Author: Ruthen, Sir Charles T
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Ruthen, Sir Charles T
There are two subjects which may be said to have gripped the imagination of engineering scientists for the past 70 years; they are the strength of columns and the fatigue of metals. Both have this in common that the further they are investigated the more we realise that, they are more complex than we previously realised, and that many of our previous ideas upon them have to be scrapped or revised. Hon. Editor
Sir,-Referring to Mr. Andrews’ article in the Jsnuary issue of The Structural Engineer, the report which he quotes from was only intended to be a summary of the actual results obtained.
THE Method of specifying the proportions of Concrete material by so many loose volumes of gravel to a definite number of volumes of cement has much to commend it, for it is easy of application. To those using concrete, however, it has been apparent for a long time that to get the best results, those proportions must be determined by having regard to the nature of the aggregate. Many examples can be recalled in which a "lean" concrete has developed much greater strength than a much "fatter" one. A recent method of investigating the matter, especially by American Engineers, is to determine how much mortar, composed of three sand to one cement, will fill the voids in the aggregate of broken stone or gravel and to specify the quantities accordingly. These methods are more or less empirical and this investigation has been undertaken to ascertain, if possible, some definite standard of aggregate material; a more or less ideal substance, towards which one might approximate. Harry Jackson