Home>ASTM Standards>ASTM C903-15(R2020) pdf free download

ASTM C903-15(R2020) pdf free download

ASTM C903-15(R2020) pdf free download.Standard Practice for Preparing Refractory Specimens by Cold Gunning
1. Scope
1.1 This practice covers a procedure for preparing refractory specimens usually containing calcium aluminate cement with or without metal fibers by cold nozzle-mix gunning. Specimens prepared in accordance with this practice are intended for use in standardASTM test methods required for evaluating gunned materials. 1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.4 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
3. Significance and Use
3.1 The properties of refractories can be affected by their method of installation. This practice attempts to minimize the variables encountered during installation by pneumatic gun- ning. 3.2 This practice provides parameters to produce gunned specimens for use in other ASTM test methods. 3.3 This practice may be used to produce specimens for acceptance testing, service evaluation, manufacturing control, and research and development. 3.4 Differences between various kinds of equipment and the differences in procedures and operator techniques may result in significant variations in the physical properties of the gunned specimens. It is recommended that the same operator use the same equipment to produce specimens for referee testing agreed to by the involved testing parties. The specific operating parameters should be shown in the report. 3.5 Although this practice is specifically designed for re- fractories containing calcium aluminate cement, it may be used with minor modifications for gun mixes containing other bond systems.
4. Apparatus
4.1 Gun, pneumatic nozzle-mix. At least 50 ft (15.2 m) of hose should be available. Acceptable nozzle diameters range from 1 to 2 in. (25 to 51 mm). 4.2 Air Compressor, capable of delivering sufficient pres- sure and volume to adequately move refractory to the gun. The compressor should be able to supply at least 250 ft 3 (7 m 3 )/min. 4.3 Forms, suitable nonabsorbent type, which will vary in size in accordance with the number and size of samples being prepared, but are at minimum 12 by 12 by 4 in. (305 by 305 by 100 mm). Forms should be sized to prevent rebound entrap- ment. The use of 1 ⁄ 2 -in. hardware cloth as sidewalls of the form allows most of the rebound to pass through.
5. Procedure
5.1 Store the refractory to be gunned at 70 to 85 °F (20 to 27 °C) for 24 h prior to gunning. 5.2 Place the form against a rigid surface at an angle of 80 to 90° to the horizontal. 5.3 If recommended by the supplier, predampen the refrac- tory by mixing with potable water in a paddle mixer for 1 to 5 min or follow manufacturer’s specific instructions. In general, regular (dense) refractories require 2 to 4 % of predampening water and lightweight (insulating) refractories require 5 to 8 %.N OTE 1—Refractories that contain a high-purity cement may benefit by aging for 5 to 10 min after dampening before gunning. This “aging” procedure should be used if gunning without it produces excessive rebound, dusting, or slumping. N OTE 2—Treat refractories containing metal fibers in a normal manner. If metal fibers are to be added to the gunning material, add them to the paddle mixer before any water is introduced. The amount of fiber to be added and the methods of reporting this amount shall be agreed upon by the parties involved. To prevent clumping of the fibers they should be added slowly through a suitable screen of 1 ⁄ 2 -in. mesh. Fibers larger than 1 in. may require larger openings. If any predampening water is to be added, dry mix for two to three min before adding water. 5.4 Gun the refractory into the form at a distance of3 to 4 ft (0.91 to 1.2 m) from gun nozzle. Hold the gun nozzle at 90° to the form. Gunning pressures are suggested to be approximately 40 psi (276 kPa) for regular-weight refractories and approxi- mately 20 psi (138 kPa) for insulating refractories. Ifmore than 50 ft (15 m) of hose is used, it may be necessary to add 5 psi (34 kPa) for each additional 50 ft. These conditions and the amount of potable water used must be adjusted by the nozzleman for acceptable rebound. The gunning pattern in- volves moving the nozzle in a circular motion, back and forth across the form, beginning at the bottom. Report any unusual dusting, slumping, or other unique characteristics of the refractory. The water, material, and environment temperature shall also be reported.

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