Hollow clay tiles for floors and roofs, Part 1: Filler type -
2009 Edition

IS 3951 Part 1 (2009) defines hollow clay filler tiles as having perforations aligned with their length, intended for use in flooring and roofing. Typical shapes are illustrated in Figure 4 of the standard. The tiles’ nominal dimensions include lengths generally between 400 to 450 mm, widths from 200 to 250 mm, and thicknesses ranging from 100 to 150 mm. Acceptable dimensional deviations are ±3 mm for length and width, and ±2 mm for thickness. The uniform perforations serve to reduce weight and enhance insulation properties. Strength compliance is verified through breaking strength tests conducted on at least six randomly selected samples.

Per IS 3951 Part 1 (2009), hollow clay filler tiles should be manufactured using suitable clay as the base material. Additionally, additives such as pulverized coal ashes—including fly ash, pond ash, mound ash, and bottom ash—as well as crushed stone sand dust may be incorporated in appropriate proportions to meet required quality and strength standards. The tiles must be well-fired to ensure uniform coloration and must be free from cracks, defects, or harmful inclusions like lime nodules or soluble salts. Due to their porous nature, when used with embedded steel, appropriate concrete or mortar cover is necessary to protect against corrosion.

The breaking strength test, as prescribed in IS 3951 Part 1 (2009) Annex A, involves selecting a minimum of six tiles at random and drying them at 110°C until a constant mass is reached, then cooling and weighing them. The tiles are supported at the centers of their outer shell walls, and a load is applied along the tile length—parallel to the perforations—using a 20 mm wide steel plate. The minimum required breaking load is 10 kgf per cm length. Bulk density is calculated by dividing the dry weight by the bulk volume (excluding grooves). This test ensures the tiles possess sufficient mechanical strength for structural applications in floors and roofs.

According to IS 3951 Part 1, the hollow clay filler tiles must not absorb water beyond 15% of their dry weight by mass, as specified in Clause 8. Alternatively, if agreed upon with the purchaser, a stricter limit of 10% maximum water absorption may be applied. The water absorption test follows the procedure detailed in Annex B, involving drying the tiles at 110–115°C, soaking them in water at 27 ± 2°C for 24 hours, and measuring mass changes. Lower water absorption values contribute to enhanced durability and structural performance.

IS 3951 Part 1 mandates that each hollow clay filler tile be clearly and permanently marked to identify the manufacturer through name or trademark. The tile must also bear the designation 'Filler' or the letter 'F' to indicate its type, along with a batch or control unit number for traceability purposes. Where applicable, tiles may display the BIS Standard Mark, provided the manufacturer holds the proper license under the Bureau of Indian Standards Act, 1986. Such markings ensure reliable quality control and compliance verification.