• Ennis, Chris
• Gonzalez, Julieta
• Sargent, Paul

Abstract

Deep dry soil mixing (DDSM) is a form of ground improvement, which involves injecting a powdered cementitious binder into soft soils via a rotating auger drill to create cemented soil columns. Ordinary Portland cement (CEM-I) is the most widely used binder in DDSM. It significantly improves the soil’s shear strength and compressibility properties. Due to the high environmental impact of CEM-I production, there is great interest in developing more sustainable binders by using industrial by-products (IBP), such as ground granulated blast furnace slag (GGBS), whose pozzolanic properties are activated by alkali agents. This paper assesses the feasibility of using Sewage Treatment Sludge Biochar (STSB) as a low-carbon 100% waste-based alternative to traditional alkali agents, for activating the cementitious properties of GGBS for stabilising an artificial soft soil. Two ratios of STSB-GGBS (0.5:0.5 and 0.67-0.33) were added to the soil at dosages of 2.5, 5, 7.5 and 10% by dry weight, and cured for up to 28 days. The engineering performance of the different binder designs and dosages were assessed by performing a suite of unconfined compressive strength (UCS), pH, water content and plasticity index testing. Results were compared with those of untreated and CEM-I stabilised alluvium, along with results published in litera-ture. Results indicate that higher concentrations of biochar and binder dosages greater than 7.5% resulted in 28 day strengths that met EuroSoilStab requirements, sug-gesting that the STSB-slag binder has encouraging prospects as a waste-based binder for use in geotechnical ground improvement.<br/>

Topics

• impedance spectroscopy
• Carbon
• strength
• cement
• plasticity