Asbestos Cement Products - Methods of Test
2003 Edition

The load bearing capacity test for asbestos cement sheets involves cutting a 100 mm by 100 mm square specimen from each sheet. The specimen is immersed in water at a temperature between 15°C and 35°C for 24 hours (or 5°C to 15°C in colder climates). The specimen is then placed smooth side up on parallel rigid supports 50 mm wide and spaced 1 meter apart, perpendicular to corrugations. A 230 mm wide self-aligning flat beam applies load at the mid-span, with 10 mm thick felt cushioning between specimen and supports and under the beam. Load is steadily applied at a rate not exceeding 2000 N per minute to measure breaking load.

For the hydraulic pressure test, pipes are positioned on a hydraulic press with sealed ends to prevent axial compression. Pressure is increased steadily using a gauge with ±0.05 N/mm² accuracy. Building pipes are tested up to 0.1 N/mm², while other pipes are tested according to their class pressures. Pressure is maintained for 30 seconds to check for leaks, fissures, or sweating; for pipes with diameters up to 350 mm, the duration can be shortened to 5 seconds if pressure is increased by 10%. Observations of any defects during testing are recorded according to IS 5913 protocols.

Impermeability testing involves preparing a 100 mm by 100 mm specimen from asbestos cement sheets, removing or protecting any surface coatings. Each specimen is immersed upright in 270 ml of 5% acetic acid at 15°C to 35°C for 24 hours in separate containers. The acetic acid concentration is measured before and after immersion by titrating a diluted aliquot against approximately 0.5 N sodium hydroxide using thymol blue indicator. The difference in acid concentration reflects the material's impermeability, with lower acid consumption indicating better impermeability.

IS 5913 requires that pigments conform to relevant standards and are tested by mixing specified quantities with ordinary Portland cement. For color comparison, 2 grams of pigment are mixed with 20 grams of cement; for staining power, 0.2 grams of pigment are mixed with the same amount of cement. The mixture is sieved and pressed between clean, colorless glass plates to form test samples. Colour and staining power are visually assessed immediately on the fresh surfaces, ensuring no cracking or surface defects, to determine pigment performance within the asbestos cement matrix.

Specimens, either full sheets or sections of 1.25 meters cut from full sheets, must be completely immersed in water at temperatures ranging from 15°C to 35°C for 24 hours prior to testing; in colder regions, water temperatures may be as low as 5°C but not less. For non-immersed specimens, 48 hours immersion is required. After immersion, specimens are wiped to remove surface moisture, weighed, and then dried in an air oven at 150°C until constant weight is achieved. During testing, specimens are placed centrally on three mild steel bearers of 40 mm diameter arranged horizontally and parallel to ensure consistent conditioning.