158 ANNUAL REPORT 
CHAPTER IV. 
MANUFACTURE OF POZZUCLANE AND NATURAL 
CEMENTS. 
POZZUOLANE CEMENTS, 
Owing to the comparative unimportance of the true pozzuolane 
cements, but little attention can be given this subject. The preparation of 
pozzuolane cement is extremely simple and may be carried out in two 
ways: 
Ist. Grinding of pozzuolane rock together with dry calcium hydrate. 
2nd. Grinding of pozzuolane alone and mixing it with slaked lime 
in the wet when used. » 
Cement made in the first way is, of course, ready for use, and-in 
building need only be mixed with water and sand to be available as mor- 
tar. The lime used should be thoroughly slaked and must be dry. When 
prepared by the second process, care must also be taken to use thoroughly 
slaked lime. In Europe the second practice prevails, although some au- 
thorities urge the preparation of pozzuolane mortar on a large manufac- 
turing scale by the first method. R. Feret advocates the grinding of 
pozzuolanes as producing a more uniform and satisfactory material. 
In some places, as in the construction of the Kaiser Wilhelm ship canal, 
the pozzuolane, which was trass, was ground together with the lime at 
the works under construction. 
Tetmayer has done considerable work with natural pozzuolanes and 
from his many results the following figures are quoted: 
: 
Zi 
a Proportions by Weight. Tensile strength in pounds per square inch. 
a 
Trass. Lime. Sand. 28 days. | 84 days. 1 year. 2 years. 
1 [ 0.66 0.33 3.00 142.8 240.8 249.2 253.4 
|| 0.66 0.33 ICO | 12 | SWS | B00 | Be 
2 0.66 0.33 3.00 239.4 343.0 309.4 316.4 
ve 0.66 OS ome ee OO 187.6 264.6 319.2 351.4 
e Ni (te | 088 |) S00 | me | mae | are | oe 
og / 0.66 0.33 1.00 $1.2 170.8 161.8 320.6 
i 
1 
