Investigation on Application of Low Percentages of Nano-Particles As A Replacement of Reduced Cement in The High Strength Concrete (Mechanical and Micro-Structural Investigation)

In this study the replacement of cement by nano-silica particles is investigated. This replacement ratio is not one by one. Up to now، the replacement of cement by any kind of pozzolanic or powder material has been held equal to the percent of cement reduction. Consequently، in this investigation، nano-silica particles were added in low quantities (0-3%)، while concurrently the reduction of cement was applied with constant higher percentage (10% cement reduction). This trend was considered based on different reasons. Firstly، nano-particles do not scatter in the mixture appropriately because of their high specific surface area; so they may produce clogs with low strength transition zone. Hence the application of large amounts of nano-silica particles to develop the strength and durability of concrete is not practical and useful. The second reason، which is the main objective of this study، is replacement of high amount of cement by relatively low amount of nano-particles. Using nano-particles even with the existence of proper apparatus to disperse these particles are not economical regarding their high expenses. On the other hand، the reduction of cement in conventional and logical amounts have been applied which clearly manifests the nano-particles ability. According to the high usage of cement as the main binding material، the lower cement quantity will result in lower strength of secondary concretes respect to basic mixture