PHYSICAL PROPERTIES OF PORTLAND CEMENT. 607 



The work may be expedited by placing in the sieve a small quantity 

 of large shot. The results should be reported to the nearest tenth of 

 1 per cent. 



NORMAL CONSISTENCY. 



27. Significance. The use of a proper percentage of water in making 

 the pastes * from which pats, tests of setting and briquettes are made, 

 is exceedingly important, and affects vitally the results obtained. 



28. The determination consists in measuring the amount of water 

 required to reduce the cement to a given state of plasticity, or to what 

 is usually designated the normal consistency. 



29. Various methods have been proposed for making this determina- 

 tion, none of which has been found entirely satisfactory. The Com- 

 mittee recommends the following: 



30. Method. Vicat needle apparatus. This consists of a frame bear- 

 ing a movable rod, with the cap at one end, and at the other end the 

 cylinder, 1 cm. (0.39 inch) in diameter, the cap, rod, and cylinder weigh- 

 ing 300 gr. (10.58 oz.). The rod, which can be held in any desired 

 position by a screw, carries an indicator, which moves over a scale 

 (graduated to centimeters) attached to the frame. The paste is held 

 by a conical, hard-rubber ring, 7 cm. (2.76 inches) in diameter at the 

 base, 4 cm. (1.57 inches) high, resting on a glass plate about 10 cm. 

 (3.94 inches) square. 



31. In making the determination, the same quantity of cement as 

 will be subsequently used for each batch in making the briquettes (but 

 not less than 500 gr.) is kneaded into a paste, as described in Para- 

 graph 58, and quickly formed into a ball with the hands, completing 

 the operation by tossing it six times from one hand to the other, main- 

 tained 6 inches apart; the ball is then pressed into the rubber ring 

 through the larger opening, smoothed off, and placed on a glass plate 

 (on its large end) and the smaller end smoothed off with a trowel; the 

 paste, confined in the ring, resting on the plate, is placed under the rod 

 bearing the cylinder, which is brought in contact with the surface and 

 quickly released. 



32. The paste is of normal consistency when the cylinder penetrates 

 to a point in the mass 10 mm. (0.39 inch) below the top of the ring. 

 Great care must be taken to fill the ring exactly to the top. 



*The term "paste" is used in this report to designate a mixture of cement 

 and water, and the word "mortar" a mixture of cement, sand, and water. 



