Welded Steel Structures - Recent Developments in Europe. Discussion on Mr. A. Ramsay Moon's Paper

Mr. D.A.G. REID, in a few words supplementing Dr. Glanville’s presentation of the paper, said that he might try to express in another form what he felt to be the value of the wet mortar test. It amounted practically to this, that if one had a strength-age curve for the wet mortar, and then immediately one had also a strength-age curve for a 1:2:4 concrete with a water-cement ratio of 60 per cent., and, with the aid of a few general relationships, strength-age curves could be constructed for any other concrete made with that cement; and the strengths taken off from such strength-age curves would be correct to within about 10 per cent. If, however, any such operation were carried out with a dry mortar test, inevitably it seemed errors of 20 per cent. or more crept into the estimates. Of course, that could be got over if the mortar- concrete strength relationship were available for the particular batch of cement, but that contingency was not very likely. Dr. Glanville had mentioned the carrying out of preliminary tests before the commencement of the main programme. The results of these tests had proved very instructive, and had been of considerable value in assisting in the interpretation of the results of the main series. Mr. Reid felt that this portion of the work would be of great interest to anyone connected with the testing of cements and concretes.

It may be stated in a general way that, for a given nature of sand and a given quality of cement agglutinant the strength of the resulting concrete increases when its compactness increases. The lack of compactness may be due in part to bad granulometry, which is a question into which it is not proposed to enter specifically in this paper; assuming that the best granulometric composition of the inert, component has been attained, lack of compactness may still be due to the fact that full advantage is not taken of the possibilities presented by the composition of the mixture, that air cavities remain in the concrete, either through the presence of mechanically enclosed air bubbles, or through the gradual evaporation of superfluous water. T.J. Gueritte

The rapid growth of aerial transportation during the last ten years so admirably illustrated by the activities of Imperial Airways Ltd., and particularly the wide interest shown in the spectacular flight of Scott and Black from Mildenhall Aerodrome to Melbourne in two and a half days, have focussed public attention on the urgent necessity for providing adequate landing fields and aerodromes in this country. It is noteworthy that H.R.H. The Prince of Wales remarked at the recent Airport Conference, “Take care of the wheels and the wings will take care of themselves.” The aeronautical engineer has indeed done his share, and such enormous strides have been made in aircraft design that the operational speed of machines is approaching 200 m.p.h. If, therefore, it is true that “time is money,” here is economy with a vengeance. H.E. Brooke-Bradley