538 



STUDIES FOR STUDENTS 



planes cannot be considered under the head of interstatial water, 

 although it is a very prominent cause for the disintegration of 

 building stone. 



TABLE V 



Granite : 

 Maximum 

 Minimum , 

 Average . , 



Limestone : 

 Maximum 

 Minimum 

 Average . . 



Sandstone : 

 Maximum 

 Minimum . 

 Average . . 



Specific 

 gravity 



2.713 

 2.629 



2-655 



2.856 

 2.70O 

 2.806 



2.660 



2.524 

 2.622 



Porosity 



•55 

 .019 



■329 



13-36 



• 53 



4.89 



28.28 



4.81 



15.89 



Ratio of 

 absorption 



. 500 



.04 



.158 



5.60 



.19 



I.946 



15.22 

 2.00 

 7.486 



Weight per 

 cubic foot 



169.05 

 163.29 

 164.98 



176.69 

 I48.50 

 166.70 



I53.63 

 115.55 

 136.36 



FREEZING AND THAWING TESTS 



As said in a previous paper, the difficulties involved in manipu- 

 lation and the many conditions which must be considered before 

 conclusions can be drawn from quantitative results of freezing 

 and thawing tests, have apparently had the effect of almost 

 excluding these determinations from reports on building stones. 

 The effect of alternate freezing and thawing may be manifested 

 in three ways: (1) cracks may form; [2] small particles or 

 grains may be thrown off from the surface, occasioning a loss in 

 weight; (3) the cement may be weakened or the grains broken, 

 causing the strength to be materially lessened. 



Cracks. — Cracking, as a result of freezing, is seldom observed 

 in the laboratory tests, owing to the careful manner in which the 

 samples are usually prepared. 



Loss in weight. — Small particles are frequently shoved off 

 from the surface of a sample which is subjected to alternate 

 freezing and thawing. Where incipient joints occur small flakes 

 are also sometimes loosened by pressure of the freezing water. 

 Many of the grains at or near the surface of sandstone samples 

 become loosened in the process of sawing or hammer dressing. 

 These grains usually adhere to the sample so loosely that they 



