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Poured concrete as ballast


Napton

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I noticed at Crick that one of the boat fitters ( the one with a big vloggers presence) was displaying a boat which had been shown to have wet poured concrete as ballast. What are peoples opinions on this? I’m aware it was common in the 1970’s but not so nowadays. The boatfitter claims it’s an “innovative” method of ballast. Is it? I’m in the market for a new build and have very little technical experience, don’t want to get caught out! Comments would also be welcome on an integral water tank on a boat in excess of £200K.

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It doesn't appeal to me for a couple of reasons in my view.

 

1 - once in position you have no way of checking whether ant rusting is taking place and if for any reason the area where the concrete is gets wet you won't be able to check that it hasn't found its way underneath. Boats can and do flex, and although it may appear to be a perfect sea, over time ot may move slightly allowing water ingress.

2 - If ever you need to remove some or all of the ballast to change the trim of the boat or if you add weighty items which may lead to a need to redistribute ballast it will be a major job to remove.

 

In my view it is a quick way of adding ballast but for the reasons above it may be a problem in later years after purchase.

 

Howard

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Apparently a very bad idea as the concrete lime can cause corrosion in the steel when damp, or when surface cracks open up, or moisture can percolate down the junction betwen the concretes and the steel sides.

 

I am no metalurgist or scientist but the whole subject of corrosion in steel boats is interesting and I have read a number of 'papers' on how steel corrodes/rusts.

 

There are a large number of scienticic papers on the subject as it is a huge problem for the construction industry where steel reinforcing bars are covered in concrete.

 

Extract :

 

Steel corrosion in any environment is an electrochemical process in which iron (Fe) is removed from the steel being corroded and is dissolved into the surrounding solution; it then appears as ferrous ions (Fe+). For steel embedded in concrete, the dissolution takes place in the limited volume of water solution present in the pores of the concrete surrounding the steel.

The ferrous ions dissolved in the concrete pore solutions usually react with hydroxide ions (OH−) and dissolved oxygen molecules (O2) to form one or a combination of several varieties of rust, which is a solid by-product of the corrosion reaction. 

 

 

Steel corrosion may process as a local pitting or a wide area corroding surface, and generally experiences initiation and propagation nonlinear with time. (Romanoff, 1957; Tuutti, 1982; Alamilla et al., 2009; Ricker, 2010). In engineering practice, the corrosion loss of steel is commonly estimated, using an simplified expression (e.g., Ricker, 2010; JSCE, 2013):

 

 

DO YOUR OWN RESEARCH before buying.

Edited by Alan de Enfield
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I think probably a bad idea for canal boats due to the nature of their use i.e. banging around in locks. 

 

One of my boats, which is a sea going craft, is ballasted with concrete. I have no way of knowing the condition of the steel internally but it doesn't leak and isn't sinking which is a good start. 

 

 

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Poured concrete ballast is a terrible idea. Its cheap, nasty and un-adjustable. 

 

The best bilge is proven to be one with open ventilation over steel/lead  ballast that will not adsorb water. Any bilge will over time occasionally get wet either from leaks or spill or normal condensation run down. If its full of damp concrete the steel will corrode. Engineering bricks adsorb very little water, steel or lead none at all.

 

Consider how the trim of the boat could ever be altered if need be due to possible eventual over-plating, change to a large battery bank for electric drive or a change of appliances/layout.  Just changing a calorifier or a ceramic shower base location will require trim adjustments.

 

I would never entertain concrete ballast.

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26 minutes ago, magnetman said:

I think probably a bad idea for canal boats due to the nature of their use i.e. banging around in locks. 

 

One of my boats, which is a sea going craft, is ballasted with concrete. I have no way of knowing the condition of the steel internally but it doesn't leak and isn't sinking which is a good start. 

 

 

 

 

I always have visions of the base of the boat corroding away completely and you wouldn't know anything about it until all that is left under the waterline is the concrete plug of ballast, which then falls off.

 

But more seriously, I'd imagine  five tonnes of concrete ballast contains a tonne or so of water which will evaporate over a year or two, leading to more ballast being needed. Or if there turns out to be too much ballast, renting a large pneumatic drill will be needed to get some out.

 

 

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I have had poured concrete since 1989.    It has given me no troubles.  I know of a number of other boats with it, again, they have had no trouble. 

 

 Like everything, it needs to be done well to be durable.  There are a number of lumpy water boats made  out of ferro concrete where a concrete shell is sprayed or trowelled over a steel rod frame.  They are insurable if they have been maintained.  There are even some concrete canal craft dating back to WW1. There are thousands (millions?)  of reinforced concrete structures from bridges to car parks around the world and where these are constructed to a good design and properly maintained they have given good service for many years.

 

 

There are negatives:

You must plan ahead.

 

  Adjusting concrete ballast is noisy, and you need to take the floor up.  You dont need a pneumatic drill though.  A Kango hammer is quite enough.

 

You have to think long and hard about how much you need and the overall trim.   I left myself needing about half a ton of extra loose ballast, which was handy for trimming..  This has nearly all gone overboard  over the years, p as middle age spread has set in.

 

The steel needs to be properly clean, and ideally cement washed before the main pour goes in.

 

You need to work quickly  get it in,  pokered and vibrated solid.  It is physical work.  Bulk concrete goes off quite fast, especially if it is warm- so dont sit down for a brew after the truck driver has shot the load into the bottom.

 

Would I do it again?  Only if I could not get hold of some lead or steel blocks instead.  If the only alternative was bricks or paving slabs, certainly.

 

 

N

 

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24 minutes ago, MtB said:

 

 

I always have visions of the base of the boat corroding away completely and you wouldn't know anything about it until all that is left under the waterline is the concrete plug of ballast, which then falls off.

 

But more seriously, I'd imagine  five tonnes of concrete ballast contains a tonne or so of water which will evaporate over a year or two, leading to more ballast being needed. Or if there turns out to be too much ballast, renting a large pneumatic drill will be needed to get some out.

 

 

Yes if the bottom were to drop orf half way across the English Chanel one could be in a spot of bother. 

 

I find life is too long to worry about such things. Boat was built 1985 and concrete from new inside a 5mm steel hull. She'll go down by the starn I think. 

 

 

 

 

Leaning to the larboard side on the way to Davy Jones locker. 

Edited by magnetman
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1 hour ago, Alan de Enfield said:

 

Apparently a very bad idea as the concrete lime can cause corrosion in the steel when damp, or when surface cracks open up, or moisture can percolate down the junction betwen the concretes and the steel sides.

 

I am no metalurgist or scientist but the whole subject of corrosion in steel boats is interesting and I have read a number of 'papers' on how steel corrodes/rusts.

 

There are a large number of scienticic papers on the subject as it is a huge problem for the construction industry where steel reinforcing bars are covered in concrete.

 

Extract :

 

Steel corrosion in any environment is an electrochemical process in which iron (Fe) is removed from the steel being corroded and is dissolved into the surrounding solution; it then appears as ferrous ions (Fe+). For steel embedded in concrete, the dissolution takes place in the limited volume of water solution present in the pores of the concrete surrounding the steel.

The ferrous ions dissolved in the concrete pore solutions usually react with hydroxide ions (OH−) and dissolved oxygen molecules (O2) to form one or a combination of several varieties of rust, which is a solid by-product of the corrosion reaction. 

 

 

Steel corrosion may process as a local pitting or a wide area corroding surface, and generally experiences initiation and propagation nonlinear with time. (Romanoff, 1957; Tuutti, 1982; Alamilla et al., 2009; Ricker, 2010). In engineering practice, the corrosion loss of steel is commonly estimated, using an simplified expression (e.g., Ricker, 2010; JSCE, 2013):

 

 

DO YOUR OWN RESEARCH before buying.

There is a danger of some misunderstanding here.  Essentially, concrete offers good protection to the steel reinforcement (or baseplate).  Something to do with its alkalinity.

 

However, over time concrete is subject to carbonation arising from CO2 in the atmosphere, which reduces its protective properties and can lead to spalling following expansion of the reinforcement.  It is then you have a problem, as the concrete hides the trouble and then obstructs the usual scrape & paint means of addressing the rust.

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1 minute ago, magnetman said:

Presumably that is what happened to the Morandi bridge. 

 

Yes.

 

Along with a poor maintenance/inspection regime which may have detected the issue before it collapsed.

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9 minutes ago, Tacet said:

There is a danger of some misunderstanding here.  Essentially, concrete offers good protection to the steel reinforcement (or baseplate).  Something to do with its alkalinity.

 

However, over time concrete is subject to carbonation arising from CO2 in the atmosphere, which reduces its protective properties and can lead to spalling following expansion of the reinforcement.  It is then you have a problem, as the concrete hides the trouble and then obstructs the usual scrape & paint means of addressing the rust.

 

Exactly - the science behind the "papers" is very complex and way beyond my A-Level chemistry which is why I suggested the OP reads up himself and decides if the builder is just giving him 'bull', or, is it really a 'new better' system ?

 

Ignoring the corrosion aspect - do the other negative features (paerticularly the fact that it is non-adjustable ballast) outweigh its 'cost benefits' ?

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The concrete will offer a protective environment and will in itself not cause corrosion .

But whether the concrete is bonded to the steel or whether a small gap appears as the concrete shrinks  is  a significant matter. If there is a  shrinkage gap where air and and moisture can get in then that could promote corrosion. So on the whole poured concrete ballast doesn't seem like  great idea. On the other hand other loose ballast could just as easily  hold moisture against the hull and promote corrosion.

 

I wonder how many narrowboats are protected from corrosion on the inside ?

 

 

 

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We bought a  a narrowboat some years ago that had concrete ballast. The ballast would have been from new maybe 20 years earlier.

We did some overplating of the baseplate.

The concrete above the welded area lost its grip to the steel. We know this as water could run underneath to the bilge on the other side.

The concrete above the un welded baseplate remained firmly intact to the steel and the steel was in good condition, we know this because following the replating some ballast had to be removed, it was not a pleasant job.

Not sure what to learn from this other than on balance probably not worth the (small) risks involved.

Edited by Phoenix_V
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1 hour ago, magnetman said:

Presumably that is what happened to the Morandi bridge. 

 

 

Colloquially known as 'concrete cancer' IIRC. 

 

I see the Chiswick Flyover carrying the M4 into London is suffering from the same when I drive along the A4 section underneath it.

 

If they end up demolishing it, one or two of the Cray Brothers' victims might turn up. They were rumoured to favour disposing of the bodies by dropping them into the flyover abutments during the concrete pouring. No eye deer if it's true. 

 

 

 

 

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1 hour ago, Tacet said:

However, over time concrete is subject to carbonation arising from CO2 in the atmosphere, which reduces its protective properties and can lead to spalling following expansion of the reinforcement.  It is then you have a problem, as the concrete hides the trouble and then obstructs the usual scrape & paint means of addressing the rust.

The absorbed CO2 will also be increasing the mass of the ballast, causing your boat to be slightly lower in the water. Of course, the same thing is happening to the concrete paving slabs that are the ballast on my boat. Even faster, as both the top and bottom surfaces, as well as the four edge faces of each slab are exposed to the air. They being raised up on plastic spacers from the base plate. I'm getting a sinking feeling...

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9 minutes ago, Jen-in-Wellies said:

The absorbed CO2 will also be increasing the mass of the ballast, causing your boat to be slightly lower in the water. Of course, the same thing is happening to the concrete paving slabs that are the ballast on my boat. Even faster, as both the top and bottom surfaces, as well as the four edge faces of each slab are exposed to the air. They being raised up on plastic spacers from the base plate. I'm getting a sinking feeling...

Console yourself; you are saving the planet as you sink

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It would be interesting to compare the specific gravity of various different ballast materials. 

 

Gold is good. 

 

I had a boat which was ballasted with gold bullion once. I asked the seller if it was his gold and he said it wasn't. 

 

Which was nice. 

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4 minutes ago, Tacet said:

Console yourself; you are saving the planet as you sink

Not really. Making the concrete gave up the CO2 to the atmosphere from the ingredients and yet more CO2 to run the kiln. Not matched by the CO2 absorbed over time. Let's not get started on the CO2 from steel smelting and processing.

2 minutes ago, magnetman said:

It would be interesting to compare the specific gravity of various different ballast materials. 

 

Gold is good. 

 

I had a boat which was ballasted with gold bullion once. I asked the seller if it was his gold and he said it wasn't. 

 

Which was nice. 

Depleted Uranium, if you can't afford gold.

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5 minutes ago, magnetman said:

It would be interesting to compare the specific gravity of various different ballast materials. 

 

Gold is good. 

 

I had a boat which was ballasted with gold bullion once. I asked the seller if it was his gold and he said it wasn't. 

 

Which was nice. 

 

It was MINE.

 

Give it back!! 

 

 

 

 

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