This section is from the book "Notes On Building Construction", by Henry Fidler. Also available from Amazon: Notes on building construction.
The strength of Portland cement varies, as has already been mentioned, according to its original composition as regards the percentage of chalk and clay used in its manufacture, with the degree of burning to which it has been subjected, and according to the fineness to which it has been ground.
The strength of gauged Portland cement rapidly increases with age, the breaking weight on a sectional area of 21/4 square inches being as shown in the second column of the following Table for neat cement weighing 112 lbs. per bushel.1
Fig. 87.
1 In some moist climates abroad cement would be deadened by this treatment, so that when sending cement to such climates it should be thoroughly cooled before it is packed into the casks.
The strength of Portland cement mortar decreases as the proportion of sand is greater, which will be seen by the remaining columns of the Table.
Age and time immersed. | Neat Cement. | Proportion of Clean Pit Sand to 1 Cement. | ||||
l to l | 2 to l | 3tol | 4tol | 5tol | ||
1 Week . . | 445-0 | 152.0 | 64.5 | 44.5 | 22.0 | |
1 Month. . | 679.9 | 326.5 | 166.5 | 91.5 | 71.5 | 49.0 |
3 Months . | 877.9 | 549.6 | 451.9 | 305.3 | 153.0 | 123.5 |
6 Months | 978.7 | 6392 | 497.9 | 304.0 | 275.6 | 218.8 |
9 Months . | 995.9 | 718.7 | 594.4 | 383.6 | ||
12 Months. . | 10757 | 795.9 | 607.5 | 424.4 | 317.6 | 215..6 |
The following Table2 shows the strength of Portland cement at different periods of time with different degrees of fineness and with different proportions of sand.
The German mould used = 5 square centimetres in section.
Age of Briquette. | Neat. | Three of Sand. | Five of Sand. | |||
10.2 per cent residue on a sieve of 25S0 meshes per square inch. | Sifted so as to pass all through sieve of 32,257 meshes per square inch. | 10'2 per cent left on sieve of 2580 meshes per square inch. | All passed through sieve of 32,257 meshes per square inch. | 10.2 per cent left on sieve of 2580 meshes per square inch. | All passed through sieve of 32,257 meshes per square inch. | |
Weeks. | Lbs. per square inch. | Lbs. per square inch. | Lbs. per square inch. | Lbs. per square inch. | Lbs. per square inch. | Lbs. per square inch. |
1 | 353 | 346 | 75 | 252 | 31 | 136 |
4 | 533 | 380 | 171 | 330 | 97 | 208 |
8 | 585 | 469 | 206 | 358 | 118 | 223 |
25 | 701 | 495 | 282 | 397 | 166 | 272 |
 
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