The Application Of Some Of The Newer Concepts To The Design Of Concrete Mixes
W. M. Dunagan
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Present day concrete proportioning practice can be benefited by (I) an up to date, srmple and reasonably accurate method for approximating mixes before work starts so that required materials may be estimated and so that a guide is furnished for the firs trial mix, and (2) a computation method to facilitate mix adjustment in the interest of workability, during the progress of the work. Good specifications are based on such a procedure. Two factors have hindered the full provision of these two details: First, no system has provided a direct approximation of the water necessary for workability, second, the rules governing the balance between fine and coarse aggregate have not been clear; these have been assumed as discover- able only by trial. Author has developed by test and condensed into diagrams a means for approximating the first item (the water requirement of a mix) and has used a formula developed by C. A. G. Weymouth to provide a clue for a discovery of the second (the fine- coarse balance). He uses these data in conjunction with procedures taken from other authors to develop a complete system for proportioning concrete mixes. Author states his system for proportioning mixes in an eight point outline citing precedent for the use of the main principles. In the body of the paper he develops the use of individual items and submits data to show the accuracy which may be expected. The paper concludes with an appendix in which typical problems are solved.