Curing of deck footings

[MrPotatohead]

Hi guys!

On the weekend I poured the footings for my deck. The footings were 400x400x700mm. I levelled out the top of the concrete so I can bolt the stirrups to them. When will it be safe to drill into the concrete? So far its been almost 3 days. Is that OK? I dont particularly want to crack the concrete and dig it up... that would suck:no:!

Appreciate your thoughts..

Cheers,
Peter

[rod1949]

28 days

[MrPotatohead]

28 days

Hi Rod,

Isnt 28 days the time for the concrete to be fully cured or something? It seems like a long time to wait before drilling into it. I read somewhere else that brickies will start laying bricks a few days after the footings for a house have been poured, but seeing as Im drilling, I wasnt sure... Is 28 days from experience, or something you were told etc?

Thanks,
Peter

[Manuka Jock]

Peter ,
what mix was the concrete , were there additives in it , did you mix it yourself or get delivered from a batching plant ?

[MrPotatohead]

Hi Manuka, I mixed it myself in a mixer. I bought a sand/aggregate mix from the local landscaping store, and mixed at the recommended ratio of 5:1 (mix:cement).

Cheers.

[Manuka Jock]

It might be advisable for you to consult a local contractor , supplier , or authority then.

[Christopha]

28 days....

[Manuka Jock]

Peter<!-- google_ad_section_end --> ,
do you have clearance to drill the holes later , after you have built the deck ?

Did you by chance use rapid hardening cement ?

[rod1949]

Hi Rod,

Isnt 28 days the time for the concrete to be fully cured or something? It seems like a long time to wait before drilling into it. I read somewhere else that brickies will start laying bricks a few days after the footings for a house have been poured, but seeing as Im drilling, I wasnt sure... Is 28 days from experience, or something you were told etc?

Thanks,
Peter

Peter, firstly you have answered your own question. Secondly laying bricks to drilling concrete are two entirley different applications. In your situation you are going to insert probably a dynabolt and by its very mechanical application its going to expand, and in doing this there is every possibility the green concrete will crack thus the holding power is deminished. In addition as a result of the cracking concrete cancer sets in which is moisture penetrating and any steel in the concrete rusts and that rust builds up and expands thus it is known as concrete cancer.

[Manuka Jock]

Is 28 days from experience, or something you were told etc?


Its a chemical process Peter

What does 28 -day strength mean?
Concrete hardens and gains strength as it hydrates. The hydration process continues over a long period of time. It happens rapidly at first and slows down as time goes by. To measure the ultimate strength of concrete would require a wait of several years. This would be impractical, so a time period of 28 days was selected by specification writing authorities as the age that all concrete should be tested. At this age, a substantial percentage of the hydration has taken place.
http://www.cement.org/basics/concretebasics_faqs.asp


If by chance you have used rapid hardening cement it will not take so long .

If not , and if you cannot do the drilling at a later stage , you could pre-cut some of the timber , do oiling or staining if needed , etc.
If not , just wait it out .

[InterTD6]

Normal concrete reaches its design strength in 28 days. from initial set its strength rises quickly for the first week & slowly rises for the next week, then rises slower over next 2 weeks, cold weather will slow the process down as well. Chemical anchors will get around most problems of expanding anchors in green concrete.
regards inter

[r3nov8or]

No experience here, just a question that may help the OP.

Would be easier to drill the holes now (not cured), than to let it cure and then have to drill the holes at maximum strength?

[Manuka Jock]

Yep, chemset anchors are an idea.
My concern with drilling green concrete is hitting a re-bar and the vibration blowing the found apart .

[artme]

Jock is right on the money.with all he says.

Spoke to some builders and concretors about this sort of thing the other day. AND they all said use chemset for the bolts/anchors.

[MrPotatohead]

Hi guys,

Thanks for all of your comments, I get it now. I tried drilling a footing taking it very slow, and it drilled fine. Its a very good point regarding dynabolts however. I definitely wont torque them up for a few weeks. I looked into chemset, but pricewise it doesnt compare to dynabolts, even if I have to wait a few weeks.

Appreciate the help guys,
Peter

[Manuka Jock]

Cheers Peter

[weisyboy]

3 days. before structural work can begin. normally.

why didn't you use stirrups that were set into teh concrete

[MrPotatohead]

Weis,

Thanks for your reply. I have since drilled all of the footings, and set the posts. At the moment I have just braced the posts, and will hold off a few days before tightening the dynabolts.

The reason for bolting stirrups over setting them, is that this is the first time Ive done this and a builder mate told me that it is easier to get them in the right position, by levelling the top of the footing and bolting, compared to messing around with wet concrete.

Cheers,
Peter

[nadroj]

The method is to work out your levels and dig the holes, and rig up the posts so they will be exactly where you want them, with stirrups attached - maybe even with bearers etc already attached as well, which helps locate the posts. Then, dangle the posts using temporary struts etc over the holes, then pour in your concrete. Quick and accurate.
Jordan

[Manuka Jock]

The reason for bolting stirrups over setting them, is that this is the first time Ive done this and a builder mate told me that it is easier to get them in the right position, by levelling the top of the footing and bolting, compared to messing around with wet concrete.

Cheers,
Peter
Yep , good idea. We may know the pitfalls after we have done it a few times , but not so the first time out .
Peter you have done it the right way for your situation .
Tightening the bolts after the job is done , even drilling and dropping them in as the job progresses , is a valid work method .

Keep us posted with pics .
cheers ,
Jock

[MrPotatohead]

Certainly will jock!

Cheers.