Fixing a groove/hole in concrete

[JohnD]

4-6 weeks ago.

I think I read it since (when trying to sort out the gate issue) but I wasn't told by them, which would have been helpful. How long do you keep it wet for?

The calculated strength is based on keeping it wet for about a month. However if you keep it wet for a week it will reach about 50% of design strength, which is adequate for a garden path. Once it has dried out if will not restart curing, even if you wet it again. You will see the colour change from dark grey to near-white.

IMO you would do well to drill or chip out an oversized hole, deep as you can, and set a non-rusting pipe (larger than the bolt) in a fine mix of your own, and put a piece of plastic or a rubber mat over it to keep the sun off, and have a watering can handy so you can water it at least once a day. Concrete cures best in dull, drizzly conditions, and worst in hot sun. Do not put the bolt into it for a couple of days to prevent early cracking.

Like a fence post set in concrete, your strong new piece will transmit the load to the weaker surroundings. The deeper you drill, the better the existing concrete is likely to be, because it will have been buried out if the sun.

Old concrete around drains and fenceposts is often remarkably hard and strong, because it may have been buried in wet ground for 50 years or more, never dried out, and never stopped hardening. The hardening process gets slower and slower over time, in a logarithmic curve.

I am sometimes annoyed by the cavalier way some builders ignore the importance of wet-curing new concrete. You can get fast-setting cements, but they are awkward to use.

 

[JohnD]

BTW, for my own garage door, I put in 15mm copper pipe stubs to receive 12mm bolts.

They are a good fit, but the doors have sagged, so I think a larger pipe is better so you can more easily bolt them even after a bit of warping.

I have seen bolt sockets with a wide, mushroom-shaped head to avoid chipping.

To avoid bending and stooping, you can use a monkey-tail or a cane bolt, which has a long handle.

There's a good range here:

Gate Bolts | IronmongeryDirect | Same Day Despatch

Shop Gate Bolts & Security at IronmongeryDirect. Galvanised Steel Animal & Drop Bolts, Monkey Bolts & More with Next Day Delivery & Free Returns on All Orders.

www.ironmongerydirect.co.uk

 

[Karolisko]

BTW, for my own garage door, I put in 15mm copper pipe stubs to receive 12mm bolts.

They are a good fit, but the doors have sagged, so I think a larger pipe is better so you can more easily bolt them even after a bit of warping.

I have seen bolt sockets with a wide, mushroom-shaped head to avoid chipping.

To avoid bending and stooping, you can use a monkey-tail or a cane bolt, which has a long handle.

There's a good range here:

Gate Bolts | IronmongeryDirect | Same Day Despatch

Shop Gate Bolts & Security at IronmongeryDirect. Galvanised Steel Animal & Drop Bolts, Monkey Bolts & More with Next Day Delivery & Free Returns on All Orders.

www.ironmongerydirect.co.uk

Thank you very much for taking your time and sharing your knowledge!

 

[noseall]

I am sometimes annoyed by the cavalier way some builders ignore the importance of wet-curing new concrete. You can get fast-setting cements, but they are awkward to ususe.

It's more to do with preventing the gear from drying out too quickly. There is usually enough water present to allow a controlled cure. Issues arise on sunny warm days especially where there is no polythene present along with a thirsty base. Covering with poly is enough as it reduces the hydration.