Corrugated and semi-Corrugated Asbestos Cement Sheets
1992 Edition

IS 459:1992 permits the use of clean, inert asbestos fibers as the primary reinforcement in asbestos cement sheets. Additionally, other suitable fibers may be incorporated if agreed upon by the manufacturer and purchaser. Cement types include Ordinary Portland Cement (Grade 33 as per IS 269:1989), Rapid Hardening Portland Cement (IS 8041:1990), and Portland Slag Cement (IS 455:1989). Inert aggregates such as fly ash conforming to IS 3812:1981 can be used optionally. Reinforcement strips may also be included subject to mutual agreement. This combination ensures durability, safety, and adherence to quality standards.

As per IS 459 Clauses 5.1.2 and 5.1.3, the dimensional tolerances for corrugated sheets are a depth of 48 mm with a permissible variation of +3 mm and -5 mm, and a pitch of 146 mm with a tolerance of +6 mm and -2 mm measured over six pitches. For semi-corrugated sheets, the depth is 45 mm with the same tolerance range, and the pitch is 338 mm with identical tolerances measured over three pitches. Depth is determined using a gauge on specified corrugations, while pitch measurement covers the total length over the designated number of corrugations, ensuring proper structural fit and consistency.

The load bearing capacity test for these sheets, as detailed in IS 459 Clause 6.1, requires the sheets to withstand a minimum load of 5 N/mm width. Testing follows the IS 5913:1989 method, applying load uniformly and measuring deformation or failure. Thickness measurements are conducted using a dial thickness gauge with a flat anvil of at least 9 mm diameter and an accuracy of 0.1 mm. Measurements are taken at three corrugations or flat spots near each end, excluding laps and within prescribed distances from edges, with a nominal sheet thickness of 6 mm. The test confirms the sheet's strength and suitability for structural use.

Under IS 459 Clause 11, every asbestos cement sheet must be permanently marked with the manufacturer's identity, the year and date of production, and pictorial warning symbols as per IS 12 (Part 2):1987. Manufacturers are also obligated to provide test certificates verifying compliance with the standard when requested (Clause 10.2). Furthermore, all shipments must include a safety rules sheet following IS 11769 (Part 1):1987 guidelines (Clause 13). These measures ensure traceability, quality assurance, and safety awareness.

Yes, IS 459 incorporates optional testing procedures to enhance quality verification. The density test (Clause 6.4) evaluates the compactness and uniformity of the asbestos cement sheets, while the impermeability test (Clause 6.2) ensures water resistance by checking that no water droplets form on the underside of a specimen after 24 hours, following IS 5913:1989. These tests, though not mandatory, are recommended to improve durability and performance assessment in various applications.