Dec., 1913
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T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
beryllium gave a tensile strength of 1 1 . 8 tons per square inch with an elongation of I O per cent on z inches. It was of a beautiful silver-white color, and could be hammered out cold into leaf; i t also withstood the action of sea water perfectly. Manganese, titanium, chromium, molybdenum, tungsten, etc., form a very interesting series of alloys, either when alloyed by themselves or in the presence of copper. Titanium and chromium alloys are both affected by sea water and ordinary atmospheric conditions. The former alloy, when polished in the presence of sea water, develops white spots on the metal which, when removed, show deep pit marks on the surface of the metal; this applies to the alloys of chromium as well. Tungsten has been recommended as being a suitable metal to alloy with aluminum to resist corrosion, but the writer did not find this very satisfactory. An alloy containing z per cent copper and 0.5 per cent tungsten rapidly disintegrated under ordinary atmospheric conditions. At least IOO different samples of this alloy were prepared in the varying proportions of 0.2 to 5 per cent pure tungsten alloyed by itself with the aluminum, and also in conjunction with nickel, manganese, copper, etc. The results of some of these were disappointing. The alloy of zinc and nickel containing 3 per cent nickel and 0 . 7 5 per cent zirconium gave extraordinary results as far as tensile strength was concerned, having 1 2 .2 tons per square inch, with elongation g per cent on 2 inches. Its behavior in sea water was very extraordinary; it was boiled for 72 hours in sea water, and when tested, after the boiling process, showed only 4 tons per square inch tensile strength. Its fracture was very crystalline, and it was also very brittle. Zirconium 0.75 per cent, when alloyed with aluminum without the presence of nickel, gave the same tensile strength after the boiling process as before, namely, 9 . 3 tons per square inch. Molybdenum, when alloyed with aluminum, had the opposite result. An alloy was made containing I . 5 per cent molybdenum with aluminum which, after being boiled in salt water, gave a lower tensile strength than before the boiling; but when the molybdenum was alloyed with the aluminum in the presence of copper in the proportions of molybdenum I . 5 per cent and copper I . 5 per cent, the tensile strength of the metal after the boiling process was the same as originally.
WATERPROOFING OF CONCRETE STRUCTURES CONCLUSIONS OF COMMITTEE O N WATERPROOFING MATERIALS OF T H E AMERICAN SOCIETY OF TESTING MATERIALS
While the committee has not arrived a t sufficient conclusions to formulate definite specifications for making concrete structures waterproof, certain results have been reached which may be of assistance in securing impermeable concrete. In the laboratory and under test conditions using properly graded and sized coarse and fine aggregates, in mixtures ranging from I cement, 2 sand and 4 stone to I cement, 3 sand and 6 stone, impermeable concrete can invariably be produced. B u t the reverse often obtains in actual construction, permeable concretes being found even with I cement, z sand and 4 stone mixtures and these are of frequent occurrence where the quantity of the aggregate is increased. This the committee attributes to defective workmanship, to use of imperfectly sized and graded aggregates, use of excessive water and lack of proper provision to take care of expansion and contraction. Properly graded sands and coarse aggregates are rarely, if ever, found in nature in sufficient quantities to he available for large construction, and the effect of poorly graded aggregates in producing permeable concrete is aggravated by poor and inefficient field work; it is seemingly a commercial impossibility on large construction to obtain workmanship even approximating that found in laboratory work. In consequence of these conditions substances calculated to make the concrete
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more impermeable-either incorporated in the cement or added to the concrete during mixing-are often used. The committee has investigated a sufficient number of these special waterproofing compounds as well as certain very finely divided mineral products, to form a general idea of the different types. The majority of patented and proprietary compounds tested have little or no immediate or permanent effect on the permeability of concrete and some are even injurious. The permanent effect of such additions, if dependent on the action of organic compounds, is very doubtful. I n view of their possible effect upon the early strength and durability of concrete after considerable periods, no integral waterproofing material should be used unless it has been subjected to long-time practical tests under proper observation to demonstrate its value, and unless its ingredients and the proportion in which they are present are known. I n general, more desirable results are obtainable from inert compounds acting mechanically than from active chemical compounds whose efficiency depends on change of form through chemical action after addition to the concrete. Assuming average quality as to size of aggregates and reasonably good workmanship in the mixing and placing of the concretes, the addition of from IO to 20 per cent of very finely divided void-filling mineral substances may be expected to result in the production of concrete which under ordinary conditions of exposure will be found impermeable, provided the work joints are properly bonded and cracks do not develop on drying, or through change in volume due to atmospheric changes, or by settlement. In large construction, no matter how carefully the concrete itself has been made, cracks are apt to develop, due to shrinkage in drying out, expansion and contraction under change of temperature and moisture content and through settlement. Hence, it is often advisable on important construction to anticipate and provide for the possible occurrence of such cracks by external treatment with protective coatings. Such coating must be sufficiently elastic and cohesive to prevent the cracks extending through the coating itself. The application of merely penetrative void-filling liquid washes will not prevent the passage of water due to cracking of the concrete. While some penetrative washes may be efficient in rendering concrete waterproof for limited periods, their efficiency may decrease with time and it may be necessary to repeat such treatment. The first effort, therefore, should be made to secure a concrete that is impermeable in itself, and penetrative, voidm i n g washes should be resorted to only as a corrective measurea While protective extraneous bituminous or asphaltic coatings are unnecessary, so far as the major portion of the concrete surface is concerned, provided the concrete is impermeable, they are valuable as a protection where cracks develop in a structure. It is therefore recommended that a combination of inert void-iilling substances and extraneous waterproofing he adopted in especially difficult or important work of any nature. Protective bituminous or asphaltic coatings are often subject to more or less deterioration with time, and may be attacked by injurious vapors or deleterious substances in solution in the water coming in contact with them. The most effective method for applying such protection is either the setting of a course of impervious brick dipped in bituminous material into a solid bed of bituminous material or the application of a sufficient number of layers of satisfactory membranous material cemented together with hot bitumen. Their durability and efficiency are very largely dependent on the care with which they are applied. Such care refers particularly to proper cleaning and preparation of the concrete to insure as dry a surface as possible before application of the protective covering, the lapping of all joints of the membranous layers, and their thorough coating with the protective material.
