LIME AND CEMENT INDUSTRIES 719 



applied to it. Tlie briquets are allowed to '^ set " either in air 

 or water and are then pulled apart after a time, the number of 

 pounds a square inch required to do this being recorded. This 

 is the usual test made on cement, and, while it is not subjected 

 to a tensile strain in actual work, still it gives a good idea of the 

 strength of the cement, and is easity carried out. The briquets 

 should be made of cement taken freshly from the barrel. 



Form of briquets. Several different forms of briquets have 

 been devised, but all have been so designed as to cause the 

 briquet to break at its miniminn cross-section. The American 

 society of civil engineers recommended a standard size of briquet, 

 which is one inch thick and the same in width and weakest in 

 the center. This is smaller than that which is made in England 

 or on the continent, but it gives satisfactory results, and the 

 smaller size makes it less likely to have air bubbles. 



Briquets may be made either by hand or by machine. When 

 made by hand, the mortar is mixed with a trowel and pressed 

 into the mold with it also. It is always desirable for the same 

 person to make all of one series of briquets. It is claimed that, 

 when the material is pressed into the mold with the trowel, the 

 pressure exerted on the briquet is not evenly distributed over 

 the surface. The briquet molds are usually constructed of brass, 

 and are made in two pieces. 



Molding briquets. There will always be some variation in the 

 tensile strength of briquets. Jameson claims that, with the use 

 of his briquet-molding machine, the variation was reduced to 

 about 4/t^; and the Bohme hammer (pi. 23) is said to accomplish 

 the same object. 



Heath in his Manual of lime and cement, p. 83, gives the fol- 

 lowing method for insuring uniformity in the briquets: 



" The mixed cement is to be lightly placed in the molds, and is 

 then to be pressed for five minutes under a load of 10 pounds 



* Jameson. Portland cement, p. 51. 



