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Water retaining concrete class C35A

For design purposes, BS 8007, Code of practice for design of concrete structures for retaining aqueous liquids, 1987 generally referred to BS 8110, Structural use of concrete. However BS 8007 specified a 35N/mm² concrete with a minimum cement content of 325kg/m³ (compared with 300kg/m³ in BS 8110) and a maximum water/cement ratio of 0.50 (compared with 0.55 in BS 8110). This variation in constituent material limitations gave rise to the class grade C35A, where A stood for aqueous. The Code also specified maximum cement contents for reinforced concrete of 400kg/m³ for ordinary Portland cement or cements containing ggbs, or 450kg/m³ for cements containing fly ash. For prestressed concrete the quantities could be increased to 500kg/m³ and 550kg/m³ respectively.

BS 8007 was withdrawn and subsequently superseded by BS EN 1992-3:2006, therefore the C35A does not exist within the current standards BS EN 206/BS 8500. The 2nd generation Eurocode 2 has included BS EN 1992-3:2006 within BS EN 1992-1-1:2023.

Please note: The civil engineering specification for the water industry (CESWI) latest edition provides guidance on the concrete strength class and limiting composition designed to retain an aqueous liquid for their works.

Acknowledgement: The Concrete Society