Engineering and durability properties of fly ash treated lime-stabilised sulphate-bearing soils

• Published in: Engineering geology Vol. 174; pp. 139 - 148
• Main Authors: McCarthy, Michael J., Csetenyi, Laszlo J., Sachdeva, Anisha, Dhir, Ravindra K.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 23.05.2014; Elsevier
• Subjects: Applied sciences; Buildings. Public works; Engineering and durability properties; Exact sciences and technology; Fly ash; Geotechnics; Ground granulated blastfurnace slag; Lime-stabilisation; Practical implications; Soil investigations. Testing; Stabilization. Consolidation; Sulphate-bearing clay; Fly ash; Lime-stabilisation; Ground granulated blastfurnace slag; Sulphate-bearing clay; Engineering and durability properties; Practical implications; Clay; Scanning electron microscopy; Property of soil; Durability; Experimental study; Stabilized soils; Water permeability; Lime; Soil test; Granulated slag; Blast furnace slag; Strength
• ISSN: 0013-7952; 1872-6917
• DOI: 10.1016/j.enggeo.2014.03.001

The paper describes a study carried out to investigate the engineering and durability properties of lime-stabilised soils treated with low-lime fly ash to limit swelling (heave) due to sulphate, associated with the ground improvement process. Two clays (Lias and Oxford with total potential sulphate levels >1.0%), a quicklime, two fly ashes (fine/low loss-on-ignition (LOI)/dry; and coarse/high LOI/wet (pond) stored) and a ground granulated blastfurnace slag (GGBS) were considered. The lime-stabilised soils contained 3% quicklime and various levels of fly ash (up to 24%) and GGBS (up to 9%), and were tested at optimum moisture content and maximum dry density. The properties considered included, immediate-bearing index, unconfined compressive strength, indirect tensile strength, water permeability and frost-heave. The results indicate that for most of these, the fly ash combinations gave improvements compared to lime-only treated soils, with the benefits generally increasing with addition level. Between fly ashes, the fine/dry material mainly gave better properties for those considered. This differs from behaviour noted previously for sulphate-heave, where coarser/wet-stored fly ash was most effective in minimizing the process. At comparable application levels, GGBS contributed more than fly ash to the properties of the lime-stabilised soils. The underlying mechanisms associated with these effects and the practical implications of the study are explored. •Practical properties of lime-stabilised clays containing sulphate are considered.•Two clays, two fly ashes (fine and coarse) and a quicklime were investigated.•Compared to lime-only treated clay, properties mainly improved with fly ash addition.•Unlike for sulphate-heave, fine fly ash gave better performance than coarse material.•Given the behaviour observed, a suggested approach for material selection is given.