The first installment of STEGO NEWSMAKERS features concrete consultant Christoper R. Tull of CRT Concrete Consulting. The Indiana-based, Cornell-educated consultant brings a career's worth of experience in tackling some of the most difficult slab design projects. He discusses the importance of below-slab vapor protection, and looks into the future of the industry with the growing trend to extend joint spacing.
Video TranscriptionI'm Chris Tull with CRT Concrete Consulting. I've been in the concrete design and construction industry for 30 years. I have a BS in Civil Engineering from Cornell University. I've worked for a concrete contractor, a construction manager and I've been active in the ready-mix business for quite some time. I started CRT Concrete Consulting in February 2000 and I focus on a relationship-approach to technical issues.
When to Call a Concrete ConsultantPeople call me generally for two things. One, I know, but maybe more importantly, they contact me from what I can find out. I don't know everything, I have a lot of relationships in the design and concrete construction community, so I'm able to find out things and provide answers to my customers. I'm really an inclusive type of person. I don't want to come in and beat the table and say you shall do this. Again I don't think what we do is all that complicated, so we can have an environment where everybody gets what they need in order to give the owner a good project. What makes the phone ring for me these days are three different areas that I primarily work in. I work in concrete mixtures, people are always trying to reduce shrinkage and curling in concrete slabs and concrete pavements. That keeps me busy from a material standpoint. That issue also keeps me fairly busy in the slab business with the curling and shrinkage of slabs and really a fundamental misunderstanding that largely exists with structural engineers when it comes to soil supported pavements or slabs, that keeps me busy. And then concrete pavements is certainly a growing industry where we're seeing pavements that are being designed and constructed as block placements rather than conventional strip boards or slipform pavings. If the phone rings before and early then typically my fees are smaller and typically owners fees are smaller when they are not engaging in consultants and attorneys and things.
Involving the Consultant Earlier Can Save Time and ResourcesTypically, when I'm engaged before the project begins, I like to review the drawings and most of the time the Structural Engineer of Record, he has a fairly good hand on the slab thickness. However what I've learned a lot from structural engineers is they like to bind everything up with reinforcing steel which can lead to slab cracking. My role, maybe, principally is not a designer but more of a slab detailer that if I can adjust some details from a conventional structural engineering to more slab and pavings from the details, then we can reduce cracking along the way. To maximize the benefit of my fees, it's best to bring me in early. "So, hey, we're building a building pad and we're putting in a big box slab and we'd like to bring you on board to work hand in hand with our contractor, hand in hand with our designer." And sometimes my role may be more of a facilitator. So really what we're all after, we are all after to make the owner happy and we're all after to make a fair living along the way. So the earlier I get involved, the less stress the situation has and the more adaptations we can make and create a win-win-win environment.
When Challenges Arise: The Consultant as TroubleshooterUnfortunately, my phone does ring quite a bit after the fact where there are problems and those are our challenges to where my customer is not very happy to see me because he's got a problem on his hands. Usually what the issue is a lack of communication and a lack of people meeting expectations. An owner might have an expectation for a perfectly flat floor that is not cracked and that may not be reality. But he doesn't know when he's buying that floor that he's going to get some variation. So a lot of times, that would be his meeting expectations and discussing expectations. And we do that after the fact sometimes that can be a contentious conversation. I think a lot of time that people say it's just a slab and I've been on projects, they call you up and they say, "We're not happy with our slab and maybe the slab is underdesigned, maybe the slab's got three-quarter-inch of curling, maybe the slab's got joints 25 feet in the center," and when you look at it, it's just that the whole team really didn't have any expertise on slab on ground construction.
Advice for Building OwnersBuilding owners, they don't know and I like working with owners that don't know what they don't know and they're willing to ask. So that typically works best even if you have a guy who's cost-conscious because everybody is cost-conscious. There's ways to detail slab, slab on grade and in concrete pavements. So there isn't problems down the road and some of the details don't necessarily cost more money. After the bid, every change costs more money. So that's why I like to get involved early, and if I could get involved and have influence with the designer and influence with the potential bidding contractors ahead of time, then everything works out to be more affordable from here on. With anybody in life, it's always good to know where your areas of expertise are and not be so stubborn to know where you don't have it.
Advice for Project Design TeamsI like working with engineers however I don't believe I've ever got a call from an engineer who said, "Hey, I want to bring you on board on this slab because I want to make sure it goes smoothly." It's usually the owner that would call me or the engineer might call me after the fact when there's a problem, but very rarely do I get a call from the Engineer of Record before the fact. What I would love to... If I had one item that I would like to communicate to the Engineers of Records or the architects is that shrinkage is not a water-cement ratio issue, it's a paste-volume issue and we've got a lot of designers that are getting artificially low water-cement ratios and the result of that is the ready-mix producer and the contractor are increasing their cement factors in order to meet a water-cement ratio, thus, increase in paste volume and increase in shrinkage and curling.
Advice for Concrete ContractorsI think concrete contractors generally want to do a good job if the specifier or the Engineer of Record creates an environment to where he cannot succeed, then I don't think there's a value in that for the owner or anybody else. So I like to make sure that what I design or what I detail is constructible, I think that's the most important thing. And furthermore, if my ideas can only be successfully built by the top 1% of contractors, I don't know that that brings value either. So I'd like to make sure that the average guy on the street can succeed in bidding and working on projects I'm involved in. While all of us in this industry are proud of what we do, we think we bring value, I don't think we're doing rocket science or open-heart surgery. There's these common concepts out there that people should be well aware of and be willing to be open-minded of it and I include myself in that too. Because there's a lot of good engineers in the industry, certainly, there are a lot of very good contractors in the industry that have taught me a great deal and there's a lot of good suppliers in the industry that have some good ideas and good technologies that should be incorporated.
The Importance of Below Slab Vapor ProtectionOne of the issues that I see out there is building codes. I'm a big fan of accurate and current building codes. There are states that I do business in that, for instance, the residential code is seven, eight, nine years old, they don't keep up with the building codes. And in the commercial code, one thing I think is a disservice to owners is the code requiring 6-mil Visqueen in the code. That's not doing anybody any good and a lot of these moisture-vapor transmission failures in flooring is a direct result that the code is not correct in having the proper vapor retarder under the slab. When I deal with manufacturers, what I want is data. I want numbers. I don't want opinions, I don't want how you feel, I'd like to have data, and there's a lot of good vendors out there in the design and concrete construction community that do a very good job of... Stego is certainly one of them. However, I'm seeing a bit of a rush on some chemical add mixtures in concrete with claims of no shrinkage, of harder slabs, and no shrinkage, and no bleed water, no moisture-vapor emissions, and I hear a lot of claims and don't see a lot of data and that's concerning to me. Lastly, with my relationship with the vendors is I'd like great communication. I wanna make sure that whoever vendor I'm talking to or manufacturer I'm talking to keeps me up to date with what, not only they're doing, but what their industry sector is doing. So when I'm talking to owners that I'm up to speed. And lastly is I'd like to be kept in the loop on projects if certainly that all vendors are trying to sell their products, that's what they're there and I think that's a good thing. But if you're calling on one of my customers, I'd like to know about it from you rather than hear about it from him. Well, I think what we're halfway through the next is extended joint slabs and extended joint pavings. I think that the idea that our slab on ground have 15-foot joints on center, I think that's a very good concept.
The Latest Trend in Concrete: Extending Joint SpacingHowever, the problem in these buildings when you talk to the owners are joints. So there's a lot of good technologies out there to extend joints, maybe that has pick another 20% of the market now and I feel in a short period of time, five years or so, that joining at column lines is going to be common place, not the exception. The joint spacing has been driven by maybe two different factions. One is that the joints themselves are problematic to an owner, that force curl, they chip, they spawl. So there's a notion fundamentally to get rid of joints. The other thing that's happening now is with these robots in these distribution centers. They don't like joints very well and they like flat floors and they like floors that are placed flat and stay flat. So like I think we're going to see a movement not only to extended joints, but we're going to have construction accountability for floor tolerances, not up to 2 feet of joints but maybe through construction joints, I think that's on the way fairly quickly as well.
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