Hydration heat control and anti-cracking mechanisms of cementitious materials with starch-modified β-cyclodextrin

Early-age cracking in mass concrete is closely related to rapid hydration heat release and shrinkage-induced stress development. This study synthesized starch-modified β-cyclodextrin (S-β-CD) and investigated its effects on hydration heat evolution, strength development, shrinkage behavior, and restraint stress of concrete. The results showed that S-β-CD reduced the early heat release rate and delayed the main hydration peak, exhibiting a peak-shaving and peak-delaying effect. At an optimal dosage of 0.14%, S-β-CD reduced drying shrinkage and restrained shrinkage stress development, while the later-age strength was maintained at a comparable level to the reference mixture. Although the ultimate adiabatic temperature rise was almost unchanged, the peak temperature-rise rate was significantly reduced, indicating that S-β-CD mainly regulates hydration kinetics rather than total heat generation. The results suggest that S-β-CD is a potential bio-based hydration-regulating admixture for mitigating early-age cracking risk in concrete.