Concrete Pumping - Why do you lose air and why does the air come back? (2023 update)
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- čas přidán 25. 08. 2024
- Concrete Pumping is a widely used method for concrete construction. However, pumping is known to change the air content of fresh concrete. This video uses lab and field data to verify that the air is lost and the important air, the small bubbles seem to return to the concrete before it hardens. This is an important finding and a chance to change current specifications that require air content to be measured after a concrete pump.
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I work for a ready mix and had an air requirement on top of the mountain. 4000ft gain in the hour it took to drive up to it. We would loose 2-4% air from 7ish down to 3 or 4 and then if it sat in the mixer for 10-15min slowly turning it would come back up to 7%. Confused the heck out of me. This is probably why. I'd love to see more about vacuum stuff. Great info. Thank you.
Thanks! Did you remix when you got to the top of the mountain? Did you mix harder then when you were driving? This typically causes the jump in air.
You could air entrain right befor pumping
Humbly this is what i would do
A project I was apart of in 2018-2019 with CDOT submitted samples for this study, but we never really heard a follow-up to it all. Colorado revised the point of sampling from after pumping to before the pump a couple of years after though, so we assumed something significant was the result. It's awesome to finally know more about the research and the conclusion! Great video too!
Love ALL your videos man!!!!! I do QC in Colorado and your entertaining and informative videos help me so much!! Thank you
I had a DOT job the spec’d 6% +/- 1.5 %. Got 7% before the pump, but after the pump it went down to 3.5%. They had me spike the air to a 12% so at the end of pump it would hit spec. I fought and fought until the threatened to reject the truck. Needless to say I had them sign off and make cylinders on both ends so they could see the weight difference. I actually sent them a video Tyler made a few years back on this topic.
I am sorry to hear this. I hope this will change soon.
Fantastic work, I love the experimental and science-driven approach to presenting the information. I wish this was the norm. But of course, there is a considerable amount of work and knowledge that goes into making a video like that. Thanks to Tyler and the students for their hard work.
Thank you very much!
Amazing! We are having a panel discussion at our next local ACI chapter luncheon. Thank you!
Bravo! This is valuable information! Thank you for the excellent content!
Thanks for watching!
Thank you, Dr. Ley, for this presentation.
Thank you for the comment!
I have a diy that even you may not have heard of. Underground roof slab for storage room.
One way design. 4x9 plywood form base. Set up to pour one 8 inch wide section at a time sleeves for distribution bars on the movable side. The idea is to pour and cover. Wait three days ,then install the next side form. Remove the side form from the poured section. Drop in the rebar cage for the next section and pour . Continue for 20 linear feet. All poured concrete remains covered with visqueen for 28 days.
Am I right, or have you seen this before ?
Always use retarder and plasticizer in pump mix.
Especially in hot weather .
Always add 1-2 yards extra to prime pump lines .
Then ensure pump has a place to clean out thoroughly.
We had a Putzmeister 43 meter on NYC.
Great tips! Thanks for sharing!!!
Seems to be like scuba diving. As you go deeper the bubbles dissolve, as you return to the surface the bubbles expand/return.
Hope you're doin' well professor! Can we have a two way slab design video?
No disrespect by saying bro, sorry Tyler, but yeah I'd love to discuss a few topics like this ,rebar , wire fiber ect
Interesting presentation. Thank you!
It has been an argument for a very long time. POP is the pump!! We have no control over the concrete when it goes thru the pump!! What happens when the pump has a leak? Or the pump operator doesn't do a good job cleaning his pipe? So many factors involved.
Your presentation indicates that the spacing factor of normal temperature concrete recovers about 45 minutes after pumping. This suggests that while concrete sampled at the pump discharge may have a non-compliant air content/SAM number, cylinders cast from this sample of concrete should experience a recovery of dissolved air and have about the same spacing factor as cylinders cast from concrete sampled before pumping.
When the concrete was sampled at various time intervals after pumping to check the SAM numbers, were cylinders cast and the spacing factor of the hardened concrete determined? If your premise is correct, the timing of casting the cylinders should not have a big influence on the results.
If so, is the data available in one of your papers? My studies of annual LT results for a municipal QC program comprising dozens of samples indicate that there is often a characteristic relationship between hardened air content, spacing factor and specific surface, often unique to the concrete admixture package. I wonder if there may be something similar happening after pumping
This is AWESOME!!! Great info. Yes should always be at the truck. With this info, why is everyone wanting more air in the concrete if 4% is great. This would mean less cement( like everyone is wanting, green world) better breaks with less air. Easier to control then the 7% or 6% required.
I agree! As long as the air is good air void distribution then 4% is perfect.
Hey bro I'm a concrete youtuber, I have some questions I'd like to ask u about on a stream! I been a fan for years and even shouted u out b4
Sure! Let me know when you want to chat.
Micro bubbles affecting concrete flexural?
I want to experiment with making Roman Concrete. I am suprised there are so few videos that even talk about it. I only found one video where a guy made it but that was before the discovery of hot mixing.
I would think the concrete industry and people like yourself would be all over the subject of concrete that has lasted over 2,000 years.
Use Sika Aer Solid for instance. What you put in you measure every where in the process and therefore you only need to measure once on the batching plant. It’s like really tiny ping-pong balls. The are specified for roadworks in Europe.
Thanks! When people have tried solid air in pumped concrete it has caused the spheres to be destroyed.
Hello tyler, can you talk about concrete repairing techniques, cracks repairing and touch on the life time expectancy of a building?
Thanks!
I have two videos on these topics coming. I have one video on repair materials and another video on crack repairs. Stay tuned!
@@TylerLey you're the best
Will you be publishing this? It would be amazing to have this as a simple reference when specifiers require sampling from the pump.
Yes, you can see two reports at www.tylerley.com/pumping
We have two other papers under review and one more about to be submitted.
So, if I wanted to make concrete with even better air entrainment and especially lots of tiny bubbles, could I compress air into the water at high pressure, then heat exchange the water down to about 40 degrees before I release the pressure and use that water to mix up the concrete? I'm thinking air dissolved into the water would tend to make really uniformly spaced tiny bubbles as it is released by the water. Is there any chemical that I could mix with the water that wouldn't mess with the performance of the concrete, but would make this technique work even better?
I have done stuff like this before and imaged the bubbles in 3D with X-ray CT! It is published in this paper. The dissolved air in the concrete will come out of solution because of the high salinity pore solution. If you de air the water before you make the concrete and don't whip the water into it while mixing then you will significantly decrease the bubbles that form. I never made a video about it. I didn't think people would care.
Moradian, M., Ley, M.T., Hu, Q, Robertson, B., Hanan, J., Xiao, X., “Direct in-situ observation of early age void evolution in sustainable cement paste containing fly ash or limestone”, Journal of Composites Part B, V175, 2019, pp. 107099, doi.org/10.1016/j.compositesb.2019.107099.
So how do we control this on site for the pour?
I think the best answer is to measure it at the tuck and if it is good then you should be good after pumping.
If you really want to minimize air loss while pumping because the specifier is going to make you measure on site then you can try and pump in a horizontal position as much as possible. You can also avoid having cold concrete because the air dissolves more in cold concrete.
This wasn't really the focus of the work.