文摘
In this study, shrinkage reducing admixture (SRA) was grafted on NanoSiO2 (NS) surfaces to synthesize novel core-shell (NS@SRA) particles and improve dispersion of NS in cement paste. The synthesized NS@SRA was characterized by Fourier transform infrared spectroscopy, dynamic light scattering, and thermogravimetric analysis. A series of tests were performed to investigate the effects of NS@SRA addition on the compressive strength and shrinkage of cement paste. It is found that NS@SRA increases the strength of cement paste, especially at later ages. Unlike conventional NS, which significantly increases autogenous shrinkage of cement paste, addition of NS@SRA does not appreciably affect autogenous shrinkage of the paste at early ages. Based on dispersion and zeta potential measurements of NS and NS@SRA particles in synthetic pore solution, we propose that hydration products around NS@SRA may result in gradual separation of SRA from the core. The released SRA may reduce shrinkage and mitigate cracking of cement composites at later ages.