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Foam Concrete - and potential for Hydrogen build up

Chris Rollins 8 years ago   Reply
G'Day,

Further to the above has anyone had experience of hydrogen build up as a result of using 'foam concrete' and if so what were the consequences/steps to reduce or prevent it.

Chris


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Gareth M 8 years ago   Reply
Chris,

Could you let me have some contact details and we can discuss.

Best regards

Gareth
STUART HAMILTON 8 years ago   Reply
There was a serious explosion last week in a sewage pumping station being decommissioned when contractors were injured as a result of a gas explosion.

The dry well had been filled with a large volume of foamed concrete over the previous three days and a spark from an angle grinder being used to cut handrails is believed to have ignited an explosive gas mix that had accumulated between the surface of the poured concretre and the underside of the chequer plate flooring around the former dry well.

The concrete contained a significant percentage of flyash. The investigation is on-going.
However there are other anecdotal reports of small fires from hydrogen evolved form foamed concrete used to cover gas/ water mains laid in the ground.

There are research papers ( fromSweden)on the internet which show that there is quite a potential for hydrogen evolution from flyash , particulatly in alkaline conditions- as found in concrete.

The initial advice is- keep the area well ventilated- avoid void spaces where gas can accululate- avoid hotwork unless the area has been tested as " gas free" for hydrogen

regards

Stuart Hamilton
Chris Rollins 8 years ago   Reply
Stuart,

Many thanks - have passed this info on to those currently investigating a similar occurrence - fortunately no injuries in this instance

Regards

Chris M.Rollins
SHES Geographic Advisor
West Midlands Network
Operations
Chris.M.Rollins@«hidden»
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There was a serious explosion last week in a sewage pumping station being decommissioned when contractors were injured as a result of a gas explosion.

The dry well had been filled with a large volume of foamed concrete over the previous three days and a spark from an angle grinder being used to cut handrails is believed to have ignited an explosive gas mix that had accumulated between the surface of the poured concretre and the underside of the chequer plate flooring around the former dry well.

The concrete contained a significant percentage of flyash. The investigation is on-going.
However there are other anecdotal reports of small fires from hydrogen evolved form foamed concrete used to cover gas/ water mains laid in the ground.

There are research papers ( fromSweden)on the internet which show that there is quite a potential for hydrogen evolution from flyash , particulatly in alkaline conditions- as found in concrete.

The initial advice is- keep the area well ventilated- avoid void spaces where gas can accululate- avoid hotwork unless the area has been tested as " gas free" for hydrogen

regards

Stuart Hamilton

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anon 8 years ago   Reply
It is well worth checking the aggregate(s) in use for such foamed concrete.

It is not uncommon for IBA - incinerator bottom ash - to be used in this type of work.

A check on the internet for use of IBA as a concrete aggregate will show many papers that indicate the presence of aluminium particles in the IBA - resulting in the reaction of aluminium with the alkaline cement paste - giving off hydrogen gas. In 'normal' concrete made with IBA aggregate, this is described in the various papers as causing swelling of the concrete and subsequent large spalling effects. If the IBA aggregate concrete is a foamed type for use as low density fill, the much greater porosity of the foamed mix will allow the very small particle size of hydrogen gas to leach more easily from the mix in wet and hardened state.

This 'hydrogen given off' effect does not happen with other recycled aggregates used in foam fill - such as recycled concrete, recycled brick. It would appear to happen only where IBA has been used.

I am not aware of any situations in the UK where PFA - pulverised fly ash - has caused hydrogen gas to be given off on contact with cement - indeed, the reaction of alkalies, PFA with deliberately introduced fine aluminium powder (plus other constituents) is the basis for the production of lightweight concrete blocks
Chris Rollins 8 years ago   Reply
Many thanks I will forward this on.

Chris M.Rollins
SHES Geographic Advisor
West Midlands Network
Operations
Chris.M.Rollins@«hidden»
Tel: 0121 333 3628 Mob: 07768 005 929

P please consider the environment - do you really need to print this email?

Fax: 0121 333 2658
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It is well worth checking the aggregate(s) in use for such foamed concrete.

It is not uncommon for IBA - incinerator bottom ash - to be used in this type of work.

A check on the internet for use of IBA as a concrete aggregate will show many papers that indicate the presence of aluminium particles in the IBA - resulting in the reaction of aluminium with the alkaline cement paste - giving off hydrogen gas. In 'normal' concrete made with IBA aggregate, this is described in the various papers as causing swelling of the concrete and subsequent large spalling effects. If the IBA aggregate concrete is a foamed type for use as low density fill, the much greater porosity of the foamed mix will allow the very small particle size of hydrogen gas to leach more easily from the mix in wet and hardened state.

This 'hydrogen given off' effect does not happen with other recycled aggregates used in foam fill - such as recycled concrete, recycled brick. It would appear to happen only where IBA has been used.

I am not aware of any situations in the UK where PFA - pulverised fly ash - has caused hydrogen gas to be given off on contact with cement - indeed, the reaction of alkalies, PFA with deliberately introduced fine aluminium powder (plus other constituents) is the basis for the production of lightweight concrete blocks

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Dereckmicro 8 years ago   Reply
All,
there is an interesting Research report by WRAP Recycled and Secondary Aggregates in Foamed concrete. DTI/ Wrap Aggregates Research Programme STBF 13/13C July 2004 to January 2005.

Dereck Adams Reinstatement Contracts Manager TMA
Morrison Utilities Redhill 01737 781109


-----Original Message-----
From: Rollins, Chris M
[mailto:construction-senderhidden@«hidden»]
Sent: 28 August 2009 15:44
To: Construction Discussion Forum
Subject: RE:[construction] Foam Concrete - and potential for Hydrogen
build up


Many thanks I will forward this on.

Chris M.Rollins
SHES Geographic Advisor
West Midlands Network
Operations
Chris.M.Rollins@«hidden»
Tel: 0121 333 3628 Mob: 07768 005 929

P please consider the environment - do you really need to print this email?

Fax: 0121 333 2658
Int: 7216 3628

-- Repeated lines have been removed. Click to show them. --


It is well worth checking the aggregate(s) in use for such foamed concrete.

It is not uncommon for IBA - incinerator bottom ash - to be used in this type of work.

A check on the internet for use of IBA as a concrete aggregate will show many papers that indicate the presence of aluminium particles in the IBA - resulting in the reaction of aluminium with the alkaline cement paste - giving off hydrogen gas. In 'normal' concrete made with IBA aggregate, this is described in the various papers as causing swelling of the concrete and subsequent large spalling effects. If the IBA aggregate concrete is a foamed type for use as low density fill, the much greater porosity of the foamed mix will allow the very small particle size of hydrogen gas to leach more easily from the mix in wet and hardened state.

This 'hydrogen given off' effect does not happen with other recycled aggregates used in foam fill - such as recycled concrete, recycled brick. It would appear to happen only where IBA has been used.

I am not aware of any situations in the UK where PFA - pulverised fly ash - has caused hydrogen gas to be given off on contact with cement - indeed, the reaction of alkalies, PFA with deliberately introduced fine aluminium powder (plus other constituents) is the basis for the production of lightweight concrete blocks


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Dr John C Bullas - Research Consultant - H&T - Atkins 8 years ago   Reply
Colleagues

WE got an email train into Atkins via two or more routes, each one augmented with information, some useful, some irrelevant, some downright misleading

YES: You CAN easily foam concrete with cement and added aluminium powder to make building blocks - you do that in factories

BUT foamed concrete in trenches is air-entrained foam using protein or shampoo ingrediants

The water treatment blast might have been Abbeystead, this was METHANE : http://www.hse.gov.uk/comah/sragtech/caseabbeystead84.htm

The case in Dudley ( foamed concrete made with some waste aggregate (IBBA?) with 5% aluminium in it) may have been made worse by capping the curing concrete with impermeable blacktop as hydrogen is lighter than air and the only way out for the H2 was out of the grids :) Site was a collapsed drain reinstatement

Personal contact with a manufacturer of foaming equipment, two suppliers of the mixes, three local authorities and two HAUC groups failed to identify any other occurances of ignition of hydrogen
Foamed concrete will go pop if you try to speed it up with heat on the top of the layer, the air inside expands and cracks off the cured crust

My own viewpoint is foamed concrete is intinsically safe so long as you don't get a lot of metals in the aggregates ( incinerators should be recovring this as it is worth ££££'s)

The presence of metals ( in particular Aluminium) in the recycled aggregates can lead to gas foaming, your supplier needs to follow best practice in removing this metal from the ash

The threshold for metals in these ashes above which "boom" is an issue is smoething I can't advise on ....possibly far greater than the threshold for metal recovery for ££££???

Please get in touch if you have any firm evidence regarding this subject as I am still awaiting the results of the "stewards enquiry"


Dr John C Bullas MIAT MIHT FGS

Research Consultant
Highways Asset Management Group (HAMG)
Highways and Transportation
ATKINS

The official engineering design services provider
for the London 2012 Olympic and Paralympic Games



Dr John C Bullas - Research Consultant - H&T - Atkins 8 years ago   Reply

Update from the contractor in Dudley involved in the incident

===============

John.

I understand that Severn Trent have now received the full safety report re this incident and the proposals moving forward, may I suggest that you discuss the issue with Anita direct.

"In a nutshell",the issue was with the particles of metal in the furnace bottom ash.

Moving forward Enterprise have insisted that no foamed concrete using furnace bottom ash will be permitted acceptable.

Tests were undertaken on foamed concrete products using other materials such as crushed brick,virgin aggregate,PFA.etc,no evidence was apparent of high quantities of hydrogen if at all.

The matter will be reviewed at WMRHAUC Materials group meeting on 29th of this month with a recommendation being forwarded to SROH working group and HAUC UK

Hope this helps,

regards,

John Crowther.
Dr John C Bullas - Research Consultant - H&T - Atkins 7 years ago   Reply
I have a copy of an alert issued by BARHALE regarding the recent explosion - foamed concrete again capped with an
impermeable layer to confine and concentrate the hydrogen

copy here: http://www.flickr.com/photos/johnbullas/3962266336/sizes/l/

So either:

Maybe a lot of IBA has metal in it AND we are just not capping it often enough for it to be a problem

OR

Most IBA used in foamed concrete does not contain enough metal to be an issue???

Any thoughts, seems a shame to stop using IBA if the problem is down to rogue materials OR working practices

=========================

On 21st August whilst Barhale operatives were in the process of cutting hand-railing as part of a decommissioning activity in a pumping station, an explosion occurred, injuring two operatives. Both injured parties were taken to hospital and treated for fractures to the ankle and foot.

The decommissioning phase required placement of foam concrete infill into an existing dry well (inside building) and wet well (outside building) The dry well infill had extended beneath an existing solid metal floor which both injured parties were standing on at the time of the incident.

The investigation into the root cause is still ongoing but it is suspected that the likely cause was as a direct result of hydrogen gas produced from the foam concrete. The gas appears to have built up beneath the metal flooring overnight. The gas is thought to have been ignited by spark created by a grinder.

The foam concrete mixture contained IBA (Incinerator Bottom Ash) which after investigation and research is likely to produce hydrogen gas. Aluminium metal particles present in the IBA react with the water and cement contents of the concrete to generate hydrogen, the volume of hydrogen produced being proportional to the quantity of aluminium metal being present in the IBA.

Early learning points:

-The use of foam concrete containing IBA is no longer permitted within Barhale. Only foam concrete using inert materials will be permitted.

-You must contact your Supplier for clarification and assurance of its safety, if you are unsure of the ingredients used in specified mixes.

-Examples of inert materials used in foam mix designs include sand, gravel or crushed stone. Always seek confirmation from the supplier that the materials used are inert and will not produce gas emissions when mixed.


Peter T 7 years ago   Reply
Many foamed concretes also show (on their MSDS) an incompatibility with oxidising agents, which could also give rise to various gases being given off depending on the exact ormula of the foamed concrete.
Many water treatment/purification plants use oxidising agents as part of their processes. e.g. Chlorinated products, ozone etc.
As all the safety alerts/warnings and incidents etc to date seem to have originated within the Water sector, I had assumed that the issue was due to this incompatibility being overlooked when performing the COSHH assessment. If you are saying that Aluminium present in PFA are the cause of gases being given off, then this incompatibility also needs to be included on the Manufacturers Safety Data Sheet.
So, two possible causes for the explosive gas being given off. We'll have to wait for the final report to find out which one is correct. Fancy a bet?
What is certain though is that irrespective of gases being given off, these explosions wouldn't happen without containment of the gases. So perhaps an assessment of potential gas pockets should be included when using foamed concretes.
Dr John C Bullas - Research Consultant - H&T - Atkins 7 years ago   Reply

Foam Concrete - and potential for Hydrogen build up

The HSE is undertaking thier own investigations at Buxton now
following the explosion in the plant where panels were confinig the
curing foamed concrete

They have issued an interim email advice note re the avoidance of use
in proximity to cutting gear and in confined/unventilated spaces etc
etc

Dr B

2009/10/19 Peter T <construction-senderhidden@«hidden»>:

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anon 7 years ago   Reply
to Peter T - you appear to be missing the main point here and are obviously confusing materials used.

Please look up precisely what PFA is & likewise IBA - PFA is NOT IBA - they are completley different animals used for different purposes. Uninformed comments like this unwittingly create problems / misconceptions regarding the true nature of underlying problems. While I respect your right to have an opinion - uninformed opinion gives rise to confusion and an unnecessary muddying of the waters - please leave it to the 'experts'

Once and for all - the H2 gas explosions have been created by using IBA aggregate that contains aluminium. This aluminium reacts with alkalies in portland cement to form hydrogen (H2) gas. The only way to ensure this does not happen with IBA is to get the IBA suppliers to guarantee aluminium removal. This I doubt is possible, since the amount of aluminium needed to create problematic quantities of hydrogen gas on reaction with cement is very small.
Lightweight block production typically only uses 0.25% aluminium powder by weight of cementitious content - so if your foam mix contains say 150 kg cement / m3 - an equivalent amount of aluminium content to cause serious problems would be 0.375 kgs - if this is expressed as a %ge of say 1300 kgs IBA /m3 - it would amount to 0.03% by weight of IBA to cause serious hydrogen problems. This goes to show you how little of it needs to be present to be a serious problem in the IBA - even used diltued with other aggs - it presents a serious threat - and one that the agg supplier needs to be able to be able to virtually remove completely from the agg (if that's even possible) to be able to say it is 'safe'
I would also add - the amount of aluminium powder used in lightweight block production gives @ 30% volume increase - in the 'problem' foamed concrete fill mixes - the foam volume effect has been created physically by foaming agents - not by hydrogen gas - so the amount of hydrogen generated in the aluminium / cement reaction has been far less than that deliberately employed in certain lightweight block production processes - from this, deduce that the actual amount of aluminium present in the IBA (that has caused this hydrogen gas generation problem) is far less than those amount indicators given above - hence my thoughts that the guaranteeing of no aluminium effects from IBA use may not be possible - unless all sources of aluminium can be TOTALLY removed before combustion process at the waste incinerator
Peter T 7 years ago   Reply
To anon, if you re-read the posting of Stuart Hamilton and even your own earlier posting, the discussion started off talking about Pulverised Fly Ash, you yourself mentioned adding Aluminium to PFA to create lightweight concrete blocks. I would humbly suggest you have missed my point. All of these instances appear to have occured in the water industry. There seems to be confusion as to what type of aggregate was involved in these occurrences and what type of foaming cement was used. Some of the investigation reports are yet to come out. Aluminium has been in contact with portland cement on many occasions on a construction site and in far higher concentrations than the 0.03% you seem to suggest is a serious hazard. Why hasn't anyone reported serious erosion to and fizzing/foaming of aluminium towers when Portland Cement has been spilt on them? Surely someone would have noticed by now? All I was suggesting is that Oxidising Agents are already contraindicated (i.e. THEY DON'T MIX WELL) with many Foaming Cements (depending on their individual chemistry). The Abbeystead blast was METHANE, the Dudley blast was Hydrogen, how does that fit with your theory? Oxidising agents are in extensive use throughout the Water Treatment Industry. How unlikely is it that contamination in a Water Treatment Site by Oxidising Agents would react adversely with foaming cement? How unlikely is it that the person doing the COSHH assessment didn't bother to read the contra-indication data found in the stability & reactivity section when all most people look at is the Risk phrases? You seem very certain that all these instances have this one cause, what makes you one of the experts? Especially when speculating on probable causes in a number of instances, some of which haven't released their reports yet. I would suggest that 'certainty' on initiating and proceeding with an investigation is far more likely to confuse/muddy waters than approaching with an open mind and letting the evidence lead.
You will also noticed that I have rebutted your argument without discounting the possibility that you may still be correct and without the "ad hominem" you seem to think is a reasoned argument.
anon 7 years ago   Reply
to Peter T - your reply indicates a total misunderstanding of this subject - with 43 years of experience in the concrete world on all aspects I suggest you stop digging an unnecessary hole for yourself and misleading others. Leave it to the experts - PLEASE.
Dr John C Bullas - Research Consultant - H&T - Atkins 7 years ago   Reply

Foam Concrete - and potential for Hydrogen build up

OK

As I understand it ( without getting personal)

Foamed concrete as a trench fill does not use aluminium as a catalyst
as does foam expanded concrete blocks ( lightweight) made in
factories, instead air is entrained in a mix containing proteins
and/or shampoo type derivatives to capture the bubbles

Foamed concrete is a trench infilling and not a modular construction
material ( these are deliberately blown using hydrogen evoved in the
mixture in response ot a catalyse designed to trigger the evolution of
hydrogen)

Foamed concrete is typically used in open trenches rather than indoors
and as hydrogen is lighter than air it disappears upwards

Potentially foamed concrete made with "stuff" which contain a
metallic content capable of evolving hydrogen could have been used on
a large number of occasions where the hydrogen vented safely to
atmosphere and was not ignited

The two "explosions" concerned where hydrogen was being liberated by
the foamed concrete mixture in situ BUT The material was capped with
an impermeable layer ( AND indoors in one case) to concentrate it and
flame/spark producing equipment ignited the gas buildup

Again "operatives" have sucessfully expolited the achilles heel of a
wonderful material if the companant aggregates (yes) /foaming
agents(?) are not controlled ), to demonstrate empirically the risks (
by getting hurt)

Dr John C Bullas
Research Consultant

2009/10/22 anon <construction-senderhidden@«hidden»>:

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AdamLamri 7 years ago   Reply
Is anyone aware of the specific alkali compounds within the cement mix that are reacting with the aluminium?
Dr John C Bullas - Research Consultant - H&T - Atkins 7 years ago   Reply

Foam Concrete - and potential for Hydrogen build up

"Aluminum is an amphoteric material, meaning it will react chemically
with either an acid or an alkali. When portland cement is hydrating it
releases free calcium hydroxide which is a very strong alkali. The pH
of a fresh concrete mix can be more than 13. Consequently any material
that reacts chemically with an alkali should be carefully considered
if it is to be embedded in or placed adjacent to fresh concrete."

from: http://www.cement.org/tech/faq_aluminum.asp

I think it is highly unlikely that the composition of PCC could be
sucessfully modifed to change the pH environment without having a
retrograde effect on the cured material performance, what would be far
more satisfactory is to find a solution (i.e. an answer) to avoid the
creation of the hydrogen gas whether via tighter material controls on
Aluminium content or controls on whatever is causing the gassing (
since there is no conclusive evidence of this to date)

Dr B

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AdamLamri 7 years ago   Reply

Foam Concrete - and potential for Hydrogen build up

I know that sodium hydroxide can induce a catalytic reaction between aluminum and water to produce hydrogen gas. If indeed sodium hydroxide resides in the cement (or hydration of the cement) then this could quite possibly be the cause. A hydrogen fuel cell works based on similar reactions.

It may be worth considering the removal of sodium hydroxide in the cement if this is possible and is attributed to this phenomenon.
This is an interesting subject and no doubt a chemical investigation will yield the answer.

AL
Dr John C Bullas - Research Consultant - H&T - Atkins 7 years ago   Reply

Foam Concrete - and potential for Hydrogen build up

Latest update on testing ( not from HSE) is that there may be a
potential for hydrogen evolution from at least one type of foaming
agent at extended temperatures +35c

I was called by an interested party today who have undertaken tests
and they are contacting HSE with their findings, once these are in the
public domain I will convey them on

The issue may be more common than we think since we don't routinely
combine foamed concrete with working in confined spaces and hot (
exposed flame) trades

There is no sense in trying to modify anything relating to the
composition of the concrete at this stage if changes to
aggregates/foaming agents will respolve it

Regards

Dr B

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