IS 3370:2021 Part 2 is the Indian Standard (BIS) for concrete structures for storage of liquids - part 2: reinforced concrete structures. This standard lays down the structural design requirements for reinforced concrete structures intended for the storage of liquids. It focuses heavily on crack width control, minimum reinforcement requirements, and durability to ensure leak-proof and structurally sound performance.
Specifies design and construction requirements for reinforced concrete liquid retaining structures.
RC liquid-retaining tank design — limit state and working-stress permissible stresses, crack-width, min steel and joint detailing.
| Reference | Value | Clause |
|---|---|---|
| Design method | Limit state (working stress permitted alternatively) | Cl. 6 |
| Min concrete grade | M30 | Cl. 7.1 (refers Part 1) |
| Max water-cement ratio | 0.45 | Cl. 7.1 (refers Part 1) |
| Min cover — liquid face | 40 mm | Cl. 8.1 (refers Part 1) |
| Crack width limit — severe (liquid face) | 0.2 mm | Cl. 9.2 |
| Crack width limit — moderate | 0.3 mm | Cl. 9.2 |
| Direct tension — concrete permissible (M30) | 1.5 N/mm² | Cl. 9.4 (Table 5) |
| Bending tension — concrete permissible (M30) | 2.0 N/mm² | Cl. 9.4 (Table 5) |
| Modular ratio (m) — M30 (working stress) | 9.33 | Cl. 9.5 |
| Min wall thickness — RC tank (typical) | 150 mm (≥ height/30 typical) | |
| Min steel — wall thickness 100 mm (each face) | 0.30 % gross area | Cl. 8.2 (Table 3) |
| Min steel — wall thickness ≥ 500 mm (each face) | 0.20 % gross area | Cl. 8.2 (Table 3) |
| Movement joint spacing | 7.5 m (full); 15 m (partial) | Cl. 10.2 |
| Construction joint — water bar required | Yes; PVC or rubber | Cl. 10.3 |
| Hydrostatic test duration | 7 days minimum after fill | Cl. 11 |
| Allowable leakage (test) | Drop ≤ 1/500 of average depth | Cl. 11 |
| Permissible compressive stress — concrete (M30, direct) | 8 N/mm² (working stress) | Cl. 9.4 (Table 5) |
| Permissible tensile stress — Fe500 steel (direct) | 180 N/mm² | Cl. 9.3 (Table 4) |
| Effective depth for crack-width calc | Surface zone 250 mm or actual cover + 5 φ | Cl. 9.2 |
| Cylindrical tank — hoop tension method | Permitted (working stress) | Cl. 12 |
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
| Parameter | IS Value | International | Source |
|---|---|---|---|
| Minimum Concrete Grade | M30 | 28 MPa (~M28) specified compressive strength (f'c) | ACI 350-20 |
| Maximum Water-Cement Ratio (Severe Exposure) | 0.45 | 0.45 | ACI 350-20 |
| Minimum Nominal Cover (Liquid Face, Severe Exposure) | 45 mm | 50 mm (2 in.) | ACI 350-20 |
| Design Crack Width Limit (Liquid Face) | Not explicitly defined; controlled indirectly by limiting steel stress to 130 MPa (for HYSD bars). | 0.25 mm (0.010 in.) | ACI 350-20 |
| Load Factor for Fluid Pressure (ULS) | 1.5 | 1.4 | ACI 350-20 |
| Watertightness Test Duration | 7 days | Generally 24 hours (after a stabilization period), but can vary. | ACI 350.1-10 |
| Minimum Cement Content (Severe Exposure, 20mm aggregate) | 340 kg/m³ | 320 kg/m³ (For comparable XD1 exposure class) | EN 1992-1-1:2004 |