The Presidential Address. The Centenary of the Invention of Portland Cement

THE above heading is the title of a recent paper dealing with the prortioning of concrete. The information is of such value that it is proposed to give a summary of the paper arranged so that the main divisions will be similar to thosc of the Bulletin fo facilitate reference. J. Singleton-Green

The subject of the attrition of concrete surfaces exposed to sea action was dealt with by me in a paper read on January 22nd, 1920, before the Concrete Institute, now known as the lnstitutim of Structural Engineers. The object of the present communication is to describe the results of the experiments referred to in that paper. I endeavoured there to analyse the mechanism of attrition, going on from that to investigate the factors governing, and the possible methods for reducing attrition. It was shown that the injury to the concrete surface was primarily due to a fracturing and breaking away of the particles forming that surface, the conditions being exceptionally favourable for the removal of the broken material by the water. In the latter respect such surfaces as are now considered differ fundamentally from horizontal surfaces upon which the products of disintegration are allowed to collect in the form of dust, forming a protecting layer. It was shown, broadly, that whether or not surface would resist the attack of boulders driven against it by the sea would depend upon two main factors :-(n) The stress produced on the material by the blows of the boulders.(b) The resistance of such material to disintegration. Dr. J.S. Owens

This issue of THE STRUCTURAL ENGINEER contains my Presidential Address to The Institution of Structural Engineers. As the reader may or may not have discovered, I took as my text the History of the Invention and Development of Portland Cement, this year being the Centenary of the invention of that cement, which has had so large an influence on the profession af Structural Engineering. Having taken a text, I had, more or less, to confine myself to a discourse upon it, and the result was that I was left with no space or time in which to dilate upon the aims, activities and engagements of the Institution of which I have the hanour to be President. I will now endeavour to give an account of my Stewardship as far as it has gone, and to foreshadow what I hope will be done during the remainder of my period of office.