The four experimental investigations, shrinking chitosan fiber-reinforced concrete,shrinking ring fiber-reinforced concrete, chitosan-coated yarn-reinforced concrete, and superabsorbent polymer-modified Portland limestone cement-based concrete, each contributed uniquely to enhancing the durability and performance of cement-based materials. In the shrinking chitosan fiber study, two subgroups were evaluated: high-grade and foodgrade chitosan. food-grade chitosan reduced compressive strength by 53% but improved freezethaw durability by 5.3%, whereas high-grade chitosan caused minimal strength loss (≤9.3%) but exhibited poor freeze-thaw resistance, with some specimens failing before the end of the test. Both fiber types increased electrical resistivity, likely due to their insulating properties rather than microstructural improvements, underscoring distinct trade-offs between fiber grades. Shrinking ring-reinforced concrete showed improved durability and moderate strength retention. At 56 days, the 1 wt% ring group slightly surpassed the control in compressive strength, exhibited 8% higher freeze-thaw resistance, and recorded the lowest water absorption, indicating a denser, more stable microstructure from enclosed voids and effective reinforcement. This suggests strong potential for durable high-performance concrete applications. Chitosan-coated yarn-reinforced concrete demonstrated consistent enhancements in both strength and durability. Compressive strength increased by up to 39.2% at 28 days and 22.8% at 56 days. Freeze-thaw resistance and length change stability also improved, with the 1 wt% dosage group performing best across multiple parameters. Slightly increased water absorption was attributed to the yarns’ inherent moisture uptake rather than microstructural degradation. Compared to direct chitosan fiber addition, coated yarns provided superior, more balanced performance. The final study assessed superabsorbent polymer and air-entraining admixtures in highperformance Portland limestone cement with fly ash and Portland limestone cement with glass ground pozzolan concretes. Control mixes achieved the highest compressive strength; modified mixes showed 16–28% reductions but remained adequate at 56 days. Freeze-thaw durability was comparable across groups, except for reduced resistance in the superabsorbent polymer-only Portland limestone cement with fly ash mix. Electrical resistivity increased by 27% in the Portland limestone cement with fly ash system, but decreased by 31% in the Portland limestone cement with glass ground pozzolan system with additives. Superabsorbent polymer improved length change resistance, while air-entraining admixtures increased it in both cementitious systems, emphasizing the importance of cautious admixture application in durable supplementary cementitious material-rich concretes. Collectively, these findings confirm that innovative reinforcement and internal curing strategies can effectively enhance concrete durability and performance. However, success depends heavily on material compatibility, optimized mix design, and precise dosage control to achieve durability gains without compromising structural integrity
Mohammad Abdul Wahab Abdul Qader (Wed,) studied this question.