CONCRETE
Shrinkage Strain of Concrete (εcs)
Volumetric strain of concrete due to drying and chemical shrinkage — per IS 456 Cl. 6.2.4.1 — typical value 0.0003 (300 microstrain).
Also calledshrinkage strainshrinkage concretedrying shrinkageis 456 shrinkageconcrete shrinkage value
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CODES
Definition
Total shrinkage strain εcs per IS 456 Cl. 6.2.4.1 ≈ 0.0003 (i.e. 0.3 mm per m length, or 300 microstrain). Higher for thin sections, low-humidity environments, and high w/c ratios. Two components: drying shrinkage (loss of moisture) + autogenous shrinkage (chemical hydration).
Typical values
Total shrinkage εcs (IS 456)0.0003 (300 με)
Drying component~80% of total
Autogenous component~20% of total
Per metre length0.3 mm/m
Where used
- Long-term deflection (additional component)
- Crack-control reinforcement sizing
- Joint spacing in slabs-on-grade
- Composite-action stress check
Acceptance / threshold
Per IS 456 Cl. 6.2.4.1 — use 0.0003 unless specific test data justifies a different value.
Site example
20 m long slab: free shrinkage = 0.0003 × 20000 = 6 mm. Controlled by movement joints at 4-5 m centres or by post-tensioning.
Frequently asked
What is concrete shrinkage strain?
Per IS 456 Cl. 6.2.4.1: εcs ≈ 0.0003 (300 microstrain, or 0.3 mm per m). Mainly drying shrinkage (moisture loss) + autogenous (hydration). Higher for thin sections + low humidity.
Related concrete terms
Concrete Mix Design
Proportioning of cement, water, aggregates per IS 10262
Concrete Grades (M15-M80)
M20=20 N/mm² characteristic strength at 28 days
Water-Cement Ratio (w/c)
Mass of water to mass of cement. 0.40-0.55 typical.
Concrete Cover
Min concrete from rebar to surface (15-50mm per exposure)
Concrete Curing
Min 7 days for OPC, 10 days for PPC, 14 days for sulphate-resistant
Slump Test / Workability
25-150mm slump per application (IS 1199)
Cube Test (Compressive Strength)
150mm cube compressive strength test at 7/28 days (IS 516)
Concrete Admixtures
Plasticizers, accelerators, retarders per IS 9103