You mentioned you’d be putting out a video on the technical level regarding vibration. Vibrating tables for pavers, loading of tables, force requirements, newton, frequency etc.
I like to make saw cuts at inside corners. I hope to see more basalt or fiberglass rebar in slabs, along with emphasis on compaction and curing for longevity. Concrete should last hundreds of years. My question is what can be used for tie wraps, that will not be subject to expansive oxidation.
YES! Fiberglass or basalt beat steel rebar in every way for a slab. 1) light weight / ease of placement 2) much higher elastic strain 3) no worries about corrosion / minimum cover.
Why do you recommend specifically two rebar at reentrant corners? I usually only see one, but is there any advantage to two bars instead of one larger bar?
Professor, I think you math is somewhat off: 2% of 3m (300 cm) would be a 6 cm slope, not 12.5mm or 1.25cm. Or in imperial: 0.2 feet (2 13⁄32 inches). What you are proposing is more like 0.4%
thank you for mentioning sloping the concrete away from the building. so many just do flat walkways etc and it causes water to run back into the building causing a lot of problems. you also have to keep in mind that many walkways/driveways end up being overland paths for storm water in big rain.
Putting in a grain bin, and have been researching/building the foundation to death. It's amazing how little reinforcement some people will put in. I settled on a 3x3 grid of #4 for the footing, which is going to be 2' wide, and 15.5" below grade on average (shooting for 12" below grade on low side as there is a slight slope), and 24" above grade. The interior "pad" or slab will be 8" thick, #4 rebar 12" OC. 16" of 3/4 in. roadstone for fill of the pad area, interior form for backfill to hold it in place and achieve a 90 degree angle, and will be moistened and plate compacted. Person I talked to for my diameter bin recommended a 2x3 grid for footing, and 24"OC for slab, so hopefully, I overengineered it enough. Also adding verticals to support the footing grid, and perpendicular cross pieces of rebar between for each set of 3 rings @ 12" OC. For a 21' bin(which is also the center of the footing), I'll use a little shy of 2000 lbs. of rebar. Hopefully its enough. :D
Curious about the 'chairs'. No doubt they are left in the pour ,but do they too not cause problems like the re-entrant corners ? I would think we end up with stress points there ?? Does the concrete naturally stick to them ? Can you suggest specific macro fiber products ?
I think he is just discussing non structural slabs here, like residential neighborhood areas. Typically reinforcement for crack width control (WWM or rebar keeps cracks tight and small) when in the upper 1/3 and at least an inch cover. Imagine a piece of drywall 4'x8' two people Hold it level and you place a 40 lbs weight in the middle. The sheet will bend down. The top is compressed and the bottom is flexing bending and starting to crack. To control cracks upper third (most contractor literature say in the middle so it's at least chaired cause that's better than on the ground). Reinforcement at the bottom 1/3 we are concerned more structurally. Also structural in nature can be load transfer from slab to slab where we use dowels. Sometimes we put rebar in the bottom and the top of a slab or rebar bottom WWM at the top. Take the time to design your slabs properly and consider all loading cases, even edge cases, for proper reinforcement.
I think the main disadvantage would be that it would make the forms more complicated. Or it might just not be the shape that most projects require, I’m guessing that by the time you made the curve big enough to help it would change the geometry too much.
Thanks for your reply. While rounding corners is not viable on commerical projects, I found it handy on small pours with last minute unplaned "adjustments" to actual layout. The extra rebar at the corners is now in the bag for the future. Thank you again for expanding my horizons.
Where do steel fibres like Helix or Dramix fit into this? Are they treated the same as the macrosynthetic fibres or are they not as good or perhaps better?
Tyler, I am curious as how you found success in getting a residential/commercial building slab redesigned to replace rebar with the correct type/dosage of fiber. I hear this conversation frequently with fiber suppliers so curious about your success.
They sell the wire mesh, or as I've always called it, welded wire fabric, with deformed wire as well. I can get it in a 6x6 grid with 3/16 wire thickness here in NC, in sheets of 5x10 or 5x20. This saves more vertical space than #3 rebar would. If I used rebar in my composite deck slab, that would push the hydronic lines uncomfortably close to the slab surface --counting the deck with its corrugations in a 4" overall slab thickness. WWF is also more convenient if you're going to run hydronic lines. There are more anchorage points than an equivalent grid of rebar. One time I had set the beams too high resulting in a vertical distance to the screed edge of about 3.5". The concrete guy came and poured and floated. But when it came time to trowel, he gave me the option: He could either power trowel and risk pulling up a hydronic line, or he could stop there. I had him stop. Now I have a rather "rustic" floor. One problem with the wire mesh though: If you lap them the way code wants, then the lapped corner intersection of four sheets is going to stack 8 wire thicknesses high. 8 x 3/16 = 1.5" in my case. So I cheat and cut out some of the wire forming the stack. Update: Man, never commit to buying WWF without seeing it first. Retailers typically stack it outside for years until it sells. My most recent batch has rust just short of pitting. I thought about returning it, but the particular slab I'm doing won't be exposed to the elements, else I'd worry about eventual spalling.
Please make a presentation about upper floor concrete slabs (not ground floor because you've covered these). How to prevent or at least minimize cracking. A new building near me that I'm aware of has diagonal cracks along all the corners of the second floor slab.
Do you have a video about or would you comment on this new "dry pour" trend I have seen popping up on TH-cam lately? Where they just dump dry premixed concrete into a form, then mist it on top. I can see several downsides, but If it is in a temperate climate with no freezing temps would this be a reliable method in certain situations?
What if the hole is not squared but round. How do you reinforce a circular void within the slab (e.g. for a circular column, or other circular feature in the slab).?
It depends on the fiber. Most fiber is polymer, which softens, melts, and can produce gases. These are less fire resistant. Other fibers are made from more stable materials, even steel fibers, which would be similar to rebar.
Spalling is a major problem in our area. (Buffalo, NY) driveway contractor blamed it primarily on bad aggregate. Even more than salt. I picture the bad aggregate deteriorating, swelling, and popping off the thin cement above it Comments?
Why is the rebar/remesh in the middle or upper third of a slab? In a beam the tensile stress is at the bottom, unless its cantilevered, so it seems sensible that the rebar should be in the bottom third of a slab when thinking of the tensile stress being greatest at the bottom surface. Also, consecrators commonly 'cut' the upper third of the slab, wouldn't this cut hit rebar then?
I have been in the slab business for years and as of late I see fiberglass rebars.........I picked up a single piece and instantly put it down like it was a cursed item........I could never see myself using it for any purpose........can you tell me why this was even Invented
@charlesw3120 ........it just feels wrong in the hands ...........like a child's playset piece..........it will take me some getting used to........if the real stuff ever gets out of reach that is......
That is what I thought. Place rebar in the bottom 1/3 rd. We walk/drive & load on top, that is compression. The bottom is bowed/stretched, therefore tension. The tables in the picture looked like bottom 1/3rd. I am not a concrete contractor but I like Tyler's videos. :-)
I absolutely hate wire mesh. I have never seen it end up anywhere other than the bottom third of the mat, and over fifty percent in direct contact with the soil. If the mesh is supported enough that it isn’t going to be stomped into the bottom of the slab, it is more efficient to install rebar on chairs. And if you design the rebar installation at the upper third point, it is very hard for the workers to stomp it down past the mid point.
Since when is a 1/2" drop over 10' a 2% slope? Is math different in Oklahoma? 1/2" = 0.5" 10' = 120" 0.5 ÷ 120 = 0.00417 Or less than 1/2% slope. For a 2% slope we use 1" per 4'. Granted 1" per 50" would be exactly 2%. But 1" per 4' is 1" per 48" which is really close. Another example is a 4' wide sidewalk. Set up one form and inch higher than the other and you're there.
Do you really think you can teach amateurs in a eight minute video what takes us professionals years to learn? Concrete is demanding. Everything about it has to be done just right because you only get one shot at it. Can you teach these guys the codes that pertain to everything concrete? Can you tell them how to put an acceptable finish on a piece of concrete? Can you teach them how to pour and finish a quality piece of concrete? You can't can you. What a joke.
You are right that it takes years to really learn all of this stuff but don't you think he is just giving information not full education? The dude is like a legit professor. Sounds like a summary more than a detailed education.
So by that account, should we teach anyone about physics since it takes decades to become a good physicist? Should we teach history? Heck should we even teach languages? Why do anything, or even get up in the morning since doing anything well takes a lot of time? I'll answer that for you: yes, we should. Specialization is for insects.
The answer is yes it can be done. I can do many things with concrete from just watching videos like this one and getting my hands dirty. You have to remember someone may have took to the time with you by holding your hand and teaching you all the ins and out that you pretend to have. All of us do not have that privilege, but thank you for reminding us that we are doing the impossible… It makes feel all rosie inside….
@@evanking6329 The fact that you say it can be done and done right proves you know nothing about concrete. I did it for four yrs before I got my license. Even then I would have given myself maybe a C+ grade. For everything you think you know there are 100 things you should know but won't. You have o know about concrete and it's values You have to know ahead of time what problems, and there many, that might happen and how to prevent them. Concrete is unforgiving and sometimes difficult to get right even for the experienced.
Please help out… when you say the rebar goes in the center or the slab, is that not the zero for bending moment in tension and compression? So if a load is applied to the slab, would this rebar serve any purpose than for cracking?
Dear Tyler, you're so great. I wish I was young and you could be my teacher, then I could finish as the God of concrete.🤪
Control joints off those corners, great point w the 2 rebar, done that b4
What a valuable video! Thank you for the information. "Rock On"
Have to get one of those shirts!!!!
Hello dr ley, please make a video about your favourite books on reinforced concrete design. Thanks
Superb sir, I learn a lot from your presentation. Thank you.
Love your videos! Thanks for the incredible info! 🙏
Woohoo! Another awesome video. Who knew learning about concrete could be so fun.
Thank you answering my questions on corners!
Facts
Informative video. Viewers should know the slope calculation near the end is wrong, as as others have pointed out.
You mentioned you’d be putting out a video on the technical level regarding vibration. Vibrating tables for pavers, loading of tables, force requirements, newton, frequency etc.
I like to make saw cuts at inside corners. I hope to see more basalt or fiberglass rebar in slabs, along with emphasis on compaction and curing for longevity. Concrete should last hundreds of years.
My question is what can be used for tie wraps, that will not be subject to expansive oxidation.
YES! Fiberglass or basalt beat steel rebar in every way for a slab.
1) light weight / ease of placement
2) much higher elastic strain
3) no worries about corrosion / minimum cover.
Why do you recommend specifically two rebar at reentrant corners? I usually only see one, but is there any advantage to two bars instead of one larger bar?
Would love to know about this too.
Thank you for your inspiring video. I was wondering how to solve the shrinkage problem of the 3D printed concrete since there is no coarse aggregate.
Professor, I think you math is somewhat off: 2% of 3m (300 cm) would be a 6 cm slope, not 12.5mm or 1.25cm. Or in imperial: 0.2 feet (2 13⁄32 inches). What you are proposing is more like 0.4%
Great information!
Thanks!
Hi from Türkiye. Thanks for the videos :)
thank you for mentioning sloping the concrete away from the building. so many just do flat walkways etc and it causes water to run back into the building causing a lot of problems. you also have to keep in mind that many walkways/driveways end up being overland paths for storm water in big rain.
Not only sloping away, but it should be lower than the floor of building it abuts because of that as well.
Do macro fibers present a problem of wicking in surface moisture?
Putting in a grain bin, and have been researching/building the foundation to death. It's amazing how little reinforcement some people will put in. I settled on a 3x3 grid of #4 for the footing, which is going to be 2' wide, and 15.5" below grade on average (shooting for 12" below grade on low side as there is a slight slope), and 24" above grade. The interior "pad" or slab will be 8" thick, #4 rebar 12" OC. 16" of 3/4 in. roadstone for fill of the pad area, interior form for backfill to hold it in place and achieve a 90 degree angle, and will be moistened and plate compacted. Person I talked to for my diameter bin recommended a 2x3 grid for footing, and 24"OC for slab, so hopefully, I overengineered it enough. Also adding verticals to support the footing grid, and perpendicular cross pieces of rebar between for each set of 3 rings @ 12" OC. For a 21' bin(which is also the center of the footing), I'll use a little shy of 2000 lbs. of rebar. Hopefully its enough. :D
To make it even gooder, I would have considered 1 loop of post tension reinforcement, and saved half of the rebar.
Keep up!
Do you have any vid on graphene in concrete
Curious about the 'chairs'. No doubt they are left in the pour ,but do they too not cause problems like the re-entrant corners ? I would think we end up with stress points there ?? Does the concrete naturally stick to them ? Can you suggest specific macro fiber products ?
At 1:28 would it still be UPPER third and not lower third, if the slab is a concrete pad for a heavy load??
I think he is just discussing non structural slabs here, like residential neighborhood areas. Typically reinforcement for crack width control (WWM or rebar keeps cracks tight and small) when in the upper 1/3 and at least an inch cover.
Imagine a piece of drywall 4'x8' two people Hold it level and you place a 40 lbs weight in the middle. The sheet will bend down. The top is compressed and the bottom is flexing bending and starting to crack.
To control cracks upper third (most contractor literature say in the middle so it's at least chaired cause that's better than on the ground).
Reinforcement at the bottom 1/3 we are concerned more structurally.
Also structural in nature can be load transfer from slab to slab where we use dowels.
Sometimes we put rebar in the bottom and the top of a slab or rebar bottom WWM at the top. Take the time to design your slabs properly and consider all loading cases, even edge cases, for proper reinforcement.
Can you able to make p-m intraction curve for t-shaped ? ..
What about rounding the interior corners to break up the stress concentration in placeof extra rebar?
I think the main disadvantage would be that it would make the forms more complicated. Or it might just not be the shape that most projects require, I’m guessing that by the time you made the curve big enough to help it would change the geometry too much.
Thanks for your reply. While rounding corners is not viable on commerical projects, I found it handy on small pours with last minute unplaned "adjustments" to actual layout. The extra rebar at the corners is now in the bag for the future. Thank you again for expanding my horizons.
Where do steel fibres like Helix or Dramix fit into this? Are they treated the same as the macrosynthetic fibres or are they not as good or perhaps better?
Soo what if I have cracks that I wish to prevent from worsening? Can they be sealed? Thank you for all the great videos!
I’d like some comment on using galvanised rebar
Nice Videos
Tyler,
I am curious as how you found success in getting a residential/commercial building slab redesigned to replace rebar with the correct type/dosage of fiber. I hear this conversation frequently with fiber suppliers so curious about your success.
2% slope on 3 m long side is rather 6 cm than 12,5 mm (like it was shown) - am I wrong?!
2%*3000=60mm
They sell the wire mesh, or as I've always called it, welded wire fabric, with deformed wire as well. I can get it in a 6x6 grid with 3/16 wire thickness here in NC, in sheets of 5x10 or 5x20. This saves more vertical space than #3 rebar would. If I used rebar in my composite deck slab, that would push the hydronic lines uncomfortably close to the slab surface --counting the deck with its corrugations in a 4" overall slab thickness. WWF is also more convenient if you're going to run hydronic lines. There are more anchorage points than an equivalent grid of rebar.
One time I had set the beams too high resulting in a vertical distance to the screed edge of about 3.5". The concrete guy came and poured and floated. But when it came time to trowel, he gave me the option: He could either power trowel and risk pulling up a hydronic line, or he could stop there. I had him stop. Now I have a rather "rustic" floor.
One problem with the wire mesh though: If you lap them the way code wants, then the lapped corner intersection of four sheets is going to stack 8 wire thicknesses high. 8 x 3/16 = 1.5" in my case. So I cheat and cut out some of the wire forming the stack.
Update: Man, never commit to buying WWF without seeing it first. Retailers typically stack it outside for years until it sells. My most recent batch has rust just short of pitting. I thought about returning it, but the particular slab I'm doing won't be exposed to the elements, else I'd worry about eventual spalling.
Self-healing concrete (SHC) is the way to go. My great great grandfather swears by it.
Mr. Tyler, can you give us tips about concrete terrazzo slabs ? What should we pay attention to pour slabs like 2-2.5cm thick
What about fibreglass rebar?
Please make a presentation about upper floor concrete slabs (not ground floor because you've covered these). How to prevent or at least minimize cracking. A new building near me that I'm aware of has diagonal cracks along all the corners of the second floor slab.
A half inch on 120 inches is just over 0.4% slope.
I was thinking the same. Should be 3000mm/50=60 mm height difference for the slope.
Easy rule is 1" per 4'
I kept repeating my calculations saying that I must have done something wrong 😂.
Do you have a video about or would you comment on this new "dry pour" trend I have seen popping up on TH-cam lately? Where they just dump dry premixed concrete into a form, then mist it on top. I can see several downsides, but If it is in a temperate climate with no freezing temps would this be a reliable method in certain situations?
How to avoid the cracks as attached in the photos
What if the hole is not squared but round. How do you reinforce a circular void within the slab (e.g. for a circular column, or other circular feature in the slab).?
What's your opinion on asbestos fiber? Do you know any way for it to be safely used in field situations and no just precast?
How can I share the actual site images?
Also, how about a round hole when possible- like for a sump pump. No corners, no stress concentration.
Is fiber reinforced concrete more fire resistant than rebar?
It depends on the fiber. Most fiber is polymer, which softens, melts, and can produce gases. These are less fire resistant. Other fibers are made from more stable materials, even steel fibers, which would be similar to rebar.
@@charlesw3120 I used fiberglass for this very reason in the concrete firepit I made alone with refractory bricks in the inside.
Spalling is a major problem in our area. (Buffalo, NY) driveway contractor blamed it primarily on bad aggregate. Even more than salt. I picture the bad aggregate deteriorating, swelling, and popping off the thin cement above it
Comments?
Why is the rebar/remesh in the middle or upper third of a slab? In a beam the tensile stress is at the bottom, unless its cantilevered, so it seems sensible that the rebar should be in the bottom third of a slab when thinking of the tensile stress being greatest at the bottom surface. Also, consecrators commonly 'cut' the upper third of the slab, wouldn't this cut hit rebar then?
I met my first girlfriend on a concrete slab parking lot before seeing Concrete Blonde in concert.
Thank you, concrete!
I have been in the slab business for years and as of late I see fiberglass rebars.........I picked up a single piece and instantly put it down like it was a cursed item........I could never see myself using it for any purpose........can you tell me why this was even Invented
No corrosion. Lighter weight. Lower cost.
@charlesw3120 ........it just feels wrong in the hands ...........like a child's playset piece..........it will take me some getting used to........if the real stuff ever gets out of reach that is......
Bars in “Upper” part of slab? I thought lower parts?
You want to reinforce the tension side of the slab. If unknown, go with the middle.
That is what I thought. Place rebar in the bottom 1/3 rd. We walk/drive & load on top, that is compression. The bottom is bowed/stretched, therefore tension. The tables in the picture looked like bottom 1/3rd. I am not a concrete contractor but I like Tyler's videos. :-)
ACI code is .03% of cross section area should be steel .. Minimum I recall.
Fiber is the ticket.
But can hamper finish operation.
Nice. This might actually be of use to someone. Rock on
I absolutely hate wire mesh. I have never seen it end up anywhere other than the bottom third of the mat, and over fifty percent in direct contact with the soil. If the mesh is supported enough that it isn’t going to be stomped into the bottom of the slab, it is more efficient to install rebar on chairs. And if you design the rebar installation at the upper third point, it is very hard for the workers to stomp it down past the mid point.
Yoda has spoken.
2% = 1/4 in per foot when grading away from structure
Since when is a 1/2" drop over 10' a 2% slope?
Is math different in Oklahoma?
1/2" = 0.5"
10' = 120"
0.5 ÷ 120 = 0.00417
Or less than 1/2% slope.
For a 2% slope we use 1" per 4'.
Granted 1" per 50" would be exactly 2%.
But 1" per 4' is 1" per 48" which is really close.
Another example is a 4' wide sidewalk. Set up one form and inch higher than the other and you're there.
2%*3000mm=60mm
It's 4.167%
Hello freaks and maniacs ✌🖐
Do you really think you can teach amateurs in a eight minute video what takes us professionals years to learn? Concrete is demanding. Everything about it has to be done just right because you only get one shot at it. Can you teach these guys the codes that pertain to everything concrete? Can you tell them how to put an acceptable finish on a piece of concrete? Can you teach them how to pour and finish a quality piece of concrete? You can't can you. What a joke.
You are right that it takes years to really learn all of this stuff but don't you think he is just giving information not full education? The dude is like a legit professor. Sounds like a summary more than a detailed education.
So by that account, should we teach anyone about physics since it takes decades to become a good physicist? Should we teach history? Heck should we even teach languages? Why do anything, or even get up in the morning since doing anything well takes a lot of time?
I'll answer that for you: yes, we should. Specialization is for insects.
The answer is yes it can be done. I can do many things with concrete from just watching videos like this one and getting my hands dirty. You have to remember someone may have took to the time with you by holding your hand and teaching you all the ins and out that you pretend to have. All of us do not have that privilege, but thank you for reminding us that we are doing the impossible… It makes feel all rosie inside….
@@evanking6329 The fact that you say it can be done and done right proves you know nothing about concrete. I did it for four yrs before I got my license. Even then I would have given myself maybe a C+ grade. For everything you think you know there are 100 things you should know but won't. You have o know about concrete and it's values You have to know ahead of time what problems, and there many, that might happen and how to prevent them. Concrete is unforgiving and sometimes difficult to get right even for the experienced.
@@garyolsen3409 yes, you are correct I know nothing. Cheers!
Please help out… when you say the rebar goes in the center or the slab, is that not the zero for bending moment in tension and compression? So if a load is applied to the slab, would this rebar serve any purpose than for cracking?
less water equals?... does shotcrete equate to stronger concrete?...