Mohammadmahdi Heidarifar - MSc graduate, Department of Civil Engineering, University of Guilan, Rasht, Iran,
Rahmat Madandoust - Professor, Department of Civil Engineering, University of Guilan, P.O. Box ۳۷۵۶, Rasht, Iran,

Concrete's considerable unit weight is one of its primary disadvantages. Growth in the size of structural parts and seismic vulnerability accompanies this phenomenon. Replacing lightweight aggregates with conventional aggregates in concrete may be an effective method for reducing the weight of concrete constructions. This study used LECA (light expanded clay aggregate) with a particle size range of ۴ to ۱۰ mm as coarse grain. considering the synergic effect of replacing micro silica and nano-silica instead for a portion of cement, the possibility of improving the mechanical properties and durability of lightweight concrete containing LECA was investigated. In this study, the relative replacement of micro-silica was kept at ۱۰% by weight of cement, and nano-silica was changed at percentages of ۰.۵, ۱, ۱.۵, and ۲% by weight of cement. The slump test was utilized for fresh concrete, while for hardened concrete, UPV, compressive strength, for ۳ to ۹۰ days, as well as ۲۸-day water absorption, were assessed. The findings of the performed experiments indicate that Although adding pozzolanic ingredients reduces the workability of concrete, the qualities of hardened concrete are significantly improved

Micro-silica, Nano-silica, synergistic impact, LECA, Lightweight aggregate concrete