Physical, mechanical and resilient properties of two types of hydraulic graded iron and steel slag for base-course construction

Hydraulic graded iron and steel slag (HMS) is a popular base-course material where it is available or economically transportable because of its hydraulic nature, and more importantly because of difficulty in getting good-quality natural aggregates due to attention to natural environment protection. In this paper, the national industrial standards on iron and steel slag for use in road construction are first briefly described with focus on the specifications for hydraulic graded slag. Then, physical and mechanical properties are presented for two types of hydraulic graded iron and steel slag base-course material: air-cooled blast-furnace slag (BF-HMS) and blast-furnace slag , basic oxygen furnace slag and fly ash (COMP-HMS). The resilient modulus (Mr) for 95%-compacted samples is discussed in some detail. It is found that the both hydraulic graded slag satisfy the standard specifications but that their physical and mechanical properties differ. COMP-HMS exhibits a better performance than BF-HMS in hydraulic nature, uniaxial compressive strength and resilient modulus. It is shown that Mr depends on mean principal effective stress, p and deviator stress, q and also curing time just as previous studies but that the relationships of Mr with p and q are slightly non-linear in log-log coordinates. A power function of p and q may be used for approximation but other types of non-linear function could be a better representation. Great care should be paid to axial displacement measurement for obtaining a proper value of Mr.