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RICHARD COWLING, ALFRED MCALPINE CAPITAL PROJECTS
A4146 BYPASS
A simple telephone enquiry gave us the opportunity to play a crucial role in the construction of a new bypass near Milton Keynes.
From reading our website, main contractors Alfred McAlpine knew we used blast cleaning technology to remove graffiti. They asked if we could transfer that expertise to the removal of laitence from the base of part-constructed bridge piers on the new A4146. We were on site within three days.
Laitence is fine cement powder which floats to the surface of all poured concrete work. It must be removed (along with any other dirt or debris) to ensure a positive bond is formed between the existing and newly-poured concrete. To remove it, we blast-cleaned the surface with recycled iron silica.
Top for health and safety
The project is ongoing, as more bridges are built, but McAlpine are delighted with the results so far. We were equally delighted to learn that of all the sub-contractors McAlpine had evaluated, we scored highest in terms of our health and safety procedures.
The final stage of the project for us will be to apply a new non-hazardous protective impregnation sealer (this replaces the use of Silanes) to all 15 completed structures. The product is called Protect All P1 and its use on this contract has been approved by Atkins on behalf of the Highways Agency. The sealer prevents water, oil, road salt and other contaminants from permeating the concrete and corroding the steel reinforcing bars. It has the additional benefit of being resistant to solvents and, thus, aids the removal of graffiti.
