Title: An Investigation into the Effect of Silicon Dioxide Particle Size on the Strength of Concrete

Author(s): J. Schoepfer and A. Maji

Publication: Symposium Paper

Volume: 267

Issue:

Appears on pages(s): 45-58

Keywords: calcium silica hydrate (CSH) formation; compressive strength; nano-silica, scanning electron microscopy.

DOI: 10.14359/51663282

Date: 10/1/2009

Abstract:
The development of nanotechnology has led to the ability to produce silicon dioxide in nano-sized particles of predictable size ranges. In this study, concrete mixtures were developed using silicon dioxide of various sizes. Compressive strength testing showed significant increase in strength with decrease in particle size of the silicon dioxide down to 12 nm (4.7 × 10–7 in.). However, the mixture under 12 nm (4.7 × 10–7 in.) had a slightly lower increase in strength. High vacuum SEM analysis was performed on the samples. High-resolution images at magnifications of 5000× to 60,000× were achieved. The photographs suggest that only the surface of silicon dioxide particles is involved in chemical reactions. The particles then appear to become nucleation sites for the development of CSH crystals. Fine silicon dioxide particles provide numerous and small nucleation sites. Silicon dioxide particles smaller than 12 nm (4.7 × 10–7 in.) do not appear to generate additional nucleation sites for CSH. SEM photos of the 7 nm (2.8 x 10–7 in.) mixture reveal a structure similar to that of the 150 nm (59.1 × 10–7 in.) mixture.