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9/22/2017 12:11:25 AM
Posted: 9/12/2005 12:37:34 PM EDT
I am building my own house and poured half of the basement walls today. I hired a line pump, so we were supposed to be using their specal mix for the pump. It was a 50/50 mix with water reducer. I am not an expert by any means on concrete. When the first truck showed up the mix was way too wet. I wanted a 4" slump, but knew the pump guys would want 5". This stuff was really wet, so I called the plant and talked to the guy in charge. He said wait a while for it to stiffen up and there would be no loss in strength. I started pumping anyways, and they pumped about 7-8 yards before I realized that it was running down my form, around two corners and filling up a wall 30 feet away. When I saw this I had them stop and sent the rest back. The next truck was 4-5" and we poured a total of about 24 yards today into the walls.

Here is my question- is there anything I can do at this point? The walls were engineered as retaining walls. so strength is important, and this weak concrete will be right at the bottom where the most force is. The actual slump was probably 8-9". Any idea how much strength loss this will cause? Also, I was thinking about using Zypex to waterproof. Will this help fill in any of the space left behing by the evaporating water, and give me any strength back? Thanks for any input.
Link Posted: 9/12/2005 12:47:57 PM EDT

Originally Posted By juslearnin:
I am building my own house and poured half of the basement walls today. I hired a line pump, so we were supposed to be using their specal mix for the pump. It was a 50/50 mix with water reducer. I am not an expert by any means on concrete. When the first truck showed up the mix was way too wet. I wanted a 4" slump, but knew the pump guys would want 5". This stuff was really wet, so I called the plant and talked to the guy in charge. He said wait a while for it to stiffen up and there would be no loss in strength. I started pumping anyways, and they pumped about 7-8 yards before I realized that it was running down my form, around two corners and filling up a wall 30 feet away. When I saw this I had them stop and sent the rest back. The next truck was 4-5" and we poured a total of about 24 yards today into the walls.

Here is my question- is there anything I can do at this point? The walls were engineered as retaining walls. so strength is important, and this weak concrete will be right at the bottom where the most force is. The actual slump was probably 8-9". Any idea how much strength loss this will cause? Also, I was thinking about using Zypex to waterproof. Will this help fill in any of the space left behing by the evaporating water, and give me any strength back? Thanks for any input.



If you know so little about concrete walls then why did you do it yourself and ask questions only AFTER it is poured?
Link Posted: 9/12/2005 12:51:10 PM EDT

Originally Posted By ArmedAggie:
If you know so little about concrete walls then why did you do it yourself and ask questions only AFTER it is poured?



Certainly are a helpful little feller, aren't you?
Link Posted: 9/12/2005 12:56:39 PM EDT

Originally Posted By juslearnin:
I am building my own house and poured half of the basement walls today. I hired a line pump, so we were supposed to be using their specal mix for the pump. It was a 50/50 mix with water reducer. I am not an expert by any means on concrete. When the first truck showed up the mix was way too wet. I wanted a 4" slump, but knew the pump guys would want 5". This stuff was really wet, so I called the plant and talked to the guy in charge. He said wait a while for it to stiffen up and there would be no loss in strength. I started pumping anyways, and they pumped about 7-8 yards before I realized that it was running down my form, around two corners and filling up a wall 30 feet away. When I saw this I had them stop and sent the rest back. The next truck was 4-5" and we poured a total of about 24 yards today into the walls.

Here is my question- is there anything I can do at this point? The walls were engineered as retaining walls. so strength is important, and this weak concrete will be right at the bottom where the most force is. The actual slump was probably 8-9". Any idea how much strength loss this will cause? Also, I was thinking about using Zypex to waterproof. Will this help fill in any of the space left behing by the evaporating water, and give me any strength back? Thanks for any input.

You fucked up, and you know it. With any luck, the heavier, later concrete displaced a lot of the weak mix.

How do you know the soup is actually weak? Did you take cylinders? What did the mix design from the ready-mix plant say? Did you sign all the delivery tickets? Why did you pump almost a full truck before noticing that the stuff was going everywhere? How were the walls vibrated, or were they? What does the designer of the retaining walls say about all this? Were they really "engineered" by like, an engineer, or is that just something you read in the plan catalog?

Yes, I'm a structural engineer.
Link Posted: 9/12/2005 12:58:53 PM EDT
Zypex is supposed to increase compression strength, but I think thats only when its entrained, call your local zypex dealer. You might have to have an engineer core and test a sample if things get ugly with the batch plant. Was there water running out of the forms on the 2nd pour? I ask because there usually is a little when you pump. Now not only do you have possibly weak concrete you have a cold joint all the way around, doesn't sound good.
Link Posted: 9/12/2005 1:01:50 PM EDT
Yes, they were engineered by a real engineer- to the tune of $1000. Yes, I vibrated them with a vibrator to 8'. I was finishing up a form when they started to pump, and wasn't watching when they started. If someone has something helpful to say, I'm all ears. If all you can do is criticize, go find somewhere else to vent about how miserable your life is.
Link Posted: 9/12/2005 1:07:46 PM EDT

Originally Posted By juslearnin:
Yes, they were engineered by a real engineer- to the tune of $1000. Yes, I vibrated them with a vibrator to 8'. I was finishing up a form when they started to pump, and wasn't watching when they started. If someone has something helpful to say, I'm all ears. If all you can do is criticize, go find somewhere else to vent about how miserable your life is.

So what does the engineer say?

What about the cylinders? Did you take any?

What was the design strength of the concrete? Any details of the mix design?

What do you want us to say, that everything is going to be just fine? Maybe, maybe not. As far as complaining about how miserable one's life may or may not be, I'm not the one with a $4000 wall that may get a visit from Mr. Jackhammer.
Link Posted: 9/12/2005 1:10:12 PM EDT
[Last Edit: 9/12/2005 1:11:49 PM EDT by ArmedAggie]

Originally Posted By Leisure_Shoot:

Originally Posted By ArmedAggie:
If you know so little about concrete walls then why did you do it yourself and ask questions only AFTER it is poured?



Certainly are a helpful little feller, aren't you?



How can I help when I have no idea how good his forms are, how well he placed his steel, ifhe used a vibrator (not that kind) as he poured. It just seems like the guy bit off more than he should have. The soupy mix is but one part of a lot of crap that could go wrong. If he knows enough to get everything else right then he'd know how to evaluate the mix he got.

ETA: I'm going to reflect upon my misery now.
Link Posted: 9/12/2005 1:10:45 PM EDT

Originally Posted By mark75101:
Zypex is supposed to increase compression strength, but I think thats only when its entrained, call your local zypex dealer. You might have to have an engineer core and test a sample if things get ugly with the batch plant. Was there water running out of the forms on the 2nd pour? I ask because there usually is a little when you pump. Now not only do you have possibly weak concrete you have a cold joint all the way around, doesn't sound good.



There was a small amount of water coming out of the forms. I don't think I have a cold joint, because we poured the rest less than an hour after the first pour (the second truck had good concrete). I am hoping a lot of the increased slump was from the water reducer and won't hurt me as much as if it was all water. I assume that if I am going to core I need to wait until it cures completely, is that correct? The pump guys thought I would be all right because there is a much higher cement concentration in their mix, and they tell me they have pumped wetter stuff in the past. They didn't seem to be that concerned, but I think its because too many people don't care about doing a job right. They said a lot of the concrete contractors do stuff like this and don't worry about it, but then my response was- that's because it is not their house.
Link Posted: 9/12/2005 1:17:18 PM EDT
sorry for being critical.

My analysis: Don't put anything valuable or living in the basement.
Link Posted: 9/12/2005 1:18:49 PM EDT
Vibrating will help some. Why did you only pour part of the foundation? I don't think I have ever seen a residential job where the whole house or condo was not poured at once. You need to get a hold of a structural engineer. Do not ask an architect, There is a reason that builders and other contractors need to be licensed
Link Posted: 9/12/2005 1:18:57 PM EDT

Originally Posted By juslearnin:
There was a small amount of water coming out of the forms. I don't think I have a cold joint, because we poured the rest less than an hour after the first pour (the second truck had good concrete). I am hoping a lot of the increased slump was from the water reducer and won't hurt me as much as if it was all water. I assume that if I am going to core I need to wait until it cures completely, is that correct? The pump guys thought I would be all right because there is a much higher cement concentration in their mix, and they tell me they have pumped wetter stuff in the past. They didn't seem to be that concerned, but I think its because too many people don't care about doing a job right. They said a lot of the concrete contractors do stuff like this and don't worry about it, but then my response was- that's because it is not their house.

This is complete and total bullshit, and I'm gonna cast me some Type-IIA shoes for the next ready-mix fuck that tries to feed me that horse-shit. The cement is the ONLY thing in the concrete mix that has any value whatsoever. Everything else - the water, the FA, the CA, the admixtures - is pennies a yard. This whole notion of "extra cement" is completely ridiculous! If that's the case, then the stuff that's going into the trucks is not in line with the mix design, so why do they even have a QA guy? Why have a mix design?

As far as coring goes, as soon as you've reached ~75% of your design strength (or whatever your engineer reccommends) and can strip the forms, you could core. However, you'll be able to see right away if you have good concrete at the bottom or not. The big hazard with concrete that is too wet is segregation of the FA, CA and cement paste.

Extra cement. Riiiiiiight...
Link Posted: 9/12/2005 1:27:08 PM EDT
What is a 50/50 mix?

Sometimes if the mix is too high in slump the driver can turn the drum a few more times to increase the heat of hydration which accellerates setting and stiffens up the concrete. It sounds like that is what the batch plant suggested. Once the truck leaves the batch plant, I don't know of any reliable way to increase the strength of the concrete. It was probably batched correctly and just didn't have enough time to develop the required slump. If the aggregate settled out of the mix because of high slump and over vibration, you may have to replace the concrete. Ask your structural engineer to inspect the concrete ASAP. Also, don't listen to advise from the pump operator.

Good luck.
Link Posted: 9/12/2005 1:27:26 PM EDT
[Last Edit: 9/12/2005 1:36:06 PM EDT by Apatriot]
You'r concrete should be ok,since you poured a 4-5 right on top of it within an hour .You want to wait 28 days before having the testing agency do the core samples,due to the concrete design reaching it's designed strength in that time per your ASTM spec.If the concrete core shows the proper compressive strenght ,no harm,no foul.
If it does'nt meet ASTM spec,the concrete supplier is responsible for the failed mix design,as long as you did not add water after the truck arrived from the batch plant.If you or anyone on site added water after the truck arrived,then the batch plant is no longer responsible,as the mix design was altered on site.Check your tickets and see if the driver wrote down any added water after site arrival.
As stated above,if there was aggregate seperation,you will see it when you remove the forms.If it is honey combed in large areas,you have a problem,If not,then the vibrator did it's job.
Link Posted: 9/12/2005 1:32:09 PM EDT

Originally Posted By juslearnin:

Originally Posted By mark75101:
Zypex is supposed to increase compression strength, but I think thats only when its entrained, call your local zypex dealer. You might have to have an engineer core and test a sample if things get ugly with the batch plant. Was there water running out of the forms on the 2nd pour? I ask because there usually is a little when you pump. Now not only do you have possibly weak concrete you have a cold joint all the way around, doesn't sound good.



There was a small amount of water coming out of the forms. I don't think I have a cold joint, because we poured the rest less than an hour after the first pour (the second truck had good concrete). I am hoping a lot of the increased slump was from the water reducer and won't hurt me as much as if it was all water. I assume that if I am going to core I need to wait until it cures completely, is that correct? The pump guys thought I would be all right because there is a much higher cement concentration in their mix, and they tell me they have pumped wetter stuff in the past. They didn't seem to be that concerned, but I think its because too many people don't care about doing a job right. They said a lot of the concrete contractors do stuff like this and don't worry about it, but then my response was- that's because it is not their house.


I must have read wrong, I thought you only poured half of your walls, total. I believe you will have to wait 28 days for a fully cured sample but I could be wrong. Here is a zypex link http://www.imxtechnologies.com/ but your better off calling a dealer, they're more likely to cover their ass and give you a better idea of what it can and can't do. I wouldn't take too much stock in what the pump guy says, like you said it isn't his house. And I'd get an engineers take on whatever the zypex guy tells you too. The engineer is cheap insurance in the scheme of things.
Link Posted: 9/12/2005 1:32:22 PM EDT

Originally Posted By juslearnin:
I am building my own house and poured half of the basement walls today. I hired a line pump, so we were supposed to be using their specal mix for the pump. It was a 50/50 mix with water reducer. I am not an expert by any means on concrete. When the first truck showed up the mix was way too wet. I wanted a 4" slump, but knew the pump guys would want 5". This stuff was really wet, so I called the plant and talked to the guy in charge. He said wait a while for it to stiffen up and there would be no loss in strength. I started pumping anyways, and they pumped about 7-8 yards before I realized that it was running down my form, around two corners and filling up a wall 30 feet away. When I saw this I had them stop and sent the rest back. The next truck was 4-5" and we poured a total of about 24 yards today into the walls.

Here is my question- is there anything I can do at this point? The walls were engineered as retaining walls. so strength is important, and this weak concrete will be right at the bottom where the most force is. The actual slump was probably 8-9". Any idea how much strength loss this will cause?



13 years Ready mix.

You have what we call "Mystery Mix". You really have no clue what the reason for the 9" slump is/was.

If it is from over WR/plasticizing the load, there is zero strength loss.

If it is from the driver having his head up his four corner point of contact (water valve left open after pressurizing tank), you may have a problem. Assuming a standard 10 yard load, assuming your 9" is accurate, that means 40-50 gallons of water added. 4-5 gallons per yard causes 500 psi per gallon per yard strength loss, if you ordered 4000 psi, and that actually mixed 4000 psi, you now have appx. 2000 psi mud. I know nobody bothered to look at his water tank sight tube to see what the level was when he started pouring, it really doesnt matter at this point. This is the worst case scenario I can think of, and I would hope the least likely.

The batch plant may have just batched it out wet, for which the water/cement ratio should still be correct.


As for "waiting for it to stiffen up to pour and having no strength loss", it still depends on why it was wet, no matter what, its bullshit. Stiff or wet, with nothing added, the strength is the same. The only difference is the effect on the walls themselves. Wet mud needs the walls to support all its strength, dryer mud holds itself up to a certain extent.

The whole strength issue has two salient points now in my mind.

1) What strength is actually needed out of the walls?

Usually retaining walls are not important as load bearing walls. You would really really be surprised what can and does happen when there is nobody guarding the proverbial henhouse. Most walls are poured between a 7-10" slump.

2) The concrete company is liable for full replacement (and damn, the collective "we" are used to it) if the mud is demonstrated to be substandard.


I think if I thought there is a potential for a problem, I would either pay a testing company to come and check it, or get a Schmidt Test Hammer to find out the true strength. Ask the concrete producer to speak to their QC department and maybe they have one. You must wait 28 days to accurately find the potential strength.


Also, I was thinking about using Zypex to waterproof. Will this help fill in any of the space left behing by the evaporating water, and give me any strength back? Thanks for any input.


We put Zypex in our mud, I have no clue what you are referring to here, doesnt soundlike a concrete admixture.

Hope this helps!

Link Posted: 9/12/2005 1:41:29 PM EDT

Originally Posted By CavVet:
We put Zypex in our mud, I have no clue what you are referring to here, doesnt soundlike a concrete admixture.



I thought you guys put sugar in the mix....
Link Posted: 9/12/2005 1:44:08 PM EDT
[Last Edit: 9/12/2005 2:01:38 PM EDT by juslearnin]
Thank you very much CavVet and others- that is just the kind of advice I was looking for. I appreciate your willingness to share from your experience. I will test it and go from there.
Link Posted: 9/12/2005 1:53:28 PM EDT
I was in the redi-mix biz...and the concrete pumping biz...from what I've heard...you will be ok..
just wait a little longer on the back fill...Dan
Link Posted: 9/12/2005 2:04:44 PM EDT
Consult your design engineer. If wall found to be defective, all fees should be paid by the offending party. If the wall is designed as a cantilevered retaining wall, the highest load is near the footing. If the wall is designed as a simple span between the footing and floor then the highest bending load is at mid-span and highest shear load is at the footing/floor. If the full design strength of the concrete is not needed, the wall may be okay if certain precautions are taken by the contractor during construction. All of this needs to be verified by the design engineer. If there is the option of keeping the wall as is, I would ask for some kind of guarateed monetary instrument from the offending party in the event the wall fails or develops problems over a period of time. Usually this requirement will get all parties to agree to replace the wall.

More on the concrete. If the mix was "wet" from the addition of more water than called for in the design, the waterto cement ratio has been screwed with and the strength will be reduced. Extra mixing to start the curing reaction in the cylinder is also not advised. Flat workers know that concrete is gray and that wet concrete is easier to work. They do not know about concrete design mixes (some might but still deny it).

Cored cylinders to investigate whether the aggregate sunk to the bottom would be one investigation technique. Compression testing the cylinders would be another. I would also try and correlate the cylinder breaks with some other investigative technique.

Good luck.
Link Posted: 9/12/2005 2:13:48 PM EDT
The sugar reference for those that don't know... many years ago sugar was discovered that sugar could be used as a retarder. Enough sugar and it would not set up at all. You could keep it agitated and it would stay liquid a month. Then you added formaldehyde, which would break down the sugar, and the cement would continue its reaction and harden as normal.

There are other retarders that can be used. Calcium lignosulfonate (made from tree bark, basically a very thick tannic acid), and some synthetic retarders.
Link Posted: 9/12/2005 7:20:53 PM EDT

Originally Posted By SperlingPE:
If there is the option of keeping the wall as is, I would ask for some kind of guarateed monetary instrument from the offending party in the event the wall fails or develops problems over a period of time. Usually this requirement will get all parties to agree to replace the wall.



I have never heard of this happening before. Either it needs replaced or it doesnt. If it does, the producer pays. Usually they do so willingly, rarely it takes legal action. When legal action occurs, they usually can demonstrate it is what it was designed to be.


More on the concrete. If the mix was "wet" from the addition of more water than called for in the design, the waterto cement ratio has been screwed with and the strength will be reduced.


While there are various factors, especially cement type dependant, the rule of thumb is one gallon added per yard reduces strength by 500 psi.



Cored cylinders to investigate whether the aggregate sunk to the bottom would be one investigation technique. Compression testing the cylinders would be another. I would also try and correlate the cylinder breaks with some other investigative technique.


If I had to let you core my wall you would pay to rip the sob out.




Originally Posted By A_Free_Man:
The sugar reference for those that don't know... many years ago sugar was discovered that sugar could be used as a retarder. Enough sugar and it would not set up at all. You could keep it agitated and it would stay liquid a month. Then you added formaldehyde, which would break down the sugar, and the cement would continue its reaction and harden as normal.



I have never heard of sugar being reversed in concrete. It was used as a retarder way back in the day, but never heard of an attempt at reversal. We wont try that in my truck.


There are other retarders that can be used. Calcium lignosulfonate (made from tree bark, basically a very thick tannic acid), and some synthetic retarders.
Link Posted: 9/12/2005 7:35:41 PM EDT

Originally Posted By CavVet:
Blah, blah, blah, blah, blah....

I'm heading to the Gorge. I know nothing about Concert Trucks....

Link Posted: 9/12/2005 7:46:37 PM EDT

Originally Posted By OneOfThosePeople:

Originally Posted By CavVet:
Blah, blah, blah, blah, blah....

I'm heading to the Gorge. I know nothing about Concert Trucks....








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