In this research work, advancement of nanotechnology is used in order to improve performance characteristics of pozzolonic concrete (concrete having 30% class F fly ash in replacement of cement) with use of nano-sized silica (SiO₂) particles, known as Nano-silica. This study may be considered as an important step towards better understanding the use of nano-silica in concrete as a remedy to overcome drawbacks of the use of pozzolans (drawback like late strength gain of hardened concrete). This research program aims at 1) further understanding the behaviour of cementitious materials when amended by nano-silicon various physio-mechanical properties (workability, compressive, tensile, flexural strength etc.) of pozzolonic concrete and 2) exploring the effect of this enhancement on the microstructure of cement matrix using SEM. The experimental program that was conducted included a laboratory investigation of concrete mixtures in which nano-silica was added to the compound cement and Class F fly ash. Three ratios of nano-silica (0%, 3% and 6% by wt. of the cementitious compound) were used in concrete mixtures to examine the extent and types of improvements that could be imparted to concrete. The conducted experimental program assessed these improvements in terms of mechanical properties and internal structure of the mixtures under investigation.