UNIVERSAL PORTLAND CEMENT CO.

Just as the available supply of limestone and coal
required to convert iron ore into pig iron for the manufacture
 of steel has contributed toward making the Pittsburgh
District the world’s largest steel center, so has the available
supply of the same materials enabled the Keystone State
to take a leading position in the manufacture of cement.
In the making of pig iron, one of the by-products is slag.
For years, no wide uses for this were found. It was waste
material. It cost money to get rid of it. But back in
the 90’s, it was discovered that the silica, alumina and lime
found in blast-furnace slag, the principal chemical ingredients
 required in the manufacture of portland cement,
could be used to make this modern material, and today
large quantities of granulated slag are used by the Universal
Portland Cement Co. in the steel centers of Pittsburgh.
Chicago and Duluth.

INGREDIENTS OF PORTLAND CEMENT

Portland Cement consists principally of silica, alumina
and lime obtained from (a) cement rock and limestone;
(b) clay or shale and limestone; (¢) clay and marl; or
(d) blast-furnace slag and limestone. Any of these combinations
 in various proportions provide the required
chemical constituents for portland cement. The important
 requisites for the manufacture of portland cement
are:

The cement mixture must be composed of properly
proportioned materials.
These raw materials must be finely ground and
intimately mixed before burning.
I'he burning must be conducted at the proper
cemperature to obtain a chemical combination
© ¢ burning, the resulting clinker must be finely