168 



UEIBLING AND SALINGER. 



The conclusion would naturall}' be drawn that the greater the density of 

 the briquette, the greater would be its tensile strength. This is not true 

 within limits of 2 per cent, as the other reasons for "personal error" 

 abo'S'e described may overcome the natural tendency to high tensile 

 strength caused by the density of the material. In sand mixtures, also, 

 a high density may simply show that more sand and less cement have 

 been used. 



These facts are illustrated in our routine work and shown l^y Tables 

 XIX and XX. 



Table XIX. — Mortar briquettes, 1 to 3 ; 12i per cent water; tamped. 



Sample No. 



Time in 

 days. 



Tensile 



strength 



in pounds 



per square 



inch. 



Weight in 

 gram,s. 



Sample No. 



Time in 

 days. 



Tensile 



strength 



in pounds 



per square 



inch. 



Weight in 

 grams. 



Fl-5 



7 

 7 



171 

 184 



131.0 

 129.9 



Fl-8 



7 



7 



191 

 177 



131.1 

 130.7 









28 



214 



130.5 





28 



221 



130.0 





28 



200 



126.5 





28 



233 



129.2 



Fl-6 



7 

 7 



176 

 192 



131.4 

 130.6 



Fl-9 



7 

 7 



188 

 177 



131.1 

 130.5 









28 



188 



131. 





28 



244 



131.0 





28 



195 



130.0 





28 



232 



132.0 



Fl-7 



7 

 7 



178 

 191 



128.7 

 129.3 



Fl-9 



7 



7 



182 

 192 



130.0 

 130.3 









28 



223 



128. 6 





28 



238 



130.8 





28 



216 



127.9 



, 



28 



235 



131.0 



Table XX. — 'Neat briquettes made from sample Yl according to American Society 



specifications. 



Age in 

 days. 



Tensile 



strength 



in rounds 



per square 



inch. 



Weight in 

 grams. 



Average 



weight in 



grams. 



Age in 

 days. 



Tensile 



strength 



in pounds 



per square 



inch. 



Weight in 

 grams. 



Average 



weight In 



grams. 



28 



28 



28 



28 



28 



28 



28 



28 



603 



665 

 (539) 



638 

 (686) 



636 

 ■ 620 



625 



137.3 

 138. S 

 138.2 

 137.0 

 137.5 

 137.8 

 137.8 

 138.6 



137.8 

 137. 9 



28 



636 

 613 

 599 

 609 

 621 

 (661) 

 631 

 617 



136.5 

 136.6 

 136.5 

 136.8 

 137. 2 

 137.7 

 137.0 



136.6 

 137.0 



28 - 



28 



28 - 



28 



28 



28 



28 



136.4 ) 1 







1 



For some time this laboratory was forced to manipulate all cements 

 strictly according to United States Army Engineer specifications, with 

 20 and 12.5 per cent of water for the neat and mortar tests, respectively. 

 Twenty per cent of water will not satisfy the chemical and physical 

 possibilities of many good Portland cements, and the following table 

 illustrates this fact: 



