You may recall the case of the exploding concrete reported in November 2009, entitled Exploding concrete banned:
Contractors are banning foam concrete on civil sites after two explosions left construction workers with fractured feet. The blasts were linked to the use of incinerator bottom ash (IBA) in foam concrete. At least two contractors – Barhale and Enterprise – have banned foam concrete containing IBA from all their sites, with others understood to be following suit.
Well, we now read that the Highways Agency have issued a guidance note (Interim Advice Note 127/09 The Use Of Foamed Concrete) in which they advise that “foamed concrete containing IBA must not be used on any Highways Agency contracts from the date of this document until the HSE investigations are complete“.
The interim advise notice (IAN) contains the following explanation:
The Health and Safety Executive (HSE) has identified several incidents involving foamed concrete, including a serious accident on 21st August 2009 at a sewage pumping station being decommissioned, when contractors were injured as a result of a gas explosion. In this incident, a 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.
The foamed concrete mixture contained Incinerator Bottom Ash (IBA) which may in certain circumstances produce hydrogen gas. Aluminium metal particles present in the IBA react with the water and cement to generate hydrogen, the volume of hydrogen produced being proportional to the quantity of aluminium metal being present in the IBA. HSE investigations are on-going.
Foamed concrete is sometimes used on Highways Agency contracts as trench reinstatement and for filling voids such as redundant structures and for other road construction applications.
As a precaution, the use of foamed concrete containing IBA must not be used on any Highways Agency contracts from the date of this document until the HSE investigations are complete and if necessary further research by the Highways Agency has been undertaken.
The use of foamed concrete without IBA is not affected.
This IAN should be disseminated across all of the HA Supply Chain. It should be used with immediate effect on all HA schemes and contracts
Once the HSE investigations are complete, the prohibition on the use of foamed concrete containing IBA will be reviewed.