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 terms
Creep & Shrinkage (Concrete)
Time-dependent deformation of concrete under sustained load
Plastic Shrinkage Cracks
Early surface cracks from rapid moisture loss before concrete sets
Creep Coefficient of Concrete (θ)
Ratio of creep strain to elastic strain under sustained load — per IS 456 Cl. 6.2.5.1 — depends on age at loading and humidity.
Segregation of Concrete
Separation of coarse aggregate from cement paste due to over-vibration, drop height >1.5 m, or low cohesion.
RCC (Reinforced Cement Concrete)
Concrete with steel reinforcement. Per IS 456:2000.
Formwork Stripping Time (Removal Schedule)
Minimum time before formwork can be safely removed per IS 456 Cl. 11.3 — depends on member type, climate, and concrete strength.
Chloride Content Limit in Concrete
Maximum acid-soluble chloride permitted in concrete to prevent rebar corrosion — per IS 456 Cl. 8.2.5.2 and Table 7.
Modulus of Elasticity of Concrete (Ec)
Short-term static modulus of elasticity of concrete per IS 456 Cl. 6.2.3.1 — Ec = 5000√fck (in N/mm² with fck in N/mm²).
Concrete Curing
Min 7 days for OPC, 10 days for PPC, 14 days for sulphate-resistant
Laitance
Weak, porous layer of cement fines and water on concrete surface. Must be removed before next pour to ensure bond.