164 



ILLINOIS ACADEMY OF SCIENCE 



TABLE 1.— STRENGTH OF SECOND SETTLE GYPSUM FROM 

 VARIOUS MILLS 

 Gypsum Compressive Strength 



No. lb. per sq. in. 



1 2250 



2 1 590 



3 1560 



4 1....1720 



5 1710 



6 1860 



Bond tests of specimens made by embedding >4-in. bars in 

 8-in. gypsum cylinders 8 in. long, showed a very satisfactory 

 bond strength. A very great increase is shown with in- 

 creased drying out. (See Fig. 7.) The smaller percentages 

 of water also show great advantage over the wetter mixes. 



700 



e>oo 



£o~00 

 \ 



=S 



400 



I 



8) 300 



x 



/oo 



1 



•Sec ondSefffe 'Gypsum "& 

 retarder ^ 



n.pla/n rouna 't>ars, 

 i^/no/ m/jefure 

 •345 % wafer 



G<% 



U 



On 



64% ca/c/'ned ' (Sypsum 

 vydferabouf 

 '>ofwei<?Mofd'r / ' 

 specimen 



700 



.eoo 



$JOO 



ZO 40 . <SO SO /OO 



34- 35 36 37 36 39 



Excess Wafer DneJOuT/n fenrenfatf? &&//& Wafer 

 rlercenfa^e of Tbta/ Excess 



F/<7. 7 r/a.8. 



( See Fig. 8. ) The driest mix shown, 34 per cent water, gave 



640 pounds per square inch in bond strength. This mix may 



have been somewhat stiffer than could be handled in practical 



work, but that containing 36 per cent water was not too stiff 



for practical work and it gave a bond strength of 500 pounds 



per square inch. 



