Top 10 Myths in Concrete Construction
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- เผยแพร่เมื่อ 24 ก.พ. 2015
- Get a candid look at ten popular, but mistaken ideas that still exist in concrete construction. Using examples, interviews, and demonstrations, this revealing video from the Portland Cement Association exposes and explains the most common misconceptions associated with the cement and concrete industry. The video is designed as an educational training tool for workers of all experience levels. Running time: 17 minutes © 2005 Portland Cement Association
- วิทยาศาสตร์และเทคโนโลยี
Reminds me of the training videos that the military and civilian servants are subjected to. Usually after lunch and in a darkened room. It's almost like an experiment to see what percentage of the class can remain awake!
Mark Jones and sitting next to some guy with horrible BO. Lol
This is by far the best top 10 myths in concrete construction I have seen to date
Unfortunately, trying to educate some people in the industry is like beating your head on concrete.
Stop trying to sound special. Every and any job needs knowledge and training. Ur just another slave like everyone else
th-cam.com/video/4lbI-cBhkm8/w-d-xo.html
Great and informative video, thank you for the hard work!
Very helpful info , not many people remember to check that agregit is smaller than one 1/5 the thinnest part of concrete
Must see video for anyone involved in the concrete industry. Thanks PCA.
6:00- BELIEVE ME.. the terms "over finishing and premature finishing" haunt ALL of us.. not only concrete finishers. :(
not sure about "over finishing" there champ :D
The acting though, perfect
This all makes alot sense now ive been a groundworker for about 3 years and still learn and understand new things everyday about the most basic of things like the concreet itself
very informative. thank you!
Great viedo!!!!!!!
as a concrete amateur, I learned an aufull lot!!!!!
smash that thumbs up button if you looooove concrete
hahahaha
I attended a concert school in Texas years ago , 50 some , things have changed I know, this video was a great refresher . I was taught on the job , boy was I shocked to learn a lot of it was incorrect . Worked mostly on federal jobs under precise specs , some in earth quake zones 5 , both of these are quite a different horse of a different color . Remember, different place different rules.
That was very informative.... thank you!
14:56 Seems this video is 16 minutes longer then needed.
I had to go into settings and watch it at 1.5X speed. I still nodded off.
I liked that almost all of the myths had a practical, counter recommendation in the body of the video. Also came a way with a greater respect for concrete application.
MrNateSPF has
thanks
I just put this on for my toddler's nap time, worked a treat! Thanks uploader.
LutonMassif don't be surprised if he/she wants to go into the construction industry when they get older
I recommend creating a video addressing concrete construction under hot weather conditions.
yeah try pourin 400 yards on a hard trial finsh on a 90 puls degree day god lord
Night pour
Been there done that , it's brutal
Very good information
Another myth they forgot: Concrete contractors make great actors!
@Colby Erik What the fuck has that got to do with concrete?
I found it finally, 4.30 myth 3, that’s which I wanted to know, thanks a lot...
Length of time is perfect. Great edu
VERY informative video thanks
What a coincidence, was watching this video and some comments, then noticed the #1 Michael Fazio had left a comment! Have a nice day
So Much to learn about the art of Concrete application
Based on our experiences the rebars must be at least 1/2 inch near the surface of the concrete bottom facing the soil and facing upwards in the op surface for any slab foundation. Preferably we require to create a monolithic floating foundation to play it safe, especially for military installations.
Old video but still very true today. The only problem I have is not added water. In a state were it is super hot almost everyday of the year, adding water is sometimes the only thing you can do.
yup i agree and for that reason if the job required 3000 psi i ordered 3500 psi
Half Star Films I live in Nevada, so I know what you're talking about. Back when I was running a triple trowel on a pour one day, the wind was already kicking in by 4:00 am, by the end of the day & 38000 ft. they had figured out the wind was sucking 300 gl. an hr. out of the slab! Yea, a big part of it had to come back out.
Half Star Films If you lay the nylon under the concrete it will dry much slower and concrete be stronger .
The one thing I wish they would mention is the air en-training concrete using a air pot to find the percentage of air in concrete. This will go a lot to reducing the freeze thaw cycles that occur in colder climates that causes cracking in concrete.
It's good to have rules of thumb and calculated values but nothing beats experience!!!
Nice old computer at 1:20! Look at the old dot-matrix printer in the background -- we used to have an Okidata just like that in our house!
They are still an industry standard due to the fact that most batch tickets are 3 or 4 part copies, and the dot-matrix "punches" the print, thus transferring to the back copies.
Nice!
Thank you very much, now I am more afraid to do anything with concrete at all. If even adding a little bit of water is such a problem. You overcomplicated it for me. Around me are many guys who built houses without knowing too much.
I've been in concrete for 15 years went to school for it most off this really only applies to big commercial jobs where the specs of the concrete must meet certain requirements. If you are wanting to build a patio or anything that's not a house foundation or something load-bearing it doesn't really matter. Patios and sidewalk don't necessarily need rebar but i always use it. Fiber mesh in the mix is usually enough. You always want control joins it gives the concrete a place to crack (it always will crack) and it hides them. If the mud shows up dry or stiff and u don't live in Alaska or Arizona (somewhere with extreme temps) add some water. The 1gal/yd3 is a good guide. Little bits at a time so u don't add too much, no way to fix that. If it is hot when u pour wet the ground first. Super dry ground will suck the moisture out of the concrete and make it set premature and under-strength, we call it a flash or snap. For driveways always use rebar or wire mesh. 4' × 8' wire fence panels from home depot or whatever work great or it comes in 150' rolls from any construction supply place. When finishing u want to seal the concrete. Use a mag float to smooth highs and lows and fill the tiny holes in the surface. Don't over work the mud u don't have to fill every hole. Look at some concrete in ur area u'll see tiny holes those allow it to absorb water over time and gain strength. If u pour on a hot day its a good idea to use a cure spray when finished or it can crack all over the surface. If it's not 90° out u can skip the cure but the next day soak it with a hose or sprinkler like all day. Oh also for basic residential concrete I usually go for 4500 psi mix that's usually enough but if ur gonna park a tractor or something heavy on it use the highest bag mix they have and pour it 6" thick. And #4 bar on a 2' grid. Hope that helps sry its so long winded.
MYTHS
1.) Concrete only last 5-6 years.
2.) You need an aggregate like marbles.
3.) You can't add dyes.
4.) One hour of setting is too early to carve your initials.
5.) You have to wait for it to stop raining to start pouring.
6.) It's tricky to make full size sculptures.
7.) You need a wheel barrow or a hopper.
8.) O'Dell can't get it on.
9.) You have to have a screed or float.
10. You need water for the mix.
Lots of guys on youtube are doing quite a bit to keep some myths alive.
If i ever saw a finisher walk on a placement to determine when to finish, that would the last job of mine he ever worked on!
I have seen that crack a slab after curing.
You walk on it with the trowel machine anyway DUH
What is the correct way to tell if it is ready?
@@DigitalAwareness feel it with your fingers
Hm. They missed a big one. MYTH: Every load of concrete you get from a Ready Mix company will be a fresh load. FACT: Some Ready Mix companies sell 'old concrete' IE 'hot concrete' to make extra profit. The only way to make sure your local concrete service is selling fresh concrete is to spy on them and see if their trucks are always dumping any left over concrete from the previous delivery and washing out when back at the plant. IF you see trucks with their drums turning going into the plant, go straight into the fill area, then drive back out and head to a new delivery, there's a good chance they're selling old concrete. Selling old concrete is a detestable practice, because each load gets hotter and so hardens faster, leaving less time to work it. Plus more and more water must be added to keep it from hardening in the chute. It's gets crazy the longer the process is drawn out.
dkeith45 its called stacking loads a lot of company's do this on foundations
It probably wouldn't matter for footings, but flatwork? Sidewalks, driveways etc? I once had to deliver a load of concrete to a home-owner doing a sidewalk, late afternoon, with concrete so hot, I emptied my water tank into the load just to get it to come down the chute, and before half of it was unloaded, it started hardening in the chute. I had to dump the rest of the load on the poor saps lawn so my truck wouldn't be fucked up. And my boss expected that homeowner to pay for the whole load to, 0_o. That's how bad it can get. Most contractors that used us, because we were cheaper than all the other ready mix companies, would only order from us first thing in the morning to just past noon, because they knew there'd be less chance of getting old concrete in their loads, or if they did, it wouldn't be too hot to deal with. With the exception of a few who had large crews and NEVER got old concrete. Never ever. I imagine they had a talk with my boss at some time and told him they'd hurt him if he ever did that to them, lol.
There's a real art to the whole process. I wish all concrete people watched this because I see a lot of shoddy work in the some of these new developments.
larjerr No many good tradesman left .
They always joke and say “job security” why not make it good u know
New subscriber from Davenport Iowa
is it necessary to pour water in newly build pillars and concrete?temperature=26.5'c?what if not poured water on it?
LOL at the guy rodding full-depth through a cylinder that's 2/3's full.
Georgia DOT used to place slab repairs starting at midnight and have Interstate traffic back on it five hours later in metro Atlanta. Try doing that with your 4+ inch slump, you guys.
exelent vid.....wish you had covered salt exposure better.....and ferro-concrete cancer.....and a bit on pouring in extreme heat.
yes im an aussie....cement drying too fast is standard here....though big pours have it sorted.
Myth #11: Slump has any bearing at all whether concrete will pass strength tests or not. Yes, added water makes concrete less strong. Water reducer, (Plasticiser) some retardant to keep it from setting up too fast, and if you feel like working really fast, add some glenium. Added on site. Comes out like soup. No added water, it makes a dry 1-2 slump into about a 10 or 11. But... you got @ 30 minutes max before you'll start having problems if it's not in place.
This was just like the public information clips in the Simpson's!
Sadly, there are idiots in the concrete construction business that make these very mistakes and cause VERY expensive problems for the property owner later on. These same idiots give those folks in the business that ARE reputable a bad name.
They also sweater that they are correct and will argue that they know what they're doing. This video is old but still true today.
A Curry True story, there are so many that if it were not for the union couldn't even pass for a journeyman.
this is because ....and i quote...."i dont have to live there".....or "you cant see it from your place....dont worry".....tragic.
If i was sober I'd give a fuck.
Looks good from my house
do a video about Pervious concrete tne myths ect
myth pervious is the greatest. fact. it is not. sub divisions in the northwest have been using it. but unless its kept clean and clear it wont work as advertised
wow i am impresed ya'll know your concrete.
so i guess i am an artist in the job as well as in every day life.
Oldie, but goodie
That's some scary ass music when it's a myth!!
There is so much to consider for poring concrete. I poured 2.2 yards for a 12x16 pad for my shed with my wife. I had a slope of about 12 inches on the 12 foot side. The digging was a nightmare. Clay, rocks, bricks and roots which pulled back each meager shovel full. I finally got frustrated and shored up one side using a 2x12 as a form board. I thought this was going to be a disaster. It has been over twenty years with no cracks. I have been looking for a good source book on setting proper forms. Do you know of a good one? Thanks for posting the video!
+robert morin Just make sure your forms are straight, level, plumb and well-braced. Unless you are going into professional work, $90-$150 dollars for a technical manual is needless. It sounds like you did a great job on the 12x16 project. www.concreteconstruction.net/table-of-contents/magazine.aspx has always been one of my favorites for seeing what is possible to do with concrete, if you want to look into the concrete construction field.
My first recommendation for any concrete work is to have a stable base to place it on.
+robert morin plumb leval square. and brace it more than you think you need. once a form starts to push. its almost Imposible to push it back!
That's a slope of 8% generally you want a slab to have a slope of 3-5 max
TheTomBevis thanks for the link your awesome
Now things r starting to make sense
Where is the test at the end of the movie? I was ready to ace this one...
Watching this video is like watching concrete dry
How can I get a job in construction company as fresher.
You're so right, I too hardly did anything hacking to concrete any part particular vital component including hammer 🔨 ing.
The guy talking never saw Concrete being poured only on TH-cam wetter the better 👌👌👌👌
Talk about worrying the sky is falling. Don't over steel like they did, add enough water so its easy to work with, and don't pour when its freezing. The end.
how did i end up watching this?
Also is there a part 2. i need to know if there are more mistaken ideas
what is this?
No mention of how much trouble water reducer will get you in and how hard it is to get a flat floor with plasticizer
This is a lot more complex than it needs to be. Engineers have a safety factor, batch plants have a safety factor, and on down the line. If Losing 200PSI is a problem just buy a lot stronger mix to start with, the difference in price is minimal compared to a failure. Concrete is cast all over the world by 2 guys with a shovel and some buckets, yet the results are overwhelmingly satisfactory. Do not try to cast a suspension bridge this way, but a house slab is very low tech.
So, ya he has some valid points, getting it wrong is not as bad as he suggests.
9.29 this is also advisiable when building near ocean salinity of soil
where I work we do a lot of state pours like bridges etc. they mostly use a lot of ice and retarder and it's always at 12 am wyf
Robby Soc
I have asked about ice we have only used delvo?
One thing that has always intrigued me is why plastic ties are not used to connect reinforcing together prior to pouring the concrete. Extensive enquiries here in New Zealand have always drawn the same response: it is not known what the structural importance of steel tie wire is, and it is not known what the objection to plastic ties might be. Can you throw any light on this issue? Regards from NZ
Kind sir, there is no structural integrity or advantage in tie wire. The amount of the tie wire used in structural concretes design is to keep the Rebar in place at the spacing and coverage specified during concrete placement. Rule of thumb double your wire on heavy mats or columns and high traffic areas. Single ties are sufficient for flatwork such as slab, mesh and light foot traffic. Gauge 15 for bridges and 16.5 for medium to light work.
@@steeltown416 Many thanks for this comment. Thought so.
@@steeltown416 This is what I have thought for very many years now. Really strange that no one in the local concrete industry can confirm this. Thanks so much, cheers.
@@evanpenny348 No worries!! Greetings from California! What also is a good indicator that Tie Wire holds no Structural integrity is that you will not find it mentioned in any of the Structural details called out in the plans. Which means it's not taken into consideration when the engineer makes his calculations. It's just a industry standard tool. Means and method for the contractor to secure Rebar in place. Similar to precast concrete spacers that hold up the Rebar, just a means to hold the bar in place. Cheers 🍻, From a Ironworker on the other side of the world.
Specifying the amount of water... and how are you going to measure the amount of water in site conditions? How much water in the sand is hard to judge, and sand usually contains some water. Surely, in practice, it will be down to the skill and experience of the person supervising mixing to get the quantity of water correct, or do the plants sending out Readymixed concrete delivered in cement lorries have sophisticated enough equipment to measure the quantity of water accurately?
This is a question. I don't know the answer.
John Bull Yes, they might be able to do it! I would say that everything must be calculated.
reminds me over at fort knox some people pourd like 100 houses in winter, come spring all houses got so fuckd up i heard that some needed to be demolishd.
Don't they shift out the soil with gravel before building on top of it?
Yes, the problem is both soil and gravel were frozen was like 10 ℉
When they pour the concrete
Concrete is still only as good as the base that it is poured on, if ground gives way underneath it, even the best concrete in the world will fail with nothing under it. Reason why it’s not supposed to be poured on frozen, or too soft of ground.
Water to cement ratio
Inc slump by using a plasticiser, delivery time. Not water
Water concrete to let it cure
Know when to finish. Choose right time to finish
Calcium chloride is an accelerator but not antifreeze
Maintain cc temp
Cc will not heat up frozen soil. In cold weather soil needs to be warm
Steel doesn’t keep cc Fromm cracking. Temp and moister cause cracks
Cc can change shape while curing. Especially if thick
Cc is permeable. Use low water to cement ration to reduce sponging
High cc break weights doesn’t mean less cracks
Thankyou for this Video . . . Chris . . . Norwich England
U can salt the surface. Makes it far warmer.
U go by p.s.i 3000 3500 4000 the humidity has to do a lot with it and u can put water in it there's water reducer u can use to make slump rader to pour and there's other ways just make sure your grade is right and compacted and joints saw cut in it u'll be ok
10:13 'How Comes is so mucha steel ober dere?
Since this video was not supposed to be reproduced I feel deliciously naughty watching it
old school rules...lol.
im playing it over closed circuit TV
I went from watching a video on non linear time to this. How the hell did I get here???
theory meets guesswork
Lol. The wonders of just letting it go to the next video. No telling where you will end up. I am sure there is some Quantum Theory to govern it, but you would be hard pressed to find it.
Answer: youtube
a good theory needs a good foundation
if pouring at a 5 or 6 slump,weaker by just a little than a 4 slump...JUST UPPING YOUR SPEC FROM 4000 PSI TO 4500 is cheap by adding a half sack per yard ...at a $5 yard cost!!!///in the U S,we have made EVERYTHING so complicated that our costs are crazy...i believe in vibrators and 4500 psi concrete...and rebar UP OFF THE BOTTOM OF THAT SLAB!...tearouts where old rebar is laying on the bottom of the slab!...are so common....THESE 3 THINGS are easy,cheap and important..
I can't believe I wasted 15minutes of my life watching this video
The last good pour, with perfect slump, was back in Greece 500BC. Today science is getting close to recreating that batch in the lab.
@HSK Kelley trial an error. Mix a pour and use it. Then wait 1000 years.
HSK Kelley they used slaves, if they wanted to add water to the mix they got whipped even more.
This video confirms my opinion that laying concrete is not for amateurs. The only thing I will do is put in a fence post.
Start small. You can do it.
Concrete studies in 2019 are still underway.
What else will we learn about it tomorrow.
Example, Bamboo was used hundreds of years ago in China, as rebar. (no cracks - no rust).
Your concrete professionals of today in the USA don't want to talk about that. I wonder why ?
So why restrict this information?
The guy in the beginning looks like Tom Arnold 😂
Didn't answer or touch on the use of a vapor barrier (10 mil plastic) and its conflicts with concrete finish and its proper installation in stem and spread footings in a monolithic pour.
most contractors let the tester get the cement off the truck first .then add water so youll never know how long it will last true story
You are 100% correct it's so bad that the inspector knows you're doing it and hears the contractor discuss to the driver that cwe will add water after he gets his test".
Most of the rediculous slumps engineers want to pour are impossible to pour and get a good product
Shade tree on
@@geraldharrington8401 I pour concrete every day! Just trying to make a real perspective out of this nonsense 💯💪
As a inspector if it fails I let them know, if they pour is up to them.
slump is?
Great video for going to sleep
Concrete non permeable lol I've installed flooring for the last 7 years in San Diego and have to do vapor barrier from ardex all the time which means bead blasting and grinding the finish off and resealing the concrete
nice.
look up Samsons Concrete videos
Curling? Never heard of it
Go to 15:00 for list of the myths.
why do you put the rebar mash on the ground and then put the concrete over it?
Rebar mesh adds tensile strength to the concrete which by itself only has compressive strength...
If you meant why have they put the mesh flat on the ground without any spacers / chairs lifting it up, my answer would be that it ia not the 'correct' way to lay mesh but in practice the concrete will lift mesh up as it's being poured meaning the mesh will set in the middle of the slab rather than on the floor.
Hope that helps?
7:36 you think we should cover this concrete with some blankets or something? Wtf hahahaha
If I was wishing to conceal a corpse in a shallow grave under a patio what would be a good mix to stop the slabs from subsiding ?
Well mate..I would have a high cement to water ratio and let the slab cure for as long as possible.Put down a couple of piers to a firm substrate to prevent slab sinking.Do not forget to put in plenty of reo,you guys call it rebar. Remember concrete is great in compression but weak in tension so more reo to the area in tension.Put the body in some plastic,throw in a couple of bags of lime and seal that bitch up.Cover the hole with dirt,form the slab and pour the concrete...Good luck..All the best from Australia.
@Richy Mark Norman: "Well mate..I would have a high cement to water ratio" - Maybe you can explain this some better? What exactly do you mean with that?
4k to 4500.
And what does this mean?
p.s.i. strength.
Jack and the beanstalk , and the tooth fairy are good tales. They are popular stories but not quite as popular as like the Bible and Santa Claus and Humpty Dumpty, Bigfoot, the Loch Ness Monster
I would specify like this, give me 4000 psi @ 4 1/2" slump with air between 3 and 6%
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0:20 Then why in the world should we believe anything in the video?
This is the U. S. of A., where you have a right to believe whatever you want. It seems the Portland Cement Association believes in protecting themselves from clever rapacious litigious jerks. I believe I'll have a beer.
Being a cement finisher brought me here.
Finisher for 14 years, and I cringe when someone calls it cement 🤦♂️ it's not just cement, ya know
are these myths cast in stone?
Stephen Owens Have you ever tried casting stone? ;)
Some would say they're concrete
Because of this video they are cemented into our psyche.
so... avoid water?
so the ways to increase slump onsite are still add water.
when you order concrete and it turns up coming out of the truck in huge blobs dry as all hell lets face it. your gonna wet it up.
tubestick00 add chemical agents
Wayne Robinson yea right.
Wayne Robinson admixtures are amazing tools if you know how to use them.
A big point is; using superplasticizer you don't need to add as much water. You'll never finish a pour if you need to pull it off the chute with a shovel, but the admix can grease it up. You can add less water, not none.
Guys like you keep us structural engineers up at night. NEVER add water at the site. If the mix is not workable, it's the redi-mix suppliers problem, not yours! Be prepared to add water reducer or super-p but not water. Period!
Someone needs to do a TL:DW on this, it'd only be a couple of sentences.
house slab knocked back by inspector because builder took photos of concreter add water to the mix. the slum weaken and have they ripped the salt and start again. lesson to learn. order your slum higher so if you add water it will not affect the strength of the concrete.
this is written by a lawyer more than a stone masson
This video needs an update, to cater for product containing high alumina..
As it's being sold as, as good as Portland, without paying for the brand name.
Another myth!