The use of lighter-weight blastfurnace slag as dense coarse aggregate in concrete* Available to Purchase

The use of imported iron ores has led, in recent years, to a lowering in the bulk density of some blastfurnace slags produced in the United Kingdom. To take account of this change, it was decided to examine the properties of this lighter-weight slag and its suitability as dense coarse aggregatefor concrete. Accordingly, studies have been made of three slag aggregates having bulk densities below the minimum of 1250 kg/m³ specified in British Standard 1047:1925, which governs the use of dense coarse slag aggregates for concrete. This investigation, which included chemical and mineralogical examination of the aggregates and concrete durability studies up to five years from casting, has now been completed. It has been established that the strength and durability of concretes made with the lighter-weight slags did not differ significantly from those of control concretes made with flint gravel, crushed limestone and normal density slag, provided that adequate cement content and workability levels were ensured by appropriate mix design techniques. The investigations carried out included examination of reinforcing steel takenfrom the concrete. These findings could lead to a lowering of the bulk density minimum in BS 1047, andfurther encourage the utilization of blastfurnace slag as dense coarse aggregate for concrete.