concreting fence post question

[leckie1]

Hi
i have just started my first outdoor diy project to put up some closeboard fencing. I managed to dig my hole to the correct depth of 2ft(8ft post) for 4"x4". but i think my have used incorrect proportions for the concrete mix (cement : aggregates )as i mixed by hand and took quite a long time. i'd heard you should not use a shovel to measure, so the only thing i had to hand was an old ladel from my kitchen! i think may have prepared mix of 1:7, instead of 1:4 based on the amount of cement i have left.

is this ok for my end post...The post has set really hard now but am worried that the concrete may not be strong enough for fence postt

 

[JohnD]

underground concrete has the advantage of staying damp permanently. Over time this enables it to grow stronger than ordinary concrete. Make sure it does not dry out at least until winter (covering it with polythene and watering it occasionally will do). It will then continue gaining strength for many months. Mixing it well and packing it firmly will have helped.

You will see a change in colour from dark grey to whitish once it dries. It will then not harden any more.

It will be a real drag digging it out and doing it again, so I would recommend leaving it unless you find it starts to crumble or break.

Remember it does not have to be much stronger than the well-consolidated ground you put it in.

If, in a couple of weeks, you find you can still scratch it with a teaspoon, or if it looks and feels like sand and gravel, and it is yellow instead of grey, then I would reconsider.

Is the top of the concrete above, below, or at ground level?

 

[leckie1]

Hi JohnD, the concrete is finished at around ground level. i can move the post a little when i hold on to the top of the post, but this might be normal for a 6ft post

i made the concrete in about 16 batches using the method of measuring i mentioned. so some of the concrete might have had the right mix, other batches stronger/weaker etc

i did tamp down well though but as it got dark i began to run out of time so i used some rubble just below the surface to fill in, didnt realise it would take so long.

thanks for your reply and advice. we'll wait and see if this topic needs to be moved to 'DIY disasters'

 

[Thermo]

a post will wobble slightly at the top, thats normal. 1:7 is a tad weak but should be ok, it would normally be around 1:6

 

[leckie1]

btw does anyone have any tips on how to finish off(smooth etc) the concrete where it meets the post at ground level. i used a trowel but could not work due to small stones/gravel

 

[Thermo]

youll struggle with dry mix. you can wet it and do it, but to be honest itll never be seen, so just finish it beolw the surface of the soil

 

[leckie1]

i have heard that rot is the main danger and was thinking of water getting in between the post and the concrete but i suppose this is inevitable in the long run.

 

[JohnD]

Or use concrete posts that don't rot.

Unless you are a slow learner, you will next time.