## 4 Qualitative Discussion
### Development of New LBAs and Their Influence on Workability
Oxidation processes without sulfomethylation were also adopted for the development of new LBAs [70; 71]. [PERSON] et al. [70] evaluated the performance of a wheat straw Soda lignin modified by alkali-oxidation when added to mortar and concrete mixtures. As a result, the incorporation of 0.4 wt.% of the oxidized lignin resulted in a higher concrete clump and mortar spread when compared to a commercial lignocellulosic. Furthermore, the oxidized lignin performed similarly in the slump test to a commercial polycarbonate-based superplasticizer evaluated at 0.2 wt.% content. The alkali oxidation was also responsible for an increase in the molecular weight of the lignin. Despite the relevance of molecular weight to evaluating sulfonated and oxidized lignins, this parameter can vary considerably concerning the type of lignin and the modification method adopted (see Table 6). Moreover, high molecular weight and sulfur content can prejudice the dispersion properties of LBAs [34]. In addition to sulfonation and oxidation processes, different polymerization methods have been reported for new LBAs production. In general, polymerization methods allow the development of more technological LBAs, with mechanisms of action similar to those of polycarbonate-based superplasticizers. These admixtures consist of copolymers composed of methacrylate acid and poly(ethylene glycol) methacrylate [73]. The plasticizing ability of polycarbonate-based admixtures results from the mechanisms of: (1) electrostatic repulsion, due to the adsorption of anionic groups (e.g., carboxylic groups) from the main chain on the cement particles; (2) stabilization of the system by steric hindrance, promoted by ether groups present in neutral side chains mostly composed by poly(ethylene oxides) [42; 90]. The research group formed by [PERSON], [PERSON], and collaborators developed sustainable superplasticizers by grafting hydrophilic polyacrylamide onto Kraft lignins by controlled radical polymerization [65; 66; 67]. [PERSON] et al. [65] evaluated the performance of polyacrylamide-modified lignin in pastes with a water/cement ratio of 0.42. At dosages of up to 0.15 wt.%, the modified lignin showed better efficiency in the Slump test than a commercial polycarbonate-based superplasticizer. These authors identified that the charges present in the lignin core and the side chains of the grafted polymer promoted steric and electrostatic interactions between the particles [65]. In the following studies, the researchers developed an admixture from the polymerization of a sodium lignocellulosic with poly(ethylene oxide) [72]. The product was compared to chemical admixtures produced from the polymerization of Kraft lignins and sodium lignocellulosic with poly(methacrylic acid) and 3-sulfopropyl methacrylate [73]. As a result, the poly(methacrylic acid)-modified lignins were the most efficient superplasticizers in the Slump test, with similar performance to a commercial polycarbonate-based superplasticizer. The studies conducted by [PERSON], [PERSON], and collaborators should also be noted [18; 59; 76; 77]. The researchers showed that the incorporation of quaternized [76] and polyethylene glycol-modified [77] lignins enhanced the plasticizing performance of a polycarbonate-based superplasticizer in clay-contained cement pastes. This occurs because the modified lignins are preferentially adsorbed on the montmorillonite surface, enhancing the clay tolerance of the commercial superplasticizer. In the following studies, the researchers developed superplasticizers from polymerization strategies involving Kraft lignins and poly (ethylene oxide) [18; 59]. The chemical admixture produced by [PERSON] et al. [59] was classified as lignin-based polycarboxylates. These authors reported that the side chains of poly(ethylene oxide) promoted steric repulsion between the cement particles, which contributed to the similarity of the plasticizing mechanism between the lignin-based polycarboxylates and commercial polycarbonate-based superplasticizers.