Overview
ISO 19044:2016 specifies a standardized laboratory method to obtain load–displacement curves for fibre‑reinforced cementitious composites (FRCC) using three‑point bending on notched prism specimens. The main aim is to evaluate the tension softening curve - the relationship between crack mouth opening (CMOD) and cohesive stress - which is essential for fracture and post‑crack behaviour analysis of FRCC.
Key topics and requirements
- Specimen geometry and fabrication
- Prisms with square cross‑section: 100 × 100 mm or 150 × 150 mm; overall length ≥ 3.5D.
- Notch depth = 0.3 D and notch width ≤ 5 mm.
- Minimum of six specimens per test series.
- Maximum aggregate size ≤ 1/4 side length; moulding per ISO 1920‑3; avoid internal vibration/compaction.
- Loading and supports
- Three‑point bending with loading span S = 3 D (±2%).
- Supports and loading block designed to avoid torsion and horizontal restraint (rotatable/hinged supports).
- Measurements and accuracy
- Load cell accuracy: ≤1% of estimated peak load.
- CMOD or LPD transducers accuracy: ≤1/500 mm.
- Clip gauges or knife‑edges (≤5 mm) permitted for CMOD; report measuring positions.
- Test procedure
- Controlled displacement rate: 0.05 mm/min until CMOD/LPD = 0.1 mm, then may increase to 0.2 mm/min.
- Data acquisition: ≥ 5 Hz during rapid load changes, then ≥ 1 Hz afterwards.
- Continue test until CMOD ≥ 0.04 D or LPD ≥ 0.03 D (longer desirable for large deformation properties).
- Data processing
- Average load–displacement curves from at least six specimens.
- Annex A describes inverse analysis / poly‑linear approximation to estimate the tension softening curve from load–CMOD data.
Applications and users
ISO 19044:2016 is relevant for:
- Materials researchers and academic labs studying FRCC fracture and post‑crack behaviour.
- Concrete and mortar testing laboratories validating fibre types, lengths, and volume fractions.
- Structural engineers and designers using fracture models (fictitious crack model) and finite element analyses that require tension softening inputs.
- Manufacturers of fibre‑reinforced cementitious products who need standardized performance data for quality control and product development.
Practical uses include comparing post‑crack load capacity, deriving cohesive laws for numerical modelling, and supporting specification or certification of FRCC materials.
Related standards
- ISO 1920‑3:2004 - referenced for specimen moulds and curing procedures.
- Use together with standards on concrete testing and material characterization when preparing specimens and reporting results.
Keywords: ISO 19044:2016, FRCC, fibre‑reinforced cementitious composites, load‑displacement curve, notched specimen, tension softening curve, CMOD, LPD, three‑point bending.