SAMPLING AND TESTING HIGHWAY MATERIALS. 



23 



reversible, and can be held in any desired position by a screw, E, and has midway 

 between the ends a mark, F, which moves under a scale (graduated to millimeters) 

 attached to the frame A. The paste is held in a conical, hard-rubber ring, G, 7 cm. 

 in diameter at the base, 4 cm. high, resting on a glass plate, H, about 10 cm. square. 



(40) In making the determination, 500 grams of cement, with a measured quantity 

 of water, shall be kneaded into a paste, as described in section 37, and quickly formed 

 into a ball with the hands, completing the operation by tossing it six times from one 

 hand to the other, maintained about 6 inches apart; the ball resting in the palm of 

 one hand shall be pressed into the larger end of the rubber ring held in the other hand, 

 completely fdling the ring with paste; the excess at the larger end shall then be re- 

 moved by a single movement of the palm of the hand; the ring shall then be placed 





1 



. 



e 



e 



"a 





«9j 







F 



I0J 





a 



s0E 



1 



| 



Al 



- 



] 



) 



.1 



11 



n 'M))iu))" ...Aimv 



Fig. 10. — Vicat apparatus. 



on its larger end on a glass plate and the excess paste at the smaller end sliced off at 

 the top of the ring by a single oblique stroke of a trowel held at a slight angle with 

 the top of the ring. During these operations care shall be taken not to compress the 

 paste. The paste confined in the ring, resting on the plate, shall be placed under the 

 rod, the larger end of which shall be brought in contact with the surface of the paste; 

 the scale shall be then read, and the rod quickly released. The paste shall be of 

 normal consistency when the rod settles to a point 10 mm. below the original surface 

 in one-half minute after being released. The apparatus shall be free from all vibra- 

 tions during the test. Trial pastes shall be made with varying percentages of water 

 until the normal consistency is obtained. The amount of water required shall be 

 expressed in percentage by weight of the dry cement. 



