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Slump test after adding Super P?


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#1 Supe

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Posted 30 September 2008 - 05:55 PM

For you concrete guys. Please forgive my ignorance on the subject, as I'm a welding guy, so the extent of my concrete knowledge goes about as far as telling my ass from my elbow.

Is it required or outlined in any code section as to when slump tests should be performed when Super P plasticizer is used? The concrete had all tests run before adding the Super P, air tested ok, slump was routinely low. These results were documented, the Super P was added, and no additional testing was performed before it was poured.

This is foundation work for a fossil power plant.

We're going under the assumption that the addtion of the Super P would pretty much invalidate any slump test anyways, but we're looking for some evidence or section of code that confirms or refutes this process of running no further tests after the plasticizer is added (break tests were all coming back good).

This is pretty much a CYA scenario in case of a QA audit or something like that. Thanks for the help.

#2 sehad

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Posted 30 September 2008 - 06:42 PM

What I've dealt with mostly, Super P is used when you want high early strength or whenever you want high slump to allow the concrete to be poured easier. Water to cemet is one of the biggest factors in the strength of the concrete. The slump test is simply a consistancy test that shows that the concrete being brought to the jobsite is the same in each truck and also as a warning if the desired water/cement ratio may be exceeded. You are correct that a slump test after the Super P is added is really not giving you anything because it will be like 10", if not more.

Super P takes the place of water, so your water/cement ratio is extremely low meaning that the strength will be higher and will reach there faster. Most of the tests that we run when dealing with Super P is a slump vs. time. This shows you how much time you have to work the concrete after the Super P is added. We then do a strength vs. time test, which is no different than a normal mix validation. Once the Super P starts to lose it's effectiveness, the slump drops very fastly and it loses its ability to be worked. These tests are done before any mix design is approved.

We do require that the Super come from an approved source and document that manufacturer recommendations as far as rate per yard were followed. On the jobsite testing we really don't do anything except normal testing (air & test speciments for breaks). I'm of the opinion as well that the slump gives you nothing and it passes our state QA inspections. At least I've never been slapped on the wrist before.

I know I've rambled and probably not answered what you were looking for but hope this helps.


#3 Supe

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Posted 30 September 2008 - 06:52 PM

QUOTE (sehad @ Sep 30 2008, 01:42 PM) <{POST_SNAPBACK}>
What I've dealt with mostly, Super P is used when you want high early strength or whenever you want high slump to allow the concrete to be poured easier. Water to cemet is one of the biggest factors in the strength of the concrete. The slump test is simply a consistancy test that shows that the concrete being brought to the jobsite is the same in each truck and also as a warning if the desired water/cement ratio may be exceeded. You are correct that a slump test after the Super P is added is really not giving you anything because it will be like 10", if not more.

Super P takes the place of water, so your water/cement ratio is extremely low meaning that the strength will be higher and will reach there faster. Most of the tests that we run when dealing with Super P is a slump vs. time. This shows you how much time you have to work the concrete after the Super P is added. We then do a strength vs. time test, which is no different than a normal mix validation. Once the Super P starts to lose it's effectiveness, the slump drops very fastly and it loses its ability to be worked. These tests are done before any mix design is approved.

We do require that the Super come from an approved source and document that manufacturer recommendations as far as rate per yard were followed. On the jobsite testing we really don't do anything except normal testing (air & test speciments for breaks). I'm of the opinion as well that the slump gives you nothing and it passes our state QA inspections. At least I've never been slapped on the wrist before.

I know I've rambled and probably not answered what you were looking for but hope this helps.



Are there any ACI codes or comparable that say that the tests other than slump must be performed with the plasticizer added? Or are whatever tests used before the addition admixtures acceptable?

Thanks for your help.

EDIT: I suppose it is also worth noting that the plasticizer is being added on site, primarily to address pumpability issues.

Edited by Supe, 30 September 2008 - 06:53 PM.


#4 I-GO-TO-11

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Posted 04 October 2008 - 10:10 PM

QUOTE (Supe @ Sep 30 2008, 06:52 PM) <{POST_SNAPBACK}>
Are there any ACI codes or comparable that say that the tests other than slump must be performed with the plasticizer added? Or are whatever tests used before the addition admixtures acceptable?

Thanks for your help.

EDIT: I suppose it is also worth noting that the plasticizer is being added on site, primarily to address pumpability issues.

6-

Usually super p is added on site. The slump of concrete should be tested prior to the addition of super p. water should never be added once the super p is mixed

#5 sehad

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Posted 06 October 2008 - 12:44 PM

QUOTE (Supe @ Sep 30 2008, 01:52 PM) <{POST_SNAPBACK}>
Are there any ACI codes or comparable that say that the tests other than slump must be performed with the plasticizer added? Or are whatever tests used before the addition admixtures acceptable?

Thanks for your help.

EDIT: I suppose it is also worth noting that the plasticizer is being added on site, primarily to address pumpability issues.


I've dug back through the few ACI codes that I have and everything dealing with concrete is saying 1 slump, density, air, & temperature per day should be taken minimum. Most concrete is accepted on 28 day strength but early breaks are needed if traffic, or heavy loads, are to be on the slab before the 28 day.

Still doesn't help you that much, but the only section in those codes that talk about materials, it talks of admixtures and no specific additional testing is required. The sections dealing w/admixtures are only refered to ASTM standards, which would be a material standard if I am not mistaken.

The ACI codes are only "best practice" suggestions and can be deviated from slightly as long as good engineering judgement is used. I would say that doing the slump test before the addition of the super P due to the slump changes and making sure that the pre-super P slump is consistent should CYA. But that's my opinion.

Sorry I can't be any more help Supe, that's as far as I can go.

#6 Supe

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Posted 06 October 2008 - 12:50 PM

Appreciate the help guys. I think QC is going to make them run a slump/time test at the very least once they've added the Super P, as they weren't doing any checks right now, only before. If ACI doesn't mention any additional required testing for admixtures, then we won't worry too much about it.

Thanks again!

#7 Road Guy

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Posted 09 October 2008 - 01:07 AM

regardless of admixtures the normal testing quidelines would still apply, for examply if you required 5000 psi concrete you would still break the test cylinders but you would hope to attain earlier strength (I think wink.gif )

#8 sehad

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Posted 09 October 2008 - 12:18 PM

QUOTE (Road Guy @ Oct 8 2008, 08:07 PM) <{POST_SNAPBACK}>
regardless of admixtures the normal testing quidelines would still apply, for examply if you required 5000 psi concrete you would still break the test cylinders but you would hope to attain earlier strength (I think wink.gif )


This is true. What you are ultimately looking for in the strength and for the water/cement ratio to not be exceeded.

You should still do the 28 day test & any early breaks to allow loads on REGARDLESS of what admixtures or water reducing agents are used.

#9 bennett279

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Posted 03 December 2008 - 08:12 PM

You should always perform your slump and air entraptment tests PRIOR to adding the plasticizer or retarding agent. Ranges of these values should be provided in the specifications of the concrete. If the concrete is given a performance spec without mix specifications (ie, 4000 psi, 28-day strength), the the concrete supplier should provide a mix design and testing results validating the mix prior to placement.

Performing a slump test is a way to provide quality control on the mix prior to placement. If the delivered concrete does not meet the slump specifications for a particular mix design, then it should be rejected because that result means that the water/cement ratio is not within tolerances (too wet and weak batch). After the slump is verified, plasticizer can be added for workability.

#10 littlewheels4

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Posted 07 February 2009 - 02:11 AM

I am not sure why ACI is so slow to adopt QC procedures for field tests. But, I have heard that places in Japan are using the list of tests below on concrete with Super Plasticizer admixture. I don't have any pictures for these apparatus but with some additional research maybe you could find some.

Slump Flow
1. make sure base is level,
2. place cone on top of base and hold down firmly,
3. fill the cone with concrete, level with trowel,
4. remove any excess concrete from around the base of the cone,
5. quickly raise the cone and allow the concrete to flow out,
6. start the stopwatch and record the time for concrete
to reach the ~20in circle
7. measure the final diameter of the concrete in two directions and average

Note: You can use a slump plate with a diameter marked at 20 in.


V- Funnel
1. Wet inside of funnel.
2. Fill the V-funnel to top without compacting or tamping.
3. 10 seconds after filling, open the trap door and allow concrete to flow out
4. Measure the time between the opening of the trap door and the complete discharge of the V-funnel.
5. When light is seen from above through the V-funnel, stop timing.
6. Wait five minutes and repeat without cleaning funnel

http://www.humboldtm...p-184-id-3.html


L-Box
1. Place metal gate in slot
2. Fill vertical part of box completely and level
3. Let stand for 1 minute
4. Remove metal slider and allow concrete to flow
5. Measure time after removal of slider until concrete reaches 8" and 16"
6. When concrete stops flowing, measures H1 and H2 and find ratio

http://www.humboldtm...p-183-id-3.html

#11 fawad kpk

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Posted 14 July 2011 - 10:18 AM

A slump test is a method used to determine the consistency of concrete. The consistency, or stiffness, indicates how much water has been used in the mix.
The mold for the slump test is a frustum of a cone, 300 mm (12 in) of height. The base is 200 mm (8in) in diameter and it has a smaller opening at the top of 100 mm (4 in).
The base is placed on a smooth surface and the container is filled with concrete in three layers, whose workability is to be tested .
Each layer is temped 25 times with a standard 16 mm (5/8 in) diameter steel rod, rounded at the end.
When the mold is completely filled with concrete, the top surface is struck off (leveled with mould top opening) by means of screening and rolling motion of the temping rod.
The mould must be firmly held against its base during the entire operation so that it could not move due to the pouring of concrete and this can be done by means of handles or foot rests brazed to the mould.
Immediately after filling is completed and the concrete is leveled, the cone is slowly and carefully lifted vertically, an unsupported concrete will now slump.
The decrease in the height of the center of the slumped concrete is called slump.
The slump is measured by placing the cone just besides the slump concrete and the temping rod is placed over the cone so that it should also come over the area of slumped concrete.
The decrease in height of concrete to that of mould is noted with scale. (usually measured to the nearest 5 mm (1/4 in).


Source
Slum Test
www.daentoes.com

#12 mizzoueng

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Posted 14 July 2011 - 02:13 PM

QUOTE (bennett279 @ Dec 3 2008, 03:12 PM) <{POST_SNAPBACK}>
You should always perform your slump and air entraptment tests PRIOR to adding the plasticizer or retarding agent.


^ This. We've had a lot of concrete on site and all tests were done prior to adding the Super P.

Not sure if its defined anywhere in code, but we stated it explicitly in the SOW that it would be done prior to adding.


#13 Archimedes

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Posted 25 November 2011 - 07:19 PM

Slump tests are a qualitative measurement, and don't really represent anything other than a consistent visible measurement of the consistenecy of the mix. Even though our specs and notes still call out the slump, I personally think the test is overrated and often allow the the results to be ignored once the concrete supplier has demonstrated consistent break stregths - this is what we are really after. Once you add plasticizer the premise behind the original slump test is no longer as valid. You could develop some criteria for a certain amount of SP but it feels like your forcing a test to fit a situation for which it wasn't originally conceived.

On the other hand it does represent a good quality control measure for the contractor. It makes the contractor more aware of the desire not to add water, and helps them spot bad mixes. But honestly, this doesn't happen that much, they usually catch it, and a good concrete supplier will not send out bad mixes. (unless their on the take?...Big dig style)




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