ISO 16938-2:2019 PDF

Overview

ISO 16938-2:2019 - Buildings and civil engineering works - Determination of the staining of porous substrates by sealants used in joints - Part 2: Test without compression specifies an accelerated laboratory method to assess whether a joint sealant causes visible staining or discolouration of porous substrates (for example marble, limestone, sandstone or granite). The procedure reproduces early-stage exudation (migration) of materials from the sealant and records staining on the substrate surface and into its depth. Results are specific to the tested sealant and substrate and cannot be extrapolated to other formulations or materials; a negative result does not guarantee no staining over longer service life.

Key topics and technical requirements

• Test principle: Sealant is applied between two substrate pieces (no compression), cured and then aged; staining on surface and internal penetration is visually inspected and measured.
• Specimen preparation: Two substrate pieces per specimen assembled with spacers (12 mm × 12 mm) on a non‑adherent backing; masking tape prevents contamination; immediate tooling and curing procedures per sealant manufacturer are followed.
• Conditioning: Specimens conditioned 28 days at (23 ± 2) °C and (50 ± 10) % RH.
• Aging procedures (accelerated):
  • Heat aging: oven at (70 ± 2) °C (remove specimens after 14 and 28 days).
  • Cold aging: refrigerated enclosure at (−20 ± 2) °C (14 and 28 days).
  • Actinic radiation aging: UV fluorescent (UVA-340) or xenon-arc exposures per ISO 4892 series (wet or dry cycles).
• Apparatus and measurements:
  • Ventilated oven, refrigerated enclosure, fluorescent UVA-340 or xenon light weathering chambers, black standard thermometer, measuring device scaled to 0.5 mm.
  • Record visible staining, measure maximum/minimum stain width and stain penetration depth.
• Reporting: Test report must describe materials, specimen prep, aging cycles, measurement results and note that findings are specific to tested combinations.

Practical applications

• Product development and quality control for sealant manufacturers to screen formulations for early staining risk on natural stone and other porous substrates.
• Facade engineers, architects and specifiers evaluating compatibility of sealants with cladding materials to reduce aesthetic defects.
• Testing laboratories performing standardized compatibility tests and issuing conformity or technical datasheets.
• Risk assessment for renovation, restoration and new construction projects where visible staining would be unacceptable.

Related standards

• ISO 16938 series (sealant staining assessments)
• ISO 4892-1 / ISO 4892-2 / ISO 4892-3 - accelerated light exposure methods (xenon, fluorescent UV)
• ISO 6927 - sealants vocabulary
• ISO 11431 - related sealant exposure tests

Keywords: ISO 16938-2:2019, sealant staining test, porous substrates, test without compression, accelerated aging, UVA-340, xenon light, sealant compatibility.