The volume of mortar required to fill the voids Is always 

 more than the voids as originally measured, increasing as 

 the stone becomes smaller and more mixed. From 9 to 

 15% of water should be used of course, varying conditions 

 must always be taken care of. Materials should always 

 be mixed dry, and the water then added. If hand mixed, 

 see that it is evenly mixed. 



STEEL. 



When the elastic limit of the reinforcing metal is 

 passed, providing all other stresses are proportionately 

 taken care of, the concrete beam fails; consequently it is 

 the chief criterion. For conservative practice a tensile 

 strength of 60,000 Ib. ; an elastic limit of 30,000 to 40,000 

 lb.; an elongation of 20% in 8 in. and bending cold 180 deg. 

 without fracture, are fair requirements of steel. 



The different patented bars have the following tensile 

 strengths: 



Elastic Limit. Ultimate Strength. 



Uansome 6 to 50,000 60,<MU) to 100,000 



Thacher .<)00 r,4.ouu 



Johnson 50 to OO.IMMI Km.ooo 



Kahn .".n.ooo GO.OOO 



Ordinary working stresses range from 15,000 to 22,000 

 lb. per sq. in. in tension. Shear at 10,000 to 12,000 lb. 



Lap bars 30 diameters to develop the grip. 



Small bars are more expensive than large, but small 

 bars distribute the stress better and have a greater per- 

 imeter. 



REINFORCEMENT. 



In a work of this kind, for the packing in small com- 

 pass of tables and data for convenient reference, it is not 

 consistent to attempt a description of the various styles 

 of reinforcing material. The subject is too large. If 

 treated in a helpful way it would require a book for its 

 exposition. It is the intention of the publishers of Con- 

 rr /c I'.n'iiim rimi to d.-votc one issue to a description of 

 the different kinds and systems of reinforcement at an 

 early date. 



Following Is a list of names of reinforcing materials 

 from Marsh. Nearly all are patent 



American Concrete Steel Co.; Bonna; Bordenave; Bous- 

 seron & Garric; Chaudy; Clinton; Colgnet; Columbian: 

 Cottancin; Coularou; Cummings; Degon; Demay; De 

 Yalliere-Simon & Co.; H:it>ri<h, or Thomas & Stelnhoff: 

 Hennebique; Johnson; Kahn; Klett; Koenen; Lorher: 

 Machiachini; Matrai; Melan; Moller; Monier; Mueller. 



