SAMPLING AND TESTING HIGHWAY MATERIALS. 
27 
(55) Immediately after mixing, the standard mortar shall be placed in the molds, 
pressed firmly with the thumbs, and smoothed off with a trowel without ramming. 
Additional mortar shall be heaped above the mold, and smoothed off with a trowel; the 
trowel shall be drawn over the mold in such a manner as to exert a moderate pressure 
on the material. The mold shall then be turned over and the operation of heaping, 
thumbing, and smoothing off repeated. 
Fig. 13.— Form of briquette as recommended by the committee on uniform tests of cement of the American 
Society of Civil Engineers. 
(56) Tests shall be made with any standard machine . The briquettes shall be tested 
as soon as they are removed from the water. The bearing surfaces of the clips and 
briquettes shall be free from grains of sand or dirt. The briquettes shall be carefully 
centered and the load applied continuously at the rate of 600 pounds per minute. 
(57) Testing machines should be frequently calibrated in order to determine their 
accuracy. 
(58) Briquettes that are manifestly fault}-, or which give strengths differing more 
than 15 per cent from the average value of all tests pieces made from the same sample 
I 
Fig. 14.— Gang mold. 
and broken at the same period, shall not be considered in determining the tensile 
strength. 
STORAGE OF TEST PIECES. 
(59) The moist closet may consist of a soapstone, slate, or concrete box, or a wooden 
box lined with metal. If a wooden box is used, the interior should be covered with 
