Concrete Problem

pegleg peggy

Help! Two days ago I dug holes for my new T-bar washing line - 18" deep for 8-foot poles - and cemented the poles in with a standard pre-measured sand-and-cement mix from Woodies. We added in some big rocks for stability and "grab" but I wouldn't say they made up more than 15% of the mix, and they didn't abut the poles.

I let it cure for 48 hours and just now when I tightened the winch after hanging up a very light wash, the concrete cracked and the poles are now leaning towards one another :eek:

The dried concrete seems very sandy to me and looks dark grey as opposed to greyish white. I have no doubt it will crack further if more pressure is put on the poles.

Anyone know what went wrong? We came up with with 4 possibilities:

(1) The soil was very dry -and leached the water right out of the mix before it cured;

(2) the poles are not in deep enuf (I put them in any deeper it will be a clothesline for dwarfs!)

(3) The mix we bought was $h1te.

(4) 48 hours was not long enuf for it to cure.

Any advice gratefully received as now we have to do it over. (And please don't say "buy a clothes dryer", because we are trying to get out ESB bills down!)

Thanks!

red sean

(3) The mix we bought was $h1te.

Most likely!
You'd really need a mix of gravel and cement rather than sand. Pre-packed stuff is usually only good for patching wall chases etc.

sky6

Those premixed bags are not great and you don't know how long they have been lying around. Cement needs to be fresh. Also you used it far too soon. Concrete needs time to cure which takes up to 3 Months to cure fully.
You will have to do it again.

Use a few bags of Sand and Gravel and a bag of Cement. Mix it at a ratio of about 3 to 1. Gravel and Sand to 1 Cement.
Mix them thoroughly dry until you cannot see any of the Cement in the mixture. Add the Water slowly until you get it like a thick mix.
Don't add too much water as it weakens the cement and can also wash the cement out of the mix.

I would secure the base in the ground first and not be depending on the Concrete to take all of the strain when the poles are in.

When you pour the Concrete in this heat I would cover it with a few boards or something to prevent it from drying out too quickly. Then after 24 Hours pour some Water on the top of the Concrete. This helps it to harden out
( Gain Strength )
I would then wait at least 2 weeks ( the longer the better. ) before I put the poles in place. Even then no heavy loads like sheets for a while.
You should then have no problems.

TopTec

Reckon it is a combination of factors as pointed out above. But, the rule of thumb for depth is a 1/3rd of the length should be below. So for an 8 foot pole 30" below. This is a general rule and will be affected by the type of ground you have and the load on the pole.

TT

pegleg peggy

Thanks everyone, great advice and between you all and my friends on Facebook I think I know what to do now. We'll have another go at it and let you know how it worked out!

One shot on kill

The premixed stuff is ****e stay away from it.

You never said what width the hole was that you dug.

You mixed mortar as suppose to concrete. Get some gravel and cement mix it again and you should be ok to work away after a few days. And remember the bigger the hole the more concrete you need therefore increasing the stability of the pole and weight to stop turning or twisting in the soil.

bbam

Remember, with the ratchet you can put huge inward pressure on the poles. Our's is made from 40mm stainless box and no doubt I could bend the poles in by winding the ratchet tight, so be careful about that..

When putting ours in we dug the hole, ~24 inches deep. then I got two scrap lengths of steel that would fit tightly inside the poles. cut them to 24inches and pointed one end. these were driven down into the centre of the hole, about anothjer 12 inches into solid ground, the poles slid down over them and then concreted in.. I also welded scrap steel offcuts onto the bottom of the poles to anchor them to the concrete..

What diameter of hole did you dig ? you need a good mass of concrete for it to be strong enough, maybe 20 inches across.

Then leave for 7-10 days.

pegleg peggy

Hi Bbam, the holes were about 20 - 24" wide. That scrap metal inside thepoles idea sounds really good... Now I just have to find some scrap metal!

CJhaughey

You can buy Postcrete which sets up fast, That and some lengths of rebar running in the direction of the line next to the pole would be better.

pegleg peggy

CJhaughey wrote: »

You can buy Postcrete which sets up fast, That and some lengths of rebar running in the direction of the line next to the pole would be better.

Have you used Postcrete? I've seen it all right (after I used Failcrete, lol)

CJhaughey

pegleg peggy wrote: »

Have you used Postcrete? I've seen it all right (after I used Failcrete, lol)

Yes, setting posts for a timber fence, works well for that but remember that washing lines often have a higher loading in one direction.
I think you are best to make an oval hole and use short 3ft lengths of rebar running in the same plane as the line but beside the pole.

monkeynuz

CJhaughey wrote: »

Yes, setting posts for a timber fence, works well for that but remember that washing lines often have a higher loading in one direction.
I think you are best to make an oval hole and use short 3ft lengths of rebar running in the same plane as the line but beside the pole.

I have used postfix ready mix for lots of things, it is fine as far as I am concerned.

I've known people also to drill the post and fix in a couple of lengths of studding and the concrete the whole thing in.

Builders in dry weather used to cover concrete with damp sacking also works for frost if I remember correctly.

One shot on kill

Jasus lads its for a close line. Mix concrete this time and put in enough it will be grand. The longer the line is the more extreme you need to be with the size of the hole and what type of anchoring you do.

paddy147

Postcrete for 4 euro in B&Q

Perfect solution and rock hard in 30 minutes.




Dig hole.

Place pole/post in hole.

Add in half a bag of postcrete

Add in 1.5 litres of water.

Wait 5 minutes.

Add in rest of postcrete

Add in another 1-1.5 litres of water.

Leave to set for 20-30 minutes.

Go make a cuppa tea and admire your handy work.





PS-The longer the washing line and taller the poles are,then the deeper and wider a hole you dig.And the more postcrete you use.

Its really is that simple.

Cerco

I am thinking of doing a "T" clothes line. Thought about using two old steel car wheels with centre holes roughly the same diameter as the poles.

Putting the wheel down about 30" , pushing the pole through the centre about 4" into the ground, then filling the whole thing with concrete.
Thought this would make a sturdy base and support the poles.


Anybody think this would work or see anything wrong in this suggestion?

red sean

Should do fine. It's a clothes line, not an ESB high voltage line!

paddy147

Nice crafty shill there Mart with your 1st post.

whizbang

If you can anyway do it, make those posts removable.
As per previous poster, get some scrap iron or whatever, that will allow the poles to fit snugly inside , and concrete these into the ground.
Go as long and deep as you can, use them as pole 'extenders'. keep the lot a couple of inches below the ground level.