ISO 1920-9:2009

Overview

ISO 1920-9:2009 - Testing of concrete - Part 9: Determination of creep of concrete cylinders in compression - specifies a standardized laboratory method for measuring the creep of concrete using standard cylindrical specimens under a sustained longitudinal compressive load. The method defines specimen preparation, curing and storage, loading and measurement procedures, required apparatus, calculation of creep parameters, and reporting requirements to ensure comparable results across tests and laboratories.

Key topics and requirements

• Specimens and sampling
  • Cylindrical specimens made per ISO 1920‑3 and meeting ISO 1920‑4 requirements.
  • Minimum of nine cylinders per test condition: 3 for compressive strength, 3 loaded for creep, 3 unloaded controls.
• Curing and storage
  • Standard schedule: initial curing 24 h ±4 h, moist curing to 7 days, then drying to 28 days before loading (all specimens stored under the same conditions).
• Loading
  • Applied stress normally not to exceed one‑third of the average compressive strength (other stress levels permitted if documented).
  • Load-maintaining systems allowed: springs, hydraulic rams or capsules; load measurement accuracy ±2% and loading maintained within ±2% during test.
• Strain measurement
  • Longitudinal strain measured to nearest 10 microstrain.
  • Gauge reference points fixed to specimens (not friction contact); at least 3 gauge lines for loaded specimens, 2 for controls.
  • Effective gauge length constrained relative to aggregate size and presence of end plates (see standard for exact values).
• Measurement schedule
  • Readings: immediately before and within 30 s after loading, at 2 h and 6 h, daily for one week, weekly to one month, then monthly for at least three months (additional readings and reporting to 1 year are common).
• Calculations
  • Determine instantaneous elastic modulus, specific creep (load-induced strain minus shrinkage of controls, expressed per MPa), creep coefficient and creep rate F(K) from semi-log plots.
• Reporting
  • Comprehensive test report required (sample IDs, dimensions, casting/loading dates, strength at loading, applied stress, gauge type/length, creep data at reported ages, deviations, and responsible technician).

Applications and users

• Useful for: materials testing laboratories, research institutions, structural and bridge engineers, precast concrete manufacturers, quality control teams, and academics studying time‑dependent deformation.
• Practical uses: predicting long‑term deflections, assessing prestress losses, validating constitutive models, specifying durable mixes for long‑span or heavily loaded structures.

Related standards

• ISO 1920‑3:2004 - Making and curing test specimens
• ISO 1920‑4:2005 - Strength of hardened concrete
• ISO 1920‑8:2009 - Determination of drying shrinkage of concrete
• (ISO 1920 is a multi‑part series on concrete testing)

Keywords: ISO 1920-9:2009, concrete creep test, creep of concrete, concrete cylinders in compression, strain measurement, loading frame, standard concrete test method.