a comparison of the microstructure of self compacting concretes containing nano and microsilica

abstract self compacting concrete (scc) is a new construction material in the world. the aim of this research is to construct self compacting concrete with high compressive strength using combination of nano silica and micro silica. for this purpose, nano silica, micro silica, portland cement type 2, superplasticizer (sp), and gravel and sand have been used. three different groups of samples with different compositions were made. in the first group samples had 11% microsilica (ms11%), second group of samples contain 11%microsilica+ nanosilica (ms1-10%+ns1-10%) and third group had 11% nanosilica (ns11%). microstructure of samples were studied 7 and 21 days after setting. the xrd results and sem studies have shown that simultaneous use of 7 weight percent (wt%) nanosilica and 4 wt% microsilica instead of cement in concrete mix leads to the formation of a microstructure with the lowest portlandite content. key words: self compacting concrete, nano silica, micro silica, microstructure