ECKEL. | 
PUZZOLAN CEMENTS. 
The heated air passes through the inner cylinder and returns 
between the inner and outer cylinders to the fan. The slag is led 
into the space between the inner and outer cylinders through a spout 
in the stationary head at the upper end of the machine. It is picked 
tip by buckets or carriers fastened to the inner surface of the outer 
cylinder and carried partly around during the rotation of the dryer. 
On dropping from these buckets it falls and is caught on the flights 
fastened to the outer surface of the inner cylinder, which carry it 
partly around and then drop it to the bottom of the outer cylinder, 
when the cycle commences again. While these movements of the 
slag are occurring it is being dried both by the heated air in the space 
between the two cylinders and by contact with the warm outer sur- 
face of the inner cylinder, and it is also being carried slowly toward 
the lower (discharge) end of the machine. 
The following table shows working results in the use of the Ruggles- 
Coles dryer on granulated slag: 
Results of use of Ruggles-Coles <lryer. 
User. 
( (riginal 
moisture. 
Final 
moisture. 
Water 
evapo- 
rated per 
hour. 
Dry 
material 
delivered 
per hour. 
Coal used 
per hour. 
Water 
evapo- 
rated per 
pound of 
coal. 
Knickerbocker Cement Co. . . 
Maryland Cement Co 
Birmingham Cement Co 
Southern Cement Co 
Per cent. 
41.82 
20. 32 
45.00 
40.00 
/'( /■ cent. 
0.20 
. 25 
Pounds. 
4, 401 
4, 114 
4,181 
4,707 
Pounds. 
6, 309 
16,173 
4,987 
7,061 
rounds. 
560 
542 
537 
550 
Pounds. 
7.87 
7. 59 
7. 60 
8. 56 
COMPOSITION AND SELECTION OF THE LIME. 
The lime used for admixture with the slag may be either a quick- 
lime (common lime) or a hydraulic lime. In usual American practice, 
and also at most European plants, a quicklime is used. At a few 
American, French, and German plants, however, limes which have 
more or less hydraulic properties are emplo}^ed. Frost has carried 
on experiments touching this point and decided that the use of a 
hydraulic lime did not noticeably increase the tensile strength of the 
resulting cement, but that it did increase the value of the product in 
another way. This incidental advantage is that slag cements made by 
using hydraulic lime are less liable to fissure and disintegrate when 
used in air or in dry situations than cement in which common quick- 
lime is used. This method of improving the product has been tried, 
to the writer's knowledge, at only one of the American slag cement 
plants. At KOnigshof, Germany, a somewhat hydraulic lime is used, 
whose analysis will be fairly representative of materials of this type, 
though most hydraulic limes would run higher in silica and alumina. 
