Arabian Journal for Science and Engineering https://doi.org/10.1007/s13369-017-3033-x RESEARCH ARTICLE - CIVIL ENGINEERING A Laboratory Investigation of Soil Stabilization Using Enzyme and Alkali-Activated Ground Granulated Blast-Furnace Slag Ansu Thomas 1 · R. K. Tripathi 1 · L. K. Yadu 1 Received: 31 May 2017 / Accepted: 21 December 2017 © King Fahd University of Petroleum & Minerals 2018 Abstract Development and use of non-traditional stabilizers such as enzyme and alkali-activated ground granulated blast-furnace slag (GGBS) for soil stabilization helps to reduce the cost and the detrimental effects on the environment. The objective of this study is to investigate the effectiveness of alkali-activated GGBS and enzyme as compared to ordinary Portland cement (OPC) on the soil collected from Tilda region of Chhattisgarh, India. Geopolymers are alkali alumino-silicates produced when combining a solid alumina-silicate with an aqueous alkali hydroxide or silicate solution. Various dosages of the selected stabilizers have been used and evaluated for the effects on optimum moisture content (OMC), maximum dry density, plasticity index, unconfined compressive strength (UCS) and shear strength parameters. Effect of curing period has also been studied. Microstructural changes of the stabilized soils show aggregation of particles. Significant improvement in properties of soil is observed with the addition of stabilizers leading to an increase in OMC, UCS and shear strength parameters. It is observed that the cohesion of soil sample increases significantly with the addition of stabilizers whereas there is a marginal change in angle of internal friction. Thus, the findings recommend the use of non-conventional stabilizer such as alkali-activated GGBS and enzyme as suitable and environmental friendly as compared to OPC for soil stabilization. Keywords Soil stabilization · Alkali-activated GGBS · Enzyme · Shear strength parameters · Microstructural images 1 Introduction Development and use of environment friendly materials which can offer improved performance compared to tradi- tional materials in terms of cost and sustainability is a great challenge in the construction field. Desired soil properties such as shear strength, stiffness, stability, durability, soil plasticity and swelling/shrinkage potential can be achieved by preloading or stage construction, over excavation and replacement, geosynthetic reinforcement, soil improvement techniques etc. [1–5]. Constitutive model is developed cap- turing the effect of cementation degradation to predict the behaviour of cement-treated soil [6] and fibre-reinforced cement-treated soil [7]. B Ansu Thomas athomas.ce@nitrr.ac.in 1 Department of Civil Engineering, National Institute of Technology Raipur, Raipur, India The clay surface generally has a negative charge, cations or positively charged ions get attracted to the surfaces of clay particles to maintain the electrical neutrality. The abil- ity of a clay particle to adsorb ions on its surface or edges is called its cation exchange capacity and these cations are called exchangeable cations. When the cation charge in the clay structure is weak, the remaining negative charge attracts polarized water molecules by filling the spaces of the clay structure with ionized water which leads to increase in plas- ticity characteristics [8,9]. As explained by the researchers [10–12], the mechanism of traditional soil stabilizers consists of cation exchange, flocculation & agglomeration, cementatious hydration and pozzolanic reactions. The introduction of a binder to the soil releases calcium ions and replace the metal ions present within the clay lattice. The calcium silicates/aluminates of the binders react with water to form hydration products includ- ing calcium silicate hydrates and calcium aluminate hydrates as shown in Eqs. (1) and 2 [10–12]. C 3 S + 6H → C − S − H + 3Ca (OH) 2 (1) C 2 S + 4H → C − S − H + Ca (OH) 2 (2) 123