## 1 Introduction  
The construction of many civil engineering structures (such as buildings, ports, airports, bridges, tunnels, among others) on/in problematic soils with poor mechanical behavior requires the implementation of improvement methods to enhance these soils' characteristics, in order to increase the strength and/or decrease the compressibility. One of the most common techniques used to improve a soil's properties is chemical stabilization, which consists of a mixture of the natural soil with binders, such as quicklime, fly ash, blast furnace granulated slag and cement (which is the most used), among others. The use of cement is associated with a significant ecological footprint, since: (i) the cement industry is responsible for about 2.6% of the global CO\({}_{2}\) emissions [1]; (ii) the use of cement in soil stabilization induces an increase in the pH of the soil treated, which has a negative impact on the natural microbiome and on the vegetation's development [2]; and (iii) the material produced by the cement-based soil stabilization is irreversible [2], which is not an advantage for construction in an environmentally sensitive area. To reduce the environmental impact of the use of cement, some alternative techniques have been investigated in the last few years, such as the reuse of materials in the construction industry [3], and the use of biodegradable [4; 5] and bio-based materials, among others. One of the most studied bio-based methods consists of the precipitation of calcium carbonate that behaves as a bio-cement. When this material is deposited in the porous spaces of the soil, it creates bonds between the soil particles, inducing an improvement in the mechanical properties of the composite material [6; 7; 8; 9; 10; 11; 12; 13; 14]. This methodology presents two variants, microbial-induced calcium carbonate precipitation [7; 15] and enzyme-induced calcium carbonate precipitation [7; 8; 9; 10; 15; 16]; in the former, bacteria are added to the soil to produce enzymes, while in the latter, the enzymes are added directly to the soil. The use of biopolymers (biodegradable polysaccharides produced by living organisms) has emerged as an alternative to the bio-based methodologies, which are also associated with a low ecological footprint. Among the several types of biopolymers studied to solve geotechnical problems (casein and sodium caseinate salt, guar, cationic e-polylysine, gellan, agar, chitosan, curdlan and \(\beta\)-Glucan, Persian gum [17], Zein biopolymer [18], etc. ), xanthan gum (XG) is one of the biopolymers most investigated in geotechnical engineering, mainly due to the significant reduction in its market price in the last years [5] and to its ability to mitigate some soil weaknesses; in particular, it: 1. Decreases the soil's erosion [19], and in parallel promotes the growth of the vegetation, which also contributes to erosion mitigation [20]; 2. Decreases the permeability coefficient of the treated soil [21; 22; 23; 24; 25; 26] due to the hydration of the XG hydrogels, which decreases the soil's porosity and consequently makes the flow of water in the porous space difficult; 3. Improves the mechanical properties of the treated soils, such as sands [23; 27], silty sands [28; 29], clayed soils [19; 27; 30], bentonite, kaolinite [26; 27; 31; 32], and residual soils [33; 34]; 4. Some one-dimensional compression tests with a bentonite and a kaolinite stabilized with XG show a decrease in the compressibility after the stabilization with xanthan gum [31]. However, it should be emphasized that not all the results published are consistent with each other; indeed, results of a soft marine soil [30], kaolinite clay [35], sandy soil [23], and silt sand [29] show an increase in the compressibility after stabilization with XG.