Investigating the Freezing Strength and Durability of Lightweight Concrete With Different Weight Ratios of Nano Montmorillonite and Microsilica

One of the suitable methods to reduce the density of concrete is to use mineral pumice instead of aggregate. But due to the many holes of mineral pumice, the strength and durability of concrete decreases and its permeability increases. But some disadvantages of concrete can be solved by using nano materials. Nano montmorillonite rapidly increases the volume by absorbing water and can increase the density of concrete. In this research, QARVEH mineral pumice was used to make lightweight concrete and nano montmorillonite was used to increase the density of concrete in the amount of 0.5%, 1%, 1.5%, 2%, 2.5% by weight of cement. Also, to increase the quality and reduce the cost of materials, microsilica was used in the amount of 10% of cement weight. The conducted tests include compressive strength, tensile strength, water absorption in hardened concrete, durability against freezing cycle, economic index and examination of concrete SEM photo. The results of this research showed that the use of 2.5% nano montmorillonite instead of cement along with 10% microsilica in lightweight concrete can increase the 90-day compressive strength by 65% compared to the control sample. But due to the high cost of preparing nano materials, the optimal amount of using nano montmorillonite in lightweight concrete was determined to be 1.5% maximum. Because the use of more than that amount has no effect on increasing the compressive and tensile strength of concrete, and the failure of concrete usually occurs in the light-grained area.