Concrete
Creep Test
Long-duration laboratory measurement of time-dependent deformation in concrete under sustained compressive load — the data engineers need to predict prestress losses, long-term deflection, and structural performance decades into a structure's life.
What is the Concrete Creep Test?
Concrete meeting its design compressive strength on day 28 answers only part of the question — the part that matters for a 50-year structure is how that concrete deforms under load it carries every day for decades. Creep is the slow, continuing increase in strain that concrete undergoes under sustained compressive stress, on top of the instantaneous elastic deformation that happens the moment load is applied. Left unmeasured, it shows up later as beam and slab deflection, prestress loss, column and wall shortening, and differential movement between structural elements — gradual, cumulative effects that strength testing alone never catches.
Global Lab conducts creep testing as per ASTM C512/C512M-24 and ISO 1920-9, applying a sustained load within 0–40% of the concrete's compressive strength and monitoring companion (unloaded) specimens alongside the loaded ones to separate true creep strain from drying shrinkage. Monitoring runs for 90 days to 1 year depending on project requirements, under controlled temperature and humidity as specified in the standard. Because creep is driven by concrete composition, paste content, age at loading and site environmental conditions — not by strength grade alone — ASTM C512/C512M-24 allows test conditions to be adapted so results reflect the actual anticipated conditions of the structure, rather than relying on generic prediction models alone.
How the Concrete Creep Test is Conducted
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1Specimen Casting & CuringConcrete cylinders are cast and cured to the specified loading age, alongside companion unloaded cylinders that are used later to isolate shrinkage from true creep strain.
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2Instrumentation SetupStrain-measuring gauges are fixed to each specimen at a defined gauge length, and an initial baseline reading is taken before any load is applied.
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3Sustained Load ApplicationSpecimens are placed in a spring-loaded or hydraulic creep frame and loaded to a constant sustained stress, within 0–40% of the concrete's compressive strength, per ASTM C512/C512M-24.
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4Periodic Strain ReadingsStrain is recorded at defined intervals across the monitoring period — typically more frequent in the early days, tapering to monthly readings — under controlled temperature and humidity.
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5Data Analysis & ReportingTotal strain is corrected for shrinkage using the companion specimens, creep strain and specific creep are calculated, and the NABL-accredited report is issued via Autovity QLMS.
Applicable Test Standards
| Standard | Title | Scope | Type |
|---|---|---|---|
| ASTM C512/C512M-24 | Standard Test Method for Creep of Concrete in Compression | Sustained-Load Creep Test Method | ASTM |
| ISO 1920-9 | Testing of Concrete — Part 9: Determination of Creep of Concrete Cylinders in Compression | International Creep Test Method | ISO / BS |
| IS 456 | Plain and Reinforced Concrete — Code of Practice | Creep Coefficient Values for Design | Indian Standard |
| ACI 209R | Prediction of Creep, Shrinkage, and Temperature Effects in Concrete Structures | Creep Prediction Models | ACI Standard |