Concrete Countertops: How reinforcing works
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- Опубліковано 2 жов 2024
- Learn from Jeffrey Girard, President of The Concrete Countertop Institute, the principles behind how properly reinforced concrete countertops can enable you to have confidence and avoid problems. Jeff explains how concrete countertops behave like beams, not slabs on grade, where to place the reinforcing and why (including cantilevers) and what materials are most reliable for reinforcing precast concrete countertops. He also touches on how GFRC reinforcing works, as well as gives amazing examples of what a properly reinforced precast concrete countertop can do. View this video if you are a concrete countertop professional who wants to make high performance concrete countertops.
For more about how reinforcing works in concrete countertops, see these helpful articles:
concretecounte...
This is a phenomenal video. I'm a contractor but have had no experience with concrete countertops up until now. I'm remodeling my own kitchen, and have decided it would be a good time to use myself as a guinea pig for my first attempt at making concrete countertops. Thank you!
Wow. Your ability to explain this in discharge logical and straightforward terms was amazing. If only every educational video on UA-cam was this clear. I would be a genius.
I'm glad you liked the video Matt!
I have always advocated using 9 gauge masonry wire for reinforcing. It's a true, structural reinforcing material, it has great properties, it is easy to work with and it can provide outstanding results when used correctly.
Very well explained. I am going to be building these in my house and needed to address these issues. Thanks for posting this.
The backdrop was simply a piece of gray cloth, and I used two 4-foot shop fluorescent light fixtures with daylight bulbs on 6-foot stands. Pretty simple!
My right ear is lonely. Give it some sound
Excellent video on the explaination of forces to a countertop.
old video...still VERY relevant information and well communicated as well. Great job.
Thanks Derek!
Perfect explanation
Wow, I just realized how little I actually knew by watching this video, very informative.
I've been searching for information that would help me make a better product. Thank you so much for sharing your expertise with anyone who finds your channel. Thanks again!!
+Grace ValRioFarms You are very welcome!
What a GREAT video!!! I'm a "why" person, so.. I don't like hearing "don't do this" or "do it this way", but... WHY to do, or not to do something. Thanks sooo much!! The last picture of the 500# on the plank.... VERY impressive! I'm SOLD! :D
Great video, very useful information. Thanks Jeffery!
You are very welcome!
Whoa. I just learned a lot. Thanks for the great video!
You are very welcome!
Wooden tops on the cabinets will not provide structural support. Wood is too flexible and weak, so you still need the proper steel reinforcing in the concrete. The dimensions of the cabinets are fine - the concrete countertop will lay over top of several cabinet boxes, depending on the layout of your kitchen.
@therealeeeo Best of luck with your first project! Definitely you will be your best guinea pig. Just FYI, I do have a self-study course designed for just this scenario - making your first (successful) concrete countertop: Check out the Level 1 self-study training on my website.
I liked the pictures you used, it was funny and explanitory.
Thanks Aiden. I'm glad you liked it.
Thanks for this video...
You are very welcome!
Easy to understand it :) Thank you
Ladder wire should never be welded since it is cold-drawn to achieve its high tensile strength. Welding anneals the steel and lowers its strength. Ties are only necessary for convenience; they offer no structural benefits. I find 4" nylon cable "zip" ties to be very effective.
3/8" rebar may be used in 2" thick concrete with care to keep it very low in the slab. 1/4" rebar would be better.
What if any reinforcement do you suggest with a fireplace hearth. dimensions are 24"x36" with 45 degree corners
Thank you
Thanks Neil! Please contact us via the website to address your question. This will require some engineering, but overall your thoughts sound on track.
Great vid
(other than the audio only on one side. Did you know that you can re-upload a new audio track to the same video, and this way you could fix it?)
Sorry about that, and thanks for the tip!
With careful placement and casting it's possible to place reinforcing as close as 1/4" from the visible surface. Note that this will not cause ghosting. Ghosting is caused by *pushing* the reinforcing through the concrete, no matter where its placement.
Your question regarding the cantilevered bartop requires design services beyond the scope of these comments. Jeff Girard does offer consulting services. Contact us for details.
Great info. Do you need to put in reinforcements if your cabinets already have a wooden tops which the counter will lay on. My cabinets have odd dimensions too (I have one of those weird, modern kitchens). Some cabinets are 12" X 40", 12"X14", 24"X30". Should I bother putting reinforcements in these or are they too small?
I'm sorry to hear about any cracking countertops! Exactly what I'm trying to prevent.
Thanks for the great video Jeffery! Very helpful. I am making 1.5" thick pre-cast countertops for our kitchen and am planning on using 9 gauge masonry wire as reinforcement. Based on the info presented in your video, am I correct in saying that you would not suggest making a perimeter loop out of rebar or any other material? Also, what distance from the edge of the countertop would you recommend the reinforcement ending? I have heard that air trapping can occur if the reinforcement is placed too close to the edge.
I read your article on ghosting and in your words, "A third way ghosting occurs is when reinforcing already buried in fresh concrete is moved or vibrated". I was planning on using a vibrator to help the concrete settle in the mold..would you recommend not using a vibrator at all?
Please let me know what you think!
Caleb
You mention AR glass mesh. I have searched online for this and I've been unable to find it except in very large quantities from overseas. Is there a special store that usually carries alkali resistant glass or should I start snooping around my local concrete countertop shop?
Thanks Bro! This video was really informative. I appreciate that you took the time to do it!
You are very welcome!
Well this certainly explains why my first attempt was a failure. Ont to number 2!
The tensile modulus of steel matches concrete while glass does not….please elaborate on this point. It seems to me that cracks will form sooner as the glass is not properly supportive within the modules of concrete .
I assume that you are talking about the AR glass fibers used to reinforce GFRC. GFRC has a radically different mix design than ordinary concrete, and is more in tune with the flexibility of glass reinforcing. I have extensive articles and videos about GFRC here: concretecountertopinstitute.com/free-training-category/how-gfrc-works/
Tensile modulus is an indication of the stiffness of a material, in other words how stretchy or not something is. A high number means the material is stiff, and a low number means the material is stretchy.
Steel has a higher modulus than glass, i.e. it is more stiff and less stretchy. Therefore, with all else being equal, a strand of steel that's the same diameter as a strand of glass will stretch less than that strand of glass under the same load.
With conventional concrete (rocks, sand, cement, and water), the concrete's overall ability to stretch without cracking is extremely limited. Conventional concrete is brittle, which means that it doesn't take much flexing to cause a crack. The structural reinforcing material must take up all of the tensile forces and at the same time prevent the reinforcing from stretching so much under load that the surrounding concrete cracks. Because steel stretches much less than glass, it takes a relatively small amount of steel to resist the tension-induced stretching.
You can't use glass fibers and glass mesh (aka scrim) in conventional concrete because there's simply far too little that can be mixed into the concrete to provide the degree of tensile capacity AND stretch resistance that ordinary concrete requires to resist cracking.
Fiberglass rebar exists and can be used in conventional concrete, but the amount of fiberglass rebar that must be used to resist the amount of stretching that is necessary to prevent cracks in the concrete is much greater than the amount of steel that is required. So steel is the preferred method of structural reinforcing for conventional concrete.
that was brilliant. thanks
You are very welcome! I'm glad you liked it.
Planetary polishers are a fantastic tool that makes producing smooth, flat and gouge-free surfaces fast and easy. Justifying their cost (and the tooling - in triplicate!) is something you need to determine. Do you do a lot of large, flat countertops? Do you or your employees struggle with keeping a single headed polisher flat? If so then maybe a planetary polisher is a valuable asset. You will still need a single-headed polisher for narrow sections, edges and inside integral sinks.
A very informative video! I'm planning a counter top (60" X 30" X 2" slab) with a 2 inch over hang on 3 sides. Should I run the ladder wire from back to front (30") or lengthwise (60")? Thanks again for the great video!
Thanks, I'm glad it was helpful! this is a good question. You are thinking about where the stresses are in the countertop. You should definitely run the reinforcing lengthwise (60"). To be safe, it wouldn't hurt also to run it back to front (30").
For counter tops plan on losing a lot of money and time before you start making money. You cant just watch a video and then make a successful business out of it. It takes experience and the only way to do that is to empty your wallet and get your hands dirty. If you just want to make various stuff out of concrete get your self some chicken wire, a trowel, bucket, and a bag of concrete and do what mrjaybird said. Tools matter. Get the right ones for the job.
Thanks Oealnc for the nice comments.
Pkqkennywood, the answer to your question is essentially no. I've just posted a blog entry. Go to the home page of my website and click Blog at the top right.
Karenwaln, I will get to your question soon. It takes more than 500 characters to explain! Basically, I used 14 individual strands of 9 gauge ladder wire. The strands were placed about 1/4" apart in order to fit all 14 in a single layer within the beam's 6" width.
Aziz, there is lots of information on my website and blog about the basics of making concrete as well as other topics. I also have a basic self-study course called Level 1 Getting Started. You might also try the American Concrete Institute website for basics of concrete not specific to concrete countertops.
Thanks for the numerous videos you guys have posted. They have been of great help. Im about to pour a 9ft x 3ft x 1.70'' thick countertop which I will then have to carry into place. Im wondering on the thickness of metal reinforcement I should use? Would 1/4" or 7mm be ok? Thank you.
Hi Jared. You're welcome! That should be okay. For a 1.5" thick countertop we typically recommend 3/16" reinforcement. Yours is a little thicker. There are more articles about reinforcement on our website: concretecountertopinstitute.com/free-training-category/reinforcement/, and we have a self-study course about it as well: concretecountertopinstitute.com/shop/reinforcing-101/
A piece that small won't need reinforcing, provided it's at least 1" thick. Set the piece just like a tile with a full bed of thinset mortar.
There are at least 7 different gauges for wire, depending on the application, material, country, etc. So depending upon which system you're looking at, a #9 wire could be anywherefrom 0.009" to 0.194" in diameter! Ordinary fencing wire (which may be classified as a #9 wire) isn't appropriate for critical reinforcing, as it doesn’t meet ASTM A-82 standard.
Hand weaving, soldering or welding sounds like an awful lot of work for very little benefit. Welded wire mesh already exists and is cheap.
WOW! I learned so much from this video!! Loved the scientific explanations--now it all makes sense. Thanks so much for making this video!! Jody
There really is not a simple calculation. It depends on the geometry of the slab, including orientation of the tensile forces, sink holes, etc.
Carbon fiber reinforcing is a great alternative to steel, however it can get expensive. Ordinary fibers used in concrete are not designed to replace steel reinforcing and as such are not suitable or effective alternatives.
have watched numerous concrete countertop videos and am thinking about usein Quickcrete counter top bag mix, is this a good option or not I have about 85 ft. of countertop to produce in three different layers or height sections.
Hi Lee. As an engineer, my preference is for from-scratch mixes. However there are advantages, such as convenience, to using a bagged mix. For an article about this, please see concretecountertopinstitute.com/free-training/diy-or-bagged-concrete-countertop-mix/. If you do choose a bagged mix, I would advise one specifically designed for concrete countertops (such as the Buddy Rhodes mixes) rather than adopted from conventional concrete. Please be aware that there are many factors other than mix that are important for a successful concrete countertop project. For example concrete related factors such as not using too much water (concretecountertopinstitute.com/free-training/the-importance-of-water-cement-ratio-in-concrete-countertop-mix-design/) and proper curing (concretecountertopinstitute.com/free-training/curing-an-essential-step-to-create-high-quality-concrete-countertops/). Non concrete related factors include templating, forming and installation. Please see the articles at concretecountertopinstitute.com/free-training/ for all of these topics and more.
Thanks for the great video. I am making a media center out of 1 1/4" black iron pipe and concrete. The two concrete shelves will span about 7 feet (x18" wide), and are supported on either end by the steel pipe skeleton. There may be up to 300 pounds of LPs on one of the shelves, dispersed evenly across the 7 feet. Can you recommend a slab thickness and rebar thickness? I was thinking of 2 1/4" slab, with 1/4" rebar running lengthwise every 6", leaving 1/4" from bottom of rebar to finished bottom
I'm doing an outdoor concrete countertop and I was wondering if I could or should use the block wire and the fiber glass together ,it will be two inches thick and i will be using 3/4 inch stone in the mix as well ,thanks for you help
If by fiber glass you mean AR glass fibers, no. Those are used as primary reinforcing in Glass Fiber Reinforced Concrete, whereas steel is used as primary reinforcing in traditional aggregate based concrete. You can use various types of fibers for secondary reinforcement to control plastic shrinkage cracking, but those fibers will not replace steel or provide/supplement structural reinforcing. Please see my blog articles about fibers: www.concretecountertopinstitute.com/blog/?s=fibers&submit=Search Curing is also a very important part of crack prevention, as is proper mix design and low water-cement ratio.
Thank you Jeff, another masterclass that help me a lot!
I have a question, why my countertop curl or bend upside or I don’t know how to say, inside the mould? The facecoat is sprayed, and the back is GFRC. I cover the pice while curing, no matter if is for one day, or 5 days, the countertop curls on the extremes. After taking out the mould, the countertop is like a bridge, not a beam, is higher in the middle.
Any idea, any advice in order to avoid this big problem?
Thank you Jeff 😁
Curling is almost always due to differential shrinkage. Please see the section on Curling in the article concretecountertopinstitute.com/free-training/6-problems-with-concrete-countertop-mix-designs-and-how-to-prevent-them/
@@TheConcreteCountertopInstitute thank you Jeff!👍🏻
@@gonzalopmolina You are very welcome.
Great details for concret maker and they have to know this priciple
Excellent explanation. I need to make a very thin rectangular countertop, say 19 mm thick x W=800 mm x L=900 mm supported at the perimeter. Can it be done? how? Thank you!
For this large, thin application, I would use GFRC instead of traditional precast. Please visit our website at www.concretecountertopinstitute.com/blog/2015/08/index-gfrc-concrete-countertop-training-free-information/ for extensive GFRC information.
one thing to always consider, At some point in time, someone always ends up sitting or even standing on the counter.
Thanks everybody, I'm glad this video is helpful. courduroycarver, AR glass mesh is also called "scrim". Fishstone Concrete Countertop Supply and Ball Consulting sell it. Fishstone sells it in small quantities.
Fantastic video! This was a really well thought out and presented explanation of reinforced concrete design. I have taken many concrete design courses and this is by far the quickest and most intuitive approach I have seen detailing tensile and compressive strength function and placement of reinforcing. Everyone needs to watch a good 10 mins of something like this, not just for concrete, but for the nature of materials and stresses for building. Thanks!
Very good video, Thanks. Like your pictures. I am making precast concrete stair treads for an outside deck. Your video has helped a lot.
Great information 👍
Thanks , My need is to know for a 3 inches slab or counter top, what the size of iron bars should i be using. Secondly we are familiar with milimeters rather than using gauge, so for 8 & 10 mm bars how to convert to gauge, Thank you sir
For a 3" (76mm) slab, you should use standard #3 rebar, which is 3/8" or 9.5mm. So 10mm would be fine if that's what you can get. The 9-gauge ladder wire you see in the video is appropriate for thinner slabs, 1.5" (38mm) thick.
Thank youSir, very helpful will go by the 10 mm. Thanks
Excellent explanation for those with little to no experience designing concrete structures. You kept it simple and very understandable.
How close may the reinforcing be to the surface of the concrete?And what type of concrete would you reccomend for the following project?I am building a 14'x21(w)x2"(t) 16" of the width to be canted. 3" bearing using #3 on 16"centers for support and #9 ladder wire tied for tensile strength A 2x6 wall provides the 3" of bearing The rebar will be L shaped with legs of 8 and 20 inches,the 8" leg will be inserted into a3/8 hole in the 2x6 studs and glued the 20 "will support the slab Thanks
great video - i suggest to others watching to set the speed to x1.5
We are building a concrete countertop for a kitchen island. It is 1-1/2" thick, 4' wide and 7', 2" long it will have a 9 inch overhang on the long edge. We are using ladder wire for reinforcement. Do we need to build 2 separate reinforcements for this or can we simple use one and add extra ladder wire where the overhang will be? We did build 2 separate ones but the one closest to the form (finished surface) is only 1/4" from the form. my concern is that it is too close to the surface and we have too much reinforcements.
I'm no expert but it sounds like two sets of reinforcements are required: one length wise (ladder wire near the bottom), and one set width wise (near the top) for the cantilever of the overhang.
(2) According to the video, reinforcement closer to the center is less effective, so further out is better, but where's the limit? How close to the surface do you want to be?
Hi Matt, sorry I missed this. Hugh is right, you do need one length wise near the bottom and one width wise near the top for the cantilever. The cantilever reinforcing can be 27" long (twice the length of the overhang). It doesn't have to be as dense as the regular reinforcing. 9" is not much of an overhang and probably not an issue unless somebody really heavy is going to be sitting on that edge.
1/4" from the finished surface is fine. 3/8" would be the maximum, and the minimum is right at the surface. Please see this article about ghosting: www.concretecountertopinstitute.com/blog/2012/10/how-to-avoid-ghostlymistakes-in-your-concrete-countertops/
I doubt you have too much reinforcing. It's better safe than sorry. Too much would be so much that there's more steel than concrete.
This is WISDOM. Thank you. Sharing is Caring. :-)
Thank you for the kind words, Carl.
would you recommend fiberglass scrim instead of rebar because scrim is extremely flexible why would anyone prefer it over rebar?
The material used to reinforce concrete with is carefully chosen to match the physical properties of the material it's used in (the unreinforced concrete). Conventional concrete (ie non-GFRC), is brittle and has a low bending strength. These two properties make the concrete very intolerant of any tension developed from bending or stretching. As you've seen in my reinforcing video, the more concrete bends, the more the tension surface stretches out. While it's not apparent from casual observation, some cracking in all concrete is allowed for and is expected. The concrete itself cannot stretch very much, which is what brittle means, so any "stretching" from bending beyond the small amount that the material can handle is made up for by open cracks. The key to managing the cracks is to limit how much stretching occurs. With brittle materials very little stretching can be tolerated, and this brings us back to the material used for reinforcing.
Structural steel used in rebar and in ladder wire is very strong. But tensile strength is not what makes steel the correct material to use in conventional concrete. The property of steel that makes it superior to glass is its stiffness, also called the modulus. Stiffness refers to how much (or how little) the material stretches when it's pulled. Think of a spring. Steel isn't very stretchy, while glass fiber is 3 times as stretchy. If glass fiber was used to reinforce conventional concrete, it would take a lot (3 times as much as steel) just to be effective. And glass scrim (the mesh used in GFRC) doesn't have a lot of glass in it compared to the amount of steel necessary for conventional concrete. It all comes down to cost and practicality. You'd be spending a lot of time and money using a lot of glass fiber just to equal the strength and, more importantly, the stiffness of inexpensive steel ladder wire.
GFRC can use glass fiber and scrim because its properties are different from conventional concrete. GFRC has a huge amount of chopped glass fiber mixed into it, which makes the bulk material have a very high bending and tensile strength. Thus, it is less brittle and thus can tolerate a lot more bending without cracking. So a more stretchy form of reinforcing (ie fiberglass scrim) can be used in GFRC with great success. It cannot be used in conventional concrete with success.
What are the non conventional properties of the GFRC that makes it less brittle? Is it the plasticizer or the added acrylics or is it something more like the pozzolans and fume?
I feel like I may have burned myself out with taking standard cement and sand throwing in chopped ar glass with scrim with plasticizer and acrylic and called it GFRC, but is it really a GFRC? Will you guys ever be in New York?
RubbinRobbin Mainly, the extremely high volume of glass fibers. It is also very important to place the fibers in thin layers and compaction roll them to align them 2-dimensionally rather than randomly 3-dimensionally. The free online seminars at www.concretecountertopinstitute.com/modules/info/gfrc_training.html#seminars explain in detail.
The Concrete Countertop Institute Also, Robbin, we have students from all over the world travel to our training facility in Raleigh, NC. The next class, we have students coming from Ireland, Guatemala and Australia. You can drive down from NY! Our next GFRC class is March 13-14, 2015. Details are here: www.concretecountertopinstitute.com/modules/info/gfrc_for_pros.html
The Concrete Countertop Institute omg, thank you for this and combing the fibers makes so much sense.. I don't know if I can afford both the class and the trip but thank you so much for all the info you have shared. I wish you and you're loved ones the best with much success and reward!
for the first time ever somebody explained to me the principles of beam in such a simple way, I have zero experience in civil eng., just an ordinary diyer .so if i place those ladder wires 1/2 inch from the bottom and another 1/2 inch from the top wouldnt that be stronger than using just a single reinforcement, assuming i am making a 2 inch countertop.
You need reinforcement only where there are tensile forces. In the case of a typical countertop supported on 2 ends, this is only the bottom. That's like the 2x4 with the Simpsons walking over it. If you have a cantilever (like the cow on the diving board), that's when you need reinforcing on the top. You also put reinforcing on the bottom in this situation because part of the countertop will also be supported on 2 ends.
I learned bugger all, because there was no audio! I wish there was, as it seems like a good video...
Oh no! The audio definitely works - please try viewing the video in a different web browser.
It seems like its only on one channel
Hello - would 1/4"-20 fully threaded zinc plated steel rod be too thick or unsuitable for a 1.5" thick concrete countertop? My sink cutout leaves the counter only about 3" to 4" wide infront and behind the sink. My first attempt cracked but had no reinforcement! Thanks for explaining tensile strength.
That size is fine, it's not too big. While steel threaded rod generally does have good strength, often small diameter common grades are made from steel that has a tensile strength lower than block masonry ladder wire. The simple solution is to use two pieces instead of one to ensure plenty of strength.
I have two major disagreements with the info in this video.
1. If concrete slabs on grade depend completely on the graded material for support why provide rebar reinforcement?
2. Why would I bridge the long axis of a countertop when I have immediately available contact points along the forward and rearward edges?
Some of the information provided is correct. However, the embellished indication of danger of using chicken wire in a countertop seems a bit overblown. What's going to happen? Is my countertop going to suddenly explode into dangerous shards of concrete when I set a cast iron pan on it? Come on. It's a fetching countertop. Yeah, if you're in business making concrete counters and they are continuously cracking, that's a problem but not a danger (except during installation, I guess).
Rebar in a floor slab is there as secondary reinforcement - not primary. This means it's there to help control cracking from shrinkage. Essentially the wire keeps the big chunks of concrete together after it cracks, it's not there to prevent the cracks in the first place. In heavy load applications (warehouses with heavy trucks, etc), the rebar in a floor slab is there to help spread the load and prevent punching failure.
Moving a beam around your shop, on a truck, into the house, etc. stresses it far more than after it's installed, because any mishandling that occurs likely will result in cracks. The main job of reinforcing is to prevent an expensive piece of concrete(expensive because of time, labor, materials, etc.) from breaking because of handling. Also, not everything made out of concrete becomes a countertop well supported by cabinets, and not all parts of a cabinet necessarily provide adequate support.
Chicken wire is too small and weak to provide the necessary tensile strength to make a beam strong enough for handling. The steel chosen for reinforcing is responsible for all the tensile reinforcement in a beam. It's best to choose strong steel and to be better safe than sorry.
The part about reo placement was well explained.
I wish my civil engineering professors explained it as well as this!
Everybody is so grateful like he's brilliant or something but no body is driving a car on ur countertop. Its just got to hold it's own weight. It's not that complicated ! I've made these countertops & put no supporting into them & still no cracks. It seems like he's selling something... I don't get it. The only info I got from this tutorial is about the overhanging outside bar top. Ur a good speaker but the info is just overkill.
You're right, usually it's not complicated and your countertop is not going to be under much stress, certainly not once it's installed. Flipping it out of the mold and transporting it to installation will usually incur the biggest stresses your countertop will ever experience. However, it is still important to understand the general principles for the cases when you do push the limits, for example with a very long, thin slab. And it's better to be safe than sorry.
Buy a bag of concrete and get started. A birdbath, or slab for a dog house is a good start. Mess it up and you still have a perfectly serviceable birdbath or dog house. If you don't like it, try again. In a week or 2 you should know if it is right for you. Wear a dust mask when working with dry, lift cement (dry and wet) carefully (it gets heavy fast) and do not mix with your hands and there is not much that can go wrong. Most of the materials are inexpensive.
you should know right? Then why are you asking...
this informed my left ear very well!!!
Thank U Professor....Really enjoyed this session...Thx. again from an old ME.
You are very welcome Jerome. Thank you for the kind words!
But glass fibers mixed into the concrete mix is a random orientation- not a longitudinal orientation. Arent you contradicting yourself here, sorry if this is a stupid question
You are absolutely right. If you just dump AR glass fibers into a GFRC mix, they will be randomly oriented. This is why commercial GFRC plants use powerful sprayers to spray the fibers into a flat plane, and concrete countertop artisans hand place and compaction roll the fibers when they want to ensure maximum strength. Many artisans use the "direct casting" or "SCC" method of GFRC, which does not properly orient the fibers, but they should be aware of the risks and use that only when they don't need high flexural strengths. See this article: concretecountertopinstitute.com/free-training/scc-backer-mix-for-gfrc-concrete-countertops-be-aware-of-fiber-realignment/
I work closely with a number of psychologists. I know exactly what he's doing.
And, believe it or not, he has irritated you. Only you won't admit it.
finally a video that actually explains something. can i use thinset with fiberglass cloth? is it a necessity to have a thickness of 1.5 to 2 inch thickness?
Fiber glass mesh vs wire mesh vs fiber
Which is the best and why. I understand fiber glass is the easiest which will give you the best strength? Should you use 3/4" plywood as a backer? What is the best way to strengthen the thin strip in front and behind the sink people are always sitting there..
So long story short use masonry remesh wire, 9 gauge? Run it longitudinal and latitudinal, how do you tie it in together? Weld?
If you make a 2" slab can you use regular 3/8" rebar? Or still too thick?
very helpful!!
Wonderful. Clear and to the point.
Easy to understand teaching that applies to a wide range of applications.
Keep it up.
+kbaxter777 Thanks for the compliment! Please note that there are several other free training presentations available at www.concretecountertopinstitute.com/class-schedule/#Webinars.
Since ladderwire bends like straw, you'd think you'd be better off loading up some corrugated steel sheet with fiber reinforced cement.
But, apparently it doesn't need all that. I wonder why.
Reinforcing doesn't work because the rebar is stiff and difficult to bend. Instead, reinforcing (whether it's rebar, ladder wire or prestressing cable) is part of a structural composite, where the concrete is (generally) in pure compression, and the embedded reinforcing acts in pure tension. The reinforcing is resisting pure tension, exactly like a rope. A rope can be flexible and bend easily, but it will still resist tension in a game of tug of war.
@@TheConcreteCountertopInstitute ah, yes! Prevent the substance from pulling apart and you've got a great deal more rigidity!
Like you said, the bottom side, if strung like a beam, would try and pull apart! Put some tension in it, by rods acting like ropes, and presto! No more pulling apart. Much more rigid as a result.
Thank you!
I'm using Quickrete Countertop Mix to lay down a 2 inch thick flooring... the downstairs has been INCREDIBLY reinforced. Able to carry an extra 10,000 pounds.
I like the idea of making such thin concrete into a beam. Therefore, I'm employing all countertop techniques.
@@russchadwell You got it!
What would you recommend for someone who is obsessed with learning this stuff, but has no experience in concrete, or construction, nor has the money to spend on a seminar or workshop, but wants to do this as a profession?
how does basalt fiber reinforcement compare to gfrc? also what about a carbon or fiberglass mesh instead of ladder wire?
great video, thanks for sharing!
err..... to piss you off?
VERY VERY HELPFUL VIDEO THNX A MILLION FOR THIS....GREAT JOB.....EXPECTING MORE VIDEOS......
in conclusion, with concrete particularly, we have so much flexibility and it will tolerate lots of flex, especially when you try to realise your designs. however, there are some basic building block engineering tenets that this man puts back in your mind. concrete is seriously underexploited, but then so are most plant fibres too.
Need HD videos
what is the process of making concrete ? Can you explain that with your primary sources please ?
I cant find Forton® VF-774 in India can you give alternate
Possible alternatives are Polyplex by Nippon Electric Glass and Polycure FT by Fibre Technologies International.
Very educational video! It's one thing to say what to do, but this says why. Thanks for putting this together.
Very interesting, and sound engineering principles applicable anywhere and everywhere.
I got no sound
Thank you!!!!! Excellent information!!
You are very welcome Sandra!
Really wonderful video. Easy to understand and apply. Great pictures to go along with your wording. So happy I found this.
Years late but... I want to make a cantilevered concrete coffee table. Ho wdo I make sure it can support itself?
Usually the issue with small cantilevers is tilting, not cracking of the concrete. The biggest risk is that the whole structure could tilt and fall over. So it's the supporting base that's important. This is the same issue with any type of table top - wood, glass, granite, etc. If you have a photo of a table you are inspired by, you should be able to simply copy the configuration of the base.
@@TheConcreteCountertopInstitute Unfortunately, the design came from my head. The concrete upper will be 2'x4' and I want it to be thin... like an inch or less. So far, I'm thinking clear epoxy blocks supporting the middle, over the wood portion.... but I'd like to go with an unsupported look. I was thinking of some non-expensive way to do that. :(
@@SyddlesFuzz I'd have to do a consulting project for a detailed design, which wouldn't be non-expensive. :-)
Nice vid! You should also add basalt to your reinforcing fix.
What is the best way to avoid the ghosting? You mention in your blog that pouring over reinforcement and placing reinforcement after pouring both can cause ghosting...as well as vibration...so what is your best recommendation on how to avoid this? Finally if it is pouring over the reinforcement, how do you suspend the ladder wire? Thanks Jeffrey!
Please see this article about ghosting: www.concretecountertopinstitute.com/blog/2012/10/how-to-avoid-ghostlymistakes-in-your-concrete-countertops/
probably could do with a new HD version but the content is essentially very good. only real problem is, you show us what NOT to do when it comes to reinforcing concrete countertops. you don't show us what to do!!!!!!!
couple of images showing correct reinforcement approaches for different countertops would do. even just providing links to them
It's important to understand the general principles of reinforcing and avoid the pitfalls that come from not having that understanding, but yes, knowing what TO do is as important as knowing what NOT TO do. Basically, the to-do is to put the reinforcing near the bottom. For typical countertop thicknesses, use 9-gauge masonry block ladder wire. How many strands to place depends on the geometry of the countertop, but generally placing them a couple of inches apart is adequate for most situations.
You're very welcome!
Jeff,
you said in this video that reinforcement that runs across the narrow width of the countertop is poor practice. I would expect that once in-service the 2' direction of the countertop is the span that see flexural load. Therefore, I would think that reinforcing is important in both directions: lengthwise is important for transport loads, while reinforcing across the narrow width is important for in-service loads. Do you Agree?
Shawn, you are correct. The need for reinforcing is greatest when you are lifting and moving slabs in your shop and during installation. Once installed, the width of the cabinet is the greatest span that the countertop will experience. Many cabinets are 30" or 36" wide and 24" deep.
Additionally, the front edge of a cabinet is "soft", meaning the front opening isn't rigid like the side walls because of door and drawer openings, and because the front of the cabinet doesn't extend all the way down to the floor like the side walls do.
So yes, you should reinforce in both directions, although the short direction is less critical. While I don't mention this in the video in order to simplify the concepts, reinforcing in both directions is included in the step by step instructions in my textbooks.
Very good question, thank you!
great help! this vid answered many Q's i had about reinforcement. now i can embark on my 1st DIY project! thank you!
That's great Stephen! Keep in mind, I do also have the Level 1 Getting Started Self-Study program. Check that out here: www.concretecountertopinstitute.com/modules/info/self-study_training.html#GetStarted.
There is also a free 3-hour seminar here: concretecounter.infusionsoft.com/app/page/diy-concrete-countertops-free-training.