A treatise on concrete, plain and reinforced : materials, construction, and design of concrete and reinforced concrete; 2nd ed. . lso the de-fects in the materials and how to remedv them. 786 A TREATISE ON CONCRETE The most valuable use of the method of proportioning by mechanicalanalysis is in cases where the character of the work warrants employingseveral grades, that is, several sizes, of stone and sand. Such mixturesare being increasingly employed as engineers and contractors more fullyappreciate the necessity of so economically proportioning the materials asto produce a mixed aggregate of
A treatise on concrete, plain and reinforced : materials, construction, and design of concrete and reinforced concrete; 2nd ed. . lso the de-fects in the materials and how to remedv them. 786 A TREATISE ON CONCRETE The most valuable use of the method of proportioning by mechanicalanalysis is in cases where the character of the work warrants employingseveral grades, that is, several sizes, of stone and sand. Such mixturesare being increasingly employed as engineers and contractors more fullyappreciate the necessity of so economically proportioning the materials asto produce a mixed aggregate of the greatest possible density, — that is,with the fewest possible voids, — thereby reducing the quantity of cementand at the same time improWng the quality of the concrete, in other words,making both a better and a cheaper concrete. The process of determining the percentages of each material is morecomplicated than where only two aggregates, sand and stone, are used,but it is not very difficult in practice, especially if one is familiar with theslide rule, and, as illustrated in Example 2, the method is more exact than. 100 DIAMETERS OF PARTICLES IN INCHES Fig. 249. — Method of Proportioning a Graded Mixture. (See p. 786.) with two materials, for the reason that the resulting curve can be made tomore nearly approach the parabola. Example 2. —Graded Materials. Given the medium sand, representedby curve in Fig. 72, page 200 and the three sizes of crushed stone repre-sented by the curves in Fig. 71, page 198, find what percentage of eachwill best combine to make the strongest and densest concrete. Solution. — Since mechanical analysis of each material has already been made, we will immediately replot the four cun^es on the same scale in Fig. 249 and draw parabola passmg through point O and the point at which curve No. 4 reaches 100%. We see at once that percentage of No. 4 Kk 36stone reqtiired is -=p^ = — = 36%. (To be sure, about 8% of No. 4 isAi&
Size: 2520px × 992px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookpublishernewyo, bookyear1912
