168 ANNUAL REPORT 
Another disadvantage is the tendency to effloresce, made mention of 
above. On the other hand it has been claimed that in sea water construc- 
tion and all other subaqueous work, slag cement appears exceedingly 
well; in fact, some claim for it superiority over Portland cement. Alto- 
eether, the slag cement is a hydraulic mortar par excellence. But it cannot 
be denied that its weak side is the tendency to shrink during the setting 
stage, so that it must be protected carefully against too rapid drying, and 
must have plenty of water in order to bring about the complete formation 
of the colloid hydrous silicates which are the cementing agent. ‘This 
tendency to shrink or crack is proportional to. the content of calcium 
hydrate, hence it is plain that the content of the latter must be kept as low 
as possible. 
Tetmayer found on preparing cements from mixtures consisting of 
100 parts of slag and 20 parts of slaked lime, 100 slag and 40 lime, 100 slag 
and 60 lime, 100 slag and 80 lime, and making them up into cubes of 7 cm. 
face, that after 28 days the linear shrinkages were in the above order: 
0.034, 0.060, 0.085, and 0.132 mm. 
If slag cement fails in the cold and hot tests for constancy of volume, 
this is almost invariably due to the imperfect grinding of the lime, or the 
slow slaking character of the latter, or poor slaking or excess of sulphur. 
Slag Cement in Ohto.—So for the only plants in Ohio producing 
slag cement are the Brier Hill Coal & Iron Company, Youngstown, and 
the Strouthers Furnace Co., Strouthers, but there is no reason why the 
manufacture could not be carried on by other blast furnaces of the State. 
A test of the Youngstown material gave the fol‘owing results: 
Per Cents. 
JUL Cr: Rene MUA SAAN EL a pemm Se tTeL) SAA a Renna tae CA Ng Bs 28.20 
Alumina anduronss se oeeee en Silk are cons: sa ers AND 11.60 
SHY Oe eRe I Se Ba SA ice i ao aread ne A 52.80 
Maen eSi als 205 e iio aie Me TEU ies ais uae ae Ut aN See 2.37 
Volatile ama tter salen he cae peer heey Sena aoe ee ee Do 
RU} 6) 040) iuar eae MectE ne PIS eel IM inane Scar ian Sori AAMINU MEG, patio I DU 
Boy ers) appear MAN SeN neers oN Ao adh GA MARE re hf Vege rn: 99.29 
It left approximately 3.8 per cent. on a 200 mesh sieve. The 
initial set was 1 hour and 20 minutes; the final set 3 hours and 10 min- 
utes. It stood both the hot and cold test. The tensile strength was 
as given in table on top of page 160. 
Hatt’s Results. —Wm. Kendrick Hatt* made extensive examina- 
tions of American slag cements which are summarized in second table 
on page 1609. 
*Hngineering Record, Vol. 43, No. 9. 
