ISO 1920-4:2020

Overview - ISO 1920-4:2020 (Testing of concrete - Strength of hardened concrete)

ISO 1920-4:2020 defines standardized procedures for measuring the strength of hardened concrete. It covers compressive, flexural and tensile (splitting) strength tests and sets out specimen preparation, apparatus requirements, test execution and reporting. The standard is the authoritative reference for laboratories and quality teams that need reliable, repeatable strength data for concrete used in construction and research.

Key technical topics and requirements

• Scope and specimens

  • Test specimens may be cubes, cylinders (ISO 1920-3) or cores (ISO 1920-6). Damaged or badly honeycombed specimens are not representative and should be avoided or recorded.
  • At least three specimens (preferably from different batches) per test age; common test ages are 7 days and 28 days.

• Apparatus and calibration

  • Compression-testing machine must be robust, calibrated at least annually, and have accuracy such that load error does not exceed ±1.0%.
  • Control system (manual or automatic) and a pacer (if manual) to maintain loading rate within ±5.0%.
  • Machine platens and auxiliary platens: hardness ≥ 550 HV; auxiliary platen thickness ≥ 23 mm; surface roughness Ra between 0.4 µm and 3.2 µm.

• Test procedure and loading

  • Measure specimen dimensions to the nearest 0.2 mm and record weight prior to testing.
  • Protect specimens from drying; test within 2 hours after removal from curing environment.
  • Centre specimens on platen to 1% of specimen size.
  • For compressive tests, apply load continuously at a constant rate within 0.6 MPa/s ± 0.2 MPa/s. Apply an initial load not exceeding ~30% of expected failure load, then continue to failure. Record maximum load.

• Assessment, reporting and annexes

  • The standard describes assessment of failure types, calculation of results, and test-report content (see clauses on test results and test report).
  • Informative and normative annexes include precision data (Annex A), specimen adjustment methods (Annex B), and sample test reports (Annex C).

Practical applications and users

• Who uses ISO 1920-4

  • Construction and civil engineering laboratories, concrete producers, quality assurance/quality control (QA/QC) teams, inspection bodies, university and research labs, and regulatory authorities.

• Why it’s used

  • To verify concrete meets design strength requirements, validate mix designs, qualify materials and contractors, support forensic investigations of failed structures, and provide consistent data for specifications and compliance.

Related standards

• ISO 1920-3 - Making and curing test specimens (complements specimen requirements)
• ISO 1920-6 - Sampling, preparing and testing of concrete cores
• ISO 679 - Cement - Determination of strength
• ISO 48-2, ISO 2781, ISO 3310-1, ISO 4662 and EN 316 - referenced for apparatus, materials and test auxiliaries

Keywords: ISO 1920-4, testing of concrete, strength of hardened concrete, compressive strength test, flexural strength, tensile splitting strength, compression-testing machine, concrete test specimens, concrete QA/QC.