A contractor has proposed using "QUIKRETE" for the installation of a pump pad. The quikrete has a listed compressive strength of 4000psi. My question is: is this an appropriate product for this application? Pump pads are subject to dynamic loading. I see nothing in the Quikrete literature or on their website concerning the use of this product for this application.
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Quikrete 1
- Thread starter steve1
- Start date
GeoPaveTraffic
Geotechnical
The biggest problem you are likely to have is keeping the mix consistant from batch to batch since it would be hand mixed on site. Unless redi-mix is not available, I would not allow hand mixed.
How big is that proposed pad, plan and thickness? GeoPave is right about the consistency. It's very easy to get too much water in these and blow all the strength out the window, especially if the guys on site don't do it according to the manufacturer's directions because they've "been doing it this way for 20 years".
If you're talking about a very small pad for a residence, it might not make a difference. If it's large, supports a large machine, or is on weak or improperly compacted soil, you might want to require ready-mix.
If you're talking about a very small pad for a residence, it might not make a difference. If it's large, supports a large machine, or is on weak or improperly compacted soil, you might want to require ready-mix.
- Thread starter
- #4
GeoPave & Uc,
Thanks for your replies. The pad is for a pump being installed in a power plant over an exist concrete slab on grade. Although the pad is not that big (approx 7' x 4' x 1 foot thick)I just don't like the idea of using a product designed for backyard applications being used in this situation. I have no problem rejecting the contractor's request I'm just looking for some justification for when the client asks why I'm rejecting it.
So far I have come up the following:
There are no test resuts from the manufacturer for this application.
There is no way to ensure the consistancy from mix to mix.
There is no mix design specified with the product, just a strength value.
We don't know all the additives in the mix.
Thanks for your replies. The pad is for a pump being installed in a power plant over an exist concrete slab on grade. Although the pad is not that big (approx 7' x 4' x 1 foot thick)I just don't like the idea of using a product designed for backyard applications being used in this situation. I have no problem rejecting the contractor's request I'm just looking for some justification for when the client asks why I'm rejecting it.
So far I have come up the following:
There are no test resuts from the manufacturer for this application.
There is no way to ensure the consistancy from mix to mix.
There is no mix design specified with the product, just a strength value.
We don't know all the additives in the mix.
how about making the contractor responsible for quality control - and providing the necessary info for your acceptance? For instance, he should be required to submit proof that the inplace concrete meets your specifications. Make him cast cylinders and break them. Make him submit the material to a lab for analysis. Ask for him to explain how he plans to deliver consistent mix to the site. Of course, to be fair - you should also do this for ready mix...
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1
- #6
Thoughts regarding premixed products.
A wet premixed product (a Ready Mix Truck) is ready to place and should only require minor retempering. Given previous documentation, the product is reasonably (but not always) predictible. Relatively minor testing is usually required for some quality assurance.
A dry premixed product (bagged concrete mix) is not ready to place. In this case, water is to be added. A very critical step is now in action on the job site. How much control over the water quantity will the specifier have?
I have had experience testing QUIKRETE and some similar products. Getting specific directions for the correect amount of water is pretty easy. The contractor's astonishment comes when he finds out what the real slump is, quite stiff. More additives are required for workability and to maintain the strength. I find this is a problem with many prepackaged construction products.
The issue of hand mixing or small batch mixing may or may not be a big issue. Remember that most of the world places concrete using small hand or partially mechanically mixed techniques. Back in my Army days (daze) I remember some significant construction using hand mixes in South Viet Nam. It was not that many years ago that the US of A used this method. Many of our accomplished constructions were placed in small batches.
At the risk of some ridicule, the following song lyrics;
Cement mixer, putti putti,
Cement mixer, putti putti,
Cement mixer, putti putti,
(Poodle-da-skoodie, poodle-da skoodie,
poodle-da-skoodie)
(Re-beat...).......Concrete!
First you get some gravel,
(From the streams) about.
You mix a mess of mortar,
(Splash) a mess of water,
See the mello-roonie come out!
Slurp, slurp, slurp....
Cement mixer, putti putti,
Cement mixer, putti putti,
Cement mixer, putti putti,
Who wants a bucket of cement?
A wet premixed product (a Ready Mix Truck) is ready to place and should only require minor retempering. Given previous documentation, the product is reasonably (but not always) predictible. Relatively minor testing is usually required for some quality assurance.
A dry premixed product (bagged concrete mix) is not ready to place. In this case, water is to be added. A very critical step is now in action on the job site. How much control over the water quantity will the specifier have?
I have had experience testing QUIKRETE and some similar products. Getting specific directions for the correect amount of water is pretty easy. The contractor's astonishment comes when he finds out what the real slump is, quite stiff. More additives are required for workability and to maintain the strength. I find this is a problem with many prepackaged construction products.
The issue of hand mixing or small batch mixing may or may not be a big issue. Remember that most of the world places concrete using small hand or partially mechanically mixed techniques. Back in my Army days (daze) I remember some significant construction using hand mixes in South Viet Nam. It was not that many years ago that the US of A used this method. Many of our accomplished constructions were placed in small batches.
At the risk of some ridicule, the following song lyrics;
Cement mixer, putti putti,
Cement mixer, putti putti,
Cement mixer, putti putti,
(Poodle-da-skoodie, poodle-da skoodie,
poodle-da-skoodie)
(Re-beat...).......Concrete!
First you get some gravel,
(From the streams) about.
You mix a mess of mortar,
(Splash) a mess of water,
See the mello-roonie come out!
Slurp, slurp, slurp....
Cement mixer, putti putti,
Cement mixer, putti putti,
Cement mixer, putti putti,
Who wants a bucket of cement?
dicksewerrat
Civil/Environmental
He can order a short load from the Ready-Mix plant. He would have to mix about sixty bags of 'Quikcrete' to do the project.
Richard A. Cornelius, P.E.
Richard A. Cornelius, P.E.
Thanks emmgjld - what's the tune to your jingle?!!
You are quite right on the hand/portable mixers. I've alluded to this on other threads. Interstate type roads in China are built with the hand mixers quite successfully. If you have good site supervision, I don't see a big problem with using site mixing - even from prepackaged materials. In some ways you can have excellent control on the water to go in. Secondly, even though the slump may be lower (stiffer mix) you are placing almost immediately after placement so there would be no loss of slump with time. I agree, though, with Richard, if you can order the short load from a ready mix supplier, it will be 'cleaner' all the way around - less mess, quicker placement, etc.
You are quite right on the hand/portable mixers. I've alluded to this on other threads. Interstate type roads in China are built with the hand mixers quite successfully. If you have good site supervision, I don't see a big problem with using site mixing - even from prepackaged materials. In some ways you can have excellent control on the water to go in. Secondly, even though the slump may be lower (stiffer mix) you are placing almost immediately after placement so there would be no loss of slump with time. I agree, though, with Richard, if you can order the short load from a ready mix supplier, it will be 'cleaner' all the way around - less mess, quicker placement, etc.
I have personally used QUIKCRETE pre-bagged concrete mix, but it was a 6,000 psi mix that is locally bagged here under the QUIKCRETE label. We were doing a RC column jacket (column enlargement to existing RC column) and access was difficult and only small volume (less than 50 bags).
We used a water-reducing admixture to reduce w/c ratio and measured slump and took lots of cylinders in addition to testing agency.
We did a trial batch to achieve the "correct" dose of admixture, water content etc to achieve a given slump and workability. Actual production concrete we recorded mix #, mix time, water content, admixture dose. All went very well...so need to any additional water, and the pre-bagged concrete product was very consistent.
Given our access problems...at $7 per 50lb bag was an economic choice too.
HTH
We used a water-reducing admixture to reduce w/c ratio and measured slump and took lots of cylinders in addition to testing agency.
We did a trial batch to achieve the "correct" dose of admixture, water content etc to achieve a given slump and workability. Actual production concrete we recorded mix #, mix time, water content, admixture dose. All went very well...so need to any additional water, and the pre-bagged concrete product was very consistent.
Given our access problems...at $7 per 50lb bag was an economic choice too.
HTH
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