Physical, mechanical and microstructural properties of road base made by copper heap leach residue (CHLR)

This paper presents the effectiveness of the copper heap leach residue (CHLR) as a sustainable alternative to the widely used natural crushed rock base used in Australia for road construction by evaluating its physical, mechanical and microstructural properties. Various contents of binders, such as 2%−3% ordinary Portland cement (OPC), 3%−5% blast furnace slag-hydrated lime (BFSHL) and 5%−10% fly ash-hydrated lime (FAHL) were employed to stabilise the CHLR of three separate particle size distributions (PSD). The unconfined compressive strength increases with the increasing content of binder and curing age for both OPC and BFSHL, regardless of the CHLR particle size distributions; the highest UCS of 4.38 MPa was obtained when CHLR without dust was stabilised with 5% BFSHL after 28 days of curing. CHLR with dust condition met the strength requirements of the base course when stabilised with 7.5% FAHL with a UCS of 1.23 MPa; however, a slight fall is noticed when 10% FAHL is used with CHLR as the MRWA specification, with or without dust. All mixes that satisfy the DCS and UCS value requirements as base and subbase construction also fulfil the CBR requirements and pH values.