ScopeThe Standard sets out the minimum requirements for the design and construction of safe, serviceable and durable concrete structures. There may be other requirements, not covered by the Standard, which also have to be considered.ApplicationA lower concrete strength limit of 20 MPa has been imposed, as strength grades less than this are not considered suitable for structures.An upper concrete strength limit of 50 MPa has been adopted, because much of the research on which the Standard is based involved concrete strengths at or below this value. Nevertheless, higher strength concretes are being used in Australia and overseas (Refs. 1 and 2). The Standard may possibly be applied without change to concretes with 28-day compressive strengths up to 65 MPa. However, beyond 50 MPa, concrete becomes increasingly brittle in its structural behaviour and, as indicated in Note 2, current detailing requirements may be inadequate for ensuring the necessary elastic and ductile behaviour assumed in the various design Sections.Concretes made from naturally occurring Australian coarse aggregates have surface-dry densities falling in the range 2100 kg/m3to 2800 kg/m3. Lightweight structural concretes in Australia generally use naturally occurring sands combined with manufactured lightweight aggregates, for which the surface-dry density is seldom less than 1800 kg/m3. Density limits for structural concretes have been set accordingly.Design of road and pedestrian bridges is covered by the 'Austroads Bridge Design Code'.In the preparation of a Standard such as this, a certain level of knowledge and competence of the majority of users must be assumed. As indicated by the Note, it was assumed that the predominant users of this Standard would be professionally qualified civil or structural engineers experienced in the design of concrete structures, or equally qualified but less experienced persons working under their guidance. It is therefore intended that the Standard be applied and interpreted primarily by such persons.