W e t Mieruporite is about 25 per cent weaker. To reach such strengths in Portland cement or gypsum products requires a unit weight two to three times as great. The heat loss of dry Microporite weighing 28 pounds per cubic foot Bas heen dcterrnined by the hot plate n d i o d as 0.70 I$. t. u. per square Soot per liour per F. pcr inch (0.08i r,alorie per sq. em. per hour per C . per em.) which seeins to place it somewhat lower than gypsum or I'ortland ceiiieiit pmr1uct.s of similar unit wciglit. The sound transurissiun loss averages about 32 decibels for a 2-inch (5-om.) tliickness, wliiali is similar to that of a partition built of 3-inch (7.6-cui.) gypsum units with half an inch (1.27 em.) of pl side and weighing about four times as IIIUCII, 14'm a fire test, :I slab 5 ctn. thick was sulistituted for me side of an electric sitrface heated to 1000° C. In one hour the temperature of t,he outer wall rose from ail initial point of 15" C. to 25" C., while a gasoline blowtoreli applicd to a slab for 1 hours pro&iced only a slight surface crazisig.
storing iii strong acids iii the outstanding feature. The loss on abrasion is also quite low. For surfacing Microporite in tlie outer wall units, sheets of Morhelli cement are fastened to the reinforcing and placed in the form. The emulsion is then run in behind and the whole is cured as a single integral unit. Results for several calcium hydrosilicate compounds are given in the following table; neveral of the lines are similar to those reported by Vigfriison, Bates, and Tliorvaklson (11) : Standaid
Mieiopoiite
Aabeaton cemeiit (.:E
B .S5 3.19" I' i o 2.66 2.20 1.70 1.333"
FIGURE 2. h~ORUEl3.ICEMENT LIEFOHE INDURATION Thia sheet i~ attached to the reinforcing oaicium hydiosilioate oi s tirick eoasistenoy ie poured i n behind, and tek whole IS indurated to iorm B single integrei unit.
Owing tu the fineness of subdivision, Microporite is inore readily attacked by reagents titan denser products, although it has a surprising resistance to the action of acids and Cora+e salt solutions. On exposure t o the weather, carbon dioxide and sulfur oxides promote a slow hydrolysis, calcium sulfate a i d carbonate being formed and silicic acid being set free; but such reactions would seem t o produce more ceinenting material in view of the strength increases (1). The small amount of solid material relative to tlie pore space results in a product not very resistant to frost action wlien saturated, but tliree samples left exposed to the weather for several months and then submitted to the standard Sreeaing and thawing test required 13, 17, and 17 cycles, respectively, for complete disintegration. During the cooling period following indurat,ion, the material is subjected to rather rapid temperature changes so that some reinforcement is required. A 4-inch (10.2-cm.) mesh of 16gage wire is adequate for this purpose. For structural units, round rods have hcen successfully applied. Figure 1 is a photograph of a 2inch partition unit.
.I hlATElII.41, as porous as Xicroporite is ubvioiislyiiot suited for direct exposure t.o tlie weatlier :ind must be adeauately. . wotected. For this purpose a special ashostos-cement sheet invcnted by .\forbelli fias been successfully applied. This diBcrs im that :L considerable part of the cement usiially used has been replaced by finely ground silica. Sufficient cement is precent i o tiint the sliects can be handled (Figure 2 ) hut tlie fiiuii sirengtli is not obtained until a.fter indumt.ion. T11e propertie. of this inaterial have been described by Ferrari (9) and by Kiihl (6); the srnalluess of the ret.rogression in strength 011
persbtence of so many silica lines nrigilt suggest that the clmrartcrist,ic quartz spiral still continues after cornbination with lime. A sample of ltostone exposed gave plenty of silica lines, as was to he expected from the silica used as aggregate, and only one line which might not be attributed also i o the silica, lime, or calcite, judging from films exposed under similar condit,ions.
SCFFICIEST units have been fabricated to erect a fourroom house (Figure 3). This house is one single unit and others could be piled upward and outward in almost any way desired to form apartment houses. The size of the units themselves permits of considerable variety of interior arrangement. One important feature of this house is the large horizontal panels which impart a considerable degree of dignity to the house, so that, in spite of the flat roof, it does not look like a dry-goods box. For this house, only four different kinds of Microporite units are required: floor, partition, and two outside wall slabs. With the increase in size of the units, very great strains are concentrated on the few remaining joints so that great care must be exercised to provide adequate resilience combined with complete adhesion between the joint material and the units. For this purpose strips of rubber, which have been protected against weathering by the use of suitable antioxidants, are cemented to the units by means of a special glue made by mixing concentrated rubber latex with aluminous cement (3). In addition, the Morbelli sheets are so shaped as to provide a lap in the horizontal joint. To carry the prefabrication to its logical conclusion, the interior surfaces of the Microporite slabs should receive their final finish in the factory. For this purpose several different treatments have been developed with due reference to the porosity and high absorbing power of the units. When paints are applied, it is necessary to thin the first coats to secure penetration. For plaster finishes very lean mixes with protein binders have given excellent results, while for protect,ing the underside of the floor slabs and the upper side of the roof slabs, cut-back asphalts are satisfactory. For floor surfaces, Morbelli cement, pressed wood, or natural woods may be used. The roof is of standard felt and tar construction. Steel casement windows and standard wood doors are being used, but the mechanical equipment has been developed by the John B. Pierce Foundation for this purpose.
Classification of Brick by Water Absorption . ‘
WALTER C. VOSS Massachusetts Institute of Technology, Cambridge, Mass.
Q I
S THE midst of current interest in better
houses and structures, there is a large and important field for scientific investigation of the individual units of the building materials of which these structures are built. Recent investigations have undertaken to explore some of the physical properties of that ancient building unit, the clay brick. These investigations include study of the capillary characteristics of various bricks by measurement of water absorptive properties.
Water Absorption by Brick When a clay brick which is highly porous comes into contact with wet mortar, it immediately absorbs water from the mortar, makes the mortar comparatively dry a t the interface, and introduces a variable condition which profoundly influences the strength of the mortar bond. When the porosity is low, it may fail to remove sufficient water from the
TO THE John B. Pierce Foundation and to its director of research, Robert L. Davidson, grateful thanks are due for supplying the funds for this development work.
Literature Cited (1) Bessey, G. G., Building Research Special Rept. 21, London, H. M.Stationery Office, 1934. (2) Bond, A. E., U.S. Patent 1,940,528 (Dec. 19, 1933). (3) Ferrari, F., Rev. matdriaux construction trav. publics, No. 283 (1933); Industria Cemento, 31, 13-16 (1934). (4) Huttemann and Csernin, U. S. Patent 1,932,971 (Oct. 31, 1933). (5) Ippach, Hugo, and Bieligk, Otto, French Patent 760,117 (Aug. 5, 1933). (6) Kuhl, Hans, 2’onind.-Ztg., 57, 1144-16 (1933). (7) Mensel, C . -4., J . Am. ConcreteInst., 6, 1 2 5 4 8 (1934). ( S ) Miller, D. G., Proc. Am. SOC.Testing Materials, 30, Part 11, 636-53 (1930). (9) Peffer, H. C., Harrison, R. L., and Shreve, R. N., IND.EXQ CHEM.,25, 719-22 (1933). (10) Thorvaldson, T., and Vigfusson, V. A., Eng. J . , 11, 174-80 (1928); Thorvaldson, T., and Shelton, G. R., Can. J . Research, 1, 148-54 (1929). (11) Vigfusson, V. 9.. Bates, G. N., and Thorvaldson, T . , Can. J . Research, 11, 520-9 (1934).
FIGURE 1. ABSORPTOMETER
RECEIVED April 27, 1935.
KOISELESS M O T O R OPERATED B Y GERMANY. Experiments conducted
DRY-ICEDEVEliOPED
IN
by a German dry-ice research organization in the use of dry-ice for the noiseless operation of motors, are alleged to have achieved complete success, with promise of far-reaching effects in motor construction and technic. It is reported that the first motor using dry-ice has been completed and has given satisfactory results in operation; the motor is said to be characterized by very simple construction, high efficiency, and very light weight, and to embrace various
innovations.
mortar; again the strength of the mortar bond is adversely affected. A method of establishing a quantitative measure of a brick’s tendency to take mater from the mortar has been devised, which is based upon determination, in a special apparatus called the “Absorptometer, ” of the amount of absorption and rate of absorption of water by an immersed brick. The absorptometer (Figure 1) is a special arrangement of a balance, a clock, and an immersion tank, with which apparatus a continuous record of the changing weight of an immersed brick is obtained. Since the change of weight of the immersed 121
