8 THE COLORADO EXPERIMENT STATION 



Reinforcement. Cement and concrete work has the prop- 

 erty of resisting great, crushing stresses, but when subjected 

 to tensile stress the best of it breaks very easily. For this reason 

 it becomes necessary to put some material possessing great tensile 

 strength into the post, in order that the full crushing strength of 

 the cement or concrete may be utilized. Iron is the most satis- 

 factory material from which to make reinforcement. The rein- 

 forcement should be placed in the post as near the corner as pos- 

 sible. This places it as far as possible from the neutral axis thus 

 giving it the greatest advantage in strengthening the post. In 

 order that the reinforcements may be properly held and protected 

 by the cement, it is a good plan to place it from ^ to 24 inch in 

 from each side. 



The material used for reinforcement should be strong, light 

 and rough enough to permit the mixture to get a firm grip upon it. 

 It should be very rigid, with little or no tendency to spring or 

 stretch. The experiments showed that ordinary iron or steel wire 

 was cheapest, strongest and easiest to procure. In order to provide 

 a means by which the cement may cling firmly to the wire, it is 

 best to twist two small wires together instead of using one large 

 one. 



Curing the Posts. In order for the cement to become 

 thoroughly cured or "set" water must be supplied to aid in the 

 action. For the first thirty days the posts should be kept wet if 

 the best results are to be expected. 



The most favorable conditions for conserving the moisture 

 consists in curing the posts in a shed where the wind does not 

 strike them. Under these conditions neither the sun's rays nor 

 the wind have a chance to dry out the posts too rapidly. The posts 

 should be thoroughly sprinkled every day for at least thirty days. 



Wire Fasteners. An inventor has devised a cast-iron socket 

 which is placed in the post. Later the wire is fastened to 

 the post by driving a staple into the socket or staple holder. The 

 staples pull out easily and the sockets add greatly to the cost of 

 the post. 



Another system consists of two staples which have the prongs 

 bent to the side. The staples are placed about one-quarter inch 

 apart, with the prongs projecting to the side. The line wire is 

 placed between the two staples and a nail or a piece of wire is 

 driven down through the staples, outside of the line wire. As the 

 tips of the staple touch the reinforcement wires, direct electric con- 

 nections are established between the line wire and the ground at 

 the bottom of the post. This, it is claimed by the patentee, insures 

 the user against loss of stock by lightning. The system is called 

 the "Double Staple." (See Fig. 2.) 



