202 



GEOLOGY OF OHIO 



It is much to be regretted that the samples were not burnt hard 

 enough to develop the qualities of the clay; in this case the results would 

 be very valuable. 



3. Plain vs. Re-pressed Bricks. Has been discussed in connection 

 with that subject; the general averages of the repressed and plain 

 materials are of interest however in another connection. 



Absorption, 



Repressed 

 Plain 



.85 

 2.05 



Rattling. 



17.92 

 17.42 



Crushing 

 sq. in. 



6,228 

 7,705 



Crushing 

 cu. in. 



1,514 

 1,869 



While the plain material shows the better abrasion test of the two, 

 the balance between the absorption and crushing strength is beautifully 

 shown. The repressed bricks were better burnt, and took much less 

 water, but their crushing strength was lower. The plain bricks, while 

 not as well vitrified as they should be, several of these going up to 4.5 

 and even to six per cent absorption, still showed a very distinct improve- 

 ment in their crushing strength. 



4. Effect of size on the strength and testing qualities. 



Fifteen samples of material, including the best known materials in 

 the state, such as the Hallwood Block, Hayden Block, Jones Block, Metro- 

 politan Block, Parto Block, Roseville Block and several others, all of 

 which were three by four by nine inches in dimensions or larger, were 

 compared against eleven samples of smaller repressed paving bricks, 

 including the Canton and other standard brands. 



The results are: 



Absorption. 



Rattling. 



Crushing 

 sq. in. 



Crushing 

 cu. in. 



Rank. 



Large. 

 Small. 



.89 

 .80 



16.69 

 19.59 



5,857 

 6,701 



1,443 

 1,604 



In this table, grading the bricks by absorption and rattling tests, 

 the large blocks have the very distinct advantage over the small ones. 



In crushing strength, they are at a distinct disadvantage; their 

 larger surface is not backed up by proportionate strength of structure, 

 and while they usually stand fully as much actual pressure per brick as 

 the small sizes do, they do not stand as much per inch of surface or 

 bulk. 



As has been previously remarked, there seems little ground to 

 attach much value to the crushing test, and it seems probable that the 

 strength of the largest sizes is ample to ensure their bearing any load 

 they will ever have to stand. 



The actual loss in ounces was perhaps the same in the large 

 bricks as in small ones in the rattling test, but the percentage loss is 

 much less. 



