Go ahead and get started here while we wait for the last few people to trickle in, we have some introduction things to go through. So welcome back again to the Post-Tensioning Institute's monthly webinar for April already. My name is Kyle Boyd and I'm the moderator of today's session. I'm also the chair of the Education Committee, which is EDC 130 within the Post-Tensioning Institute. And the Education Committee is the group that really sponsors this monthly webinar, puts them together. For those of you who are returning, we're glad to see you back. For those of you who it's your first time joining, we have this webinar at the same exact time every single month. So it's always the second Wednesday at 1 o'clock PM Eastern, 10 o'clock AM Pacific, and in between, depending on where you land in the US or elsewhere on there. So as you can see, today's topic is about construction and maintenance of post-tension slab-on-ground foundations. We get a lot of questions, comments about this here at the Post-Tensioning Institute, and we're trying to do more and more webinars to respond to all these questions that we're getting. Back in November and December, we had two webinars that were more focused on design. November was more about geotech, and December was the concrete design itself, getting into some of those initial design principles from there. Those were great webinars. We got a lot of awesome feedback from there, and then we received requests. They wanted to see more on construction, maintenance, those type of items, now that we've kind of talked a little bit about that design. So therefore, today's webinar is on the construction and maintenance. If you're at those webinars, great. If not, we do record them all. You can go online to the Post-Tensioning Institute, watch any of our previously done webinars. You can go on and watch it for free. You can get continuing education credit through there. So great to go back, watch those others as a primer after this one, get some credits, and we have a year and a half worth of previous webinars for you to go watch there too. So before we really dive in and introduce our speaker, Jack, today, we do have our typical housekeeping items to go through. First one being our webinar sponsor that we have. It's Host Tech Manufacturing. They've been a sponsor for the last few webinars, and they've been a great partner with us. They provide cable systems, wedges, materials, anchors, and they have a tendon shearing machine. So a shearing machine helps take care of the issue that we see in the field of torsion tendons, the mess caused with it. It's a more efficient way to go through. It's a cleaner way to do it, and they have a machine called the Minimax. I highly recommend you go to their website if you have not already to check it out. It's a great product. It really helps the quality with the construction with post-tensioning in there. So with that, we'll talk about the continuing education. If you are registered for today's webinar and you stay on for the full hour, you will get a continuing education credit through RCEP. That credit typically gets sent within one to two weeks afterwards. There's a little bit of lag time, but you will get that to your email. Once again, you have to be registered under your email, and you have to be on for the entire time. If you do miss it, you can go online and watch it, though, and get that credit as well. We are also registered through AIA, so you can get your credit through there. And then with those is the next one, our copyright materials. So we do not provide PDFs of our webinars for copyright reasons. If you do want to see anything, once again, you can go online, you can see it. Or if you have specific questions, reach out to us at the end, but so we do not send out PDFs of the webinar afterwards from there. And then the rest of our webinar protocol topics is all the attendees. You guys are muted. We can't hear you. We can't see you. So if you do have questions, ask them through the Q&A feature on there. If you do attend, like I said earlier, the entire hour, you get the continuation credit. If you miss it, go online. You can watch this or any of the previous ones. You take a little quiz, you get that free credit as well. So any of the professional engineers who need your continuing education, this is a great way to get it, or any other professionals that require continuing education on there. So with that, I think we can go and introduce our speaker for today. So Mr. Jack Graves. Jack is a legend at Post-Tensioning Institute and has been involved for many, many years. I think more years than he'd like to admit, probably more years than a lot of the audience members on here today have been alive. So with that being said, he obviously really knows his stuff. He's received numerous awards from the Post-Tensioning Institute and has been involved with many, many different committees at varying degrees of running the committee to other officer positions within the Post-Tensioning Institute itself. That list just kind of goes on and on. He's the Executive Vice President of Builders Post-Tensioning, which is a Post-Tensioning material supply group with offices out of Houston and Dallas. They kind of serve that Southern region there. He's presented on this particular topic many times. So he's obviously our in-house expert based on all the committees he's involved with when it comes to slab on ground and the fact that their materials fly, and he's been around doing it for so long. So with that, Jack, I'm going to hand it to you so they can learn about this topic that would just keep getting so many questions about. Okay, thank you, Kyle. You make me feel really young today. First of all, I just want to bring out this is going to be kind of a tough thing to cover. It's an 80-page document, so we're going to try to do it in 45 minutes, which is very tough. I also want to make sure everybody understands that this manual is a guideline. It's not a code document. It's recommendations put forth by the Post-Tensioning Institute. There's a lot of different ways to do things. We had to put something in the manual, so you can do things different ways, but we feel like the ways we've come up with are consensus-based and the way to do it. It was basically written for the owners, LDPs, builders, contractors, and fill personnel. It's a very good document. If you don't have a copy of it, I highly recommend you get online and order it. The other thing, too, is these are recommendations. You always want to follow your LDP and your local municipality guidelines. They trump us on what to do, so just keep that in mind. The learning objectives today, we're going to try to understand the importance of document control, material handling, and storage, understand the importance of proper site preparation, learn the key role site preparation plays in the proper construction of a slab-on-ground project. I tell people that the site prep, the soil you're dealing with, is just like any other building material. It's a key component. It has to be done right or you're going to have problems. In fact, a lot of the major issues I've seen with residential construction is because of site preparation or lack of. We're going to learn about proper forming, PT installation, concrete placement, stressing, and finishing. We're going to understand key job site troubleshooting topics and understand the importance of proper landscaping and long-term maintenance. Let's go over the outline of the construction maintenance document. That's the publication you see on the right of your screen. Here again, I highly recommend you get one if you haven't already. It's broken down into an introduction, document control, acceptance, delivery, handling, and storage, building pad preparation, PT installation. We do mention encapsulated systems, concrete, tendon stressing, elongation measurements, tendon finishing, job site troubleshooting, property owner maintenance, landscaping. There's example plans and details, and then there's some appendices that we'll go over. Document control. These are the basic documents that you need to have in your files and utilize. A geotechnical report, hopefully a grading plan. A lot of your custom homes have grading plans. A lot of your tract builders have grading plans, but it's a very important part is to have proper drainage and so forth. LDPs, foundation construction documents, PT shipping documents, material certifications, stressing equipment calibration, inspection reports if they're required, stressing records. That's either a stress verification letter or in some cases elongation records, and then concrete records. Concrete records, a lot of builders don't keep those, but they're very important. You want to keep those delivery tickets. They'll note how much water was added. A lot of things like that are important, so keep track of your concrete records. Acceptance, delivery, handling, and storage. Handling and storage is a big part of a lot of the problems we see. You want to make sure that you accept them, you get the proper paperwork, they're delivered properly, and that you handle and store them correctly. The handling and storage, you want to use either individual bundles or bundles on pallets. You want to lift these bundles properly. You want to use a forklift with a pole if they're bundles. A forklift with a normal forklift on pallets. You want to use nylon straps or lift by individual tendons by hand. You never want to lift with chains or hooks. You never want to drag these across the ground with a tractor or backhoe. You want to try to avoid excess handling. Never store in standing water. You'd be surprised how many times we see cables that are delivered and they are sitting in water. Always store long-term under a covered area. And when I say a covered area, that means in a building, in a container, some kind of tent structure. Do not wrap them long-term in polyethylene. It creates moisture. You can have problems with rust and so forth. So, you want to stay away from trying to wrap tendons on site for long-term storage. I've got a couple of pictures of vertical bundles and how they're delivered to the job site. Here's a picture of bundles on pallets that you can lift with a forklift. These are horizontally loaded. Short-term storage on job sites. You can put them on racks. You can set them on the ground as long as they're not in an area that's going to hold water. You also can, if you know they're going to be sitting on the ground, you can have them put on pallets. A couple of pictures of what you're not supposed to do. You don't want to put them where they're going to get wet and be underwater. We've actually had people reject deliveries because they were, you know, put in a position like this. So, proper short-term storage is very important. Here's an improper long-term storage. Here again, you don't want to wrap cable packs with poly. It's just not a good idea. You're going to get condensation. You're going to get rust. It's just not a good way. They really need to be in a facility, a storage facility, in a container or tinted where the sun's off of them. They're out of the elements, but they're not going to get condensation on them. Poor handling. Here again, these were obviously drug around the job site by a tractor or a backhoe. This has to be an encapsulated anchor system, but you can see the damage that was done. So, you've got to be careful when you're handling these things on site. Get into the building pad preparation. You want to follow the specifications of your LDP. That's also your geotechnical and foundation engineer, not just one or the other. It's very important that you follow their specifications. Utilize a grading plan to ensure proper drainage. Remove all organic material. Utilize select or reconditioned fill to elevate the pad as required to meet grading plan requirements or establish positive drainage away from the foundation. Properly compact any and all fill materials and give special considerations where you have a severe cut and fill situations. A lot of times when you have severe cut and fill, you need to retain that fill material. You can get a rebound in the cut areas. You may get an area where you cut it where you're on rock on one side and fill on the other. There's just some special things when you have a lot of severe cut and fill that you have to do. The key items are the proper drainage and that the fill material is installed properly, compacted properly. It's proper moisture content. Some of the biggest problems I've seen, the serious problems with foundations, were all due to improper drainage and or improper fill material construction. I've got a picture of a famous house up in Fort Worth that was improper fill. That was caused by some fill. They cut and fill. They didn't compact it at all. These things weren't very old and that whole side of that structure collapsed. Also keep in mind when you're talking fill material, you get to a certain height of fill material. You got to retain it somehow. Retaining walls, those type of things, are critical and should be addressed. Drainage. This is a picture of some good drainage. This is a picture of some poor drainage. You don't want to have ponding water. The key to the soil is trying to keep it a constant moisture content, which is impossible to do, but you don't want it to get saturated in the rainy cycle. You want to have ground cover, something to help keep it moist during the dry cycle, sprinkler systems and so forth. You don't want to start out like this. This guy obviously didn't have a grading plan. He just built it and you can see what happened. There were some problems with this house, by the way. PT installation. What I tried to do with it, I'm going to show you some checklists later. There's a lot of details, a lot of figures, a lot of information about the installation. We couldn't go over every one of those details and illustrations, so I'll come up with a later in a minute. You'll see a checklist that kind of incorporates all the items that are super important for a proper installation. This is an installation of a uniform thickness slab. This is another picture of a uniform thickness slab. And this is a typical mat slab foundation like you'd see here in Texas. RIP foundation is another name for it. This is a picture. All the cables need to be installed and tied at all intersections and chaired properly. There's a detail in the manual that you need a chair. If your cables are four foot six or over, you need a chair. A lot of LDPs have that as three foot on center. So keep that in mind. Here again, this is a guideline. A lot of engineers, a lot of LDPs require three foot max on center on your chair spacings. That's why I bring this up. It does vary. This is showing an intersection of two beams and a rib slab and a way to elevate those over the top. You can also use vertical dowels to profile those tendons. You just don't want them to slope and have a lot of wobble in them down. So that's a beam intersection installation. The anchor installation is important. Dead ends, you want to have some concrete coverage on the end of the tail, three quarter inch. You don't want to nail it up tight to the form. You're going to end up with a little rough spot. And that's a problem. On the stressing end, you want to nail those up. Either nail them up with 20 penny nails or double tie wire them. You don't want them at an angle like you see the incorrect on the details on the right. You want it like this where it's nice, flush, and tight. It's not only a profile situation. It's also, if it's nailed up tight, you'll keep the concrete paste out of the anchor, which is important for proper stressing. This is something that a lot of people aren't familiar with. This is another way to, you put a little grease on the pocket form and nipple as done on the right. You don't need a big gob of it like on the left. But the clients that we have that do this, they very rarely have any stressing issues. They very rarely get concrete paste up in the anchor, so it's highly recommended. That's one reason I've shown this slide. And you can get little buckets of grease from your PT supplier, or you can actually take grease off the live end and smear it on there. This is the checklist that I've come up with. Instead of going over multiple details and illustrations, if you follow these, I think there's 14, 15 items, you'll cut out most of the problems you have with the installation. So this is kind of a bullet point checklist that covers a lot of stuff. You want to make sure you have the correct installation plan with the most current revisions noted. You'd be surprised how many times we get out to a job site and the contractor is using the wrong plan. He's got the original plan, and it's been revised. So make sure you're using the right plan. Make sure a number of tendons match those shown on the LDP's drawings. We'll get tendons that are lost out in the bushes, or they forgot to get them out of the back of their truck, whatever, and they come up a tendon short or two when we go to stress it. So just a quick count to make sure the tendons match what you're supposed to have on the drawings. All tendon anchors placed minimum four inches down from the top of concrete, and that's the top of the edge of the concrete. If you have a brick ledge, it's from the top of the brick ledge, not the top of the finished floor. So it's four inches down from the top of concrete. All tendon anchors placed minimum six inches from all exterior and interior re-entrant corners. So six inch horizontally, four inches vertically. All stressing end anchors to be secure against form boards and plastic pocket formers placed properly. We recommend using a 20-penny nail or a double tie wire to fasten the anchors. Special attention to locations requiring a 45-degree pocket formers. Note on the 45-degree pocket former, a lot of houses have bay windows and diagonal corners and stuff. You can flip cables either direction. So if you don't want to mess with stressing at a 45, just reverse that and stress it out the flush side on the other end. Cables can be, just because they're shown being stressed left to right or up and down on a plan, you can change that. And there'll be a note on your LDP's drawing about that. You also can move them horizontally 12 inches to get away from a plumbing riser or a block out or something like that. That's going to be all on your LDP's drawings. No exposed cable is recommended behind the stress end anchors. Use discarded cutoff split stress in plastic or tape to cover any exposed cable at the live end. You can have up to 12 inches of exposed cable at the dead end anchor. That's because as the cable elongates, it's not elongating much in that first 12 inches at the dead end, so it's not going to be restricted. So the 12 inch at the dead end is acceptable. All dead end anchors to be secured to form boards, leaving three quarter inch clearance between tendon tail and form board. That's important not to get the little rough spots. They actually make a little spacer. You might talk to your supplier about providing a little plastic spacer to help do that. But that is available. Not everybody uses those. All tendons need three inch horizontal clearance from any vertical or horizontal penetration or block out. You basically just want three inches of concrete between any opening riser and your tendon. So that three inch horizontal clearance is key. Minimum 12 inch exposed tendon tail recommended beyond the form board for stressing. Shorter tendons can be stressed with special equipment. Typically, your supplier, when he calculates or does a takeoff on the strand, he adds a foot and a half and rounds up. So you should have more than 12 inches exposed tendon tail to stress. If you don't, it may have been stepped on and sucked up into the slab. It could have been kicked. But you want to check. Normally, your supplier has more than 12. If you don't have 12, then it takes a special piece of equipment to stress that. We can still do it, but it's really not the way it was intended. So look for that 12 inches exposed tendon tail. All tendon tails to be 12 inch horizontally away from any exterior obstruction. These are things like an HVAC, condenser pad, plumbing risers, electrical riser. We've got to put the jack on there. You can't have it right up against something. And here again, the LDP will allow you to move your tendon 12 inches horizontally either direction, typically. So just be aware of that. We also see where they're right up against a tree. First of all, a tree shouldn't be that close to your foundation. But if you have a tree, you need to move the tendon. And likewise here, if you have an HVAC, condenser pad, plumbing riser, just flip the tendon. Stress it out the other end. It's a simple fix. Adequate chairs installed. Place at all intersections and at 4 foot 6 maximum spacing. Throughout here again, a lot of LDPs like the 3 foot on center. Chairs are cheap. And you want those tendons to have a nice level profile. Tie tendons at all intersections. Properly install vapor retarder. To get back on the tying tendons too, some engineers want you to tie the chair to the tendons. It's kind of an awkward thing to do, but that is sometimes requested. But PTI stance is you want to tie the tendons at all intersections. If you use the proper chairs, they clip on pretty tight and don't necessarily need to be tied. Properly install the vapor barrier retarder. That's the poly. Some areas do not require that. But if they do require it, you want to do it properly and make sure there's not a lot of cuts or tears in it. No tears or exposed areas in tendon sheathing shall exceed 6 inches without repair to prevent bonding of concrete. This does not include the area I mentioned earlier about the 12 inches near the dead end. Here again, you can take the cut sheathing from the live end, split it, and stick it over those areas. They also make special tapes you can put on it. Just make sure you don't have anything over 6 inches or it is not acceptable. And then last, all your details, all your engineers will have different miscellaneous rebar. They'll have hairpins. They'll have L bars. Some may have backup bars. Some will have areas where you can't put tendons in, so they'll have some miscellaneous rebar. So make sure you get all that miscellaneous rebar in there properly. So that pretty much goes over 15 key items, and if you check that on every slab, you'll eliminate 95% of any problems you might have if you do this correct, dealing with the install. I told you we're going to talk about encapsulated systems just briefly. It's not real common to see encapsulated systems on residential construction. It's more commercial-oriented. But just for those who aren't familiar with it, I wanted to show a slide. Basically, you have a lockable sleeve on the back. You have an encapsulated anchor, and then you have a cap. You also have, if you go with an encapsulated system, they require 50-mil polyethylene sheathing, which is important. A lot of PT suppliers do 50-mil anyway, so it doesn't make a difference. That is your typical encapsulated system. That's some fabricated encapsulated systems showing the caps on the end, the encapsulated anchors, and the sleeves on the inside. Where you want to use encapsulated systems would be in corrosive environments along the coast, somewhere where you have brackish water, somewhere where you're going to have elevated finish grade, where you know that one part of your slab might have actual soil or vegetation up against the concrete that could cause some problems with the live ends or the dead ends, up north where you might be using de-icing salts or chemicals, and then, obviously, if your LDP specifies that, you need to do that. I just want to briefly go over encapsulated systems because I'm going to say probably 90%, 95% of residential construction does not use encapsulated unless there's a specific reason for it. Concrete, we're not going to spend a lot of time on concrete just because it's kind of a course in itself. You can spend the whole day on concrete. The main thing I want to point out about the concrete is in single-family residential, the manual specifies a minimum of 2,500 PSI concrete. On the multi-family, it's 3,000 PSI at 28 days. I rarely see 2,500 PSI concrete used. The majority of the stuff that we see by the LDPs is a minimum of 3,000. You also want a low water to cement ratio. Most engineers specify a slump of four to six inches, and you want to make sure you don't have a lot of calcium chloride-type material in your concrete that could harm any reinforcing or PT material. The placement, we won't get into placement or finishing a lot. The big thing with placement and finishing is to have adequate crews available and proper scheduling. That's where we see problems with placement and finishing is that you don't have enough people on site to handle it, and you don't have the right equipment, and you have a bunch of trucks showing up at the same time, which is not good. The other thing with placement and finish is weather. There are certain times of the year you should not pour concrete. One of the rule of thumb is if you're comfortable, then the concrete is probably comfortable. If you're freezing or you're just miserably hot, it's probably not a good time to be pouring concrete. There are some additives you can do. There are some things that they can do to place in any environment, but try to use some judgment on that. The other thing with concrete, too, I'll mention there's a lot of this L1 concrete out now. It's kind of a new thing. We're seeing some problems with it, but it seems like the good ReadyMix guys have it down pat. Also, with material, be careful with too much fly ash. Most engineers will have a maximum percent fly ash that you can use in a mix, so be careful not putting too much fly ash. The big problem we see with concrete problems is addition of too much water, and we see that on those hot August days where the crews are miserable and they want that self-flowing concrete, so they put a bunch of water into the mix. That's one reason you want to keep delivery tickets. You'll find it if you, as a builder, if the concrete contractor knows you're wanting delivery tickets, they won't add a bunch of water to it because the concrete driver will note how much water he adds to that. Curing in residential, you don't see a lot of curing. There are spray-on cures. There are tarps. There's different ways you can do the curing, but it's not real common in residential. And then the restraint or shortening cracks. Post-tensioning is popular because it helps eliminate cracks. you can't say it it's going to eliminate all of them. The restraints are shortening cracks, most of the cracks we see are going to be due to poor finishing, here again too much water being added, hot windy days, those are what are going to cause a lot of your cracking. So that's kind of the key items with the concrete without getting into too much detail. These are a couple of photos of one on the left is pumping concrete, one on the right is using a chute. You can see that concrete is, it looks good, it's not self-leveling. Taking cylinders, a lot of builders will take cylinders to keep the concrete guys honest. I've had one client who he took cylinders every house, he never broke them unless there was a problem, but the ready mix plant knew he was taking those cylinders and could have it tested, so he never had any problems with his concrete. So his superintendent would just take those cylinders on the various trucks. We'll get into stressing. Stressing is obviously very important. This picture I want to emphasize there is a safety factor to stressing that everybody needs to be aware of. You never want to stand above, behind, or near the stressing jack when it's being stressing is going on. If you see this picture, we've got safety glasses on, hard hat, safety vest, steel-toed boots, and we're away from the actual stressing. If anything were to break and go up or sideways or backwards, that technician is out of the way, so you can't emphasize the safety part of this. We normally stress to 80 percent of the ultimate tensile stress of the tendon. After seating losses and so forth, it's anchored at about 70 percent, and you never want to exceed 85 percent. The typical stressing equipment is an electric pump. The gauge is very important. It has to be calibrated with the stressing jack, which is in the front there. That one has a long nose piece on it, so that looks a little different, but that's what you see over here. So that's your typical set of equipment everybody's familiar with. Let me go back to that, too. The other things on stressing equipment that are important, you've got to have the proper power to that pump. The rule of thumb is you want to use a 12-gauge extension cord of no more than 100 foot long. You want to have a power source, preferably a standalone generator, of 110 volt, 30 amp. You don't want to run over with a 200-foot extension cord and plug into a temporary pole that has tensiles plugged into it and a vibrator and all this other stuff. You can burn up your pump and have some problems, so you do need the proper electrical source to run that equipment. Another key to stressing is the orientation of the wedges. This is showing the jack sits down over the cable, so it has a horseshoe look to it. To get the proper bearing on the wedges, your wedges need to be oriented vertically like they're shown in this picture. This is improper. You wouldn't want them horizontally one on top of the other. That's critical. It's very important to get proper wedge seating to have the the wedges properly installed. Properly calibrated gauge is super important. This is obviously an old photo from 99, 6-2-99. What you have on there, you have the the gauge number, the date it was calibrated, and it was calibrated at 7,500 psi gauge pressure, which equates to that 80 percent, 33 kips for your initial force. Also, to go along with this, there should be in every gang box a calibration chart dated that date that goes along with that gauge and that jack. You can check that on site, and it should be there. Most companies calibrate their equipment, probably we calibrate ours once a month, but most people probably every 90 days at least. If it gets knocked around or something happens and you obviously want to calibrate, it sounds funny, you want to calibrate it. Those calibration charts should be available on site. Stretching gauge readings, you also want to make sure, if you look at the one on the left, the needle's actually below the zero mark. Most of your gauges have almost like a, it's not a mark, it's like a T, so you have a little range, but you want that arrow to be within that zero range. That one's below, this one's above, this one's right on. So, if you get on job site, you see your needle's not zeroed properly, there's something going on, you need to have another set of equipment brought out, or a lot of crews will carry two gauges for the same jack, so you can take off the damage, the one not reading right, and put on the other one. But here again, you ought to have paperwork for both those gauges for that ram. We'll get into elongations. In single-family residential, very few people require elongations. In your multi-family, it's more common. In your commercial slab-on-brown, it's more common. But elongations, we talk about it, but it's not something that you see every day on single-family residential. But if you're going to do it, you need to do it right. You want to have a standoff measurement device, a reference marking device that's a piece of metal. You want to put it up against the concrete, you want to spray your mark on it. It's very tough. An eighth of an inch is pretty normal for discrepancies, but it's tough. You've got a seven-wire strand made up of seven individual wires that are all round. Spray paint is thick, it's thin, it can run. It's not an exact science, so everybody needs to be careful when looking at elongations that an eighth of an inch discrepancy is tolerable. Unfortunately, with residential where you have short tendons, that eighth of an inch can really make a difference whether it's in or out. On your high-rise construction, you have a plus or minus seven percent. When you're talking elongations, slab-on-ground is plus or minus 10 percent. Some LDPs have different, they'll do it quarter-inch instead of a plus or minus, they'll say quarter-inch. Some engineers don't care if it's over, they just don't want it under. What we look for is consistency. Elongations are based on a friction calculation that has variables that can change. You have each individual wire, and that seven-wire strand has a tolerance as far as the diameter. You have a bunch of thick wires, it's not going to stretch as much. You have a bunch of thin wires, it's going to maybe stretch a little bit more. You have modulus of elasticity, which can vary between strands. You also have friction coefficients that can change, especially on longer tendons. Just keep in mind that elongations are a good tool, but they're not a real accurate measurement. You look for consistency. If they're all coming up a little bit short, it's probably not a problem. If they're all over the place, you have one long, one short, then you might have a problem. It's just an indication, it's not an exact science. This is measuring the elongation. You either want to measure from your standoff device, your reference marking device, or you can actually measure off the face of the concrete. But if you measure off the face of the concrete, you obviously got to take the width of your reference marking device away from that dimension. I like showing this picture because it shows a tendon that's stressed on the bottom there, and one at the top that's not stretched yet. So it's an indication of how they actually do stretch. Also keep in mind, too, that you do get a typically get a three-eighths inch seating loss due to the mechanical process of seating the wedges. That can vary. Most of your slab-on-ground stressing equipment use spring-loaded nosepieces So those wedges are mechanically set, and the spring load is not as precise as the hydraulic nosepieces typically used on high-rise work. So keep that in mind, too. There is a difference between the seating loss, but three-eighths inch seating is typical. Some causes of improper elongations. The majority of the ones we see are improper tendon marking, improper measurement, or improper measurement recording. The guy measures off the face of the concrete and forgot to take the standoff dimension from it. Like I said, it's hard to measure off the face of the concrete, and it's hard to measure off the face of the to take the standoff dimension from it. Like I said, it's hard to measure a round tendon with seven round wires. So it's kind of, it's not an exact science. It's tough. You can have equipment issues. Those are normally pretty obvious during the stressing operation, but you can have equipment issues. A lot of the time, equipment issues that we might see would be wore springs. So your springs are wore out. They need to be replaced. Or some guys will insert spacers to make the springs a little shorter, and it's a way to get by with it, to get by not replacing them. But those are the major ones. Improper tendon installation. That's pretty rare, but you can have a case where you have a tendon that has been, has a lot of wobble in it, was not installed very properly. So it's almost got a profile to it, which it's not supposed to have. You can also have problems where the tendon sheathing was cut, and so you do have concrete bonding to the actual metal strand. You normally can see that, especially if it's a live end, because the ram will start twisting when you stress. Design material specification discrepancies. Here again, when they do the friction calculation, they're using an average modulus of elasticity, an average diameter, an average friction coefficient. And so normally if they're off, you can go back and look at the actual mill cert for the particular material, get the dimensions, get the actual modulus, and can redo those calcs to see if that was the problem. And then short tendon measurement tolerance issues. It's when you've got a slab on ground, you can go to even as low as a 15 foot cable. Well, when you take a 15, 20 foot cable and you lose three-eighths inches to the mechanical seating of the wedges, you have an eighth of an inch marking discrepancy. You can be out 10% really easy. So be careful with the short tendon measurements. It's really easy to be out of tolerance. And you just got to be realistic about that. To give you an example on a 20 foot cable, if you're out an eighth of an inch and nothing else is wrong, you're 9% out of tolerance. You could be. So just be careful. Don't get too worried about your short tendons. The next slide we've got is tendon finishing. Most people do not use, it's real common back in the day to use an acetylene torch to cut tendons. That's pretty much gone the wayside. So what you have pretty much now is you have saw cut with a strand cover cap, or you have a flame shear or plasma cut. Like I said, the flame is not common anymore. The shear is. That's more common on high-rise work than residential because a lot of those shearing machines don't perform well in dirt and sand and dirty environment. And then the plasma cut is not very popular. Here again, it's just kind of cumbersome. But if you got to do it one of the two ways, saw cut with a cap, flame shear cut plasma with just a grout pocket. Those are the two ways that you typically finish the tendons. Troubleshooting on the job site. Review that checklist that I presented earlier to prevent many of these issues. You can have strand slippage or stress jack hang-ups. Strand slippage is usually because you got the dirty anchors. You've got dirty wedges. So you want to make sure everything's clean. And that little piece of grease on the pocket form and nipple will keep the cavity clean. Honeycombs and concrete. A lot of your blowouts and so forth are because of honeycombs and concrete. A lot of your residential don't use vibrators behind the anchors. They'll tap the form for their hammer and that's their vibration. Okay. I don't know what happened. I just went away. I hope I'm back. Yeah, you're back, Jack. Okay. Thanks. I don't know what happened. I just disappeared. Honeycombs and concrete are pretty common. Like I said, the tenon and concrete blowouts, those are usually caused by the anchor being too high in the concrete, too close to an edge, too close to a vertical penetration. The tendon ruptures, we don't see a lot. Tendons don't just break for any reason or rupture normally. It seems like our tendon bundles make great saw horses. So you'll see people out there cutting forms on our tendons. They knit cables with saws and so forth. You also have tendon ruptures when people install anchor bolts, concrete nails, those type of things. And then obviously plumbers, they'll come into a slab and they'll sever tendons. So you can't have tendon ruptures because of that. Tendon is too short to be stretched using typical stretching equipment. We talked about that earlier. We can splice tendons that are cut. That's very common. We can fix pretty much just about anything. Cracked wedges, a lot of people worry about cracked wedges. And that's not uncommon. They do crack. So don't worry about cracked wedges after stressing. I also want to talk about the stress check or a liftoff. It's real common to do liftoffs and high-rise work where you're trying to check that you have the force required on there. In residential, because of the nature of the short tendons, we prefer, and a lot of engineers prefer, what we call a stress check. Like I said, we stress to 80% initially to get 70% final force. On a stress check, you basically are pulling to 80%. And if you haven't broke the wedge loose at 80%, then you assume that the tendon has the proper stress on it. If it's under stress, it's going to break loose before you get to 80%. On some of the short tendons, you have to overstress to break the wedges loose. And you never want to exceed that 85%. So we prefer a stress check over a liftoff. Next. Okay, trouble-stirring stressing equipment. I'm going to go through this quick because we're running out of time. Jack leaking, jack damage, jack leaking, jack damage to strand or won't grip the strand, dirty grippers, excessive seating loss over three-eighths of an inch, pump will not reach required gauge pressure reading, pump is operating too slowly, gauge issues. Those are the things you see with stressing equipment. Landscaping, very important. The slope, the proper ground cover, sprinkler systems, keep large trees and shrubs away from the foundation, install gutters and downspouts to divert water away. Property owner maintenance, the very key, proper drainage, maintain that proper drainage, maintain underground drainage systems, maintain proper ground cover, maintain and utilize sprinkler systems, do not plant trees or shrubs near the foundation, and maintain those gutters and downspouts. There also are appendices in the book, definitions, strand material certifications, jack calibration forms, installation tolerances, stressing elongation record form, and table of elongation values. And with that, I'll turn it over to Kyle for Q&A. Yeah, awesome. That's, you know, guys, I think Jack just gave us, in my opinion, a couple of big ones. You know, guys, I think Jack just gave us, in my opinion, a couple of days worth of information that he tried to cram into an hour here. And so we'll talk about a little bit later, but there are other avenues within the Post-Tensioning Institute to do a much deeper dive on this, because this was just so much information here, which is great. With that, we've received a ton of questions. Jack, so I'm going to kind of hit a few of them here, and then the rest that we don't get to, we'll be sure to try and respond to you guys via email or other means. And then we'll do a look ahead to some future webinars here. So one thing, can you give your opinion on any stressing sequences that should be considered or may be considered with slab-on-ground? I don't think slab-on-ground residential is that critical to have a sequence. In my experience, that's very uncommon. So I don't think that's really a big issue with residential. Yeah. With the wedge orientation that you discussed, there was a question about the importance of that. And really, I believe what they're getting at is how that relates to the jack itself. Well, like I said, the jack nose piece is shaped like a horseshoe. So you have an open end, so you can set the jack over the strand. So you want to have as much bearing on both the wedges and equal bearing. So if you don't have them oriented properly, you can, if you have them the wrong way, if you have them horizontally, there's a tendency for the upper wedge to set farther in than the bottom one. So you want to have them oriented to the nose piece. You can turn, if you have them the wrong way, you can turn the ramp 90 degrees. But usually on slab on ground, you don't have that ability because you don't have that much clearance. So it is important to keep the wedges oriented with the nose piece. Early on, you had mentioned temperature and shrinkage and how post-tensioning helps with that. Can you elaborate a little more just how it helps to the point of not needing saw cut joints? Yeah, concrete, as concrete shortens and cures, it wants to shrink into little pieces based on the depth of the concrete and the friction between the soil or the polyethylene, whatever you've got underneath it. So concrete wants to crack as it wants to crack and that the tendons don't necessarily prevent it from cracking. They just keep those cracks tight where they're not a nuisance or visible. The cracking in concrete is more a function of the concrete and the subgrade and the place and finish. In some large slabs, you actually do put in some type of a keyway joint, an expansion joint, but in most residential, you don't. A lot of people can also, if they're worried about... We have builders who will do what we call a partial stress. We'll put 30-40% of the stress on at 24 to 48 hours to try to get some tension in the slab to help prevent those cracks. But most of your cracking develops fairly early on in the process. So that's why I always say PT may not prevent cracking, but it'll keep cracking from becoming a problem. Right, and induces a lot of those early compression forces for the tension to have to overcome on it, which I think helps a lot. Yeah. Durability, there's some questions about... So in the residential on-ground solutions where it does not have to be encapsulated, do you just follow similar clear covers that you'd see for typical reinforcing down there, especially if you're up against hot soils? Does pre-compression help with long-term durability of the concrete in those type of scenarios? I think it's proven that post-tensioning really helps. Most conventional reinforced slabs move. The movement shows in any cracks, and those cracks hinge over time and deteriorate over time. The post-tensioning keeps the foundation in compression. It resists those movements, and it keeps the slab together. I also find that the forensic stuff I've done, conventionally reinforced slab with mesh or rebar, half the time that mesh and rebar stomp down during the placement, and it's under the concrete, not in the concrete. So you basically have unreinforced concrete. The other thing with durability and sustainability is that with the post-tensioning, you're using less concretes. Thinner concrete slabs, shallower beams. So there is a sustainability benefit to the use of post-tensioning also. All right. We have several other questions. We just run out of time here. So we're going to quickly go through a few other slides just to close out the webinar on there. Hey, Carl, one thing. If anybody wants to contact me direct with questions, that they're feel to have them feel free to contact me. Be glad to talk to them. Perfect. And you guys can see his information there. Post-tensioning Institute is doing this Stronger Standards Exceptional Structures campaign on there. And I highly recommend you guys go to this website, check it out. It does talk about a lot of different benefits that post-tensioning can bring. And some recent changes that we've seen in the international residential code in the 2024 code on there. So highly recommend going and checking that out. Another thing is there's a ton of different resources out there. Go online. You can watch all these webinars. There's a lot of publications that you can purchase. There's frequently asked questions, tech notes that you can download online. There's these webinars, as we discussed earlier. All of these are recorded and available online for free. You can ask technical questions. And then when it comes to the install, like I mentioned, Jack today went over a couple of days worth of information. There are programs out there through PTI that do with certifying installers and inspectors that have a ton of information for those guys out in the field that really dive into this in a greater detail that's offered. So highly recommend going and checking that stuff out. So next three months, looking ahead, we jump up vertically. We're going to barrier cables. First webinar will be in May on barrier cables, on screen barrier cable design. Then in June, we're going to go to the construction and maintenance side of it. And then July, we're going to jump over to bridges. So new technologies for post-tension bridges. So that we look forward to seeing you guys next month at the same exact time, the second Wednesday of the month at 1 o'clock Eastern, 10 o'clock Pacific. Thanks so much, guys. And look forward to seeing you again. Bye. Thank you, guys.

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