VOLCANIC TUFF. 



Table II. — Tensile strength of stone being used in Manila. 



395 



Sam- 

 ple. 



Number 

 of de- 

 termi- 

 nations 

 made. 



Tensile strength per 

 square centimeter. 



Tensile strength per 

 square inch. 



1 



Max- 

 mum, 



Mini- 

 mum. 



Aver- 

 age. 



Maxi- 

 mum. 



Mini- 

 mum. 



Aver- 

 age. 



1 

 2 

 3 



7 

 4 

 2 



KHos. 

 7.38 

 5.70 

 8.23 



Kilos. 

 4.85 

 5.27 

 4.64 



Kilos. 

 5.77 

 5.48 

 6.40 



Lbs. 

 105 

 81 

 117 



Lbs. 

 69 

 75 

 66 



Lbs. 

 82 

 78 

 91 



A sample of stone taken from the Majayajay, Laguna quarry gave the 

 following results : 



Table III. — Tensile strength of Majayjay stone. 



Number 

 of de- 

 termi- 

 nations 

 made. 



Tensile strength per 

 square centimeter. 



Tensile strength per 

 square inch. 



Max- 

 mum. 



Mini- 

 mum. 



Aver- 

 age. 



Maxi- 

 mum, 



Mini- 

 mum. 



Aver- 

 age. 



3 



xaos. 



10.05 



Kilos. 

 6.61 



Kilos. 

 8.79 



Lbs. 

 143 



Lbs. 

 93 



Lbs. 



125 



The transverse strength of a stone is the ability to withstand a stress 

 applied at right angles to the length of the block. Its determination is 

 valuable in estimating the thickness of stone required when supported 

 only at the ends or uniformly from end to end. The cracking of stone 

 and brick walls or of single blocks is usually the result of transverse 

 stress due to unequal support throughout their length. 



The transverse strength of a number of samples was determined in 

 the following manner. Samples having a cross section of approximately 

 2.5 by 3,5 centimeters, and a length of 18 to SO centimeters were 

 jDrepared; after air drying in my laboratory they were dried at 100° and 

 finally broken in a testing machine. 



The modulus of rupture was computed from the following formula : 



^=-^rr R from which R=;r7-p 

 6l 2l)k 



W where 



VV=concenti'ated load at center in kilograms 



!)= breadth in centimeters 



?i^^depth in centimeters 



J^ length in centimeters 

 R= modulus of rupture in kilograms per square centimeter. 



