The test of resistance to rupture by flexion shall, in the case of ordinary bricks, be made with whole products placed upon two knives .2 metres apart, and loaded at the middle gradually until rupture occurs.
1 If the specimens have borne without deterioration the tests of resistance to frost, it will be advisable to compare the resistances of those specimens to compression and flexion, after another desiccation, with those of specimens of the same origin which have been subjected to the same pressure after drying, but without having been submitted to the action of frost (Note of the Commission).
The gross weight which determines the rupture of each specimen shall be noted.
Products greater in length than ordinary bricks (floor bricks) shall be tested with a bearing-space between the two supporting knives equal to that usually given in practice.
The tests of resistance to rupture by flexion shall be made upon whole tiles placed upon two knives, and loaded at the middle gradually until rupture occurs.
When the tiles have not a rectilineal section, small transverse horizontal ridges of pure Portland cement and I centimetre broad shall be placed in a line with the supports and the middle of the knives, with the object of levelling the undulations and dividing the pressure uniformly over the whole width.
One of these ridges shall be placed at the point where, in roofing, the tile is to rest upon the laths, and the other at the point where it rests upon the tile below.
The load which produces rupture shall be noted.
It will be advisable to make the test with tiles which have been soaked in water, the degree of imbibition being noted.
The determination of the resistance to wear by friction shall be made under the same conditions as in the case of natural building-stones, both as regards the dimensions of the object tested and the test itself.
[To determine the resistance to wear by friction, the quantity of the specimens worn away shall be measured, when they are subjected, under a given pressure, to the friction of standard sand spread uniformly over a circular horizontal cast-iron track which moves with known speed.
The specimens shall have the dimensions : .06 m. by .04 m. base and a variable height of from .10 m. to .12 m.; they shall be placed in pairs on opposite sides of the axis and on the same diameter of the grinding-mill, in such a way that their centres shall be on the circumference of a circle of radius .261 m. the lesser dimension being in a direction perpendicular to the radius.
The total pressure on the friction plane shall be 250 grammes per square centimetre.
The standard sand used shall be obtained by pounding, and then sifting, medium hard Fontainebleau quartz sandstone, passing through a No. 50 sieve (324 meshes) and retained completely on No. 200 sieve (4900 meshes).
The quantity of sand to be spread upon the grindstone shall be one litre per specimen and per thousand turns of the mill.
The machine shall be turned at the rate of 1000 turns per half-hour, and the specimens shall be subjected to 4000 turns of the mill. The diminution in the height of the specimen shall be measured, and the loss of weight determined. Similar notes shall be made during the course of the test after 1000, 2000, and 3000 turns.
The specimen may be turned over after 2000 turns of the mill, in order to compare the results obtained on the upper surface and the lower surface].
The experiments now being carried out do not yet allow of rules being laid down for this test.
These experiments should be continued.
The tests of resistance to rupture by internal pressure shall be made either with a force-pump or a hydraulic accumulator.
The unit of pressure to be adopted is a kilogramme per square centimetre, and the numbers, unless otherwise stated, refer to effective pressures.
The pipes to be tested should be exactly filled with water. It is important that the pressure should be exerted upon them gradually and without shock. The manometre should indicate without risk of error the pressure acting within the pipe.
The test can be made with a single pipe or several pipes combined.
The joints closing up the ends of the pipes should be arranged so as not to leak, and should be made in such a way that the fixing of them shall not cause a premature rupture of the pieces being tested.
The Committee expresses the wish that the experiments now being carried on with a view to finding a convenient closing arrangement for the ends of pipes will be continued.
With the object of determining whether, in terracottas, there exist lime or magnesium caustic, five specimens shall be immersed in boiling water for three hours, and it shall be noted whether, under these circumstances, exfoliations are produced.
To determine the proportion of soluble salts that a terra-cotta may contain, five specimens shall be taken, chosen in preference from the middle of the terra-cottas, and they shall be pulverised so as to make them pass entirely through a sieve of 900 meshes; 25 grammes of the powder thus obtained shall be taken, and boiled for an hour in 250 grammes of distilled water, the evaporated water being replaced. After filtering, the liquid shall be entirely evaporated, and the residue obtained shall be weighed.