Influence of different types of nano-SiO2 particles on properties of high-performance concrete

The aim of this study was to evaluate the effects of applying low replacement ratios (0.75% and 1.50% of the binder weight) of nano-SiO2 particles with different specific surface areas (200 and 380 m(2)/g) on the properties of high-performance concrete (HPC). Mechanical (compressive and splitting tensile strengths), electrical resistivity, non-destructive (ultrasonic pulse velocity), and microstructural (mercury intrusion porosimetry, X-ray diffraction, and scanning electron microscopy) tests were conducted to investigate the macroscopic and microscopic effects of nano-SiO2 particles on HPC characteristics. The results indicated that the performance of nano-SiO2 particles significantly depended on their specific surface areas and the water to binder (w/b) ratio of the mixtures. By decreasing the HPC w/b ratio from 0.35 to 0.25, nano-SiO2 particles with lower specific surface area performed better than finer one (higher specific surface area). Microstructural investigations demonstrated that the decrease in efficiency of nano-SiO2 particles with higher specific surface area at lower w/b ratio correlates to the formation of nanoparticles agglomerates, particularly at the higher replacement ratio of nanosilica (1.5%). However, the influence on the compressive and splitting tensile strengths and electrical resistivity varied due to differences in performance of nano-SiO2 particles affected the mechanical and durability properties. (C) 2016 Elsevier Ltd. All rights reserved.