Overview
ISO 6446:1994 - Rubber products - Bridge bearings - Specification for rubber materials defines material requirements and test methods for rubber used in elastomeric bridge bearings (plain-pad or laminated). The standard focuses on the rubber material (composition, hardness or shear modulus, environmental resistance and test-piece preparation) rather than bearing design, dimensions or full quality-control regimes for the complete bearing. Test pieces may be taken from finished bearings to determine material properties.
Key topics and technical requirements
- Rubber types and composition: Recommended base polymers are chloroprene rubber (CR) and natural rubber (NR); the use of other rubbers must be declared. Reclaimed vulcanized waste is not allowed.
- Load/deflection control: Material is specified by either shear modulus (quadruple-shear test, ISO 1827) or IRHD hardness - not both. Overall hardness range is 45–75 IRHD; common nominal hardnesses are 50, 60 or 70 IRHD. Example correlation for CR/NR at room temperature: IRHD 50 → ~0.65 MPa, 60 → ~1.0 MPa, 70 → ~1.35 MPa (guidance only).
- Environmental resistance: Requirements include ozone resistance (ISO 1431-1 - e.g., 96 h at 40 °C, 20% elongation; ozone 25 or 50 pphm depending on service), and five low-temperature resistance grades (Grade 1 to Grade 5 covering mild to severe cold climates, including down to −40 °C).
- Adhesion for laminated bearings: Rubber must form a durable bond to reinforcing layers; adhesion is assessed by direct-peel, overload-deflection or shear-break tests (methods described in the standard).
- Quality-control tests: Specified tests include hardness (ISO 48), tensile strength and elongation (ISO 37), compression set (ISO 815) and accelerated ageing (ISO 188). Tear strength and creep resistance are optional tests to be included where relevant.
- Test-piece preparation: Procedures for extracting and preparing specimens from finished bearings are defined (ISO 4661-1) so test results reflect in-service material.
Applications and users
ISO 6446:1994 is used by:
- Bridge designers and structural engineers specifying elastomeric bearings
- Bearing manufacturers and compounders selecting or qualifying rubber compounds
- Materials and testing laboratories performing acceptance and QC testing
- Procurement and standards writers creating material specifications for infrastructure projects
Its practical value is ensuring consistent material performance for load-bearing, weathering, ozone and low-temperature service conditions in bridge bearings.
Related standards (selected)
Keywords: ISO 6446:1994, elastomeric bridge bearings, rubber materials, IRHD hardness, shear modulus, chloroprene rubber, natural rubber, ozone resistance, low-temperature resistance, adhesion testing.
