Concrete tower base

[Colin Blackburn]

I'm currently putting in a base for a tower. The base is about a metre cubed of concrete with a ragbolt assembly in the cube. The hole is dug and the ragbolt is in position, filling it with concrete is next. However, the bottom of the hole is in clay and with the current weather rain is collecting in the bottom of the hole and not draining away. There is probably an inch of water in the bottom. Will this water have any significant effect on the concrete (C35 mix) if I was to fill the hole with one prepared load?

Colin

[Ian Stirling]

Me, I'd avoid the whole issue. Dig an extra spade depth at the middle of the bottom of the hole, and empty it with a wet+dry vacuum cleaner.

[Brian Reay]

I think I'd do the same.

The hole needs to have a good square bottom, even better undercut the base to prevent the lump moving (which I've seen happen).

Let me guess what the tower is for ;-)

[Dave Stanton]

That will be for his own personal celluar base station !!.

Dave

[Huge]

Four 17 ele Tonnas and an 80m trapped dipole?

[Brian Reay]

Drool ;-)

Came in from work today to find new neighbour having "Sky" installed (2nd attempt- first seemed to stop Saturday when installer put dish lowish on wall, in gap between houses. A blind man could have seen it wouldn't get a clear path).

2nd company go for chimmney option, dish is pointed directly at my 2m/70cm/6m and 4m antennas and maybe 4m from same. If the installer didn't notice the antennas in the sky, the fact he had to pass the mast base to put the ladder in my garden (with permission), should have given him a clue.

Oh well, not much on Sky worth watching ;-)

[Huge]

With about 2.4kW ERP into his dish, will it matter if there's anything worth watching anyway?

:o)

[Brian Reay]

And that is just if my M3 daughter is operating ;-)

73

Brian

[Colin Blackburn]

Fair enough.

It has been undercut to some degree. It is also slightly oversize compared to the specified size. The rag bolt is also supported on three enormous stones which will add extra mass.

A domestic wind charger. Did you guess wrong ;-)

Colin

[Brian Reay]

Sure did. I didn't think anyone was that sad ;-)

Make me feel better, stick at least a small antenna on the top

[nightjar]

Concrete sets by chemical reaction, so it is quite happy setting underwater. Some yachts carry a bag of sand and cement mix (well-sealed) as part of their emergency repair kit because of that.

Colin Bignell

[Ian Stirling]

However, water will diffuse in, and wetten the mix, making it weaker. This is probably not relevant in this case.

[Colin Blackburn]

Not sad, desperate. We live off grid.

Only if it would be happy going around with the wind direction!

Colin

[Colin Blackburn]

Okay, I have the hole sorted and most of the water will be out by the time I have concrete. I need 1.1 cubic metres of concrete and I'm looking at ways of getting it there.

Because of restricted access a standard (RMC, say) concrete mixer could only deliver it onto the ground for me to barrow it in by hand. If I was to take this route then has anyone any idea of the extent of the spread of the pile so that I can plan for laying out polythene?

I may yet get it mixed on site or find some local mini-mixer delivery that could get the stuff directly into the hole.

Colin

[Set Square]

I've just done a rough calc on the assumption that the heap will be a cone with sides at 30 degrees to the horizontal. Not sure whether this is reasonable, but if it is, the base would be a circle of diameter approx 2.5 metres.

[Ian White]

Just in case there's anything similar near you, Colin: at the main branch of May's Carpets near here, they have a bin full of large sheets of heavy polythene - 25p a sheet in the charity box. Some of them are even reinforced, and would be just the thing for dumping concrete on.

Seems like a very good way of recycling used packaging.

[The Natural Philosopher]

42 degrees is about the angle most natural 'scree slopes' end up at.

[Set Square]

OK - if the angle was 45 degrees, the base diameter would be about 2.1 metres - so it's still in the same general ballpark. [I don't know how wet concrete compares with scree in this respect - it probably depends on *how* wet it is.]

[Rob Morley]

Seems to me it would be no more effort to mix it yourself, with the mixer placed at the edge of the hole.

[Alan]

Hi,

What size is the tower? Would guy wires be a good idea?. If you are off grid then I would guess your turbine is large - I would hate to see it topple in 100+mph winds.

I for one would like to know more about what you are doing. (does that make me sad?) Perhaps you could start a new thread telling us how you are doing this. Are you installing the whole system yourself or just the concrete? What turbine are you going for? Inverter? Batteries?. What site analysis have you done? I am sure there are lots of others on this NG who are looking into alternative power and would love to hear from someone actually doing it

Cheers,

Alan.