SAMPLING AND TESTING HIGHWAY MATERIALS. 73 



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 u feet, along the road, and also at such other points as 



his judgement may dictate, where evidence of unsatisfactory 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. 



58. SAMPLING BITUMINOUS MATERIALS. 



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 wherever possible all materials should be sampled at the 

 point of manufacture, and sufficiently in advance of shipment of the material repre- 

 sented to allow for the testing and reporting upon the samples before shipment. When 

 impracticable 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 neccessary to insure the uniformity of 

 the material. 



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

 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. 



When impracticable to follow the above method it is recommended that samples 

 be taken from the storage tank at three different levels. 



Material in barrels or drums at a plant should be sampled by taking samples from 

 not less than 3 per cent of the containers. 



Whenever possible, the portion of the sample from each drum or barrel should be 

 taken from near the heart of the barrel after it has been split open. Where samples 

 must be taken from the top of the barrel, the material lying within 3 inches of the 

 surface should not be included. A hatchet or any sharp-pointed tool is suitable 

 for the purpose of digging into the barrel. (Important. — -Do not use kerosene on 

 the blade.) The several portions are then to be pressed in a can of not less than 

 1 quart capacity, using a quantity of material which will nearly fill the can, which 

 is then to be tightly covered. If cans are not available and some other type of con- 

 tainer is used, it must be entirely free from paper or any other substance to which 

 the bituminous material adheres readily. 



Check field samples are recommended on plant-inspected material. 



Field sampling. — For barrel shipments, see plant barrel sampling. 



1 4 Intervals of 500 feet are suggested. 



