124. Data on Strength

Table VIII., from the report of the Committee of the American Society of Civil Engineers on Uniform Tests of Cements, gives the results of the average minimum and maximum tensile strength per square inch which some good cements have attained when tested under the conditions above described.

Table VIII. - Tensile Strength Of Cement Mortars

AGE OF MORTAR WHEN TESTED.

AV. TENSILE STRENGTH IN POUNDS PER SQ. INCH.

PORTLAND.

ROSENDALE.

Clear cement.

Min.

Max.

Min.

Max.

1 day - 1 hour, or until set, in air, the remainder of the time in water.

100

140

40

80

1 week - 1 day in air, remainder of the time in water.............

250

550

60

100

4 weeks - 1 day in air, remainder of the time in water...............

350

700

100

150

1 year - 1 day in air, remainder of the time in water..................

450

800

300

400

1 part cement to 1 part sand

1 week - 1 day in air, remainder of the time in water...............

30

50

4 weeks - 1 day in air, remainder of the time in water................

....

50

80

1 year - 1 day in air, remainder of the time in water.............

...

200

300

1 part cement to 3 parts sand.

1 week - 1 day in air, remainder of the time in water..............

80

125

....

....

4 weeks - 1 day in air, remainder of the time in water............

100

200

....

....

1 year - 1 day in air, remainder of the time in water...................

200

350

...

The quantities in the "Min." columns give the average strength of the weaker brands of Portland and Rosendale cements, and those in the "Max." columns the average strength for the stronger brands. By comparing his results with the values in this table, the architect or superintendent can judge whether his cement is satisfactory or not.

Limit to Increase of Strength with Age. - From a series of experiments made by Mr. Grant in England with a heavy cement, he was led to the conclusion that it attained its maximum strength after constant immersion for two years, and that there is no reason to fear that a good cement ever deteriorates. With a light cement the maximum strength would probably be attained much sooner.