Poured concrete ballast

[Burgiesburnin]

Not at all determined to do it. As of yet I've not had a 'concrete' reason not to do it apart from a couple of cases where it went wrong. But was the preparation done correctly?

Concrete sticks to steel like glue. So can anybody with any evidence of a properly prepared surface failing?

It's outlawed in France but nowhere else.

Reinforced buildings would be falling apart all over the place if it was shite.

 

It maybe that when the concrete has failed it is due to the concrete drying too quickly. If it is allowed to dry quickly then it will contract and leave spaces between the concrete and the steel. These crevices can then fill with water and inevitably the steel will rust.

If the concrete dries slowly its own weight will push it against the steel and no crevice created.

[bag 'o' bones]

About 10 years ago I was looking at selling up and buying a Dutch barge. During my research, I read about concrete poured directly onto clean grit blasted steel. It supposedly bonds to, and protects the bilge. I've not heard of it in the narrowboat world. Any reason why?

I think it pretty obvious why poured concrete is a bad idea. Unlike reinforced concrete where the steel is encapsulated on all sides and is fashioned in such away that the various contraction and expansion forces migrate through the structure evenly, concrete ballast is a separate mass that expands and contracts at a different rate therefore gradually breaking down the steel/concrete interface. The result is the poured slab breaks away from the underlying steel allowing in moisture and air and the inevitable expanding corrosion which accelerates the process.

[fudd]

I think it pretty obvious why poured concrete is a bad idea. Unlike reinforced concrete where the steel is encapsulated on all sides and is fashioned in such away that the various contraction and expansion forces migrate through the structure evenly, concrete ballast is a separate mass that expands and contracts at a different rate therefore gradually breaking down the steel/concrete interface. The result is the poured slab breaks away from the underlying steel allowing in moisture and air and the inevitable expanding corrosion which accelerates the process.

Well it's not that obvious to me. The expansion coefficient isn't that different.

[smileypete]

Was thinking about this while out walking today, a kind of weak 'limecrete' mix could be better, if any water got in it would keep it alkali to reduce the chance of rust, and it'd be easier to remove afterwards if you want:

 

http://en.wikipedia.org/wiki/Types_of_concrete#Limecrete

 

Maybe the best would be to cast in situ with it shuttered into sections, plus a bit of mesh/fibre reinforcement, some rope handles, and plastic sheet to act as a mould release. Then once set lift the sections up and support them off the bilge plate a little. If the bilge floods the lime would dissolve and help keep the water alkali to help prevent corrosion, but still be removeable for inspection.

 

Reason I thought of lime earlier was because of moss growing on the pavement next to an old churchyard wall, some of the lime must have been dissolving and providing a mineral nutrient.

 

Having said all that, if you're going to the trouble and expense of grit blasting, why not just coat the bilge with an epoxy paint? With an existing bilge that's rusty, maybe a cement wash would be OK, easier to tell if the cement is 'blowing' away from the metal. (With reinforced concrete it's better if the rods are a bit rusty as it helps the cement grip better.)

 

If you get some standing water and corrosion in the cabin bilge from condensation, a couple of dishwasher detergent tablets will help keep it alkali, they also contain a silicate corrosion inhibitor which will help a little too.

 

cheers, Pete.

~smpt~

Edited November 19, 2013 by smileypete

[Graham Davis]

I'm not talking about just pouring concrete into an untreated bilge. I'm talking grit blasted steel.

Grit blasted steel is UNTREATED!!

It has no protective coating because the blasting has removed it. It will start to corrode.rust as soon as the blasting has passed over it.

To "treat" steel it has to be given a protective coating such as paint.

 

And you cannot compare a boat to a pre-stressed concrete beam. Totally different, plus nowadays most "wires" are galvanised.

[fudd]

 

Grit blasted steel is UNTREATED!!

It has no protective coating because the blasting has removed it. It will start to corrode.rust as soon as the blasting has passed over it.

To "treat" steel it has to be given a protective coating such as paint.

 

And you cannot compare a boat to a pre-stressed concrete beam. Totally different, plus nowadays most "wires" are galvanised.[/quote

 

Right.

Steel is steel. Grit blasted steel has received a treatment. As far as I understand the blasted steel gives a better bond.

I never mentioned prestressed concrete. I said reinforced. Completely different. Not a wire in sight.

[Graham Davis]

Rubbish!

Grit blasting is used to remove mill scale, corrosion, paint etc. It does NOT provide a protective coating. That is a different process.

 

And if you want to be really pedantic, steel is not just steel. There are many different formulas and qualities of steel available. Do some research.

[fudd]

Rubbish!

Grit blasting is used to remove mill scale, corrosion, paint etc. It does NOT provide a protective coating. That is a different process.

 

And if you want to be really pedantic, steel is not just steel. There are many different formulas and qualities of steel available. Do some research.

Now you are talking rubbish.

I never said grit blasting was a protective coating.

I said it was a treatment. And I'm not being at all pedantic. You are. I'm talking about a grit blasted steel shell that has had all the mill scale removed leaving a key for the concrete to adhere to. Jeezus. I don't want a row. I'm asking questions and you haven't yet given a valid reason why it's a bad idea.

[Guest]

Rubbish!

Grit blasting is used to remove mill scale, corrosion, paint etc. It does NOT provide a protective coating. That is a different process.

 

And if you want to be really pedantic, steel is not just steel. There are many different formulas and qualities of steel available. Do some research.

To be fair, the OP described grit blasting as a "treatment," not a protective coating. A "treatment" is a method of dealing with something, e.g. millscale might be one example in this case.

[fudd]

To be fair, the OP described grit blasting as a "treatment," not a protective coating. A "treatment" is a method of dealing with something, e.g. millscale might be one example in this case.

Yeah, see. Ner ner na ner ner!! ?

Edited November 19, 2013 by fudd

[Graham Davis]

Read what you said at #31:

Steel is steel. Grit blasted steel has received a treatment

 

By grit blasting something you are cleaning steel and as others have said it will start to corrode almost immediately.

 

Do what you want, but don't complain on here when it goes wrong.

Your childish reply above really does you no favours.

 

Good night

Edited November 19, 2013 by Graham Davis

[fudd]

Read what you said at #31:

Steel is steel. Grit blasted steel has received a treatment

 

By grit blasting something you are cleaning steel and as others have said it will start to corrode almost immediately.

 

Do what you want, but don't complain on here when it goes wrong.

Graham, I don't intend to do it. I'm asking why it isnt done. Neither you, nor anyone else has come up with a reason why not, that hasn't been countered by another point of view. Lighten up mate.

Steve P.

Read what you said at #31:

Steel is steel. Grit blasted steel has received a treatment

 

 

By grit blasting something you are cleaning steel and as others have said it will start to corrode almost immediately.

 

Do what you want, but don't complain on here when it goes wrong.

Your childish reply above really does you no favours.

 

Good night

Before you go to bed, I'd like to point out that I was trying to be light hearted about it. Nighty night.

[Jigsawged]

I inherited (when I took on a marina business) a 43 foot concrete yacht. It's design, I was told, was tried and tested and the plans were produced by a highly respected architect. The original owners abandoned it before lunching it because of the concrete chemistry which whilst looking nice and solid etc. was reported to be likely to dissolve over time.

 

The test on the concrete was conducted by a boffin or two at Manchester University. I mention this only to point out that in order to retain longevity, the chemical mix is crucial. I imagine that most concrete structures will meet the required spec. Something pumped into a boat as ballast may not have the properties that the OP is hoping for and could break down sooner rather than later, thus introducing corrosive properties to the integrity of the steelwork.

 

Edited for clarification

Edited November 19, 2013 by Jigsawged

[Guest]

I inherited (when I took on a marina business) a 43 foot concrete yacht. It's design, I was told, was tried and tested and the plans were produced by a highly respected architect. The original owners abandoned it before lunching it because of the concrete chemistry which whilst looking nice and solid etc. was reported to be likely to dissolve over time.

 

The test on the concrete was conducted by a boffin or two at Manchester University. I mention this only to point out that in order to retain longevity, the chemical mix is crucial. I imagine that most concrete structures will meet the required spec. Something pumped into a boat as ballast may not have the properties that the OP is hoping for and could break down sooner rather than later, thus introducing corrosive properties to the integrity of the steelwork.

 

Edited for clarification

Just out of curiosity, did the yacht dissolve? I have seen a couple of really old concrete boats over the years seemingly in really good nick. I think more were made in the USA than UK, and are epoxy coated?

[fudd]

If, and only if I was to even think about putting concrete in the bottom of a boat, I would do all the homework necessary and make sure I was doing the right thing.

I have tried, through the thread make it clear that I wasn't going to do it and I wasn't thinking of just lobbing a load of old concrete in the bottom of a boat as ballast. I have repeatedly used the word 'treatment'. By this I mean using the alkaline properties of said concrete to overcome the problems of corrosion. I may not have made this very clear but I am trying to do so now. So thanks for all your answers.

Steve P

[mark99]

As you know by now concrete has virtually no resistance to tensile stress, bonding a hull to one exterior surface of the concrete does not "reinforce" concrete as it's not an integral or truly composite member (the steel is not "incorporated").

 

I would think of it in terms that the concrete is almost just a form of cladding or render onto steel.

 

Concrete shrinks over time and this may break the bond.

Edited November 19, 2013 by mark99

[John Williamson 1955]

As far as I can tell, every boat mentioned in this thread that has had concrete poured into the bilge has suffered from rapid corrosion of the steel. That's a *very* good reason not to do it. If you're away from your home port, and your steel hull starts leaking, then it is a quick, effective, but above all, temporary cure.

 

When steel reinforced concrete is used as a structural component, it is vital that the concrete surrounding the steel is thick enough to prevent *all* contact between water and steel. As pouring concrete into the bilge leaves the lower surface of the steel in contact with water, this condition is not fulfilled, and the steel will suffer form corrosion on the exterior, and, if there is even a hairline crack in the concrete cover, accelerated corrosion on the inside, which will expand any cracks, further accelerating the corrosion, and so on. So far, touch wood, none of the reinforced concrete stuff that I have designed and built has failed....

 

In normal use of steel and concrete, when making a beam or other structure, if the concrete coating is not thick enough or of poor quality, premature failiure takes place due to the steel rusting and blowing off the thin concrete skin. For a view of this problem, drive along the A4 below the Chiswick flyover, where they are currently patching up many hundred of instances of "blown" concrete cover. Hammersmith flyover is suffering from a more serious version, and has had to have most of its reinforcement and a large amount of concrete replaced over the last couple of years due to water ingress causing corrosion, with more similar work scheduled for next Summer. Just don't ask about the Birmingham elevated motorways.... Cruise along the canals near them and wonder at the work going on.

 

Concrete as normally used in construction is easily attacked by salt water as well as sulphates, so any battery leakage, for instance, must be kept well away, or the concrete will disintegrate in fairly short order.

 

Incidentally, the true concrete cancer as recognised by the building industry is caused by using some types of quick setting concrete and then exposing it to chlorine as released from a swimming pool or cleaning chemicals. There were many reports in the 1980s of relatively new swimming pool buildings collapsing due to this problem.

 

Bye!

 

John.

[fudd]

As far as I can tell, every boat mentioned in this thread that has had concrete poured into the bilge has suffered from rapid corrosion of the steel. That's a *very* good reason not to do it. If you're away from your home port, and your steel hull starts leaking, then it is a quick, effective, but above all, temporary cure.

 

When steel reinforced concrete is used as a structural component, it is vital that the concrete surrounding the steel is thick enough to prevent *all* contact between water and steel. As pouring concrete into the bilge leaves the lower surface of the steel in contact with water, this condition is not fulfilled, and the steel will suffer form corrosion on the exterior, and, if there is even a hairline crack in the concrete cover, accelerated corrosion on the inside, which will expand any cracks, further accelerating the corrosion, and so on. So far, touch wood, none of the reinforced concrete stuff that I have designed and built has failed....

 

In normal use of steel and concrete, when making a beam or other structure, if the concrete coating is not thick enough or of poor quality, premature failiure takes place due to the steel rusting and blowing off the thin concrete skin. For a view of this problem, drive along the A4 below the Chiswick flyover, where they are currently patching up many hundred of instances of "blown" concrete cover. Hammersmith flyover is suffering from a more serious version, and has had to have most of its reinforcement and a large amount of concrete replaced over the last couple of years due to water ingress causing corrosion, with more similar work scheduled for next Summer. Just don't ask about the Birmingham elevated motorways.... Cruise along the canals near them and wonder at the work going on.

 

Concrete as normally used in construction is easily attacked by salt water as well as sulphates, so any battery leakage, for instance, must be kept well away, or the concrete will disintegrate in fairly short order.

 

Incidentally, the true concrete cancer as recognised by the building industry is caused by using some types of quick setting concrete and then exposing it to chlorine as released from a swimming pool or cleaning chemicals. There were many reports in the 1980s of relatively new swimming pool buildings collapsing due to this problem.

 

Bye!

 

John.

Thank you.

Steve P.

[Capt Ahab]

Not at all determined to do it. As of yet I've not had a 'concrete' reason not to do it apart from a couple of cases where it went wrong. But was the preparation done correctly?

Concrete sticks to steel like glue. So can anybody with any evidence of a properly prepared surface failing?

It's outlawed in France but nowhere else.

Reinforced buildings would be falling apart all over the place if it was shite.

What - like the M5 steel reinforced pillars over the old main line - its been on life support for years. Steel and concrete are a bad mix.

[billh]

We have two canal boats with poured ballast:

One is a dredger built by BW in 1968, most of it's bilge has six inches depth of concrete , this was done over 40 years ago to aid stability when working.

When I last looked at the hull it was no worse than any other aged vessel and doesn't leak.

The other boat was built in 1972 and re-fitted , new cabin etc in 1985. The work was carried out by a well respected boat fitter who recommended the poured concrete option before commencing the fit out. This proved to be a bad choice as there is no opportunity to correct the slight list to port due to the cabin layout. So far, this boat doesn't leak either- no doubt someone will tell me the bottom is about to fall out. Even if it did, I reckon she's had a fair life and many other boats of that age, without poured concrete are due for re-bottoming.

I should point out that I had nothing to do with the decision to pour concrete in either vessel.

Bill

[Jigsawged]

Just out of curiosity, did the yacht dissolve? I have seen a couple of really old concrete boats over the years seemingly in really good nick. I think more were made in the USA than UK, and are epoxy coated?

No it didn't unfortunately but it was a bugger to get rid of. Eventually I had to have it carved up like a wedding cake and skipped away (expensive). My predecessor toyed with fitting it out but decided against it. The same design of concrete yacht had apparently partaken in a Whitbread Round The World Race quite successfully and I did hear of other concrete yachts that were fine.

 

There were some concrete boats from WWII at the Boat Museum, Ellesmere Port a few years back and they were still floating. I'm not saying that they are a bad construction generally, or anything like that; I still wouldn't want poured concrete ballast though!

[Guest]

No it didn't unfortunately but it was a bugger to get rid of. Eventually I had to have it carved up like a wedding cake and skipped away (expensive). My predecessor toyed with fitting it out but decided against it. The same design of concrete yacht had apparently partaken in a Whitbread Round The World Race quite successfully and I did hear of other concrete yachts that were fine.

 

There were some concrete boats from WWII at the Boat Museum, Ellesmere Port a few years back and they were still floating. I'm not saying that they are a bad construction generally, or anything like that; I still wouldn't want poured concrete ballast though!

You could have filled it with soil and put a few plants in it

 

I saw some at the museum, and there was a boat on the Bridgewater that certainly looked like a concrete hull.

 

I believe that the best concrete ballast is that which can be lifted out in small units for inspection and trim purposes (paving flags/bricks.) We will likely only hear about concrete filled bilges that failed, and nothing about the numerous successful ones, though I still wouldn't fancy the idea.

[PhilR]

What - like the M5 steel reinforced pillars over the old main line - its been on life support for years. Steel and concrete are a bad mix.

 

There is nothing wrong with reinforced concrete if properly specified and adequately supervised during construction. You can draw your own conclusion as to why much of the elevated sections of the M6 and M5 failed prematurely.

[Roadsteam]

There are quite a few cases of blown concrete covering over rebar on the concrete GU bridges going north from Braunston. There is also a lock in the 3 at Fosse IIRC that the facing has gone and the rebar mesh is exposed at the top gates.

[fudd]

Thanks for all the replies.

A lot of them have gone off in a tangent but nonetheless have been informative. I have said that I had no intention of doing it, but I still have no hard and fast reason not to, if it was done with the right mix, maybe some sort of mesh reinforcing and with the proper preparation to the steel, ie. grit or shot blasting.

We may never know!?