Poured Concrete for Ballast

[TimRatRace]

Looking at buying a boat with a poured concrete ballast (liquid concrete instead of Blocks) for ballast - any idea what the pros and cons are. I've heard it said that a lot of hire boats use this method and also that it started in Holland with Dutch Barges - any adice and views would be gratefully received please!

[fender]

Looking at buying a boat with a poured concrete ballast (liquid concrete instead of Blocks) for ballast - any idea what the pros and cons are. I've heard it said that a lot of hire boats use this method and also that it started in Holland with Dutch Barges - any adice and views would be gratefully received please!

 

no no no! I had a boat with this sort of thing many years ago.

 

Its a cheap form of ballast. But its not removable.

 

Its a good way to ensure the hull rusts faster - water (eg damp) gets in between the concrete and hull itself and there is no way to keep it dry or wire brush/restore badly affected areas.

[Gary Peacock]

Nothing wrong with it if it is done correctly but not really the thing for narrow ditch crawlers.

 

If it's a big boat than it becomes the only real option these days other than lead or using other metal ingots.

 

The big boat I have been posting pics of the build on here will almost certainly have at least some concrete along the keel.

[stuart]

Why not just use 2" concrete slabs? If you have a flat bottom boat they fit easily enough and can be removed and cut/broken to fit the space.

[Alistair]

Hmm. I thought about using tarmac for ballast - as the bitumen will 'black' the inside of the hull and protect it, while the gravel will provide the necessary weight.

 

Or am I barking up the wrong tree?

[Gary Peacock]

Why not just use 2" concrete slabs? If you have a flat bottom boat they fit easily enough and can be removed and cut/broken to fit the space.

 

That's alright if it's flat bottomed and the water is flat too.

 

Bit more complex when you move away from ditch crawling unfortunately.

[blackrose]

Although many people say that concrete slabs can be removed, how many boats with slabs could practically do this without ripping out most of the fitout? I know some people are going to say "yes, I can get my entire floor up and can remove my ballast", most narrowboats just don't have access. However, having had a boat with poured concrete ballast I would also avoid it. Since concrete slabs are not supposedf to be in direct contact with the steel (because the lime may promote corrosion?), why would anyone want poured concrete in their bilges?

Hmm. I thought about using tarmac for ballast - as the bitumen will 'black' the inside of the hull and protect it, while the gravel will provide the necessary weight.Or am I barking up the wrong tree?

Seems reasonable - might smell a bit? Edited September 27, 2007 by blackrose

[tidal]

I have actually used poured concrete ballast on a v hulled river boat. However it was poured in small(ish) shuttered sections onto plastic sheets Each section had steel bars set in like handles so that sections could be lifted and moved when clearing rust and so that sections could be locked together to prevent the ballast shifting in even a fairly big seaway.

 

Not sure I would want to have a fixed concrete ballast system judging by the rust we had to remove every few years.

 

edited to point out that the plastic sheet was removed after aech section had set otherwise the whole idea would seem silly

Edited September 27, 2007 by tidal

[ChrisPy]

Since concrete slabs are not supposedf to be in direct contact with the steel (because the lime may promote corrosion?), why would anyone want poured concrete in their bilges?

lime wash is commonly used to protect water tanks from corrosion.

I remember (just) when I was a lad we had a big builder's galvanised water tank in the garden when we were building a house, used for storing water for mixing concrete. there was no mains water on site. over the years dipping in cement-splashed buckets and cleaning cement off tools it became caked with cement deposit. not a sign of rust after 10 years.

[blackrose]

lime wash is commonly used to protect water tanks from corrosion.

I remember (just) when I was a lad we had a big builder's galvanised water tank in the garden when we were building a house, used for storing water for mixing concrete. there was no mains water on site. over the years dipping in cement-splashed buckets and cleaning cement off tools it became caked with cement deposit. not a sign of rust after 10 years.

 

So why is it standard practice to lay bitumen soaked cloth sheets on the baseplate of canal boats before concrete slabs go in?

[tony collins]

lime wash is commonly used to protect water tanks from corrosion.

I remember (just) when I was a lad we had a big builder's galvanised water tank in the garden when we were building a house, used for storing water for mixing concrete. there was no mains water on site. over the years dipping in cement-splashed buckets and cleaning cement off tools it became caked with cement deposit. not a sign of rust after 10 years.

 

Yeah but was a GALVANISED water tank! Do you think that had some significance?

 

Tony

[John Orentas]

Far from promoting corrosion wet concrete and steel go together very well. The concrete actually prevents corrosion, in civil construction steel sections are routinely set into wet concrete. Personally though I am not sure I like the idea 'not really boat like' but no logic behind it.

[ChrisPy]

So why is it standard practice to lay bitumen soaked cloth sheets on the baseplate of canal boats before concrete slabs go in?

nothing to do with lime, Mike. ideally the inside of the bottom should be blacked, then bitumen felt laid down to provide a nice cushion that the blocks can rest on. even better is to space the blocks up a little on pieces of flexible cable to allow air to circulate, still with the bit-felt in place.

Yeah but was a GALVANISED water tank! Do you think that had some significance?Tony

no. Those tanks only lasted a couple of years before rust appeared wherever there had been dents and damage.

[fender]

Far from promoting corrosion wet concrete and steel go together very well. The concrete actually prevents corrosion, in civil construction steel sections are routinely set into wet concrete. Personally though I am not sure I like the idea 'not really boat like' but no logic behind it.

 

Not when the concrete cracks/fails and there is water ingress.

[ChrisPy]

Not when the concrete cracks/fails and there is water ingress.

now you really are quibbling.

 

John is completely correct in principle. Steel rebar in normal well made dense concrete, ebedded with the correct cover distance (usually 1") is immune from corrosion for ever, except where there is saline ground water (like in Dubai) which percolates through the slightly porous concrete, in which case all concrete is blacked up to a height of say 50mm above ground level (this may mean casting it against a bitumen membrane below ground).

 

Failure to maintain the surface of concrete will allow cracks (spalling, stress, frost) and if the water gets in it can mean trouble for the steel.

 

I have added some balance ballast in the engine ole of my wide beam by lining the right hand well beside the engine bearer with bitumastic and bitfelt, then pouring in concrete level with the bearer. Makes a great platform to stand on when servicing the engine or attending to the batteries.

Edited September 27, 2007 by chris polley

[blackrose]

now you really are quibbling.

 

John is completely correct in principle. Steel rebar in normal well made dense concrete, ebedded with the correct cover distance (usually 1") is immune from corrosion for ever, except where there is saline ground water (like in Dubai) which percolates through the slightly porous concrete, in which case all concrete is blacked up to a height of say 50mm above ground level (this may mean casting it against a bitumen membrane below ground).

 

Failure to maintain the surface of concrete will allow cracks (spalling, stress, frost) and if the water gets in it can mean trouble for the steel.

 

I have added some balance ballast in the engine ole of my wide beam by lining the right hand well beside the engine bearer with bitumastic and bitfelt, then pouring in concrete level with the bearer. Makes a great platform to stand on when servicing the engine or attending to the batteries.

 

Wasn't there some issue with the moisture in the set concrete promoting the embedded steel to corrode causing cracks to appear in the concrete, or was that only the reinforced concrete put up in the 60s & 70s?

[smileypete]

Looking at buying a boat with a poured concrete ballast (liquid concrete instead of Blocks) for ballast - any idea what the pros and cons are. I've heard it said that a lot of hire boats use this method and also that it started in Holland with Dutch Barges - any adice and views would be gratefully received please!

 

Hi,

 

I expect it's good if it's done well, however I'd be concerned any potential buyer would see it as covering up something nasty, and use it as an excuse to haggle the price down.

 

To that end I'd try to ensure it's cast in sections to make it removable, or at least take lots of pics of the baseplate before it's put in.

 

I have some cast in ballast in my boat, as it keeps a cool and even temperature it's an ideal place to keep stuff including tomatoes, apples and bread where the fridge might be too cold or dry.

 

To that end I'm going to use it as the basis for a 'pantry' if/when I get round to redoing the galley.

 

cheers,

Pete.

[fender]

now you really are quibbling.

 

 

me quibbling??

 

I seen lots of structures with failed concrete segments and the steel rods or beams exposed and rusting away pleasantly.

 

The idea of reinforced concrete is that if properly maintianed water should not get inside. But sod's law will ensure that the inevitable happens.

 

If its a narrowboat, I cant see the idea of having concrete on one side of a hull when the other is exposed to the waterand subject to the large variations in temperature which can cause the concrete to fail and/or condensation to form thus providing a nice rusty topping between the concrete and the hull

 

It might be "ok" in small sections where it is might be "neccessary" (such as in your boat) but i do remember having bought my other boat, I then found that to make some modifications to the engine room because of some niggling prob (since part of the prop shaft went through a tube encased in concrete) I had to hire a pneumatic drill to get the stuff out. It probably a bad design but the expereince taught me never to go for any boats with this sort of thing, not even one single bit of concrete poured in anywhere

[ChrisPy]

the point I was making is that the concrete (cement, lime, etc.) is not part of the corrosion mechanism.

 

but poor workmanship or bad maintenance may allow water to lodge against the steel allowing corrosion. and because it is trapped the process continues unseen and uncorrected.

 

no I would not recommend casting concrete straight against a steel hull. it is rigid and if there is any distortion, then water will get in. that is why I used a bitumen separation layer.

[Hairy-Neil]

Tarmac? - might smell a bit?

 

Fresh laid tarmac is my favorite smell.....

[Guest]

Fresh laid tarmac is my favorite smell.....

And a cure for colds and sore throats according to my old mum, bless her soul. I can remember being hauled out of the car whenever I had a cold, and some road laying was going on. "Now breath the fumes in," she used to say. Probably where my asthma started.

[smileypete]

I seen lots of structures with failed concrete segments and the steel rods or beams exposed and rusting away pleasantly.

 

The idea of reinforced concrete is that if properly maintianed water should not get inside. But sod's law will ensure that the inevitable happens.

A lot of this is due to weathering and freeze/thaw cycles worsening any cracks, this won't happen so much in the hull of a boat.

 

Concrete is naturally alkaline too which helps stop steel from rusting even if there is moisture around.

 

Also if bitumen is laid first this helps oxidise any oxygen before it can reach the steel.

 

The worst thing for steel is probably fresh rain water, not only does it have a lot of dissolved oxygen but it also absorbs CO2 making it slightly acidic.

 

Wasn't there some issue with the moisture in the set concrete promoting the embedded steel to corrode causing cracks to appear in the concrete, or was that only the reinforced concrete put up in the 60s & 70s?

I think it was due to the cement being too alkaline:

 

http://en.wikipedia.org/wiki/Concrete_cancer

 

cheers,

Pete.

[TimRatRace]

I should have said that the boat is 72 foot long - have no idea if that makes any difference!

[Big Steve]

My 1976 Hancock and Lane has poured concrete ballast on a 1/4" baseplate, no problems yet!

[ChrisPy]

My 1976 Hancock and Lane has poured concrete ballast on a 1/4" baseplate, no problems yet!

yeah, but it's still a young 'un, innit?