An appraisal of the hydro-mechanical behaviour of polysaccharides, xanthan gum, guar gum and β-glucan amended soil

Highlights

• Efficacy of polysaccharides in modifying soil’s permeability was investigated.

• Strength of biopolymer amended soil was also studied.

• Heavy metal attenuation capacity of the biopolymer amended soil was examined.

• Xanthan gum showed highest efficiency and was selected for base liner application.

Abstract

The study aims to investigate the hydro-mechanical behaviour of the polysaccharide amended sand-clay mixture and analyse the soil – biopolymer interaction. Parameters like permeability, strength and heavy metal attenuation capacity of the amended soil were characterized and studied particularly for its use in landfill applications. The permeability of the soil was investigated for a period of one year. The results of the investigation show that all the selected polysaccharides significantly reduce the permeability and improve the heavy metal adsorption capacity of the sand-clay mixtures. The biopolymer also contributes to the increase in the strength of the soil. The improved mechanical properties of the amended soil can be ascribed to the bio-clogging through gel plug formation and bonding action of the biopolymers. Xanthan gum amended soil showed the least permeability, highest strength and adsorbed the selected heavy metals almost entirely, showing the best performance as a liner material.

Introduction

Hydraulic barriers are necessary for several construction activities like groundwater remediation, contaminant barriers, temporary impermeable barriers during the construction of underground structures, tunnel linings and seepage control in hydraulic structures (Shin, Potts, & Zdravkovic, 2005; Stretch & Parkinson, 2006). Conventional methods for arresting seepage involve chemical stabilization and grouting. Conventional chemical stabilizers include lime, cement, bituminous and asphaltic materials & industrial by-products like the residue of calcium carbide, fly ash, ground granulated blast furnace slag, pond ash and bottom ash etc. (Arulrajah, Mohammadinia, Phummiphan, Horpibulsuk, & Samingthong, 2016; Kampala, Horpibulsuk, Prongmanee, & Chinkulkijniwat, 2014). These chemicals and industrial by-products are often toxic, hazardous and permanently modifies the soil and groundwater regime. The use of these conventional stabilizers increases the pH of the treated soil and renders the treated soil matrix brittle affecting their performance (Latifi, Horpibulsuk, Meehan, Majid, & Rashid, 2016; Chang, Im, Prasidhi, & Cho, 2015; Chang, Kharis, Im, & Cho, 2015; Chang, Prasidhi, Im, Shin, & Cho, 2015). Production of lime and cement consumes a large quantum of energy and resources, leading to greenhouse gas production like carbon dioxide and particulate emissions, both of which are harmful to the environment (Chang, Lee, & Gye-Chun, 2019; Dash & Hussain, 2012). This environmental concern raises the need for an eco-friendly and sustainable alternative for soil modification.

Several authors have attempted a number of biological approaches for modifying the permeability of the soil to arrest seepage (Reddy & Rao, 2018; Cabalar, Wiszniewski, & Skutnik, 2017; Chang, Im, & Cho, 2016; Latifi et al., 2016; Wiszniewski & Cabalar, 2014; Bouazza, Gates, & Ranjith, 2009; Khachatoorian, Petrisor, Kwan, & Yen, 2003). Additives other than the conventional stabilizers include chemicals in the form of liquid or powder-like resins, enzymes, polymers, acids, silicates, ions and lignin derivatives (Latifi, Marto, & Eisazadeh, 2015, 2016; Chang, Im et al., 2015; Chang, Prasidhi et al., 2015; Blanck, Cuisinier, & Masrouri, 2013). Most of these substances occur naturally and can also be manufactured industrially. Biopolymers, particularly polysaccharides, are the most popular biological additives used to modify the geotechnical properties of soil. They form a highly viscous suspension with water and are stable over a wide range of pH and temperature. They show favorable properties like pseudo-plasticity, gelling tendency and resistance to shear degradation that enable pore plugging (Wiszniewski & Cabalar, 2014). There are also a number of benefits of using biopolymers like they have a quicker setting time, very small quantity of biopolymers is sufficient to modify the soil properties compared to conventional stabilizers like cement or lime, soil strength is appreciably improved using biopolymers, they do not adversely affect the soil and the groundwater environment and yield a sustainable solution (Chang & Cho, 2012; Saha & Bhattacharya, 2010). Biopolymers can be used for improving the geotechnical properties of the soil, bio-remediation, liquefaction mitigation, etc. (Chang, Im et al., 2015, Chang, Prasidhi et al., 2015; Dejong et al., 2013; Ivanov & Chu, 2008).

Biopolymers like xanthan gum, guar gum, gellan gum, β-glucan, chitosan, Persian gum, alginate and modified starch have shown an increase in the unconfined compressive strength (UCS) of the various types of soil like poorly graded sand, low plastic clay, marine soil, silty-clay mixture, mine tailings, red mud, highly compressible clay, etc (Ghasemzadeh & Modiri, 2020; Hataf, Ghadir, & Ranjbar, 2018; Kumar & Sujatha, 2020; Soldo & Miletić, 2019; Soldo, Miletic, & Auad, 2020; Sujatha & Saisree, 2019; Ayeldeen, Negm, & El Sawwaf, 2016; Chang et al., 2016). The strength of the 2 % gellan gum-treated soil displayed a strength greater than that of 12 % cement-treated soil (Chang et al., 2016). The increase in the strength of the stabilized soil tends to become asymptotic at dosages of 3–4 % (Choi et al., 2020; Qureshi, Chang, & Al-sadarani, 2017). Choi et al. (2020) report that stabilizing soil with biopolymers in quantities less than 8 % resulted in a significant reduction in the permeability, approximately to the order of 3–4 magnitudes. Cabalar et al. (2017) observed that permeability of biopolymer stabilized soil decreased after short curing periods, say 7 days but tends to increase after long curing periods (i.e) 28 days. But, Anandha Kumar and Sujatha (2021) reported a reduction in permeability on curing the stabilized soil to 28 days. Chang et al. (2016), Chen, Wu, and Harbottle (2019) and Sujatha and Saisree (2019) have observed that biopolymer treated soil shows appreciable resistance to extreme changes in moisture (i.e) under alternate wetting and drying cycles. However, they are sensitive to moisture changes. Despite the potential advantages, their use in geotechnical applications is limited in construction practice and they lack widespread acceptance. Ivanov and Chu (2008) suggest that non-standardization and inadequate knowledge of the materials, laboratory testing procedures and methods for evaluating field performance is a key factor that limits their use in the field.

Several investigations have been carried out to prove the efficacy of the biopolymers in improving the strength of soil but only a few literatures are available on the effect of biopolymer on the permeability of the soil (Anandha Kumar & Sujatha, 2021; Kumar & Sujatha, 2020) which is the most important factor for the selection of material as a landfill baseliner or a contaminant barrier.

Also, there is a lacuna in the studies that investigate the long-term effect performance of the biopolymer amended soil (BAS). Permeability of clayey sand treated with xanthan and guar gum decreased over a short duration of 28 days due to the formation of gel plug and subsequent clogging of pores in the soil (Kumar, Sujatha, Pugazhendi, & Jamal, 2021). Authors Kumar et al. (2021) advocated the choice of guar gum stabilized soil as a base liner in landfill and studied the effect of guar gum on the permeability of the soil for a period of 120 days. Both the studies underline the need for studying the long-term permeability of the biopolymer stabilized soil to translate the choice of biopolymers for various geotechnical applications to practice in the field particularly as a liner material. This present study attempts to advocate the choice of select polysaccharides, xanthan gum (XG), guar gum (GG) & β-glucan (BG) to modify soil properties and to promote the use of these BAS as baseliners. Biopolymers in quantities of 0.25 %, 0.5 %, 0.75 %, 1 %, 1.25 %, 1.5 % and 2 % to the dry weight of the soil have been used for the study. The rheological behavior of the biopolymer solutions is studied. The permeability of the biopolymer-modified soil has been investigated for one year to understand the long-term performance. Selected biopolymers also augment the strength of the soil. Micrographs from scanning electron microscope (SEM) have been used to understand the surface morphology and mechanism of modification on biopolymer addition. Inductively Coupled Plasma Emission Spectroscopy (ICP-OES) has been used to determine the influent and effluent concentration of the synthetic leachate. The addition of these biopolymers in small quantities of 2 % has resulted in a drastic reduction in the permeability of the soil – from 10⁻³ cm/s to 10⁻⁸ cm/s. The results of the study strongly promote the choice of these biopolymers to modify soil as liners or contaminant barriers.