FIXING BOLTS IN MASONRY. 



381 



bolts split at G7,000 Ibs. in tho case of the smooth one, and at 

 50,000 Ibs. in the case of the threaded one. 



It is thus seen that cement is more reliable, stronger, and 

 easier of application than either lead or sulphur, and that its 

 resistance is from 400 to 500 Ibs. per square inch of surface 

 exposed. It is also a well-ascertained fact that it preserves 

 iron rather than corrodes it. The cement used throughout the 

 experiment was an English Portland cement. 



In recent investigations of the strength and adhesion of iron 

 anchor-bolts set in stone masonry, Mr. Robert Moore, Chief 

 Engineer of the St. Louis Merchants' Bridge Terminal Railway, 

 experimented with full-sized rods set with lead, sulphur, cement, 

 etc. From a photograph taken after testing the results of 

 two experiments, A and B are illustrated in Fig. 338. Stone 

 blocks, of a size adapted to the test- 

 ing machine, were drilled through, 

 and 2-inch iron rods were set into 

 them 11 J inches, and the space 

 around them was filled with a thin 

 mortar or grout of Harris's Portland _ 

 cement, which was allowed to set / 

 ten days. The stone and rod were j 

 then placed in a testing machine 

 and subjected to tension to pull out \ 

 the rod. Briquettes of the cement, 

 tested in the usual manner, deve- 

 loped a strength of about 475 Ibs. per square inch in seven days, 

 and 550 Ibs. in ten days. In A the rod had a screw thread to 

 improve the grip of the cement, and the stone began to yield at 

 a load of 32,000 Ibs., and broke at a load of about 50,000 Ibs., 

 without developing the strength of the cement joint. In B the 

 rod was plain and smooth, and the cement began to yield at a 

 load of 34,000 Ibs., but did not entirely part when the rock 

 broke at a load of 67,000 Ibs. Larger blocks of stone could not 

 be accommodated in the machine, but it was inferred that in a 

 suitable setting the cement joint on a smooth rod might be 

 made to break the rod. 1 



Experiments on the holding power of anchor-bolts set in 

 stone with different materials, made by Mr. E. F. Miner, gave 

 the following results : 



1 Engineer, vol. Ixxi. p. 387. 



FIG. 338. 



