## 4 Concluding Remarks  
This paper has extensively explored the realm of viscosity-modifying admixtures within the context of cement-based materials, highlighting their impact in enhancing concrete's performance. With the construction industry facing increasing demands for concrete, driven by global population growth and infrastructure development, optimizing concrete properties in both fresh and hardened states becomes imperative to ensure superior durability and resilience of construction projects. VMAs, characterized as water-soluble polysaccharides, have emerged as indispensable agents in this pursuit, showcasing their efficacy in improving the rheological properties, water retention capacity, stability, and mechanical properties of concrete. This comprehensive review has unveiled the history and classifications of VMAs, emphasizing their critical role in modifying rheology and addressing common issues such as bleeding and segregation, particularly in specialized concrete applications. Furthermore, the paper has explored environmental concerns linked to synthetic VMAs and advocates for \begin{table}
\begin{tabular}{c c c} \hline \hline
**Biopolymers** & **Advantages** & **Drawbacks** \\ \hline \hline \multirow{6}{*}{Pectin} & \multicolumn{2}{c}{Pectin enhances the following fresh properties of concrete:} \\  & - Plasticity. & \\  & - Workability. & \\  & - Flexibility. & \\  & - Water absorption. & \\  & Pectin improves the hardened properties of concrete: & \\  & - Compressive strength. & \\  & - Splitting tensile strength. & \\  & - Deflection of concrete. & strength. \\  & Pectin boosts the durability of concrete: & \\  & - Water resistance. & \\  & - Porosity. & \\  & - Resistances to sulfate attacks. & \\  & (k)-carrageenanan: & \\  & - Improves the shear-thinning & \\  & behavior and the plastic viscosity & \\  & at high and low shear rates. & \\  & - Enhances the stability, the water’s & \\  & absorption, and the dispersion. & \\  & (k)-(f)-carrageenanan: & \\  & - Enhances both the elasticity as & \\  & well as the thixotropy of & \\  & (k)-carrageenanan gels under shear. & \\  & - Reduces the setting times. & \\ Carrageenanan & (k)-carrageenanan-based superabsorbent & \\  & polymers enhance the durability of & \\  & concrete: & \\  & - The shrinkage is reduced. & \\  & - The freeze-thaw resistance is & \\  & improved. & \\  & _K. alvarezii_: & \\  & - Offers comparable performances & \\  & with (k)-carrageenanan in terms of & \\  & yield stress and plastic viscosity. & \\  & - Causes no hydration delay. & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: _Cont._the exploration of natural sources. Plant-based biopolymers like cellulose, starch, alginate, pectin, and carrageenanan have been discussed, shedding light on their effectiveness in enhancing concrete properties. In summary, this review serves as a valuable resource for understanding past research endeavors and offers insightful recommendation for future investigation aimed at fostering more efficient, eco-friendly, and cost-effective construction practices. It highlights the importance of leveraging natural biopolymers as alternatives to synthetic VMAs, thereby contributing to sustainable development in the construction industry. This review has yielded the following conclusions:  
* The incorporation of cellulose ethers into cementitious materials enhances viscosity, water retention capacity, and shear-thinning behavior. However, the effectiveness of this enhancement depends on various factors, including the type of the cellulose ether, its concentration and molecular properties, the intrinsic parameters of the cement paste, and the type of the HRWR. * PMS exhibits superior compatibility with cellulose-based VMAs in comparison to PNS. * The behavior of starch in concrete can vary according to its origin, the length of its molecular chains, whether it is modified or not, and the modification's type. * The behavior of starch varies depending on the HRWR it is combined with.