Hong Kong Regulations

BUILDING (CONSTRUCTION) REGULATIONS - REGULATION 56

General

Designed mix concrete

(1) Subject to regulation 60, each grade of concrete shall be designed mix
concrete and shall be denoted by a specified grade strength in MPa with the
suffix D and the nominal maximum size of aggregate in millimetres.

(2) The cement content of any concrete mix shall not exceed 550 kg per cubic
metre of the compacted concrete.

(3) The total chloride content of the concrete mix shall not exceed the limits
specified in Table 4 expressed as a percentage relationship between chloride
ion and mass of cement in the mix.

TABLE 4

MAXIMUM TOTAL CHLORIDE CONTENT OF CONCRETE MIX

Type of concrete Maximum total chloride content Pre-stressed concrete
Steam-cured concrete 0.1 Concrete made with sulphate resisting Portland cement
0.2 Concrete containing embedded metal and made with ordinary or rapid
hardening Portland content 0.35

(4) All concrete shall be considered as being subjected to one of the
following exposure conditions namely-

   (a)  moderate exposure conditions, which are those conditions experienced
        by surfaces protected by adequate permanent finishes or otherwise
        sheltered from driving rain, surfaces of buried concrete in contact
        with the ground and concrete continuously under fresh water; or

   (b)  severe exposure conditions, which are those conditions experienced by
        surfaces exposed to driving rain or alternate wetting and drying,
        surfaces subject to heavy condensation or corrosive fumes, and
        surfaces in contact with flowing aqueous solutions including
        sea-water. (Enacted 1990)