814 
Journal of Agricultural Research 
Vol. V, No. 17 
Table; V. — Effect of variations in temperature on penetration of asphalt cements « 
Tem¬ 
pera¬ 
ture. 
Conditions at test. 
California. 
Mexican. 
Blended. 
Blown. 
Load. 
Time. 
Bath. 
8961 
8962 
8963 
8948 
8949 
8950 
8994 
8995 
8996 
8956 
8957 
8958 
•c. 
20. 
Gm. 
100 
Seconds. 
5 
Water. 
24 
47 
69 
29 
55 
87 
38 
61 
94 
32 
63 
93 
23 . 
100 
5 
...do.. 
37 
7 i 
xo6 
40 
73 
118 
5 ® 
77 
X26 
38 
81 
120 
24. 
100 
5 
.. .do.. 
40 
80 
115 
45 
81 
126 
53 
80 
136 
40 
84 
X 2 X 
24.6. 
100 
5 
.. .do.. 
46 
86 
X 2 X 
47 
86 
136 
56 
85 
145 
44 
89 
X 29 
35. 
100 
5 
.. .do.. 
46 
92 
132 
49 
9 r 
142 
60 
90 
156 
44 
9 i 
134 
26. 
TOO 
5 
.. .do.. 
53 
100 
149 
54 
99 
*53 
65 
97 
169 
47 
98 
144 
27 . 
100 
5 
.. .do.. 
60 
120 
172 
58 
106 
174 
68 
105 
187 
50 
XOI 
153 
0. 
100 
5 
Ice.... 
I 
XO 
13 
XO 
16 
23 
8 
XI 
13 
it 
17 
20 
0. 
100 
5 
Brine. 
z 
3 
4 
4 
7 
10 
6 
XO 
XI 
8 
15 
19 
4 . 
100 
5 
Water. 
2 
5 
8 
7 
14 
17 
XX 
17 
*7 
14 
24 
31 
0. 
200 
5 
Ice,... 
xo 
13 
18 
13 
26 
30 
13 
20 
24 
16 
28 
37 
0. 
200 
5 
Brine. 
2 
6 
8 
8 
13 
16 
12 
l8 
20 
19 
29 
35 
4 . 
200 
5 
Water. 
7 
XX 
15 
12 
17 
25 
x6 
*5 
27 
22 
39 
49 
O. 
200 
60 
Ice.... 
13 
17 
23 
28 
36 
39 
20 
37 
4 i 
28 
SO 
62 
O. 
200 
60 
Brine. 
3 
X2 
18 
13 
26 
40 
22 
36 
39 
27 
47 
59 
4 . 
200 
60 
Water. 
15 
25 
35 
18 
38 
59 
30 
48 
73 
36 
70 
89 
44 . 
50 
1 
...do.. 
139 
239 
99 
177 
268 
x °5 
152 
264 
45 
108 
175 
45 . 
50 
z 
.. .do.. 
147 
263 
108 
188 
290 
118 
161 
281 
49 
Xi6 
185 
46 . 
50 
1 
.. .do.. 
180 
318 
Soft. 
xi6 
204 
308 
121 
174 
306 
54 
X24 
200 
47 . 
50 
1 
...do.. 
189 
Soft. 
Soft. 
126 
224 
Soft. 
130 
190 
Soft. 
56 
X29 
21X 
44 . 
50 
5 
...do.. 
294 
Soft. 
Soft. 
195 
330 
Soft. 
190 
277 
Soft. 
64 
155 
264 
45 . 
50 
5 
...do.. 
318 
Soft. 
Soft. 
204 
Soft. 
Soft. 
209 
286 
Soft. 
67 
165 
28s 
46...... 
50 
5 
.. .do.. 
Soft. 
Soft. 
Soft. 
227 
Soft. 
Soft, 
220 
310 
Soft. 
70 
176 
305 
47 . 
50 
5 
...do . 
Soft. 
Soft. 
Soft. 
245 
Soft. 
Soft. 
244 
Soft. 
Soft. 
73 
186 
Soft. 
a In this and succeeding tables it will be noted that at 25 0 C. under a load of 100 gm. applied for 5 seconds, 
sample 8950 shows a materially lower penetration than in Tables II, III, and IV. No satisfactory 
explanation has as yet been found for this variation, as the maximum difference of eight points is too large 
to be attributed to experimental error. Numerous checks have been made upon the later results, which 
were obtained about three months after the first determinations. It is possible that the material had 
undergone some change during that period. 
Considering first those tests made with a ioo-gm. load applied for 5 
seconds at temperatures ranging from 20° to 27 0 C., it will be seen that 
a difference of 1 degree makes a very decided difference in the recorded 
penetrations. In fact, the difference in penetration for all but the 
blown products and the harder grades of the other types is quite marked 
between 24.6° and 25 0 . Allowing for experimental errors, this dif¬ 
ference of 0.4 0 is, in the case of sample 8963, responsible for a difference 
of 10 points' penetration. In general, the softer the material the greater 
the difference for any type. As specifications for the penetration at 25 0 
of asphalt cements are frequently limited to a variation of 10 points, it 
is at once apparent that the temperature of the bath should be carefully 
maintained at the exact temperature required, and that accurately cali¬ 
brated thermometers, which may be read to tenths of a degree centigrade, 
be used for this purpose. 
Considering any or all of the three sets of tests made at low tempera¬ 
tures it is evident that the ice method is inaccurate, inasmuch as it 
frequently gives a higher penetratiofi than the corresponding result 
with the 4 0 bath. It is evident, therefore, that if the temperature of o° 
is used, a brine bath which may be maintained at o° should be employed. 
It is further of interest to note that marked differences in penetration 
for all of the types are obtained between the o° brine test and the 4 0 
water test. Prom this it is apparent that the 4 0 test should not, as has 
sometimes been done, be considered the practical equivalent of a o° test. 
