Molding. ments for these sieves as given in the Standard Specifications for Sieves for Testing Purposes (Serial Designation: E11). 51. Immediately after mixing the standard mortar in accordance with the methods for mixing cement pastes and mortars the molds shall be filled heaping full without compacting. Then the mortar shall be pressed in firmly with the thumbs, applying pressure 12 times to each briquet, at points to include the entire surface. The pressure shall be such that the simultaneous application of both thumbs will register a pressure of between 15 and 20 lb. Each application of the thumbs shall be maintained not longer than sufficient to attain the specified pressure. Then the mortar shall be heaped above the mold and smoothed off with a trowel. The trowel shall be drawn over the mold in such a manner as to exert a pressure of not more than 4 lb. The mold shall then be turned over upon a Rad plane plate oiled with mineral oil, and the operation of heaping, thumbing and smoothing off repeated. No ramming or tamping shall be used, nor any troweling in excess of that required to smooth off the specimen. 52. The briquets shall be tested as soon as they are removed Testing. from the water. Tests may be made with any machine meeting the following requirements: The machine shall be capable of weighing the applied load within 0.5 per cent of the nominal value. The sensibility reciprocal (the weight required to be added to the load to move the beam from a horizontal position of equilibrium to a position of equilibrium at the top of the trig loop) shall not exceed 1 lb. at the full capacity of the machine or at any lesser load. The clips for holding the tension test specimens shall be in accordance with Fig. 7. The bearing surfaces of the clips and briquets shall be free from sand or dirt, н Fig. 6. Gang Mold and the roller bearings shall be well oiled and maintained so as to insure freedom of turning. The briquets shall be carefully centered in the clips and the load applied continuously at the rate of 600 lb. per minute. 53. Testing machines should be frequently calibrated in order to determine their accuracy. Briquettes. 54. Briquets that are manifestly faulty, or which give Faulty strengths differing more than 15 per cent from the average value of all test specimens made from the same sample and tested at the same period, shall not be considered in determining the tensile strength. XIV. STORAGE OF TEST SPECIMENS 55. The moist closet may consist of a soapstone, slate or Apparatus. concrete box, or a wooden box lined with metal. The interior wall surfaces of all closets shall be covered with felt or broad wicking kept wet. The bottom of the moist closet shall be covered with water to a depth of at least 2 in.. 56. All test specimens, immediately after molding, shall be Methods. kept in the molds on plane plates in the moist closet for from 20 to 24 hours in such manner that the upper surfaces shall be exposed to the moist air. 57. The briquets shall then be removed from the molds and immersed in clean water in storage tanks constructed of noncorroding material. 2. STANDARD SPECIFICATIONS FOR BILLET-STEEL CONCRETE REINFORCEMENT BARS American Society for Testing Materials 1. (a) These specifications cover three classes of billet-steel Material concrete reinforcement bars, namely: plain, deformed, and cold- Covered. twisted. (b) Plain and deformed bars are of three grades, namely: structural-steel, intermediate and hard. 2. (a) The structural-steel grade shall be used unless other- Basis of wise specified. (b) If desired, cold-twisted bars may be purchased on the basis of tests of the hot-rolled bars before twisting, in which case such tests shall govern and shall conform to the requirements specified for plain bars of structural-steel grade. I. MANUFACTURE Purchase. 3. (a) The steel shall be made by either or both the following Process. processes: Bessemer or open-hearth. (b) The bars shall be rolled from new billets. No rerolled material will be accepted. 4. Cold-twisted bars shall be twisted cold with one complete Cold-twisted twist in a length not over 12 times the thickness of the bar. II. CHEMICAL PROPERTIES AND TESTS Bars. 5. The steel shall conform to the following requirements as Chemical to chemical composition: Composition. Phosphorus Open-hearth. Bessemer.. not over 0.10 per cent .not over 0.05 per cent 6. An analysis of each melt of steel shall be made by the Ladle manufacturer to determine the percentages of carbon, man- Analyses. ganese, phosphorus and sulfur. This analysis shall be made from a test ingot taken during the pouring of the melt. The chemical composition thus determined shall be reported to the purchaser or his representative, and shall conform to the requirements specified in Section 5. 7. Analysis may be made by the purchaser from finished Check bars representing each melt of open-hearth steel, and each melt, Analyses. Tension Tests. or lot of ten tons, of Bessemer steel. The phosphorus content thus determined shall not exceed that specified in Section 5 by more than 25 per cent. III. PHYSICAL PROPERTIES AND TESTS 8. (a) The bars shall conform to the following requirements as to tensile properties: Modifications in Bend Tests. (b) The yield point shall be determined by the drop of the beam of the testing machine. 9. (a) For plain and deformed bars over 3/4 in in thickness or diameter, a deduction from the percentages of elongation specified in Section 8 (a) of 0.25 per cent shall be made for each increase of 32 in of the specified thickness or diameter above 3/4 in. (b) For plain and deformed bars under 16 in in thickness or diameter, a deduction from the percentages of elongation specified in Section 8 (a) of 0.5 per cent shall be made for each decrease of 32 in of the specified thickness or diameter below 6 in. 10. The test specimen shall bend cold around a pin without cracking on the outside of the bent portion, as follows: EXPLANATORY NOTE: d=the diameter of pin about which the specimen is bent; t=the thickness or diameter of the specimen. |