Identifier: standardtentativ949unit (find matches)
Title: Standard and tentative methods of sampling and testing highway materials : recommended by the Second Conference of State Highway Testing Engineers and Chemists, Washington, D.C., Feb. 23-27, 1920
Year: 1921 (1920s)
Authors: United States. Bureau of Public Roads Second Conference of State Highway Testing Engineers and Chemists (1920 : Washington, D.C.)
Subjects: Road materials
Publisher: Washington, D.C. : U.S. Dept. of Agriculture
Contributing Library: U.S. Department of Agriculture, National Agricultural Library
Digitizing Sponsor: U.S. Department of Agriculture, National Agricultural Library

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uld be placed on a levelnonabsorbent surface and filled with 3-inch layers of concrete. During filling, themold should be held down by the operator placing his toes on the lip at the bottomof the mo d. As each layer of material is introduced, it should be puddled by astirring motion with a one-half-inch rod to uniformly distribute the material. After the upper layer has been placed the top shall be struck off and the moldremoved by slowly pulling it vertically tipward. The height of the frustum shallbe measured and the slump calculated from the difference of the height of the moldand the frustum. SAMPLING AND TESTING HIGHWAY MATERIALS. 67 In making the slump test in the laboratory or in the field it is recommended thatthe form be filled immediately after mixing and withdrawn three minutes aftermixing has been completed. When central mixing plants are used slump tests shall be made at the plant andat the end of the haul. At the plant the sample or concrete shall be taken after the h 4-
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PLAM Fig. 35.—Cone for concrete slump test. entire batch has been discharged from the mixer. At the end of the haul the slumpsample shall be taken from the batch after it has been dumped on the subgrade.The slump at the points of deposition shall be suitable for the particular type offinish employed. 68 50. DETERMINATION OF PERCENTAGE OF PIGMENT IN PAINTS. The per cent of pigment shall be determined by extracting a weighed amount offrom 10 to 50 grams of the paint, or from 5 to 30 grams of the paste, several timeswith light paraffin naphtha (preferably 86° B.), using approximately 50 c. c. of freshnaphtha for each extraction, and repeating the operation until the liquid of extrac-tion remains clear and colorless. The amount taken for analysis may be variedaccording to the nature of the material. The extraction and washing of the pigmentshall be completed by the use of two or three portions of about 50 c. c. of ether, thepigment finally dried to constant weight at 105° C, and the p

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