OK. We finaly got the lightweight concrete pumpable by using a smal amount of VMA. But now the test results show that the concrete we pumped is heavier than the concrete straight from the mixer.

This is very strange because the air% went up after pumping. How can the concrete get heavier after pumping?

One theory could be that the aggregate is not completely soakt when it arrives. It a very non-absorbing vulcanic rock. Then by pumping we push more moist in to the aggregate which takes a long time to dry out. They checked the weight only the day after the pour so there might stil be moist in the rock.. Maybe if we wait longer the weight will level out again?

Or could there be other reasons?

Help

if they put more cement in the mix to try and help it pump  or if the batch man didnt moisture adjust for what the agg actuly was and over yeilded on his sand .   Now as far as the testing  its weight is in 28 days or baked in a testing oven or (microwave)   the mix water tha will evaporate from concrete exposed to ambiant air at 50% relitive humidity is about 1/2 t0 3% of the total concrete mass.   I would like to be more help but im not getting all the info   like i said before its nothing that your doing the problem is in the plant. if it wasnt them they would have had a mix that could pump and test pours.  the first time i pumped steal pins over 400' in a 4" line  i did it in my yard first!

Pumpkid thats my problem to. I am also not getting all the info. I asked for the recipe but I don't get it. Its a big problem for us. Doing such an extreme job without a good cooporation with the factory

with out the info all you can do is guess at the problem.   lol  sounds like that is what they are doing as well     good luck

Hydrating the mix is the key of course. If you use chemicals, it will take longer to cure out the additional weight of the fluids. The same thing with the water. If the rock wasn't soaked properly it will absorb it and slowly cure and release the moisture. I think you just have to wait it out here. You can never tell if something screwy happened at the batch plant that could sway your batch weights.

impossible for the concrete to get heavier after pumping , any absorption by the aggregate during pumping would still mean the water was already in the mix , something isn't making sense.

I think he is referring to the test cylinders being different weights. Which means a sample pulled from ready mix truck wouldn't be as heavy because the rocks haven't absorbed max water. And the sample from end of system has had more water absorbed into the rock from the pressure of the pump. Making it heavier. IMHO

Concrete pumpers move the concrete from the mixer to the forms. Period. Whatever happens before or after is not of our concern. The solutions to THIER problems should be found amongst their ready-mix suppliers and their experts. Asking a bunch of pumpers about technical ready-mix issues is like asking your proctologist why your tooth aches. We just care that it comes smooth out the other end. Good luck.

I agree with Beast.  If they took a sample from the truck and then one from the end of the pipe the only way I can see a weght difference would be that they took the sample from the truck off the first fin or two and waited until the middle of the load for the pipe sample.  We all complain about this at sometime or the other it is why we blend loads at the start and finish .  I don't know if this is what happened but it's the only thing I can see that makes any sense pushing the water into the rock will happpen but that water content was already there and shouldn't increase the weight.

Dipstick you are saying one end is heavier than the front end witch would be off the mixer after its dry are they both the same weigh,what you got is to many engineers and not enough Brains.

if the water was in the mix absorption into the rock would not make a rock any heavier than what the water already weighed , just because it absorbs into a rock , the weight of water was already in mix , therefore no weight should change.

Beast is right you really have to weigh it when it dried out.

Reason I care is that if this concrete is not pumpable they will switch to plan B which doesn't involve my company..

It could indeed be that the heavy cylinders where from the middle of the truck and the light ones from the first 300liters.. But not likely. They took a huge amount of cylinders all the way.

I see what you mean with the water already being in the mix. But Biged understands what I mean.. The water will not dry away as quick when its pushed in to the rock. If its so hard to get it in to the rock it might be hard for it to come out again also

It all just very irritating that this factory is just guessing and not getting in some expert help.. I don't know whats happening, I get so little information and are actualy starting to care less and less

If thy are willing to do another test pour ask them to weigh the concrete at the truck when its wet and at the end of the pipeline whe it is wet.  I believe the air metre will contain a cubic foot of concrete, correct me if I'm wrong , however if you can get an accurate weight at the truck and at the end of the pipeline then that should eliminate the finger pointing at the pump for increasing weight.  What kind of pressure did you pump was it considerably less than the first pour or about the same?  

We did use a lot less pressure than at the first poor. The VMA worked great. I will keep this in mind for the next test. But I am afraid it will be so that the weight after pumping will be slichtly higher than before pumping. Thats the whole problem. But my hope is that this will level out again when the concrete is totaly dried out..

Dipstick, since it seems like your company does a lot of very extreme projects that most others aren't capable of doing why not threaten to walk away? Would the contractor be able to find someone else willing to take on the job with such little help from the ready mix company? To me it sounds like it would be a headache for anyone else to take on the job, so maybe play your hand a little and see if that puts more pressure on the concrete supplier to help figure out what the issues are.

Ready mix companies are shady in a lot of things they do, wouldn't suprise me to see them come around if you put more pressure on them and the responsibility for the issues you've had in their court. Everyone always likes to blame the pump, but more often than not the issues lie with the mix.

Hey Concrete Jef. We are not the kind of people that walk away when things get difficult. We always try to think in solutions and not in problems. We believe in longtime relations whit our customers.

And beside that playing hardball can sometimes work on many places but not in Norway, it will work against you . people will be chocked and by that very bad for your repetation.   

IF you can provide a machine and system that can move concrete from point A to point B then YOU have figured out YOUR end of the job.... every thing else is just blowing smoke... If YOU suggest a modification to THEIR mix and it pumps like a dream and then cracks and crumbles a month after the job is done then YOU are the bad guy. Stick to pumping and let THEM go look for answers at a Ready MIx Suppliers chat/blog whatever for solutions to HIS problem. MY operators are not even allowed to help ready mix flop their chutes or give them any hand signals while backing up until the mixers are lined up and 20 feet from the pump hopper. We had a pumper try to help out a mixer that was already getting off the side of the road, so our guy ran down the hill and stood behind him, in his mirrors, giving hand signals and tried to help the guy get straightend out and get back onto the road, well the mixer driver had his own ideas and eventually rolled the truck over and WE got in a LAW SUIT by the property owner for trying to HELP give hand signals. This whole discussion boils down to liability.

THEIR job is to "design and deliver a pumpable mix" OUR job is to "unload and place" whatever they decide to bring. I understand wanting to be part of the solution, I get it....  but Know your place.

Normally I would totaly agree with all this. But in this case they have started to look for a solution without use of concretepump. And that would cost us 8 months with good work.

I am only giving the factory smal hints and hope they will get on the right track that way but it is indeed their job to fix it.. We will see what happens. Most people I talked to say its impossible that the weight goes up while the air % also goes up. Its all just a load of... I think the tests are wrong or something like that.. We'll see what happens.

Hey Dipstick I don't know what the cost might be to you but perhaps it would be worthwhile to bring on your own testers, have them pull the air and weights and also make cylinders from the mixer and from the end of the system. Just a way to cover yourself and perhaps point you in the right direction as far as whether it is the mix or the testers are causing you the issues.

Dipstick I hope it all works out for the best because your company has worked very hard on this project,the pipe line is and  a work of art, I will never get to Norway I bet its a nice country to visit.

Just a thought, you are fighting to give the best results possible for your customer which benefits yourself as well as said customer. BUT you are feeding the ready mix supplier ideas and possible solutions on how to make the mix pumpable, which I understand completely. Meanwhile if all goes to shit with pumpability they MAY have a solution to cut you out of the job and still may not pass the job specs. Let them pay for the MAYBE THIS WILL WORK crap and rest well at night. In the end you will know that you have done MORE than you needed to do and some day they will look back and say "damn that guy was okay". Not meant to start a firestorm just rest well knowing you have done your part!!! Best of luck and God Bless

Thats exactly what we are doing. We try to give them some hints but not paying for anything or taking any responsibility.

Has the air content been checked before and after the pump?  After all, Air is a portion of the volumn

Yes. Air was higher after pumping.  Sounds almost impossible doesn't it?

If the air was higher shouldn't the weight have gone down? Seems kind of hard to believe.

Thats what I and all the people I talk to think aswell. I think there have been made mistakes in the testing.

But if there is anyone that can explain why the air AND the weight can go up at the same time please shout it out  And if the weight is to high after pumping and not straight from the mixer who can guarantee that the weight doesn't go to high during pooring. If they don't use a pump they will use crane and bucket. The bucket will be lifted up on the bridge and then driven to the end by some vehicle. The concrete will be in the bucket for a long time, lot of shaking, then the pressure in the high walls while vibrating.. The weight might get higher during that procedure also..

yup

Haha. Thats funny. I am affraid they have already made up their mind. Just got the comfirmation. No more pumping. They have a whole package of reasons for choosing a different solution and I kind of see their advantages also. Funny thing is they are so sattisfied with our service (we do all kinds of other helpfull jobs in times when there is no pumping) that we are alowed to stay for a while. This gives us good tme to find a new interesting project

Glad we did not play the hardbal. Remember this is a goverment job and when goverment is involved politics are involved. And I think we where a victim of politics. No more and no less I can smell it.

I can smell it over here to