Doping engineering for controlled hydration and mechanical properties in Portland cement mortar with ultra-low ZnO concentration

The incorporation of ZnO into cementitious matrices elicits notable alterations in the hydration process, consequently influencing the setting time. Nonetheless, comprehensive investigations exploring the impact of ZnO particle morphology on cement hydration remain limited. In this study, we present a comprehensive exploration of how the morphology of ZnO dopants can be harnessed to modulate the hydration process, concomitantly resulting in significant improvements in mechanical properties. Specifically, we have identified that ZnO nanoparticles (ZnO-Nps) exhibit a unique capacity to delay cement hydration by instigating the formation of a continuous zinc hydroxide coating. This coating remarkably inhibits the progression of cement hydration. Notably, this delay in the hydration process amounts to an approximately 76% compared to the reference material. However, a distinctive transformation occurs with ZnO microparticles (ZnO-Mps) exhibiting a flower-like morphology. In this case, the continuous coating becomes discontinuous, leading to a marked enhancement in mechanical properties. These enhancements manifest as an increase ranging between 13 and 10% in comparison to the reference material. Our results underscore the pivotal role of ZnO particle morphology in tailoring the hydration process and concurrently elevating mechanical properties. This study contributes to elucidating the intricate interplay between morphology, hydration kinetics, and mechanical behavior within cementitious systems. The ability to harness these morphology-dependent effects offers a promising avenue for optimizing material properties and advancing our understanding of cementitious systems.