10 DEPARTMENT BULLETIN 12 16, U. S. DEPT. OF AGRICULTURE 
water used and the amount of kneading the paste received, but by the tempera- 
ture and humidity of the air, and its determination is therefore only ap- 
proximate. 
45. The time of setting shall be determined by the Gillmore needles. The 
Gillmore needles should preferably be mounted as shown in Figure 3 P>, and the 
needle ends shall be maintained in a clean condition and shall be plane and at 
right angles to the axis of the rod. 
46. The time of setting shall be determined as follows : A pat of neat cement 
paste about 3 inches in diameter and one-half inch in thickness, with a flat top 
(fig. 3 A), mixed to a normal consistency, shall be kept in moist air at a tem- 
•W/////;////////^^ 
Fig. 3. — Pat and instruments for determining time of set; (A) Pat with top surface tau- 
tened for determining time of setting by Gillmore method; (B) Gillmore needles 
peratuie maintained as nearly as practicable at 21° C. (70° F.). The cement 
shall be considered to have acquired its initial set when the pat will bear, 
without appreciable indentation, the Gillmore needle one-twelfth inch in diam- 
eter, loaded to weigh one-fourth pound. The final set has been acquired whin 
the pat will bear, without appreciable indentation, the Gillmore needle one- 
twenty-fourth inch in diameter, loaded to weigh 1 pound. In making the test 
the needles shall be held in a vertical position and applied lightly to the surface 
of the pat. 
TENSION TESTS 
47. The form of test piece shown in Figure 4 shall be used. The molds shall 
be made of noncorroding metal and have sufficient material in the sides to 
prevent spreading during molding. Gang molds when used shall be of the 
type shown in Figure 5. Molds shall be oiled with a mineral oil. 
48. The sand to be used shall be natural sand from Ottawa, 111., screened 
to pass a No. 20 sieve and retained on a No. 30 sieve. This sand may be 
obtained from the Ottawa Silica Co., Ottawa, 111. 
