FOEMS FOR SPECIFICATIONS, ETC., FOE EOAD MATERIALS. 49 



The composite sample is to be taken as follows: Roughly divide the area to 

 be represented by the sample into squares not exceeding 50 feet in size. At the 



corners of all squares loosen a 3 by 3 foot area to a depth of 1 inches. 



Thoroughly mix the loose material. Garry an equal amount of the material 

 from each such point to a central point and intimately mix the various samples. 

 Not less than 200 pounds of material must be so mixed. From the center of 

 the pile of mixed material fill a container and label for shipment. 



Where the material occurs as a substratum sink no less than four 3 by 3 

 foot pits per acre or smaller area to intersect the material. Remove the cover- 

 ing and sample the exposed bed as for a local sample described above. 



How to take Class II samples. — These are the most important samples, and 

 should be taken by the engineer or competent inspector while work is in 

 progress. 



When the materials have been spread and intimately mixed in accordance 

 with properly drawn clauses covering methods of construction, the engineer 



should fill a container at intervals of 2 feet, along the road, and also at 



such other points as his judgment may dictate, where evidence of unsatisfac- 

 tory mixing is apparent. 



Very prompt examination of these samples should be made in order that 

 defects of composition may be remedied by the builder before consolidation has 

 progressed. 



Sampling Bituminous Mateblals. 



General recommendations. — All samples should be selected to represent as 

 nearly as possible an average of the material, care being taken that they are 

 not contaminated with other materials. It is recommended also that special 

 care be taken to forward the samples in clean, suitable containers, and wher- 

 ever possible all materials should be sampled at the point of manufacture, and 

 sufficiently in advance of shipment of the material represented to allow for 

 the testing and reporting upon the sample before shipment. When imprac- 

 ticable to take samples at the point of manufacture they should be taken by 

 the engineer or inspector, from the shipment immediately upon delivery. 



In collecting samples, if there is any doubt of the homogeneity of the material 

 it is recommended that individual samples be lifted as hereinafter described, 

 and such samples should be forwarded to the laboratory, where tests should be 

 conducted to determine the uniformity, after which a composite sample of 

 equal parts of the individual samples may be mixed for complete tests. 



Samples should be taken as frequently as necessary to insure the uniformity 

 of the material. 



Marking samples. — Samples should be marked for identification in such man- 

 ner that the identification will not be removed in transit. Notification of 

 sampling containing this identification, together with such other information 

 as is required or of advantage to the laboratory, should be separately forwarded 

 to the laboratory immediately upon taking the sample. 



Size of samples. — No sample should be less than 1 quart, whether for complete 

 testing or for individual test. 



Plant sampling. — Drip samples are recommended. In taking drip samples, 

 the pumping should be continued until sufficient time has elapsed to clean the 

 line before sample is taken. The drip valve should be so regulated that the 

 collecting of the material continues through the entire time of pumping. 



1 A depth of 8 inches is suggested. a Intervals of 500 feet are suggested. 



