CHARACTERISTICS OF SAND-LIME BRICK. The makers of sand-lime brick usually claim that their product is equal in appear ance and quality to any dry-clay (pressed) face brick; and that sand lime brick will gain in hardness under the action of either air or water.
Sand-lime brick have plane faces, free from kiln marks. The corners are square and sharp as they come from the press, but are likely to crumble off in being placed in the harden ing cylinder. The color is usually white, sometimes pure and uni form, and sometimes tinted according to the color of the sand; and it is easy to give the brick almost any color by mixing coloring matter with the sand and the lime before moulding.
Three whole bricks from one maker in Arizona, when crushed flatwise with pressed surfaces set in plaster of paris, gave an average crushing strength of 3,000 lb. per sq. in., the variation from the mean being about 7 per cent each way; and four other bricks from West Point, N. Y., gave an average crushing strength of 3,717 lb. per sq. in., the range being from 2,940 to 4,260.* Forty-five half brick from five makers, tested under the author's direction, flatwise with plastered surfaces, gave an average crushing strength of 3,693 lb. per sq. in., the range for the different makes being from 2,412 to 6,123.* Five tests of German sand-lime brick hardened under high pressure gave an average crushing strength of 2,710 lb. per sq. in., the range being from 1,704 to 4,189; and three samples hardened under low pressure gave an average strength of 1,199 lb. per sq. in., the range being from 850 to 1,353.t No details are known as to the method of making the above experiments.
Most of the clay brick used in New York City have an average crushing strength of about 4,000 lb. per sq. in. for half brick tested flatwise (see 4 80); and brick masonry is seldom subjected to a com pressive stress of more than 200 lb. per sq. in. (see 4 628-29). There fore the above results show that sand-lime brick can be made strong enough for use in any ordinary brick work.
The average of fifty-five brick from five makers, tested under the author's direction, gave an average transverse strength of 571 lb. per sq. in., with a range for the different brands from 420 to 766.* Absorption. Sixty-six samples from six makers, tested under the author's direction, gave an average absorption of 10.6 per cent by weight, the range of the brands being from 8.5 to 13.5 per cent.*
The absorptive power of sand-lime brick seems to be less than that of equally strong clay brick.
One-inch cubes of sand-lime brick were practically disintegrated after being frozen and thawed daily for twenty-nine days.$ Three cubes each of three brands when frozen and thawed eighteen times gave losses by weight as follows: 100 per cent, 13.2 per cent, 2.7 per cent.¶ Soft pressed clay brick in the same tests lost nothing. Two half brick after freezing and thawing twenty times lost 14.3 and 5.3 per cent by weight respect ively; and a soft clay brick in the same series lost nothing.* Apparently, ordinary sand-lime brick do not stand frost as well as equally strong clay brick.
Two each of three brands of sand-lime brick were placed in the open air where they were exposed to the sun, wind, and rain from August to March inclusive. One each of each brand was kept in a closed box in a dry place. The exposed brick were thoroughly dried and tested. The average modulus of rupture of the unexposed brick was 791 lb. per sq. in., and of the exposed 640—a loss of 19 per cent;—and the average crushing strength of the unexposed sample was 3,423 lb. per sq. in., and of the exposed 3,115—a loss of 9 per cent.* Effect of Fire. In three tests, made under the direction of the author, which can not be briefly described, no one of the six brands of sand-lime bricks seemed to stand the effect of fire as well as dry clay bricks having about the same compressive strength. It is said that many of the fire inspectors of Germany have pronounced the fire-resisting qualities of sand-lime brick satisfactory. American manufacturers of sand-lime bricks claim that they can be used as fire brick.
It is claimed and also denied that under equally favorable conditions sand-lime brick of the grade of dry-pressed clay brick can be made as cheaply as common clay brick; but the probabilities are that the sand-lime brick industry is too new to have settled the controversy definitely either way. In localities in which clay or fuel is scarce and in which lime and sand are plentiful, sand lime brick can probably be made cheaper than clay brick.
The average selling price of common sand-lime brick in the United States in 1905 was $6.44 per thousand, and of front brick $9.42.t Compare these prices with those for clay brick in Table 9, page 44.