## 4 Discussion
Firstly, the influence of increased dosage and wind speed 4-12 m\(\cdot\)s\({}^{-1}\) showed \(<\)30 g/m\({}^{2}\cdot\)h\({}^{-1}\) loss of material compared to the negative control at 2600 g/m\({}^{2}\cdot\)h\({}^{-1}\) at maximum wind speed; secondly, the mass loss of the treated material was \(<\)100 g/m\({}^{2}\cdot\)h\({}^{-1}\) compared to 750 g/m\({}^{2}\cdot\)h\({}^{-1}\) of the untreated; therefore, the biological carbonates possessed rainfall resistance properties ([PERSON] et al., 2020; 2021). To introduce new bio-based products in the road industry (construction practice), strategic large-scale experiments (test sections) with real weather and site conditions are necessary. Since soil characteristics for road construction purposes are highly dependent on location (as a result of soil formation mechanisation, climatic condition) and are affected by construction techniques, field trial sections are essential. The trial sections will provide the best method to assess, demonstrate, and verify performance of the bio-stabiliser within the actual operational environment. Trial sections are planned for the next stage of the technology development process and are beyond the scope of this study. The small-scale tests provided a rapid method to select the best performing bio-based fractions of interest. The initial testing programme focused on demonstrating the effectiveness of the bio-additive in terms of bonding performance. Determination of the strength properties for design purposes, including compressive and advanced strength testing, such as triaxial shear strength and resilient modulus, will form part of the next phase of the testing programme using the prototypes. Two different soil types obtained from specific sites in South Africa were selected for in situ/in-place soil stabilisation. Focus was on the potential for improving weak subgrade soil, as well as wearing course for unpaved roads. Better understanding of the multiple components derived from microbes could result in potential application on unpaved, low volume roads and expansion of applications (i.e., pavements, bio-bricks, slope stability, reduction of base material) and ultimately result in cheaper manufacturing processes and environmentally friendly road construction methods. It is important to consider the bio-compatibility of the stabiliser and the varying soil types (i.e., fine grained, coarse grained, highly plasticity or clay soil). High plastic soil commonly shows bonding mechanisms via hydrogen or ionic bonding--as shown by using gellan gum, an anionic polymer which is expected to attach to positively charged kaolinite particle edges and to enhance plate particle stacking. Whereas, coarse grains (low-medium plasticity) showed improvement by interparticle cohesion with stronger bonds and the resultant strengthening property can be attributed to the conglomeration of the soils ([PERSON] et al., 2021). [PERSON] and [PERSON] (2021) show different soil stabilisation mechanisms, (a) bio-additive soil matrix may be enhanced by the direct sheer cohesion, and conglomeration effect by the bio-additive induced matrices, (b) higher strength due to reduced liquid limit induced by hydrophilic additive treatments, and (c) as with non-plastic soils, when fully dried the bio-additives displayed an increase in frictional angle contact between the soil particles, forming surface coating and enlarging the interparticle contact area. The high strength achieved with gellan gum-treated soil was shown to be due to the water absorption characteristics of hydrophilic polymers but, with varying soil types, the interaction may vary, e.g., between expansive soil as opposed to a coarse grained ([PERSON] et al., 2021). Furthermore, the SEM-EDX images show bio-based cementitious gel-material produced from the candidate prototype, and their \"sticky agents\"/bio-polymers derived from the various components provide evidence of improved soil applications.