What is the minimum grade of concrete required for an RCC water tank?

M30, as per Table 1 of IS 3370 Part 1.

What is the maximum allowed water-cement ratio for concrete retaining liquids?

0.45 to ensure impermeability and durability.

What is the permissible crack width for structures storing liquids?

The maximum calculated surface crack width should not exceed 0.2 mm.

IS 3370 Part 1

: 2009

Concrete Structures for Storage of Liquids - Code of Practice - General Requirements

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This code specifies the general requirements for the design, construction, and materials of plain, reinforced, and prestressed concrete structures meant for the storage of liquids. It emphasizes durability, impermeability, crack control, and proper joint detailing to prevent leakages.

Specifies general requirements for design and construction of concrete structures for the storage of liquids.

Quick Reference Values

Minimum grade of concrete for RCC liquid retaining structuresM30

Minimum grade of concrete for PCC liquid retaining structuresM20

Minimum grade of concrete for Prestressed liquid retaining structuresM40

Maximum water-cement ratio0.45

Minimum cement content for RCC320 kg/m³

Maximum design crack width for liquid retaining face0.2 mm

Practical Notes

Proper execution of construction and expansion joints is as critical as structural design to achieve watertightness.

Continuous and adequate moist curing is vital to prevent early shrinkage cracks which can compromise impermeability.

Concrete for liquid retaining structures is deemed to be subject to 'Severe' exposure conditions by default.