Enhancing the Fresh and Early Age Performances of Portland Cement Pastes via Sol-Gel Silica Coating of Metal Oxides (Bi 2 O 3 and Gd 2 O 3).

Incorporating metal oxide nanoparticles into cement-based composites delays the hydration process and strength gain of cementitious composites. This study presents an approach toward improving the performance of bismuth oxide (Bi₂O₃) and gadolinium oxide (Gd₂O₃) particles in cementitious systems by synthesizing core–shell structures via a sol-gel process. Two types of silica coatings on cementitious pastes with 5% and 10% substitution levels were proposed. The rheology, hydration, and mechanical properties of the pastes were analyzed to determine the relationship between the coating type and nanoparticle concentration. The results indicate that despite the significant disparities in the performance of the resulting material, both methods are appropriate for cement technology applications. Bi₂O₃'s silica coatings accelerate the hydration process, leading to early strength development in the cement paste. However, due to the coarse particle size of Gd₂O₃, silica coatings exhibited negligible effects on the early age characteristics of cement pastes. [ABSTRACT FROM AUTHOR]