Under the above title and from the pen of Mr. Sathan C. Johnson, Consulting Engineer of New York City, there has,recently appeared a series of four articles in Engineering News-Record, which should be read by everyone honestly interested in the betterment of the production of concrete in large or small quantity. These articles constitute a carefully considered and thoughtful review of the extent to which the existing practice of producers comes up to the demands of consumers. In plain language, are the best efforts being directed to the production of a uniformly high quality of concrete on the works and is the best interpretation being put upon the mass of valuable information accumulated from failures, practical tests and laboratory research during the past two decades? During that period we have undoubtedly advanced a long way on the road towards a thorough understanding of the interactions which take place when
water, cement, sand and stone are mixed together in varying ratios, yet the further we advance, the more does it become apparent that this seemingly simple material is actually most complicated in its properties and behaviour. The state of our
knowledge of the chemistry of cements is still far from complete. We have reached a stage, however, when, given the necessary time and leisure, small quantities of laboratory-made concrete may be produced which, under meticulous testing exhibit remarkably high strength properties. The methods by which such iaboratory samples are produced obviously cannot be applied to the production of concrete in bulk. As Mr. Johnson aptly remarks, "On the job, cement is cement, sand is sand, stone is stone, water is water and weather is weather. No time for niceties, no leisure for reflection and, perchance and even possibly, a most wordy flow of language here and there to speed the laggard hand. Men and machines and materials in an unceasing stream are everywhere in evidence, all governed by, the plans prepared by the engineer or the architect and, presumptively, by the specifications."