and grouted, the live ends where the jack applies the stressing is also grouted. Required fields are marked *. Multi-strand ducts forming a concrete beam. Post-tension foundation is slab-on-grade foundations. They are used within beams and slabs. Project Name: Legends at Centennial Project Date: 10/20 to 12/20 Post Tension LF of tendon: 33,614 Construction type: Post Tension Project Name: Caliber at Southlands Project Date: 5/10 to 5/20 Post Tension LF of tendon: 175,430 Construction type: Post Tension Project Name: HRTC Senior Living Project Date: 7/20 to 10/20 Post Tension LF of tendon: 6,685 Construction type: Post Tension A post tension slab is a concrete slab with steel cables running through it that have been placed under 33,000 +/- pounds of tension. What Is A Post Tension Slab Does Your Home Have One? {"@context":"https://schema.org","@type":"FAQPage","mainEntity":[{"@type":"Question","name":"Post-Tension Slab","acceptedAnswer":{"@type":"Answer","text":"Post tension slab is a combination of conventional slab reinforcement and additional high-strength steel tendon. Hey, I am Bhadresh Khatri. It has a greater resistance to tensile stresses, thanks to its manufacturing method. Residential new construction is a cornerstone of our business. No problem. Post Tension Cable Repair Cost. The only concern is to always remember not to cut or drill into post-tensioned concrete slabs since once a tendon has been cut, it is very difficult to repair. Have a problem with an existing post-tension slab? Post-tension slabs are lasting about 15-20 years and are failing at a much higher rate. Our installers used a Hilti PS 30 Ferrodetector to locate the cables and rebar in the concrete. How to tell if you have a post tension slab. This type of slab is used in building construction to save money and time. CMSWILLOWBROOK, INC.620 NE 36TH STREET, OKLAHOMA CITY, OK | 405-224-1554 | INFO@CMSWILLOWBROOK.COM, sneak peak, bids, subcontractors, upcoming projects, delay, critical path, scheduling, subcontractors, contractors, general contract, construction claims archives, construction management, contracts. This website uses cookies to improve performance and enhance the user experience. The cable is going to be in the centre of the slab. For residential construction, tendons at 48 inches on center are common. Post-tensioning cables are used in construction. This may weaken the slab structurally or the cable (which is under tremendous pressure) may occasionally rip right out of the slab and injure someone near it. Construction Process of Post Tension Slab, Advantages & Disadvantages of Post Tension Slab. Also Read :What Is Folded Plate? In unbonded post tensioning, there is no bond between the pre-stressing steel and the concrete surrounding it anywhere except at the anchorages. In prestressed members, compressive stresses are introduced into the concrete to reduce tensile stresses resulting from applied loads including the self-weight of the member (dead load).