Anyone have any placing or finishing experience with exposed aggregate ?

The reason I ask is, the other day I pumped a pool deck for a guy that was 20 meters total. There was 3 guys placing and finishing the concrete and the temperatures was around 29*C outside with humidex around 32*C, I go back today and what they had poured the other day looks terrible, cold joints, pitted and in other areas no stone showing, almost like there was no retarder or perhaps it was the 4.5 hour old concrete.

The contractor is blaming the concrete supplier and of course the supplier is blaming the contractor. I personally have looked at 2 jobs the contractor has done they look great, I also seen 2 jobs the concrete supplier has supplied to different exposed contractors and they too look great ??

The only thing that has changed, so it would seem would be that on this particular job there it was pumped and the rest were not.

My question is this, could pumping exposed aggregate versus conventional methods affect the quality of finish you will get, could it be possible that pumping the mix could actually compact the stone and bring too much creme and fines to the surface ?

I'm curious to know, I can't say I have or at least remember ever pumping a exposed mix before

 

Never seen EA pumped in the 31 years I've been building. My guess is that the pumping action alone may have been enough to overwork the mix and bring either too much creme up or too quickly. Were there site conditions that required pumping?

 

I can call my concrete sub in the morning and post back his thoughts.

 

Residential, was over the house with a 45 meter boom pump.


Appreciate it,

 

Oh jeeze, thats a long run. I'm thinking I might be not all that far off base that the mix got churned up to much in the process. It may have been hitting a little hard on the drop end also, further compacting the aggregate. He's up early, I will def post his thoughts. Good luck.

 

Yea I'm kinda leaning towards that reasoning myself, the 45m pump is a 5 section boom with a lot bends and now matter how I configured the boom the jib had 30'ft of free fall slamming the concrete into the jib elbows then out the whip hose and free falling another 10'ft. ... not to mention the 1200 psi pump ramming the concrete down 130'ft of boom..

Like I say I can't recall ever doing one !

Thanks Ed

 

Just talked to Sam, sent text and he was up. First he s old school so his thoughts are likely biased. Said the only thing he will pump is footings, walls and plain flatwork like a basement or garage floor. He also said that if you wind up doing a breakout and have to redo using the pump again, he would drop it into a couple of site mixers at the pour location and remix, but not too much, to redistribute the ag and fines. Also said something about using care on the wash if the mix has been worked a lot...and then he started losing me. I'm no finisher. Hope this all works out to everyones satisfaction.

 

You and me both, I'm no finisher by any means I have pumped a few thousand meters in my day but as far as finishing I leave that to the pro's. Well perhaps there may be a rip-out in order, but that's up to the Home Owner, Contractor and Supplier to sort out, I just pump it from A to B.. quality issues with the concrete and finishing are generally not my concern unless I can't pump the mix. If the pump does in fact affect the finish on exposed, if ever asked again to pump it I'd suggest finding another means of placing it,

This could be a leaning experience for a few people including myself.

 

Do you remember the slump that was requested by the contractor ?...

 

The mix was 32Mpa C-2 6% air 10% slag delivered @ a 4" slump

 

Did he ask for a 4? Did you add to it before pumping ?

I assume it was hand troweled. 4 being fairly stiff shoots my theory of the retarder siting on top of too much water or running off ....

 

Also wondering if you normally send a PSI mix ?..Aprox 3200 ,4.5 hours old , 80 or so degrees , stiff pour ,, sounds like trouble all the way around , the ash soaks op a lot of moisture as well

Just thinking out loud ....

 

When I had my house back in Indiana done in 2002, had a porch and sidewalk put it with exposed surface, I loved it on my barefeet. BUT,,,,, It was a BEAR to shovel in the winter time! Never used any ice melt on it , just took time to shovel carefully to clear it.

 

All of this combined with the o/p saying that there were cold joints in it makes it sound to me like they never really got it laid down, and it just got away from them.

20 yards is a pretty big pool deck for only three guys in the summertime sun IMO, particularly if the mud's being poured that stiff - lots of edges, joints, drains etc...

 

Contractor ordered it @ a 4" I never add water to the mix unless I can't pump it, then I stop the pump and wait for the Contractor, Mixer driver or engineers to make that call, my only concern is being able to pump the mix, the quality is up to the pro's to figure out, I'd rather not see any more water than that of it's design, I had a "Boom " party once.... Once. from concrete way too wet that separated in the boom, that took 9.5 hours to unplug........ needless to say No washing in my hopper and no I won't pump wet 6" + concrete without plastisizer...more so with the lower Cement ratio's like wall mixes and that garbage.

They used a Fresno and Bull float