MIL-PRF-24176C
a. Paint system "A". Specimens shall be coated with primer conforming to MIL-DTL-24441, Type IV or
primer conforming to MIL-PRF-24647 to produce a dry film thickness of 65 to 90 µm (2.5 to 3.5 mils). Two
coats may be required to achieve the specified dry film thickness.
b. Paint system "B". Two coats 115 to 140 µm (4.5 to 5.5 mils) total dry film thickness of anti-fouling
paint conforming to MIL-PRF-24647.
After drying, the coated specimens shall be examined for any signs of incompatibility between the paint systems
and cement. After conditioning for a period of 4 days, the specimens shall be completely immersed in a 4 percent
sodium chloride solution and maintained at the test temperature specified in 4.5.1 for 1 month. The specimens
shall then be subjected to the impact tests specified in 4.5.8.2. Causes for rejection shall be as specified therein.
Poor adherence of the paint system to the cement, as evidenced by lifting shall also constitute a cause for
rejection.
4.5.10 Alkali resistance (Type I only). A 1.6 mm (1/16 inch) layer of the cement shall be applied to the
outside surface of a clean glass test tube, approximately 152 mm (6 inches) long by 19 mm (3/4 inch) in diameter.
The specimen shall be cured for 48 hours and then immersed to a depth of 102 mm (4 inches) in a 4 percent
solution of sodium hydroxide and maintained at the test temperature specified in 4.5.1 for a period of 3 weeks.
The alkali solution shall be maintained at 4 percent by addition of water as necessary. The specimen shall be
examined periodically and upon completion of the 3-week exposure, for evidence of deterioration.
4.5.11 Compressive strength.
4.5.11.1 Preparation of specimens. A split mold capable of forming a rectangular specimen slightly
larger than 13 mm by 13 mm by 76 mm (1/2 by 1/2 by 3 inches) shall be constructed of steel. A hole 1.6 mm
(1/16 inch) in diameter shall be placed at the lower end of the mold to allow for the escape of entrapped air. The
upper end of the mold shall be fitted with a steel plunger whose cross-sectional dimensions shall be slightly less
than 13 mm by 13 mm (1/2 inch by 1/2 inch). A light coating of a mold release agent shall be applied to the mold
cavity. Freshly prepared cement shall be introduced into the mold cavity prior to assembly. After assembling and
clamping the mold in place, the plunger shall be depressed slightly to permit cement to exude from the 1.6 mm
(1/16 inch) orifice and expel any entrapped air. The mold shall then be firmly secured to a flat surface so as to
prevent further exudation of the cement through the orifice. A weight of 2.27 kg (5 pounds) shall be applied to the
plunger and the cement specimen allowed to cure for 24 hours while under pressure. The cement specimen shall
be removed from the mold and aged for 1 week at 23 ± 1°C (73 ± 2°F) followed by a cure for 24 hours at 66 ± 1°C
(150 ± 2°F). Two test specimens shall be prepared and machined to 13 mm by 13 mm by 25 mm (1/2 by 1/2 by 1
inch) with a tolerance of plus or minus 127 mm (0.005 inch) in each dimension.
4.5.11.2 Procedure. The 0.2 percent offset yield stress of the cement in compression shall be
determined in accordance with ASTM D 695 and the average value obtained from two tests noted and recorded.
4.5.12 Shrinkage. Two steel molds, capable of being disassembled to facilitate removal of the test
specimens, shall be constructed with cavities 102 mm (4 inches) long by 25 mm (1 inch) wide by 64 mm (1/4
inch) deep. The molds shall be assembled, firmly secured in place and the cavity length of each mold measured to
the nearest 25 mm (0.001 inch). A light coating of mold release agent shall be applied to the mold cavities. The
mold cavities shall be completely filled with freshly prepared cement and the excess removed by drawing a steel
straight edge across the top edges of the mold. The specimens shall be allowed to cure in the molds under the test
conditions specified in 4.5.1 for a period of 2 weeks. Upon completion of the 2-week curing period, the molds
shall be disassembled and the specimens removed. The length of each specimen shall be measured to the nearest
25 mm (0.001 inch). The percent shrinkage shall be calculated based upon the decrease in length of each
specimen from the length of its respective mold. The average percent shrinkage of the two specimens shall be
reported. ASTM C 531 may be used as an alternative procedure.
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