SPECIFICATIONS FOE BITUMINOUS ROAD MATERIALS, 



49 



r— 



h — _, 



a 



pointed hardwood stopper d. Pointed metal projections are placed on the 

 inside of a at equal distances from the bottom and serve for measuring the 

 charge of material, which is 240 cubic centimeters. The thermometer e is used 

 to ascertain the temperature of the material to be tested. The vessel a is 

 surrounded by a brass jacket /, which holds the material used as a heating 

 bath, either water or cottonseed oil, according to the temperature at which 

 the test is to be made. A tripod g serves as a support for the apparatus 

 and also carries a ring burner li by means of which the bath is directly 

 heated. The measuring cylinder of 100 cubic centimeters capacity, which is 

 sufficiently accurate for work with road materials, is placed directly under the 

 outflow tube. 



As all viscosity deter- 

 minations should be com- 

 pared with that of water 

 at 25° C, the apparatus 

 should be previously cali- 

 brated as follows: The 

 cup and outlet tube 

 should first be scrupu- 

 lously cleaned. A piece 

 of soft tissue paper is 

 convenient for cleaning 

 the latter. The stopper 

 is then inserted in the 

 tube and the cup filled 

 with water at 25° C. to 

 the top of the projections. 

 The measuring cylinder 

 should be placed directly 

 under the outflow tube so 

 that the material, upon 

 flowing out, win not 

 touch the sides, and the 

 stopper may then be re- 

 moved. The time required for 50 cubic centimeters to run out should be ascer^ 

 tained by means of a stop watch and the results so obtajnecl should be checked 

 a number of times. The time should be about U seconds, 



Bituminous road materials are tested In the same manner as water and the 

 temperature at which the test is made is controlled by the bath, The material 

 should be brought to the desired temperature and roalntalned there for at 

 least three minutes before making the test, The results are expressed as 

 specific viscosity compared with water at 25° C, as follows ; 



S-— 



5^ 



^s^ 



Fig. 3.i=~Engler viscoslmeter. 



Specific viscosity at a° C. 



seconds for passage of given volume at a° C 

 seconds for passage of same volume of water at 25° C. 



VOLATILIZATION TEST. 



[Bulletin 314, p. 19.] ' 



The oven shown in figure 4, known as the New York testing laboratory oven, 

 is used by the office of public roads and rural engineering, although any other 

 form may be used that will give a uniform temperature throughout all parts 

 where samples are placed. The bulb of one of the termometers is immersed 



