LIME AND CEMENT INDUSTRIES 733 



Europe lias 175 meslies per linear incli." 75;^ of tlie cement 

 should pass tlirougli a sieve of tliis fineness. 



Johnson recommends that a sieve of 120 meshes be used, and 

 that not more than 20^ of the cement shall remain on it. Most 

 cements will pass through this. 



Sand cement. If Portland cement has a certain amount of 

 sand ground up with it to extreme fineness, it is found that as 

 much sand can be mixed with it to form mortar as could have been 

 added to the undiluted cement. This product is known as sand 

 cement, and its manufacture was first begun in this country in 

 1895 by the Standard silica cement co. of Glens Falls (E". Y.) 

 In Europe it was introduced some time before this, and is man- 

 ufactured there quite extensively. 



According to ^N^ewberry, " It is claimed by the manufacturers 

 that the sand cement supplied hj them gives only 5/» residue on a 

 180 mesh sieve, and that 6000 barrels of this cement were used 

 in the concrete foundations of St John's cathedral at !N^ew York. 

 A description of the industry has been published in the Engineer- 

 ing news, Ap. 16, 1896, page 252. This paper gives the follow- 

 ing comparative tests of sand cement 1-1, and Portland cement^ 

 each with three parts of ordinary sand. 



Pounds to 1 square inch 

 7 days 14 days 28 days 



Sand cement 1-1, and 3 parts sand 156 188 200 



Portland cement and 3 parts sand...... 137 170 179 



"An extensive series of tests has also been published by Wallin 

 ( Thonindustrie zeitung, 1896, p. 18) who concludes that the high- 

 est economy is obtained by grinding three parts of sand with one 

 of cement." Mr ISTewberry says: 



The good results given by sand cement are easily explainable^ 

 for it is wholly a question of filling up the voids in the sand. 

 These voids in ordinary building sand amount to about one third 

 of the total volume; therefore, if more than three volumes of 

 sand be mixed with one of cement, the voids will not be wholly 

 filled. By grinding a part of the sand to great fineness the pro- 



