Iranian Research Organization for Science and Technology Journal of Particle Science and Technology 2423-4087 7 2 2021 10 01 The effect of adding nano-silica on the ultrasonic pulse velocity of geopolymer concrete 99 105 1168 10.22104/jpst.2022.5334.1198 EN Behzad Mehdikhani Standard Research Institute, Technical and Engineering Faculty, Construction and Mineral Department, Karaj, Iran Behzad Saeedi Razavi Standard Research Institute, Technical and Engineering Faculty, Construction and Mineral Department, Karaj, Iran Jamal Ahmadi Department of Civil, Faculty of Engineering, University of Zanjan, Zanjan, Iran Ali Goharrokhi Applied Science Center of Khorasan Razavi Municipalities, Mashhad, Iran Journal Article 2021 11 30 Nanotechnology plays an important role in the current construction industry. It has been observed that several properties of cement-based concrete are affected by different nano materials. In this study, different weight percentages of nano-silica (0, 1, 2, and 4 wt%) were used to build geopolymer specimens. The mechanical properties of the specimens were then measured, including the compressive and flexural strength. Results demonstrated that increasing the percentage of nano-silica from 0 to 4 wt% increases the compressive strength of the specimens from 50.4 to 75.2 MPa and the flexural strength from 11.4 to 26.2 MPa. Furthermore, it was observed that the ultrasonic pulse velocity was altered by increasing SiO₂ (nano-silica), decreasing the ultrasonic pulse rate from 7.0 to 4.5 km.s^-1. https://jpst.irost.ir/article_1168_2f29b6e3abc6ebdefb55456ea6ca5dc8.pdf