12 
S. DEPARTMENT OF AGRICULTURE. 
Mortar 
strength test. 
Methods of 
sampling. 
Methods of 
testing. 
When that portion of the combined dustless screenings and 
sand which passes a one-quarter-inch laboratory screen is mixed 
with Portland cement in the proportion of 1 part of cement to 
3 parts of the combination, by weight, according to standard 
methods of making 1 : 3 mortar briquets, the resulting mortar at 
the age of 7 and 28 days shall have a tensile strength of at least 
* per cent of that developed in the same time by mortar 
of the same proportions and consistency, made of the same cement 
and Ottawa sand. 
Preliminary acceptance samples shall be subjected to both 
7 and 28-day tests, and acceptance based thereupon. Samples 
tested during the progress of the work will be accepted on the 
basis of the 7-day test. 
Stone shall be sampled for quality in accordance with the 
method described on page , paragraphs , of these 
specifications. Dustless screenings and mixtures of the dustless 
screenings and sand shall be sampled for grading in accordance 
with the method described on page , paragraphs , of 
these specifications ; and sand shall be sampled in accordance with 
the method described on page , paragraphs , of these 
specifications. 
Tests of the physical properties of stone shall be made in ac- 
cordance with the method described or referred to on page 
of these specifications, test No. Tests of the grading of 
dustless screenings and of the combination of dustless screenings 
and sand shall be made in accordance with the method described 
or referred to on page of these specifications, test No. 
Note. — It is recommended that volumetric analyses be reported 
by the laboratory to facilitate field control. 
General. 
Physical prop- 
erties. 
Dimensions. 
Visual Inspec- 
tion. 
SPECIFICATION FOR STONE BLOCK. 
The stone block shall be of (.^sert types allowable) i , of medium- 
sized grain, showing an even distribution of constituent minerals. 
They shall be of uniform quality and texture throughout, and 
free from seams, scales, or disintegrated material. 
Sample blocks shall meet the following requirements : 
Per cent of wear not more than 
(or French coefficient not less than ) 
Hardness to 
The blocks shall meet the following requirements: 
Inches. 
Length on top to 
Width on top to 
Depth to 
The stone block shall be subjected to inspection subsequent to 
delivery at the place of use, prior to and during laying, in order 
to cull out and reject those which fail to conform with the general 
♦ It is recommended that the strength ratio be 100 per cent for this 
purpose. 
