Concrete design information

Exposure classification

Initially the relevant exposure condition(s) should be identified. In BS 8500 exposure classification is related to the deterioration processes of carbonation, ingress of chlorides, chemical attack from aggressive ground and freeze/thaw (see Table 1). ALL of these deterioration processes are sub-divided. The recommendations for XD and XS exposure classes are sufficient for exposure class XC and it is only necessary to check each face of the concrete element for either XC, XD or XS exposure class.

Selecting concrete strength and cover

Having identified the relevant exposure condition(s), a recommended strength class and cover should be chosen. Table 2 indicates the minimum cover and strengths required to meet common exposure conditions for a 50-year working Life; further explanation is given beLow. Table 2 is not intended to cover aLL concrete exposure situations and reference shouLd be made to BS 8500 for those cases not incLuded, and where a 100-year working Life is required.

This chapter is taken from The Concrete Centre's publication, How to design concrete structures using Eurocode 2 (Ref. CCIP-006)

Compressive strength

BS 8500 uses 'compressive strength class' to define concrete strengths; the notation used gives the cylinder strength as well as the cube strength (see Table 3). It is important to quote the compressive strength class in full to avoid confusion.

Cover to reinforcement

The durability guidance given in BS 8500 is based on the assumption that the minimum cover for durability is achieved. An allowance should be made in the design for deviations from the minimum cover (4cdev).This should be added to the minimum cover to obtain the nominal cover.

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