Thread: Curing of deck footings

28 days

Originally Posted by rod1949

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

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

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.

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

28 days....

Peter ,
do you have clearance to drill the holes later , after you have built the deck ?

Did you by chance use rapid hardening cement ?

Originally Posted by MrPotatohead

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.

Originally Posted by MrPotatohead

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 .

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

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?

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

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.

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