polished building stones, Part 1: Granite
1995 Edition

According to IS 14223 Part 1 (1995), the acceptable physical parameters for polished granite include moisture content not exceeding 0.15%, specific gravity minimum of 2.75, water absorption capped at 0.50%, and porosity within defined ranges. Strength values such as compressive strength range between 1000 to 1500 kg/cm² for pink granite and 1300 to 2200 kg/cm² for multi-coloured or grey granite. Additional properties like tensile strength (minimum 90 kg/cm²), shear strength, hardness (Mohs scale 6 to 7), ultrasonic pulse velocity (not less than 5000 m/s), and resistance to wear are also specified with corresponding IS test methods.

The code mandates that granite slabs must be either rectangular or square with length and breadth tolerances within ±2 mm and thickness tolerances within ±1 mm. The top surface of the slabs should be finely polished without any hollowness or spalling, while the bottom face may remain rough. Joint faces are to be dressed consistent with the top surface finish. Any slab failing these dimensional or surface finish criteria is considered defective, and lot acceptance depends on the maximum allowed defective slabs per sampling tables.

IS 14223 Part 1 prescribes a series of test methods referenced from other Indian Standards for assessing granite's mechanical properties: compressive strength is tested as per IS 1121 Part 1 (1974), tensile strength by IS 1121 Part 3 (1974), shear strength via IS 1121 Part 4 (1974). Hardness is measured using the Mohs scale according to IS 13630 Part 13 (1993) and Schmidt and Shore hardness tests per IS 12608 (1989). Ultrasonic pulse velocity tests, a non-destructive method, follow IS 13311 Part 1 (1992). Sampling for these tests is conducted in accordance with clause 8.1.1 of the standard.

The IS 14223 Part 1 standard disallows the presence of hairline cracks or joints, texture anomalies such as flowers, moles, and knots, and segregation lines characterized by white or dark streaks. It also forbids harmful mineral inclusions including pyrite, marcasite, biotite, chlorite, and ilmenite. These defects compromise the slab’s structural integrity, durability, and surface polish quality. The finish must be a mirror-like polish with at least 95% reflectance, free from any hairline fissures.

Surface finish quality under IS 14223 Part 1 requires a mirror-like polish free from hairline cracks, verified using a glassometer which measures reflectance. The polished surface must achieve a minimum of 95% reflectivity. Top surfaces are finely polished without any hollowness or spalling, while bottom surfaces can be rough. Dimensional tolerances are strictly maintained at ±2 mm for length and breadth, and ±1 mm for thickness. Slabs failing the polish reflectance or exhibiting defects during inspection are rejected to ensure high-quality finished products suitable for architectural and structural applications.