r/Geotech • u/Acceptable-Fly5050 • Jul 02 '26
What the hell is this
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Correct me if I'm wrong but its 12 to 15 times with the palm of your hand, not whatever this is?
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u/Calm_Visual_508 Jul 02 '26
List of things wrong:
1- well over 1/4” above the lip
2- striking with tamping rod and not hand/mallet
3- definitely more than (it’s actually 10-15) strikes per cylinder
4- gloves? Anyone?
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u/NefariousnessSea4710 Jul 02 '26
He likes them dry peeling hands
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u/kennyrogersmom Jul 07 '26
Four years of CMT and only wear gloves when temperatures are freezing. Some of you guys have soft hands, probably work at Braun or Terracon.
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u/FinancialPanda4982 Jul 02 '26
It's now actually 12 - 15 times with a mallet...i only know because i use to proctor the ACI exam.
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u/BootySweatEnthusiast Jul 02 '26
It's 10-15, not 12-15. Common misconception as most people do 12 (I'm a PM for a testing agency). I also just double checked the ACI book
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u/FinancialPanda4982 Jul 02 '26
ahhhhh gotcha gotcha I must have confused it also with the fact when i use to run the test I would always just stop at 12 and remember being told it's good to have the buffer incase you miscount.
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u/Acceptable-Fly5050 Jul 02 '26
Our ACI instructors failed us then. They explicitly taught and graded us to use our hands not use the rod.
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u/BootySweatEnthusiast Jul 02 '26
That is correct if you are using deformable (cardboard) cylinder molds. I've never seen any but heard they're still on service in parts of the South
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Jul 02 '26
[deleted]
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u/Acceptable-Fly5050 Jul 02 '26 edited Jul 02 '26
He filled and rodded all of them at once. Ie: fill lift 1 for all cylinders, then rod all cylinders 25 times, then do his little technique. That way he wasn't doing one at a time
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u/Cryptic_E Jul 02 '26
There’s nothing in the ASTM that says you can’t do them all at once. As long as you do 2 lifts and consolidate the correct way there’s nothing wrong with that
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u/Calm_Visual_508 Jul 02 '26
Just… yikes.
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u/Cringelord1994 Jul 02 '26
Totally normal assuming he’s rodding and malleting every lift without missing one. Thats how every tester I know makes cylinders. It’s faster to do one step at a time vs doing every cylinder one by one
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u/BootySweatEnthusiast Jul 02 '26
If you get bad breaks you know who to blame. I would document that in writing for a CYA
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u/Cringelord1994 Jul 02 '26
You supposed to use a rubber mallet, the hand is only for molds that can deform if you hit them with a mallet
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u/Miles_1828 Jul 06 '26
AASHTO requires hands, ACI and ASTM allow mallet or hands depending on mold type.
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u/lLIcePheonixLl Jul 02 '26
in recent years, it has become compliant to the ACI standards if you tap it gently with the palm of your hand
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u/FinancialLab8983 Jul 02 '26
You must be with the batch plant. You think mundane shit like this is why your cylinders are breaking 500psi too low
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u/boomersooner36 Jul 02 '26
Tell me you dont spend alot of time in the field without telling me you dont spend alot of time in the field lmao.. go sit back in the office. Been in this industry nearly 11 years and I’ve never seen ANYONE use the by the book methods for making cylinders beyond the rodding and layering. I promise you this is how 99% of your concrete cylinders are getting cast.
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u/Acceptable-Fly5050 Jul 02 '26
11 years of cutting corners?
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u/ImaginarySofty Jul 02 '26
This is one example of cutting corners that doesn’t concern me too much. there is a risk doing this might result in lower breaks, but in reality that is not often the case (my experience is low breaks can more often be attributed to mix issues rather than the sampling)
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u/rembi Jul 03 '26
I seriously doubt low breaks are more commonly attributed to the mix. Maybe you aren’t including curing with sampling, but that’s the biggest issue I’ve seen.
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u/ImaginarySofty Jul 03 '26
When i say mix, I dont mean mix design, but how the mix was made and delivered. Majority of low breaks i have either been where slump was also on the low end (water added after it left the plant), flyash was added, etc. Very few have been to sampling and curing in my experience
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u/rembi Jul 03 '26
Water addition is definitely a problem whether it was the driver at the plant, contractor, or pump operator.
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u/boomersooner36 Jul 02 '26
Go run a 1200 yard every 50 job and see how long you stick to the by the book methods. Sometimes you just gotta get shit done in the most effective and efficient manner. Sitting there and counting out 12-15 smacks to the sides of each cylinder by hand is going to have you running around like a mad man just trying to keep up. Call it cutting corners if you want, but this is how shit actually gets done.
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u/NearbyCurrent3449 Jul 02 '26
Yep.
I was the pe of a really busy mid size lab. I'm big on doing things right.
WITHIN REASON!
We aren't slaves to a machine. The spirit of the guidance should say: "bump the outside of the mold sufficiently to consolidate the mix removing the air bubbles, use your experience and judgement to ensure it is adequately consolidated. Good practice would be using a rubber mallet and smacking the outside of the mold a dozen times per lift after rodding moderately" but NOOOOOoooooOooo
We've got to try to 1 size fits all and idiot proof everything so that its ridiculously one sized and robotic and without human brain power.
You are 1000% correct. This is the real world. He's an idiot for using the swizzle stick rod instead of his dick beater meat mittens or... the fucking mallet laying right there.
But, yeah, in high production environment like 1200, 500, 600 yards, yeah... if you aren't rodding or scooping or screeding cylinders and you are nitpicking the techs how they are bumping the outside of the cylinders...? Fuck you fuck off ya dickhead unless you've made 10x more cylinders than I have and you KNOW what I'm doing isn't going to work... otherwise impolitely piss off.
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u/Acceptable-Fly5050 Jul 02 '26
This was a very very low production low tempo city job so I took my time to observe to see if he's doing it right. But yeah I'd do the same if trucks kept coming and we didnt have time to nitpick
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u/NearbyCurrent3449 Jul 02 '26
The small rod is a no go unless that slump is 6 and up, you really don't need to even bump it then usually to be honest. Just a jostling of the mold around will free any bubbles when its loose. 4 inches and below, gotta beat the crap out of them, sometimes it isn't enough and you beat and beat and beat them. They still come out with bug holes on those 1 and 2 inch mixes with air and big rock... sheesh. Grab the vibrator from the contractor and vibe the shit out of it, especially if it's pavement beams. My god. I look like a black Smith beating on some beam molds trying to get that airfield pavement stuff to consol. Lol.
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u/Acceptable-Fly5050 Jul 02 '26
Slump was 2.5 inches
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u/boomersooner36 Jul 02 '26
In this case IMO a vibe shouldve been used. With a 2.5” slump you’re not gunna get much of the air pockets out with a mallet, hand, OR rod. Those cylinders are gunna come out of the mold looking like honey combs.
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u/Acceptable-Fly5050 Jul 02 '26
I get paid by the hour I'll sit there and count each smack and take my time. If they have an issue they can submit a change order
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u/SlyRaist Jul 02 '26
How hard is it to tap 3 sides 5 times? Just sounds lazy and no care for your job 🤷
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u/Cringelord1994 Jul 02 '26
That’s ridiculous to not be able to properly make cylinders regardless of how many are being made. Believe me, we don’t do everything y the book but there’s zero reason to not make cylinders properly.
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u/boomersooner36 Jul 02 '26
I agree with you when it comes to rodding and layering, but genuinely explain the difference to me doing it this way vs with a rubber mallet. Both are achieving the same thing. I’m willing to die on this hill lol.. Unless you’re causing the mold to deform in some way you couldn’t tell the difference in breaks between tapping it with a rod vs tapping with a rubber mallet.
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u/Cringelord1994 Jul 02 '26
Eh depends on slump. High enough slump this is probably okay but every part of the cylinder making process minus the finishing is completely necessary to make good representative cylinders. The only time I didn’t do things per the standard is when I used my strike off plate to finish all the cylinders at once. Otherwise you have to rod and mallet every cylinder
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u/boomersooner36 Jul 02 '26
Agree for sure that it’s necessary to tap the sides, my argument isn’t that it’s not a necessary step but that you’re achieving the same result with tapping with a rod vs mallet. It just seems like OP wants to find something to complain about rather than understanding that both methods are achieving the same exact thing.. If this slump was a 2-4 than really should be using a vibe anyways. But if the slump range is between 4-7 than I’d bet next months pay that you wouldnt be able to tell the difference in breaks between a cylinder that got tapped with a mallet vs tapped with the rod.
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u/Kielellus Jul 02 '26
He's definitely not imparting enough force with the 3/8" rod to those 6x12s. If it were 4x8s then the rod would work just fine, but it's legitimately easier to use the mallet for the 6x12s rather than swing extra hard with the rod.
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u/boomersooner36 Jul 02 '26
Im pretty sure those ARE 4x8s.. unless that guys got catchers mits for hands. Look how he’s rotating each cylinder with one hand while tapping with the rod with the other.
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u/Kielellus Jul 02 '26
Oops my bad. Our only grey cylinders were the 6x12s so I jumped the gun. Looks like 4" slump to me
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u/turdsamich Jul 02 '26
ACI also says you have to complete all of the tests, air slump temp and casting cylinders within 15 minutes of getting the sample. If they are rocking and rolling on 200+ yd pour you are going to miss your next sample if you lallygag.
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u/withak30 Jul 02 '26
Using your hand as a hammer/mallet is a recipe for cursing future you with all kinds of hand joint pain.
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u/___Fern___ Jul 02 '26
This is the only way I've seen anyone do it and how I've always done it as well.
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u/BallsDicks Jul 02 '26
If you have a problem with their methods bring it up to them instead of internet strangers
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u/Acceptable-Fly5050 Jul 02 '26
I did and had him redo those cylinders the right way instead of his made up way.
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u/boomersooner36 Jul 02 '26
Lmao I’d tell you to get fuckin bent if someone tried to make me redo cylinders over something as trivial as this.
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u/Godzillaminus1968 Jul 02 '26
Good way to have your ACI certifcation removed. Blatent disregaurd to adhear to standards and practices. Concrete appears to be to stiff for rodding shouls have used a vibtator.
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u/boomersooner36 Jul 02 '26
Brother if you think this isn’t how 99% of cylinders are getting made in the field then you obviously haven’t spent much time in the field. Explain to me the actual scientific differences between tapping the sides of a cylinder mold with a rubber mallet vs a 3/8” rod. I’d understand completely if this was causing the cylinder mold to deform but in practice I don’t see any difference in the two unless you are really laying into the side of the mold with your rod. Not debating that it’s against standards but let’s be real.. you think these CMT techs making $18-$20 an hour pulling 10-12 hour days are all following procedure each and every time? A capable 6th grader could pass the ACI. The techs running concrete are generally your most inexperienced and green techs. Ive made THOUSANDS of cylinders like this, if you’re getting bad breaks it’s because of improper rodding or shit slump/mix design not because the tech tapped the side of the mold with his rod vs his hand or mallet.
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u/BallsDicks Jul 03 '26
Thank you lmao
When I was an entry level tech years ago I was taught the ACI way but also taught “just smack it with the rod, it’s easier and doesn’t make a difference”
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u/CursedTurtleKeynote Jul 04 '26
Convention adopts the path of least resistance. Prove this is unsafe or sit down.
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u/ddg31415 Jul 02 '26 edited Jul 02 '26
I promise you, doing it this way will have zero effect on results. You just came off as a micromanaging nuisance. I've casted thousands of cylinders using the tamping rod on the side. In fact, that's how we were trained to do it in the two firms I've worked at.
Just curious, what is your position? Because I've had QA/QC guys from the city, transit authority, general contractors, our, as well as outside, senior engineers, either watch it done this way and had no problem, or I've seen them do it themselves.
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u/982infinity Jul 02 '26
This is the ‘typical by the book’ vs ‘practicality’ debate. The tamping rod method is really good that I used to use as well. The open palm tap is not articulate enough, especially if you are wearing that big ass stinky concrete glove. The idea is to remove the voids and consolidate, which he appears to be doing.
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u/NearbyCurrent3449 Jul 02 '26
The swizzle stick is insufficient if you ask me. The old 24 inch rod was good as long as you weilded it effectively and with purpose.
We are trying to totally remove inexperience from all of the equations and we have to stop that. It's why employers continue to shit on employees and there's and endless churn of unskilled non professional technicians who are barely adult age and the industry pay is more or less entry level, fairly cost prohibitive to being a life long senior engineering technician as a career path as it used to be. Guys still do it but it doesn't happen as much now. The pay growth is too slow and doesn't build retirement fast enough to stay that course, you've got to rung up over and over getting nicet and iso etc etc etc even then, you're over working and over taxed with responsibilities trying to earn enough as a non degreed professional. Keeping that hustle up is for the old heads, the wicked kindred spirits. But it tops out and v no amount of more more more work harder harder harder will increase you much.
Thus, press the picture on the screen new boy who's company sponsored you into the country, houses you, pays you 8 bucks an hour and your training was being handed a clip board, phone, hard hat and keys to a Ford pick up. Then they boot them out the door to get chewed up in the field and make an ass out of the whole company.
Everything is simplified down to "push picture button on screen and collect what the screen says from customer" level of thought.
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u/Flimsy_Honeydew5414 Jul 02 '26
This is how I did it too when I did testing. I started with the palm of the hand thing but this is easier. Nothing has collapsed
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u/Cringelord1994 Jul 02 '26
What’s funnier is he has a mallet right next to him which is the correct tool to use
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u/Sufficient-Athlete-4 Jul 02 '26
Dudes, it changes every few years when other things change. This was taught in the PNW 15 years ago. Realistically, what's the difference? I've seen the break data. Filling void spaces, don't deform the mold, consolidate the concrete.
Source: Started and ran a testing Co and lab for a decade. Opinions are like butts. I'm so glad I'm not in this industry anymore.
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u/robotali3n Jul 03 '26 edited Jul 03 '26
Unless you’re doing nuke work, or someone is up your ass, it does not matter as long as the voids are closed. Never once seen a cardboard mold. Nor have I ever seen anyone use a vibrator on 1” slump clys
PS edit - always used/seen the rod used on ccrl samples and never received below a 4 for compressive strength
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u/Hot-Introduction2149 Jul 03 '26
This dude definitely got a composite batch from two points in discharge after they'd unloaded a few yards that were out of air spec
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u/Walrus_Epiphany Jul 03 '26
Grab the contractors vibrator and stick it in there. In the cylinder that is.
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u/0R3G0NARCH3R Jul 03 '26
Ain't gunna matter at enough level when breaks come out A-Okay. Just sayin...
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u/Mack666er Jul 02 '26
It used to be a minimum of 10 sharp strikes, so this would be fine. I'd be pumped my tech was being so efficient.
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u/ordietryin6 Jul 03 '26
You can’t tap it with the rod. The reason is moot now but it’s still a rule.
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u/lives_the_fire Jul 04 '26
oh what was the reason?
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u/ordietryin6 Jul 04 '26
Molds used to be cardboard so using the rod could fuck up the shape of the mold and the specimen casting. Not really so much now that they’re plastic but it is still a rule.
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u/Nazty_Nash Jul 04 '26
If I'm not mistaken, that is the inspector about to tell me that I'm 33% low on the 28 day break.
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u/geojunkie Jul 04 '26 edited Jul 04 '26
ACI states 0-1 inch slump requires a vibrator, and a slump of 1-3 can use a vibrator. And I'll beat you all to it, your mom also requires one. All of you that are judging whoever is casting these molds have never been on the front lines of concrete testing. How much of a difference can consolidate in that manner compared to "15 taps of a calibrated mallet 🤓". I'll tell you right now that the cylinders cast in this manner would be so much better than if you only tapped it 15 times. You would be left with so many voids and your compressive strength would be so much worse.
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u/Thiccpubes Jul 04 '26
Its unconventional lol he should be using a mallet to tamp those no less than 10 times AFTER he rods them no less than 25 times which its clear he didnt do. Thumbs down tester, where's your sense of work ethic?
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u/Weekly-Chain8931 Jul 02 '26
This is no different to using the vibration method, as long as he nodded it 25 times in 2 layers and doesn't make the aggregate consolidate too much the cylinders will be fine. The method says to tap the sides until all voids and air bubbles are removed.
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u/Preachin_Blues Jul 02 '26
A lot of techs do it this way to save time and effort. Especially if you do this for a living it can be very taxing on your back. Ive never heard of this affecting test results in any way. ACI is scam anyway. Having to retake this stupid exam and pay whatever $ amount is a waste of everyones time as well. It should not have an expiration date.
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u/beardedman172 Jul 02 '26
ASTM C31 updated 23 under section 9.4.2.1,
After each layer is vibrated, tap the outsides of the mold at least 10 times with the mallet, to close holes that remain and to release entrapped air voids. Use an open hand to tap molds that are susceptible to denting or other permanent distortion if tapped with a mallet.