Should I be worried?!

[Delinquent]

Had foundations concrete pumped today. As I didn't want to tackle this all by myself in a deep trench the builder who will be doing the blockwork said he'd come out with a labourer to help.

Pump arrived, but the mix was so dry that even with the (large!) poker going full pelt it would hardly shift along the trench. The builder asked the concrete chap to wet it up a bit so it would flow better, which he did, and it did.

After an hour of seriously hard slog, arms and face burning from the concrete (yeah I should have washed it off immediately) I signed off the load without really reading it (yeah I know!!!) - now I have, it says he added 200 ltrs of water to 6+cu m (so 6000 ltrs) of C35 mix and the bit I signed was said it's now "non-conforming" . By my reckoning that's about a 2-3% increase in water content - Is Mr Building Inspector going to tell me to rip it all apart again?!

 

[noseall]

no.

 

[noseall]

it does shrink down the pegs as it dries but it will set like bell metal.

eventually.

 

[noseall]

by the way if it is any consolation i think freeflow additives do more harm than adding more water.

it can cause the aggregate to settle at the bottom.

ho hum.

 

[Delinquent]

Many thanks Noseall, I might just get some sleep now.

Had horrific visions of trying to shift it all back out with a kango - having taken a strip of previously laid pump mix only measuring about 1cu m I was just about to throw the towel in.

time for beer and bandages...

 

[Delinquent]

BTW - as to setting like Bell metal "eventually"... it's now 5 hours since we finished, and it's already bloody hard - I know because I just fell over onto it (hint - don't check handywork in the pitch black)

 

[noseall]

BTW - as to setting like Bell metal "eventually"... it's now 5 hours since we finished, and it's already b****y hard - I know because I just fell over onto it (hint - don't check handywork in the pitch black)

concrete will remain green for the immediate future but will harden slowly.

it takes weeks for deep filled trenches to fully hydrate and become mature.

 

[Delinquent]

aye, experienced the difference recently with the piles - some of which were chopped to height when green, some were left a bit too long and I had to reduce height a month or so later...

Still a bit worried about the water, don't know why - probably because of the implications if they weren't happy (or at least, what my imagination tells me the implications could be...)

 

[Shytalkz]

Don't be. Additional water slightly weakens the strength and the extent of shrinkage, neither of which are a major concern for strip/trenchfill footings, as the concrete spec is waaaay over the top for what is actually required, strengthwise.

Edited to add, uh duh, it's an rc footing, I presume. In which case, if it was RC35 and you wetted it up a bit, it still will be fine, the disclaimer is just a clause that the conc co get you to sign, because, technically, the mix doesn't comply with the BS.

 

[noseall]

Still a bit worried about the water, don't know why - probably because of the implications if they weren't happy (or at least, what my imagination tells me the implications could be...)

just bare in mind that some older properties were built off soil.

some 1960's houses had as little as 7" of poor concrete.

 

[noseall]

the disclaimer is just a clause that the conc co get you to sign, because, technically, the mix doesn't comply with the BS.

every now and again, a man with a sampler, will take a bit from the batch and test it. i don't know to whom he is affiliated but the driver told me it is done randomly and on a regular basis.

p.s this was done on site and not back at the works.

 

[Delinquent]

cheers chaps, it wasn't so much the strength of it I was concerned with (hell after 1 day setting I've been trying to clear some off the oversite and it's 100 times stronger than any hand mix I've used - plus the whole thing is ludicrously over-engineered to protect the S.E.'s PI!!!) It's purely keeping happy those that have to be pleased enough to sign my build off.

 

[noseall]

It's purely keeping happy those that have to be pleased enough to sign my build off.

then you truly have no worries. building control will ask for the found's to be at a certain depth or minimum thickness but have little to do with the quality of the concrete.

 

[Delinquent]

definitely a beer moment then (again )

oh - ironically, while digging out the oversite, we came across the founds of the original house... all 5 inches of soft holey stuff, I say stuff as I don't think it could really be classed as concrete. It's 1/2 inch below ground level.

 

[Coniferman]

Why does Mr Holmes always say "Never Ever Ever, Just add Water!"

I'm not saying there is any reason to worry. I wouldn't have a clue. Just wondering why he says it.