The high specific density of concrete significantly increases the dead load in buildings. Preferring the aggregate used in concrete as pumice, which is a volcanic material, decreases the concrete's density. However, pumice causes a decrease in the mechanical properties of concrete due to its pores structure. The improvement of the mechanical properties of concrete provides material savings by reducing the cross-sections of the structural elements to be used in buildings. Ultra-high-performance concrete, which has been an important subject of studies in recent years, is an important construction material for civil engineering. In this study, fresh concrete, physical and mechanical properties of lightweight ultra-high-performance concrete (LW-UHPC) with pumice additive were investigated. Nano carbon black was added to the mixture as 5, 10 and 15% of the cement weight. Significant increases were observed in the mechanical properties of nano carbon black added concrete. The addition of nanocarbon black to concrete at a certain ratio increased the compressive strength and flexural strength of concrete by 9.9% and 10.6%, respectively. In addition, it was observed that the sulphate resistance increased in direct proportion to the increase in the amount of nanocarbon black.