598 



CEMENTS, LIMES, AND PLASTERS. 



These tests were made on 2-inch cubes of neat Portland cement, all 

 being crushed at a period of 1 year, 1 month, and 16 days after making. 



"The cubes for this series were prepared and set in air or in water 

 for a period of one year to a year and a half before they were heated, 

 and intervals ranging from four days to nearly four months intervened 

 between the time of heating and the time of testing. 



" The heated cubes were gradually raised to the temperatures recorded, 

 and slowly cooled in dry sawdust or powdered asbestos. The time 

 of heating was one hour, and the maximum temperature was main- 

 tained for one hour. 



" Cubes which were set in water were dried off on a radiator for twenty- 

 four hours before heating in the muffle to the temperatures recorded. 



" During heating some of the cubes developed fine cracks, at first faintly 

 shown, which enlarged after a few hours or days had elapsed. In other 

 cases the cracks appeared more promptly. Among those which were 

 heated to the higher temperatures of the series, which ranged from 200 

 to 1000 F., there were cubes so badly cracked as to be unsuitable for 

 testing." 



TABLE 232. 

 EFFECT OF HEATING ON COMPRESSIVE STRENGTH. 



(WATERTOWN ARSENAL.) 



Report of Tests of Metals, etc., at Watertown Arsenal, 1902, pp. 459-46U 



Effects of salt and freezing. The use of cement or concrete in build- 

 ings constructed during very cold weather has led to a long series of 

 experiments, designed to determine the effects of using salt and other 

 anti-freezing agents in the water used in mixing the mortar. 



The results of a number of such tests are shown diagrammatically 

 in Figs. 153 to 158 inclusive. The results as to strength are rather con- 



