Overview
ISO 11528:2016 - Buildings and civil engineering works - Sealants - Determination of crazing and cracking following exposure to artificial or natural weathering - specifies a standardized visual assessment method for detecting and rating crazing and cohesive cracking in cured sealants after outdoor or laboratory weathering. The standard defines inspection conditions, specimen preparation, lighting (artificial daylight D65), magnification, photographic documentation, and a three‑part rating system (crack quantity, width, depth) to ensure reproducible evaluation of surface defects.
Key Topics and Requirements
- Scope: Assessment of surface defects (crazing and cracking) on sealants after natural or artificial weathering.
- Specimens: Minimum cured sealant thickness 3 mm; inspection area 10 × 20 mm up to 40 × 50 mm; flatness deviation ±2 mm.
- Conditioning: Standard atmosphere 23 ± 2 °C and 50 ± 10 % RH (ISO 291) for at least 16 h prior to inspection.
- Lighting and viewing: Controlled artificial daylight (D65, 6 500 K), illumination 2 000–4 000 lx; viewing 30–40 cm distance at 45°–60°. Quality of daylight simulation evaluated per CIE Publication No. 51.
- Instruments and observer: 10× microscope for surface defects; calliper gauge accuracy ±0.05 mm for flatness; observers with normal colour vision.
- Rating system: Three ratings - quantity (Q) from 0 (none) to 5 (dense), width (0 to 5: not visible to >1 mm), and depth (0 to 5: none to >10 mm). Measurements by devices readable to 0.05 mm.
- Photographic documentation: Digital photos (minimum 9 MP, true colour) and prints (≥75 × 100 mm, 800 dpi) taken near‑vertical (80°–90°) with the specimen long edge occupying ≥80% of the horizontal frame.
- Reporting: Document exposure method (natural or artificial), extension state, cleaning procedures, and minimum/maximum ratings when variability exists.
Applications and Who Uses It
ISO 11528:2016 is used for:
- Sealant manufacturers - product development, comparative durability testing, QC and formulation optimization.
- Independent test laboratories - standardized weathering assessments for reports and material certification.
- Specifiers, architects, and façade engineers - evaluating expected in‑service appearance and specifying acceptance criteria for joints and sealants.
- Claims handling and warranty - objective evidence of weathering‑induced surface defects.
This standard supports reliable communication of sealant performance in contexts where weathering resistance, aesthetic durability, and cohesive integrity matter.
Related Standards
- ISO 291 (conditioning)
- ISO 3668 (lighting for colour comparison)
- ISO 6927 (sealant vocabulary)
- CIE Publication No. 51 (daylight simulators)
- Cross references: ISO 8339 (test specimen size), ISO 11617 and RILEM recommendations for weathering methods
Keywords: ISO 11528:2016, sealants testing, crazing, cracking, artificial weathering, natural weathering, D65 illumination, crack depth, crack width, visual assessment.