AS 3610.1:2018 Formwork for concrete
C3.2.3 In keeping with the theme of this Standard, Table 3.2.3 is expressed in performance terms. Particular examples of the use of the several classes are as follows:
Class 1 shall not be specified for concrete surfaces (as is common practice) other than prominent elements of monumental structures. This class represents the highest standard of workmanship. It is very expensive and extremely difficult to achieve. It should only be specified for surfaces that will be subject to close scrutiny. It should not be regarded as representing perfection as it, like the other classes, has permissible deviations for both colour and dimensions. The high standard of work required for its achievement precludes its use in all but elements contained in a single pour. Ideally, the concrete should come from a single concrete delivery because of the near impossibility of repetitively meeting the stringent requirements of this class. Foot or other traffic on the formwork usually leaves marks that are reflected in the poured face. For this reason Class 1 cannot be used on trafficable formed areas. Formed tops of elements usually have a problem of excessive blowholes and they are also excluded from Class 1.
Class 2 This class is also expensive. It would normally be used for general architectural work, e.g. the complete facades of buildings, public access areas, visible areas of bridge work and areas subject to close scrutiny. Its parameters are such that with stringent supervision and consistency of material supply, formwork, concrete placing, curing and protection, it can be repetitively achieved over large areas. This is the highest class for trafficable soffit work and is the highest class necessary for surfaces that are to be totally treated.
Class 3 Class 3 is for buildings and structures that are to be viewed as a whole, and where minor blemishes and defects do not tend to detract from the overall appearance. Carparks, basement walls, industrial constructions, and portions of bridgework not readily visible, are suitable cases for its use. It is the lowest class for visible surfaces that do not have an applied finish or are untreated. It is also the lowest class for which colour control may be specified.