nealtw

Follow instruction on the bag.

MoreCowbell

Well, it turned out OK after all (I think).



I was mixing batches of about 2 cu.ft. at a time in my small mixer. I didn't use any slump tester, just eyeballed it. The first couple batches were probably stiffer than normal and the last few probably a little looser than they needed to be. In any case, it's been almost a week now and I'll probably wait the full 28 days before taking my temporary supports out and putting weight on it.

Nealtw, I think I'm safe with that 45 deg stress cone. There is 14 inches between the column and the edge of the footing. Including the 3.5" curb on top, I have 15.5" of concrete depth.

Now, just 4 more to go.

Thanks for all the input.

mudmixer

Cowbell -

You do not have to wait the fictitious 28 days. That number is only for standard laboratory testing procedures and they frequently test much more often and after a couple of days you will have 70% of ultimate and your loads are no where high enough to have to wait.

Your soil was warm and you are buried, so the conditions for curing are good.

Dick

CallMeVilla

In 14 days, you get 80% strength. In 28 days, you reach the 100% strength. In reality, you have to make the call.

Here is a curve which gives you a strength versus time curve: http://www.ce.memphis.edu/1101/notes/concrete/section_3_properties.html

Nice job on the pour. Good to see quality work being done out there.

MoreCowbell

Well, I was iching to remove the temporary supports and get the weight on the new column. You gave me that last push. I did that a few hours ago. That made 8 full days of curing. It looks like it's supporting the weight just fine.


Thanks for all the tips.
-Rob

BridgeMan

Regarding slump (although too late now), if he's really anal about it, he will acquire a K-slump tester. It's a handy little device that you poke into a pile of concrete, and it immediately gives you a slump reading. Uses a calibrated, perforated hollow tube that lets the mortar in the mix flow into the tube. Paid around $25+ for mine 30 years ago (made in Canada, as I recall), so they're probably double that by now.

If he decides to "guesstimate" his slump, placing a shovel-full of mud (on a dry surface) that almost stands up by itself will be good-to-go. Somewhere between 2" and 3".

Jasone

interesting...