How long does it take for concrete to 'cure'?

[alittlerespect]

Humm!

You have some half baked idea's - get a Structural Engineer to do the calcs for you, or you could find yourself taking the lot up and starting again!

Given the daily punishment the posts will recieve you would be best advised to wait a minimum of 28days for the concrete to reach its design strength before adding the gates. The SE should advise you on this element.

Regards

 

[RonnyRaygun]

after 2 weeks it will have reached 50% of its ultimate strength

it must be kept damp all this time. Once it dries it will stop gaining strength and will not start again.

the strength and hardness gaining gets slower and slower as time extends. The hardest and strongest concrete is usually underground where it has stayed damp and continued curing for 20 years or more.

BTW 2ft deep is not enough for a 15ft gatepost

i disagree..... concrete can take up to 40 years to cure... so reaching 50 per cent in two weeks is not quite right...... but in most installations it is strong enough the next day....

Most structural concrete is specified with a 28 day strength...so - in case you don't know - it should have reached its design strength in 28 days (4 weeks). So at 28 days a specified 20N concrete should, in theory, have a strength of 20N/mm^2.

However, concrete curing isn't linear, so after 2 weeks it will have reached around 75% of its 28 day strength, which in turn is around 90% of its ultimate strength, which it might take years to reach.

 

[^woody^]

The only time an engineer gets involved with gate posts, is when he opens the gates to drive up to his charming out of town mansion

 

[RonnyRaygun]

The only time an engineer gets involved with gate posts, is when he opens the gates to drive up to his charming out of town mansion

I wish! Builders earn more than engineers these days

 

[JohnD]

after 2 weeks it will have reached around 75% of its 28 day strength, which in turn is around 90% of its ultimate strength,

I stand corrected. My memory is not as good as I thought.

so 14 days is (75% x 90%) = 67.5% or thereabouts of ultimate strength, not 50% as I said

depending on temperature and wetness, of course

 

[RonnyRaygun]

Yeah, sorry John, I got the impression GRRRRaint thought it was less than 50%...so was correcting him, not you