44 KANSAS ACADEMY OF SCIENCE. 
To make a strong and reliable cement mortar there should be sufficient ce- 
ment to fill the voids of the sand, and it should be evenly distributed in the mor- 
tar. By careful mixing, less cement than 1 to 3 will give fairly good results; but 
with the ordinary workman it is not safe to do so, for which reasons it is in many 
cases necessary to use a cement mortar of greater strength than is required. To 
overcome this unnecesary cost it has been sought to use a portion of lime mixed 
with the cement. 
For reasons above given of the different causes of setting of lime and cement, 
this has not been found to be satisfactory; hence, it is extremely desirable to 
devise some method of making a mortar combining as nearly as possible the low 
cost of lime mortar with the strength and durability of cement mortar, suited to 
the special requirements. To meet this demand, F. L. Smidth, C. E., of Copen- 
hagen, invented a process that satisfies these requirements when the conditions 
allow of the use of a mortar of less strength than would be obtained with propor- 
tion of one to three. This process consists in mixing cement and sand in the 
requisite proportions, and then in a special mill pulverizing them toa fine powder. 
This product is termed ‘‘sand cement,’’ and is then used as ordinary Portland 
cement, when mixed with the usual proportions of sand and water to form a mor- 
tar, in which the voids of the finely ground sand are filled with cement and the 
voids of the coarser sand are filled with the sand cement, thus satisfying the 
requirements of filling the voids and also uniformly distributing the cement 
throughout the mass of the mortar. 
Experiments made with lime mortar, hybrid mortar and enribet mortars of dif- 
ferent proportions of cement and sand gave as follows: 
Briquette of lime; broke at 36 lbs. 
Briquette of cement 1, lime 5; broke at 111 lbs. 
( cement 1, sand 284; broke at 118 lbs. 
cement 1, sand 35: broke at 100 lbs. 
( cement 1, sand 38; broke at 67 lbs. 
In actual building with sand-cement mortar, the theoretical advantages above 
set forth have been surpassed. 
A laboratory building was erected in Sweden in which sand cement was suc- 
cessfully used in proportions of cement 1, sand 51. The advantages obtained by 
the use of sand cement led to the erection of several plants in Europe, one in 
Brooklyn, and one at Glens Falls, N. Y. The cost of plant and the freight on 
sand has restricted the use of sand cement to where sand is plentiful and the 
building to be erected is of some magnitude. The foundation for the cathedral 
of St. John the Divine in New York city was of this material. The time required 
for grinding 2100 pounds at the Brooklyn works was one and three-fourths hours. 
We found that there is the same physical difference between the form of the 
particles of silica and of ground sand as between those of natural cement and 
Portland cement; a fact that will justify us in believing that silica cement will 
be of greater value as an ingredient of mortars than sand cement. The fineness 
we found was an important factor in the value of sand cement. That as made at 
the Brooklyn works was ten per cent. residue in a 180-mesh sieve; while silica 
obtained from McPherson gave a residue of four per cent. in a 200-mesh sieve. 
Briquette of sand cement: 
