The test, proposed by Mr. Faija,* a British authority, is made with a covered vessel partly full of water maintained at a temperature of 100° to 115° F., in the upper part of which the pat is placed until set. When the pat is set, it is placed in the water for 24 hours. If the cement remains firmly attached to the glass and shows no cracks, it is very probably sound.
The hot-water test, proposed by Mr. Maclay,* an American authority, is substantially like Faija's test above, except that Maclay recommends 195° to 200° F.
The boiling test, suggested by Professor Tetmajer, the Swiss authority, consists in placing the mortar in cold water immediately after mixing, then gradually raising the temperature to boiling after about an hour, and boiling for three hours. The test specimen consists of a small ball of such a consistency that when flattened to half its diameter it neither cracks nor runs at the edges.
The flame test is made by placing a ball of the cement paste, about 2 inches in diameter, on a wire gauze and applying the flame of a Bunsen burner gradually until at the end of an hour the tem perature is about 90° C. (194° F.). The heat is then increased until the lower part of the ball becomes red-hot. The appearance of cracks probably indicates the presence of an expansive element.
The kiln test consists of exposing a small cake of cement mortar, after it has set, to a temperature of 110° to 120° C. (166° to 248° F.)
in a drying oven until all the water is driven off. If no edge cracks appear, the cement is considered of constant volume.
The chloride-of-lime test is to mix the paste for the cakes with a solution of 40 grams of calcium chloride per liter of water, allow to set, immerse in the same solution for 24 hours, and then examine for checking and softening. The chloride of lime accelerates the hydration of the free lime. The chloride in the solution used in mixing causes the slaking before setting of only so much of the free lime as is not objectionable in the cement. The chloride of calcium has no effect upon free magnesia.
Expansion Test. Various experimenters test the soundness of cement by measuring the expansion of a bar of cement mortar. The French Commission recommend the measurement of the expan sion of a bar 32 inches long by inch square, or the measurement of the increase of circumference of a cylinder. The German standard test requires the measurement of the increase in length of a prism 4 inches long by 2 inches square. The apparatus for making these tests can be had in the market. The tests require very delicate manipulation to secure reliable results.