28 The Philippine Journal of Science i9i6 



specimens. Mix C having the largest amount of lime had the 

 lightest color ; it resembled in appearance white Portland cement. 

 The following tests were made: (1) Percentage of water neces- 

 sary for normal consistency ; (2) fineness; (3) specific gravity; 

 (4) setting time; (5) tensile strength, neat, in air; (6) tensile 

 strength, neat, in water; (7) tensile strength, mortar, in air; 

 (8) tensile strength, mortar, in water; (9) compressive strength, 

 neat, in air; (10) compressive strength, neat, in water; (11) 

 compressive strength, mortar, in air; (12) compressive strength, 

 mortar, in water. All mortars were made with one part by 

 weight of the tuff -lime mixture and three parts by weight of 

 standard Ottawa sand. 



RESULTS OF TESTS 



The results obtained are shown in Table VII. 



Fig. 1 shows curves obtained by plotting the tensile and 

 compressive strengths in pounds per square inch against time 

 in days. There is a very marked diflference in curve slope be- 

 tween air specimens and those kept in water. The strength of 

 those specimens stored in air is practically negligible, whereas 

 the strength developed by some of the test pieces kept in water 

 is considerable. The compressive neat strengths in water of 

 mix C are remarkable in that the curve is practically a straight 

 line and at ninety days still does not show any tendency to 

 parallelism to the X-axis as do the rest. The increment in 

 strength per unit of time during ninety days is constant — about 

 300 pounds. All other specimens show a falling off in the in- 

 crement of strength after the 60-day period. When the neat 

 specimens of mixture C stored in water were tested at the 90- 

 day period, failure was accompanied by a sharp report; the 

 spalls had a stonelike ring. The ultimate strength per square 

 inch is 2,202 pounds. 



Mix A gave good results, also, although the unit strength 

 did not reach the high figure shown by mix B. 



All test specimens, with the exception of those made out of 

 mix C, were allowed to remain in moist air for two days just 

 as made without removing the molds. Mix C was kept in 

 moist air with molds for five days on account of the softness 

 of the specimens. I tried removing some of the test pieces at 

 the end of the second day, as in the case of mixes A and B, 

 but found them so frail that removal without injury was 

 impossible. Two series of tests were conducted upon the various 

 mixtures. One half was stored in air, and the other half was 

 immersed in water. It is common practice in making tests of 

 these kinds to keep the specimens in moist air for a short period, 



