Column discoloration
Column discoloration
(OP)
What is this discoloration in the lower part of the column? it's not honeycomb because I tried hammering it and there is no honeycomb. Anyone has encountered this? How do you fix it?
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RE: Column discoloration
RE: Column discoloration
What's fly ash? why is it in the lower part of the column? I'm thinking whether it may be cause by some water leaking out leaving the cement behind (that's why it has color of cement, is this possible)? It's not honeycomb. No one has encountered this yet?
RE: Column discoloration
Dik
RE: Column discoloration
RE: Column discoloration
the original picture has no honeycomb but has same color pattern as the honeycomb.. could it be lack of water in the concrete or in the verge of honeycomb?
About the picture above... hammering it appear it is only in the concrete cover.. is it serious enough to warrant removing the entire layer of the concrete and pouring new one? What have you experienced?
RE: Column discoloration
Are you worried about structural issues? I wouldn't worry about structural issues, however I'd suggest that any loose material be removed and then the honeycombing should be patched; if it's truely just in the cover as you've stated. If you're still worried about structural issues, not exactly conclusive, but you could have the surface tested with a swiss hammer or something of the like.
RE: Column discoloration
How do you tell how deep it extends? I see solid concrete inside but not sure if there is micro honeycombs.. I don't want to keep hammering it because it can reach further inside.
When you use hammer on concrete.. is it supposed to be damaged significantly? how do I know if the hammer is removing honeycomb or normal concrete?
RE: Column discoloration
RE: Column discoloration
how long in your experience does the concrete stay green before it gets super hard? during green, it can be strike with hammer? i use a normal carpenter nail hammer
RE: Column discoloration
by the way.. in honeycombing pictures in the net, they honeycomb is same color as concrete (whitish).. but in the columns I saw, the honeycombs have color of fresh cement grout, the first picture has the same color but no honeycomb.. any theory where the colors come from especially in the first page picture?
RE: Column discoloration
RE: Column discoloration
RE: Column discoloration
The slump is 3/4 aggregates and it's 4000 psi concrete with only $2 difference to 3000 psi so admixture is probably used. The concrete supplier won't say what they use since it's company secret and they said they only supply concrete. But let's say it's ash fly, why is it at the bottom only? The contractor doesn't know either although the foreman said before concrete is pour, a liquid basin of grout cement is poured inside to seal any cement cracks in the surface of the previous lift at the floor level, could the discoloration at the bottom be from this liquid basin of grout cement? Vibrator technique is adequate as the hose is lowered all the way to the bottom and every sides and center vibrated.
Here's another picture of it at another angle. Is there no possibility it is caused by water leaking out of the cement rather than the honeycomb principle of cement leaking out of the aggregate?
RE: Column discoloration
RE: Column discoloration
but if you will note about the second picture (or again the following), the discoloration is half the height of the column in the location of the honeycombs. So it could be related to some liquid leaking. So i guess micro liquid leaking just cause the discoloration at bottom without honeycomb. More liquid leaking gives full fledge honeycomb. What do you think of this theory?
RE: Column discoloration
RE: Column discoloration
mortal "pig" from pump? what's that? no, the pump crete hose wasn't directly aimed inside the formwork but the column was filled up by aiming at a board on top of the column opening.
for the separate issue of honeycombing. Has anyone ever used epoxy in treating honeycomb? a worker suggested the honeycomb need not be removed but epoxy can be pumped thru the holes at high pressure filling up all spaces inside the honeycomb. has anyone ever used this technique? or is this never used?
RE: Column discoloration
Don't listen to that worker. You can't be sure of filling all honeycombing voids by injecting epoxy.
RE: Column discoloration
this is close up of the discoloration in the vicinity of the honeycomb (the left I hammer to see how deep it is, it's not deep enough is it).. haven't any of you guys ever encountered it before? it's only in the vicinity of the honeycomb so it must be related to leak or segregation problem. any other theories?
RE: Column discoloration
this is close up of the discoloration and honeycomb, i hammer the left side to see how deep it is, it doesn't look deep enough, is it. The discoloration must be related to the honeycomb because it only appears in the vicinity of the honeycomb (left and right side). Any other theory beside fly ask, mortal pig, etc.? note it only appears in the vicinity of the honeycomb. haven't anyone amongst you encountered this before?
RE: Column discoloration
RE: Column discoloration
http://img441.imageshack.us/img441/3513/honeycombh...
RE: Column discoloration
RE: Column discoloration
do you suggest demolishing the column and recasting it? but it is 4000 psi, can the concrete be safely demolished without damaging the more fragile grade 60 bars?
btw.. it's not a mortal "pig" problem because I remember that when the pump hose were connected and before concrete was put in the columns, the initial mortal was thrown away so it couldn't be mortal pig.
RE: Column discoloration
RE: Column discoloration
RE: Column discoloration
RE: Column discoloration
unfortunately there are already beams and slabs in next floor cast above the column. So only the lower one third column needs to be replaced. But if you will insert new concrete, concrete can settle.. how do they handle this? is this even possible at all? What have others actually use in solving this? The supports of the upper beams and slabs are still in place.. we just didn't notice the honeycombs because the formworks were taken out too late.
RE: Column discoloration
It is always best to inspect lower elements first before casting something above...but I'm sure you know that now.
RE: Column discoloration
RE: Column discoloration
RE: Column discoloration
the bar is a dowel to connect the the column to the wall at the side.. the blue i don't know...
anyway.. i found out the reason for the discoloration, it's because water was used 20 minutes before I photographed it and they stayed in the honeycomb section longer that's why the honeycomb section appeared darker. In the following picture is the same column but with no water sprayed for an hour. So it may not be as bad as the earlier picture. Although hammering indicates it is not honeycomb passed the concrete cover section. I'm worried it may be soft inside. Can anyone recognize if the column is salvageable without replacing an entire section... what equipments like x-ray can be used to inspect inside.. has anyone used one
http://img692.imageshack.us/img692/5261/honeycombw...
RE: Column discoloration
Low frequency ultrasonics or other similar scanning techniques would be less expensive and can be used to locate larger interior voids. Will be good substantiation if you reject the column.
Efflorescence is simply and indication of excessive moisture moving in and out of the concrete. It can indicate that your concrete is more permeable than desired. It has little effect on the concrete or the performance of the column structurally, but can more quickly allow carbonation of the concrete to greater depths, thus increasing the potential for rebar corrosion if exposed.
RE: Column discoloration
after removing all the honeycomb soft concrete and creating a key like shape, can one just fill it with epoxy instead of concrete? what is the psi of epoxy.. maybe this would be better for shallower honeycomb as it would adhere better to existing concrete since it is epoxy?
RE: Column discoloration
In Russia building design you!
RE: Column discoloration
The concrete does not appear to be discoloured by excessive form oil, but appears to be suffering from poor concrete placement. What is the height of the column and what percentage of reinforcing. What sort of placing procedure did you use for the concrete and what mechanical vibration? The discolouration appears to be from segregation.
Rather than spend time examining the condition of the poor concrete, it's better to remove it ASAP. This can be done with hydroblasting or carefully use some mechanical means as not to damage the reinforcing steel.
Dik
RE: Column discoloration
The column size is 400x500mm... reinforcement percentage is 2.51%, the concrete came from a concrete truck that is rotating, placement is via pump crete and then the concrete down in a 3 meter tall column with vibrators inside. The following is the picture after we remove all the soft honeycomb, only the outer part is soft so I think the column is salvegeable since no bars exposed, all the concrete are already hard inside. Maybe the vibrator was not used on the outside. You agree it is salveable? Now my next step is what mortal to use to patch it. Do you think normal concrete in 1-2-3 combo will be sufficient?
RE: Column discoloration
here
http://imageshack.us/photo/my-images/844/honeycomb...
RE: Column discoloration
Just because the concrete seems "hard" on the inside does not by any means indicate you don't have a problem with it. Assuming that can get you into a lot of trouble.
Stop playing with it and get on with the remediation. As dik recommends, hydroblasting would work.
RE: Column discoloration
Ron, are you saying it is still soft inside? but we tried hammering and it looks hard. Is it not you fix honeycomb by removing the soft part. The concrete supplier explained that when the concrete is poured from the concrete truck, it hits one side so the aggregates go to the outside part and the vibrator missed the outside part.
About this "potentially insufficient paste in areas of accumulated coarse aggregate".. is this not what honeycomb is all about? or is it worse than honeycomb? how? by the way, it's just the lower 1 meter of the 3 meter high column.
RE: Column discoloration
by the way, here's the picture of the entire column, the upper part is ok.. only the 1/3 lower part is the problem, so it couldn't be bad concrete mix from the concrete truck.. maybe just the fact the lower part is not vibrated properly? what do you think?
http://imageshack.us/f/442/honeycombentirecolumn.j...
RE: Column discoloration
RE: Column discoloration
The stirrups are about 2mm behind where the soft honeycomb is removed. Can anyone give a theory whether it is leaky formwork or the outer part not vibrated that cause the problem? But the 2/3 upper part of the column is good.
Discussing it with the foreman in case the lower portion of the concrete have to be removed. We don't have the technology to pump it from below. So the best we can do is remove the 1 meter portion of it.. put formworks and put concrete via the upper part by extending the formwork outwards and overfilling with concrete. Has anyone amongst you actually tried replacing a portion (say whole 1 meter part) of a portion of a column? We haven't tried it so if the honeycomb removed is sufficient. We don't wanna try something we haven't done before.
RE: Column discoloration
That wa s my thought too... Longitudinal corner bars, let alone the ties, should be visible with that amount of concrete removed. This looks very suspect.
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Column discoloration
RE: Column discoloration
In your photo, you appear to have elongated coarse aggregate particles with preferential, stratified alignment. Further, these stratifications appear to have little paste between them, indicating accumulated, segregated aggregate. This is different than "honeycomb" which is evidenced by sparse coarse aggregate and little paste.
You stated that the concrete was pumped. The concrete in the column has little to do with how it came out of the truck, since it was pumped from there. It is likely the segregation occurred from dropping the concrete a long distance, as you can see that consolidation was better as you when up the column. Further, you stated that vibration was done from the top. This would not allow full vibration of the concrete to the bottom of the column. Each of these is a bad practice in itself.
If you review the ready mix delivery tickets, you might find that the concrete was relatively old when placed and was losing slump. Further, there's a chance that the aggregates were not in a saturated surface dry (SSD) condition with the concrete was batched, thus caused water loss by aggregate absorption.
You further indicated that the drum of the truck was rotating when delivered....well of course it was. It should have been. Your comments suggest that you know little about concrete technology and yet you are being placed in a position of accepting conditions about which you know little and have not determined some critical aspects of the concrete as it exists in place, particularly interior to the column (strength, voids, segregation, etc.). I suggest that if you have any authority whatsoever that matches the responsibility you seem to have been give, you should exercise it and get the bad concrete out of the column.
Concrete is not nearly as simple as it appears. It takes concerted effort by multiple parties to get concrete design, batching, mixing, placement and curing done correctly. Much of the time that seems to happen without such effort; however, that is with experienced actions all around.
Good luck.
RE: Column discoloration
Ron, you wrote : "In your photo, you appear to have elongated coarse aggregate particles with preferential, stratified alignment. Further, these stratifications appear to have little paste between them, indicating accumulated, segregated aggregate. This is different than "honeycomb" which is evidenced by sparse coarse aggregate and little paste."
so there are placement that is different from honeycomb. The following pic is in opposite side of the column we are talking about. Is the column bad portion a result of
this descriptions "elongated coarse aggregate particles with preferential, stratified alignment. Further, these stratifications appear to have little paste between them, indicating accumulated, segregated aggregate"?? I've been looking for ways to describe it. Did the above describe it accurately? if not, pls. add more so we know what went wrong and can decide how bad it is.
http://imageshack.us/f/822/columnback.jpg/
we are just small company and don't have much crews and engineers.
RE: Column discoloration
Problem is not going away... time to quit dikkin'
RE: Column discoloration
Anything else we can provide from photographs is purely speculation. You need to decide if you want to do further testing or just take it out and re-do the column. I think if you do testing it will lead to the same decision as you should be making now....tear out the bad concrete.
Being a small company has nothing to do with it. If your company was large enough to do the job, they are large enough to fix their mistakes. You are simply prolonging the inevitable.
RE: Column discoloration
RE: Column discoloration
Dik, Ron and hokie, etc. the following picture is what the rebars look like inside (I photographed it before the column was casted with concrete). The lower portion has stirrups spaced 80mm apart and 3 sets of stirrups with 4 bars at each side of the column (total of 16 bars). Let's say we remove the concrete at the lower one meter. How are we going to put concrete and insert vibrator when the stirrups are 80mm apart in the lower part and we can't pump it up from below but have to do forms with concrete put from the top. Btw.. the building is 3-storey with metal roof, the column is in the second floor so it has one floor to support above and a metal roof above it. The column is somewhat overdesigned for safety factor.
http://img824.imageshack.us/img824/8219/columnreba...
RE: Column discoloration
The building main and only seismic system is concrete special moment frame so I may try to remove the concrete for peace of mind. Based on the above picture of the rebars inside and the stirrups being mere 80mm apart in the lower bottom. Can we just use chipping gun? But how can it even be inserted inside the 80mm spaced stirrups? And for a 1 meter concrete replacement, can it do without vibration at the bottom since we can't insert any vibrator thru the closely spaced stirrups?