What is the minimum grade of concrete for reinforced concrete water tanks?

M30 as per the general requirements for liquid retaining structures.

What is the maximum allowed water-cement ratio?

0.45 to ensure sufficient impermeability and durability against water.

What exposure condition applies to the liquid retaining face?

It is generally treated as 'Severe' exposure for determining cover and concrete mix design.

IS 3370 Part 1

: 2021

Concrete structures for storage of liquids - Part 1: General requirements

CurrentEssentialCode of PracticeBIMStructural Engineering · Water Supply and Plumbing

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This part of the code specifies the general requirements for the design and construction of plain, reinforced, and prestressed concrete structures intended for the storage of liquids, emphasizing durability, crack control, and water-tightness.

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

Quick Reference Values

minimum grade of concrete for RCCM30

minimum grade of concrete for PCCM20

minimum grade of concrete for prestressedM40

maximum free water cement ratio0.45

minimum cement content RCC320 kg/m3

minimum nominal cover severe exposure45 mm

Practical Notes

The inside face of liquid retaining structures is typically considered to be under 'Severe' exposure conditions for durability checks.

Proper planning and detailing of construction joints, including the use of PVC or rubber waterstops, is critical to prevent leakage.

Ensure continuous moist curing for a minimum of 14 days to minimize early thermal and shrinkage cracking.