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Not so fast. . .

Letters

The last paragraph in the piece on EME2 (NCE last week) regarding the 'folly' of not using this material more widely was clearly and successfully intended to provoke a response.

The costs involved with EME2 as a base material vary, but are 15%-20% more than conventional asphalt. The benefits are much less obvious.

The nub of the problem is the quantification of additional durability. In fact, the durability of asphalt is notoriously difficult to predict.

There are few, if any, validated accelerated test regimes that UK engineers can use for mix design and the material is very sensitive to a range of factors including climate, traffic, laying conditions, and site conditions.

In the limited number of locations in France where it has been laid, it has performed reasonably well. However for all the reasons stated above, successful performance, when translated 1,000km north, is not a foregone conclusion.

The best solution and one already used by the Highways Agency, is to let a design and maintenance contract with a contract period exceeding at least the half-life of any proposal, without any restriction or recommendation on materials to be used.

In such a contract, the materials supplier/contractor who is responsible for the mix design and the selection of the binder, has to live with the consequences of his decisions technically and financially.

Ian D Walsh, Bower Mount Road, Maidstone, Kent ME16 8AU

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