From D. G. ELLAN
While the theme of your article ‘Concrete claim for conservation’ (Technology,
30 October) is entirely praiseworthy and effective, may I draw your attention
to an innovative invention which takes a different approach to the mixing
of materials by nonmechanical means?
The method of using compressed air to create turbulence in a tube while
the medium is falling by gravity has a number of advantages: it permits
the ingredients to be transported dry to a site, does not require a purpose-built
cement mixer lorry, and is totally self-cleaning. So it can be seen to be
even more environmental-friendly than the method suggested in your article.
D. G. Ellan Whitehaven, Cumbria
