36 
CEMENT MATERIALS AND INDUSTRY. 
[BULL. 243. 
United States and Canada lying north of the southern limit of the 
glaciers. 
Marl beds are found in the New England States, where they are 
occasionally of important size, and in New York, where large beds 
occur in the central and western portions of the State. Deposits are 
frequent and important in Michigan and in the northern portions of 
Ohio, Indiana, and Illinois. They occur in Wisconsin and Minnesota, 
but have not been as yet exploited for cement manufacture. 
( 'out position. — As shown by the analysis below, marls are usually 
very pure lime carbonates. They therefore require the addition of 
considerable clay to bring them up to the proper composition for a 
Portland-cement mixture. 
The marls are readily excavated, but necessarily carry a large per- 
centage of water. The mixture, on this account, is commonly made 
in the wet way, which necessitates driving off a high percentage of 
water in the kilns. Analyses of typical marls and clays are given in 
the following table: 
Analyses of marls and clays used in cement plants. 
Marl. 
Clay, 
Silica (SiO a ) 
Alumina ( A1 2 3 ) 
Iron oxide (Fe 2 3 ) 
Lime carbonate (CaC0 3 ) 
Magnesium carbonate ( MgC0 3 
0.25 
.10 
94. 39 
.38 
3.0 
93.0 
1.5 
1.60 
1.55 
88.9 
.94 
40.48 
20.95 
25. 80 
.99 
52.0 
17.0 
5.0 
20.0 
63. 75 
16.40 
6.35 
4.0 
2.1 
ALKALI WASTE. 
A very large amount of waste material results from the manufac 
turing of caustic soda. This waste material is largely a precipitated 
form of calcium carbonate, and if sufficiently free from impurities 
furnishes a cheap source of lime for use in Portland-cement manu- 
facture. 
The availability of alkali waste for this purpose depends largely ol 
what process was used at the alkali plant. Leblanc-process waste, fori 
example, carries a very large percentage of sulphides, which prevents 
its use as a Portland-cement material. Waste resulting from the use 
of the ammonia process, on the other hand, is usually a very pure 
mass of lime, mostly in the form of carbonate, though a little lime 
rrydrate is commonly present. As pyrite is not used in the ammonia i 
process, the waste is usually low enough in sulphur to be used as a 
cement material. The waste may carry a low or a very high percent- 
