Mechanical properties and microstructure of high performance concrete containing stabilized nano-silica

Resumo

Nanotechnology can significantly improve the mechanical strength and durability of concrete. At the
nanoscale, good dispersion of constituent materials is an essential factor for the improvement of concrete
properties. In this scenario, the objective of this research was to evaluate the mechanical properties of high
performance concrete containing stabilized nano-silica. The incorporation of nano-silica to the
polycarboxylate chemical admixture allowed its application in concrete, since the nano-silica was evenly
dispersed in the concrete mass. For this study, three different concretes were employed: a reference concrete,
one containing stabilized nano-silica and another containing a mixture of silica fume and stabilized nanosilica.
The evaluated concrete mechanical properties were the axial compressive strength and secant modulus
of elasticity measured in three different ages. The results indicated a substantial increase in concrete
compressive strength and modulus of elasticity with the addition of stabilized nano-silica combined with a
reduction in cement content. The results also showed that use of stabilized nano-silica proved to be very
advantageous, especially when mixed with silica fume. When they were combined, a synergy effect occurred
in the concrete that was of chemical nature in addition to the physical effect of better concrete particle
packaging. Analysis by scanning electron microscopy showed the improvement in microstructure of
concretes with stabilized nano-silica, which contributed to gains in mechanical properties.