. Railway maintenance engineering, with notes on construction . 177 (a) Weight per cubic foot. (6) Water absorption in poundsper cubic foot. (c) Per cent of wear. (d) Hardness. (e) Toughness. (/) Cementing value. (g) Compression test. The advantage of using approvedphysical tests of stone for ballast is todetermine the character of the stoneand its fitness for ballast without theexpense of opening quarries and usingthe stone before it is known whether itwill be suitable for ballast or some method of determiningthis by physical tests, railroads willundoubtedly be put to considerable
. Railway maintenance engineering, with notes on construction . 177 (a) Weight per cubic foot. (6) Water absorption in poundsper cubic foot. (c) Per cent of wear. (d) Hardness. (e) Toughness. (/) Cementing value. (g) Compression test. The advantage of using approvedphysical tests of stone for ballast is todetermine the character of the stoneand its fitness for ballast without theexpense of opening quarries and usingthe stone before it is known whether itwill be suitable for ballast or some method of determiningthis by physical tests, railroads willundoubtedly be put to considerableexpense by opening quarries and apply-ing stone ballast, which in some caseswill have to be replaced with betterballast from other quarries.* In the test for toughness, , theability of the stone to resist fracturedue to impact, the office of PublicRoads use the Page impact machine,shown in Fig. 104. This machineconsists essentially of a 2-kilogramhammer which is guided by two verticalrods. This hammer does not strikethe specimen to be tested directly, but. Fig. 104.—Page ImpactTesting Machine. * For the description of the physical tests of stone for ballast as recom-mended by the American Railway Engineering Association and full in-structions as to how the samples should be obtained and shipped to theGovernment for the test which is made free of charge at the office of PublicRoads, see Proceedings, Vol. 11, Part 2, pp. 910-914,and Report of theBallast Committee for 1912. 178 RAILWAY MAINTENANCE when released strikes a plunger made of witha spherical end and the blow is delivered through this test piece rests on an anvil of hard steel. The test consistsof a 1-centimeter fall of the hammer for the first blow, and anincreasing fall of 1 centimeter for each succeeding blow untilfailure of the test piece occurs. The number of blows requiredto cause failure is used to represent the toughness. Rocks which have a toughness which runs below 13 are
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