374 
CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1902. 
[hum, .213. 
The coarse sand used in making the mortar with the sand cement 
and with the pure (Portland) Colton cement was of the ordinary grade 
of fineness used for making cement tests. It was screened from ordi- 
nary gravel, all residue. on the 20-mesh screen being rejected and all 
left on the 30-mesh screen being retained. 
The briquettes for testing were made according to the specifications 
recommended by the American Society of Civil Engineers. After the 
briquettes were made they were kept under a damp cloth for twenty- 
four hours, then placed in vats of water, where they were left until 
the time for breaking arrived, namely, seven days or twenty-eight 
days. The fine grinding and diluting of the Portland cement with 
fine sand did not materially affect the time of hardening or setting. 
The beginning of the setting process of the ordinary Colton cement 
mortar, or initial setting, was thirty-three minutes, and the time of 
final setting was eighty-five minutes. This applies to samples Nos. 
3, 4, and 9 of the following list. The corresponding periods for the 
sand cement were thirty and eighty minutes. The cement mortar 
continues to harden and increase in firmness for a year or longer. 
Results of tests of Port/mid saml cements. 
No. 
Material. 
( nit on and Buttos pearlite, 1 
tol. 
( !olton and San Carlos quartz- 
ite, 1 tol 
Colton, regular 
do 
Colton, fine ground. 
do 
Sand. 
Colton and Butte pearlite, 
tol.. 
< !( ilt i .li and San Carlos quartz- 
ite, 1 to 1 
( tolton, regular 
Imported 
Imported and sand, 1 to 1 
....do 
....do 
....do... 
Imported, regular 
....do 
Port- 
land 
cement 
to 
sand. 
Fineness 
Water. 
50 
mesh. 
L00 
mesh. 
200 
mesh. 
Per ct. 
Perct. 
Per ct. 
Per ct. 
1 to 5 
0.00 
0.00 
0.00 
10 
1 to5 
.1X1 
.(H) 
.(H) 
Hi 
1 to 2 
. 42 
7.20 
33.20 
in 
1 to3 
. 42 
7.20 
33.20 
10 
1 to 2 
.00 
.(H) 
(a) 
L2 
1 to3 
.(HI 
.(HI 
(a) 
L2 
1 to 7 
.00 
.(H) 
.00 
10 
l in; 
.00 
.00 
.00 
10 
l toO 
.42 
7.20 
33.20 
IS 
1 toO 
.80 
7.80 
29. 33 
IS 
1 to 5 
.(H) 
.(H) 
.(H) 
1(1 
1 to5 
.(HI 
.(H) 
(a) 
10 
Lto7 
.(H) 
.(HI 
(a) 
10 
1 to 7 
.(H) 
.(H) 
.(H) 
10 
1 to 2 
.80 
7.80 
29.33 
10 
lto3 
.80 
7. SO 
29.33 
10 
Strength. 
1 days. 
/As', 
so 
90 
170 
140 
370 
170 
615 
345 
li:, 
L25 
55 
90 
210 
L20 
28 
days. 
Lbs. 
300 
34") 
385 
240 
465 
260 
185 
Of ill 
525 
11)0 
1S5 
( .M) 
140 
270 
175 
«Some left on 200-mesh screen. 
Note.— The above cement stood the boiling test for free lime satisfactorily. 
Comparison of test No. 3 with No. 5, and of No. 4 with No. 0, shows 
that increased fineness of grinding very materially increases the 
strength and sand-carrying capacity of cements. The ordinary Col- 
ton cement of tests No. 3 and No. 4 was ground finer than commercial 
Portland is usually ground. Recent improvements in mills for grind- 
