Poured concrete as ballast

[David Mack]

There's a world of difference between just dumping a load of wet concrete in the bilges of a boat that hasn't specifically been designed for it, and a properly engineered reinforced concrete structure. In buildings and bridges it is common to have a reinforced concrete slab supported on steel beams. The connection between the two is provided by a series of studs with enlarged heads welded onto the top surface of the steel. The size, number and spacing of the studs is designed to ensure that the shear load is continuous across the interface, so that the steel and concrete act compositely to resist bending forces. The heads on the studs also prevent the concrete and steel separating. The concrete is reinforced with steel bar or mesh reinforcement, which is designed both to carry the applied loading and also to distribute the inevitable shrinkage cracking in the concrete, so that you get a large number of small cracks, which over time are self-healing, rather than a few large cracks which can allow moisture and air to get down to the reinforcement and cause corrosion.

With mass concrete just poured in a boat (and with no studs or equivalent) the inevitable flexing of the hull is likely to lead to an early breaking of the bond between steel and concrete, so moisture can get in and corrode the inner surface of the steel. Once corrosion occurs the expansive force generated will tend to separate the concrete and steel, breaking any bond in adjacent areas, and so the corrosion can spread.

 

Incidentally years ago friends of mine hired a brand new boat. So new in fact that when they arrived at the boatyard, staff were still pouring concrete ballast into the triangular spaces in the stern either side of the propshaft between the swim plates and some wooden shuttering. My friends took the boat away with the concrete still wet. But I imagine the engine ensured the concrete was well vibrated!

[Momac]

30 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. 

Water is 1

Concrete is 2.4

Lead is 11.3

[MtB]

1 minute ago, MartynG said:

Water is 1

Concrete is 2.4

Lead is 11.3

 

Gold is 19.32

 

 

WAY denser than even lead. 

 

 

Iron (and probably steel plate) is part way between concrete and lead at 7.8.

 

 

[Momac]

2 minutes ago, MtB said:

 

Gold is 19.32

 

 

WAY denser than even lead. 

 

 

Yes but not economically viable as ballast

[LEO]

Poured concrete as ballast, not really a good idea, and you also asked about integral water tanks, again not a good idea, they rust internally and require regular treatment, I have had two boats, the first had an aluminum self contained tank, the second has a polysomething or other tank, both give good service.

 

Not sure if I would trust a boatbuilder who used concrete as ballast or incorporated integral water tanks.

[MtB]

22 minutes ago, LEO said:

Poured concrete as ballast, not really a good idea, and you also asked about integral water tanks, again not a good idea, they rust internally and require regular treatment, I have had two boats, the first had an aluminum self contained tank, the second has a polysomething or other tank, both give good service.

 

Not sure if I would trust a boatbuilder who used concrete as ballast or incorporated integral water tanks.

 

 

I agree. Concrete ballast and integrated water tanks are both no-no's for any reputable builder so being told by one builder they do both of these would have me running for the hills. Unless you want the narrowboat equivalent of a Trabant car.

 

Water tanks should be in a material that needs no internal maintenance e.g. stainless steel or PVC. Mild steel is just daft for a £200k new boat. 

[magnetman]

44 minutes ago, MartynG said:

Yes but not economically viable as ballast

It could be. 

 

My aunt is a multi millionaire and lives in a 1 bedroom cottage and drives a Nissan Micra. 

 

Things are not always predictable. 

 

 

[MtB]

1 minute ago, magnetman said:

It could be. 

 

My aunt is a multi millionaire and lives in a 1 bedroom cottage and drives a Nissan Micra. 

 

Things are not always predictable. 

 

Indeed. 

 

The richest man I ever (knowingly) met was an Arab oil sheik, when doing some work in his £20m 'English country cottage' (as he put it) in Stoke Poges. (14 bedroom country pile to you and me.) He drove around in a rusty 20 year old Ford Mondeo. 

[BoatinglifeupNorth]

4 hours ago, Napton said:

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.

Just name the builder, they don’t know who you are. Anyone know who he’s talking about?

 

Edited June 5, 2023 by BoatinglifeupNorth

[Hudds Lad]

1 minute ago, BoatinglifeupNorth said:

Just name the builder, they don’t know who you are. Anyone know who he’s talking about,?

Oakums (shhhhhh, i never told you)

[MtB]

Just now, Hudds Lad said:

Oakums (shhhhhh, i never told you)

 

Lol I was about to suggest the same!

 

Did anyone ever win their "£200k narrowboat for a fiver" raffle?

[Hudds Lad]

1 minute ago, MtB said:

Did anyone ever win their "£200k narrowboat for a fiver" raffle?

Ends on August 5th, or if last ticket sells before then

[Guest]

2 hours ago, magnetman said:

One of the woman's sisters drove over that bridge the day before it fell apart. I was disappointed as never liked her much !

 

Well she was very lucky because (according to a documentary I viewed a few months back) signs of imminent collapse appeared several days previous, and the authorities did nothing to even reduce the load.

[BoatinglifeupNorth]

23 minutes ago, Hudds Lad said:

Oakums (shhhhhh, i never told you)

I take these are the new must have boats that are being heavily endorsed by the Vloggers now, Just as was Bickerstaffe a few years ago. Remember the most famous boat on the Canals😂Poured concrete ballast and rusty integral water tank for £200K come and join the “Oakums” family. 

Edited June 5, 2023 by BoatinglifeupNorth

[Pluto]

I have seen a concrete wash applied to the inside of the bows on a number of L&LC short boats. It appeared to have been done by Yarwoods, and was, perhaps, a standard anti-corrosion finish at the time.

[Bee]

Integral water tanks. No, cheap way of doing it but no, the boat will corrode from outside and also the inside, just get a plastic one with a good big lid, the window cleaners ones are pretty good. Concrete ballast is also a cheap (and nasty) way to do it. A good rule with boats is not to cover stuff up so you cannot get at it. Re bottoming steel narrowboats is a frequent repair and also the bottom few inches of the sides. Concrete will be a sod to rempve and the boat will be pretty much dismantled when you finish, Besides, ballasting is not that difficult or expensive to do with engineering bricks or old paving slabs and is removable, adjustable and inspectable. Also the practice of flooring with big sheets of ply and fitting out the boat on top of it should be punished by flogging. One day you will need to lift it - probably in the bath / shower room - and you will want to murder the 'boatbuilder'.

[Dav and Pen]

The Dutch barge I brought in Belgium had concrete ballast. The barge was built in 1917 and the build was 5.5mm steel, it was converted to a pleasure boat in 1985 when the concrete was put in. At the time this was very common and the inside of the hull was covered in what they called bilge grease a very thick black grease and the concrete was poured on top, looking at it from the top it appeared to be well compacted and not a large aggregate mix. They left a hole against the rear bulkhead for a bilge pump.

We had the boat surveyed before purchase and the expert was not worried about the concrete and some of the bottom was still above 4mm after70 years. During our ownership we had some doubling done and the shipyard was used to working on boats with concrete ballast and knew how to proceed.

In my former life I owned a precast concrete company and amongst our products we made pre stressed bridge beams and all the beams for west ferry circus at Canary Wharf. To lessen the problem of the so called concrete cancer the mixes were designed to be as low alkaline as possible which involved cement from a certain plant, large aggregate from the Trent valley but the local sand was ok. 
We also made paving slabs using granite and the manufacturing method made them very dense and they would absorb very little moisture once fully cured. Many of you with paving ballast in boats from the 70s to 95 could well have our product.

[Napton]

Many thanks for all your comments both for and against concrete and integral tanks. You’ve sort of reinforced the impression I got that this was a load of bull. I guess if I won that boat, I’d sell it and get a decent one. But I haven’t bought a ticket! 🤣

[Machpoint005]

6 hours 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.

 

 

 

The water doesn't evaporate, it becomes chemically combined within the concrete.

 

Concrete doesn't dry, it goes off.

 

 

[cobaltcodd]

6 hours ago, BEngo said:

They are insurable if they have been maintained

The above comment refers to concrete boats, the inference being that if not maintained, they are not insurable, presumably because something happens to it? - but how many of us maintain our ballast (I don't)?  Would you have to set up a maintenance regime for it if it was concrete?

 

Edited June 5, 2023 by cobaltcodd

[robtheplod]

Number one thing on a boat is being able to get at everything.... poured concrete seems to stop access for inspection of the hull...

[howardang]

38 minutes ago, Napton said:

Many thanks for all your comments both for and against concrete and integral tanks. You’ve sort of reinforced the impression I got that this was a load of bull. I guess if I won that boat, I’d sell it and get a decent one. But I haven’t bought a ticket! 🤣

 

39 minutes ago, Napton said:

Many thanks for all your comments both for and against concrete and integral tanks. You’ve sort of reinforced the impression I got that this was a load of bull. I guess if I won that boat, I’d sell it and get a decent one. But I haven’t bought a ticket! 🤣

There is nothing too problematical about integral tanks as long as they are coated properly and maintained regularly. When i first went to sea and for many years after, most ships had integral fresh water tanks which were cement washed every year. 
 

rRegarding concrete boats, there have been many examples  over the years, barges, yachts and other floating structures. If they are constructed properly, there is nothing wrong with their method of construction. However, over the years I have come across a number of sea going yachts which have been built using cement which have  started to corrode internally due to trying to use this method on the cheap, and the cost for the repairs is horrendous, and sometimes not worth doing which may have given this method of construction a bad name. It is often the case that the reinforcing bars that are corroding rather than the cement which is failing.

 

Howard

[blackrose]

5 hours ago, MartynG said:

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. 

 

Yes. Concrete bonds well to steel if correctly prepared and doesn't cause corrosion, but whether that bond will last within a dynamic structure like a boat which will flex when dry docked or craned out is unknown. If a gap does develop between the concrete and steel that's bad news because sooner or later you'll have a plumbing leak, leaky window or just condensation build up which will get into that gap. Then you've got a corrosion trap which you can do nothing about. 

 

I used to have a narrow boat with poured concrete ballast and there was water under the concrete. I certainly wouldn't recommend it. I don't see any advantages and one big potential disadvantage.

[ditchcrawler]

A built in tank will give more water volume as there is no waste of space, If its better than a free standing stainless one depends how it is treated prior to use.

[roland elsdon]

5 hours 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. 

On Taggs island?