Nanomodified Portland cement paste
with a water/cement ratio of
0.4 was prepared with the addition of TiO2 nanoparticles
at 0.1, 0.5, 1.0, and 1.5% by mass of cement. The flexural strengths
of the prepared cement-based composites were tested, and the fracture
surfaces were observed by scanning electron microscopy (SEM). The
flexural strength of the nanomodified TiO2 Portland cement
paste reached the highest value with a dosage of 1.0 mass %. The SEM
observation shows that admixing of the TiO2 nanoparticles
largely decreased the quantity of internal microcracks in the cement
paste. A new type of needle-shaped hydration product was observed,
and its potential growth mechanism was proposed. Atomic force microscopy
was introduced to observe the microstructure of nanomodified Portland
cement paste, and the results show that the nanoroughness of the hardened
cement pastes with admixed TiO2 nanoparticles was much
lower than that without the TiO2 nanoparticle addition.
Coupled with X-ray diffraction data, the morphological information
obtained at the micrometer and nanometer scales shed light on the
role of TiO2 nanoparticles in the cement-based composite.
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