Portland cement types: Type I to V and when you need sulphate resistance

Key points

ASTM C150: Type I general, II moderate sulphate resistance, III high early strength, IV low heat of hydration, V high sulphate resistance.
Sulphate resistance is linked to C3A content: Type II a maximum of 8%, Type V a maximum of 5%.
Type V is used for concrete exposed to soil or groundwater rich in sulphates.
The engineer chooses the cement type for footings and buried parts based on the soil investigation report.

Written for:OwnerContractorSupplier

When your engineer says "footings in resistant cement", they usually mean sulphate-resisting cement. To understand why, start with the reference classification.

1) The five types under ASTM C150

Type	Description	Use
Type I	Normal / general purpose	General use where there are no special requirements.
Type II	Moderate sulphate resistance	General use, especially when moderate sulphate resistance is needed.
Type III	High early strength	When forms must be struck or loads applied early.
Type IV	Low heat of hydration	Large mass pours, to limit internal heat.
Type V	High sulphate resistance	Concrete exposed to soil or groundwater rich in sulphates.

Sources: ASTM C1501 and the US National Precast Concrete Association's explanation2.

2) Why do sulphates attack concrete?

Sulphates are present in some soils and groundwater, and a cement's resistance to them is linked to one of its compounds, tricalcium aluminate (C3A): the less C3A, the more resistant the cement is to soils and water containing sulphates2:

Type II: C3A content 8% maximum.
Type V: C3A content 5% maximum.

3) What does this mean in practice?

Soil investigation first: the soil report shows sulphate and salt content and the groundwater level. See soil and foundations.
The structural engineer specifies the cement type and concrete requirements (water–cement ratio, cover, waterproofing) for parts in contact with soil.
Check the cement type on the ready-mix delivery ticket matches the drawings.
Sulphate resistance doesn't replace waterproofing of footings and buried walls, nor good mix quality and curing.

Note: other cement classifications exist in European, Gulf and Saudi standards, as well as blended cements with additions such as fly ash and slag. The reference is the standard specified in your project drawings.

Sources

The number next to a statement points to its source in this list. Sources back the general information; anything marked “practical advice” is editorial experience, not a quoted source. Anything that affects safety, structural design or electrical installations needs a licensed professional, and in Saudi Arabia the binding reference is the Saudi Building Code.

1ASTM C150/C150M — Standard Specification for Portland Cement — ASTM International
2A Closer Look: Cement Types I Through V — National Precast Concrete Association (NPCA)

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This guide is for general information and planning, based on standards and technical guides. Standards are revised periodically; in Saudi Arabia the binding reference is the Saudi Building Code and the instructions of the competent authorities. For design and execution, use a licensed engineer or technician. Found an error? Tell us.