Gravel or expanded clay provided with hard coating of mortar - and then used for mfg. terrazzo, facing, or lightweight concrete

摘要

Gravel or expanded clay aggregate (a) is pretreated before use in concrete or lightweight concrete, by mixing it (a) with (b) fresh mortar contg. an aggregate (b1) with a much finer particle size than (a), or a mixt. of cement and water. Mixing is continued until material (b) has hardened as a coating on each individual stone or grain in aggregate (a). The vol. of material (b) is pref. somewhat larger than the vol. of coating required on aggregate (a); and the very fine aggregate (b1) is pref. sand with a natural colour different from the colour of aggregate (a). A pigment may be added to material (b); and at least two aggregates (a) of different colours may be used. Different colours can be obtd., giving artistic effects. The hard coating prevents water being driven into capillaries in the clay during pumping of the concrete mixt. being transferred e.g. from a mixer lorry to a site.