SAMPLING AND TESTING HIGHWAY MATERIALS. 
33 
the base. 4 centimeters high, resting on a glass plate about 10 
centimeters square. 
39. In making the determination, 500 grams of cement, with a 
measured quantity of water, shall be kneaded into the paste, as 
described in section 36, 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 rest- 
ing in the palm of one hand shall be pressed into the larger end 
of the nil »:>er ring held in the other hand, completely filling the 
ring with paste; the excess at the larger end shall then be 
removed by a single movement of the palm of the hand ; the ring 
shall then be placed 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 then be read, and the rod quickly released. The paste 
shall be of normal consistency when the rod settles to a point 
10 millimeters below the original surface in one-half minute after 
being released. The apparatus shall be free from all vibrations 
during the test. Trial pastes shall be made with varying percen- 
tages of water until the normal consistency is obtained. The 
amount of water required shall be expressed in percentage by 
weight of the dry cement. 
40. The consistency of standard mortar shall depend on the 
amount of water required to produce a paste of normal consistency 
from the same sample of cement. Having determined the normal 
consistency of the sample, the consistency of standard mortar 
made from the sample shall be as indicated in Table 2, the values 
being in percentage of the combined dry weights of the cement and 
standard sand. 
Table 2. — Percentage of water for standard mortars. 
For neat 
For one 
For neat 
For one 
cement paste 
cement, three 
cement paste 
cement. Ihree 
of normal 
standard 
of normal 
standard 
consistency. 
Ottawa sand. 
consistency. 
Ottawa sand. 
15 
9.0 
23 
10.3 
16 
9.2 
24 
10.5 
17 
9.3 
25 
10.7 
18 
9.5 
26 
10.8 
19 
9.7 
27 
11.0 
20 
9.8 
28 
11.2 
21 
10.0 
29 
11.3 
22 
10.2 
30 
11.5 
XII. DETERMINATION OF SOUNDNESS." 
41. A steam appartus which can be maintained at a tempera- Soundness. 
ture between 98° and 100° C. is recommended. The capacity of 
this appartus may be increased by using a rack for holding the 
pats in a vertical or inclined position. 
42. A pat from cement paste of normal consistency about 3 
inches in diameter, one-half inch thick at the center, and tapering 
to a thin edge, shall be made on clean glass plates aboul 4 inches 
square, and stored in moist air for 24 hours. In molding the pat. 
11 Unsoundness is usually manifested by change in volume which causes 
distortion, cracking, checking or disintegration. Fats improperly made 
or exposed to drying may develop what are known as shrinkage cracks 
within the first 24 hours: these are not an indication of unsoundness. 
These conditions are illustrated in Plate I. The failure of the pats to 
remain on the glass or the cracking of the glass to which the pats are 
attached docs not necessarily indicate unsoundness. 
67096°— 24- 
