We read with interest the article by John Thornton on concrete ('Update on concrete', aj 4.11.99). One area where we think it is pertinent to add a little clarification is on the use of high-strength concretes. Not wishing to start 'bidding' on the highest-strength concrete used in this country in in-situ applications, it may be appropriate to record certain facts.
Using high-strength in-situ structural concrete is becoming more and more common. It is believed that the strongest concrete used in this country to date had a 28-day cube strength of 159 n/m2. This concrete was used three years ago for an industrial suspended structural slab in one of the Philips organisation's process buildings. The structure was designed by Mark Lovell Design Engineers in conjunction with Oscar Faber of Bristol and built by m & w Pearce of Bristol.
Using even higher strength concrete is being considered at the moment - conventionally cast and cured concrete has been manufactured up to 250 n/m2.
We hope that these additional facts augment the story that high-strength concretes are being used in a creative way in in-situ applications.
Mark Lovell, Devizes, Wiltshire
The letter from Rab Bennetts (aj 11.11.99) should have stated that the top floors of his bt building are 1.5 degrees warmer than the lower floors, not 15 degrees as we printed. Apologies.