69439 AlfaBuild AlfaBuild 2658-5553 3 10.57728/ALF.37.3 Hybrid effect of carbon nanotubes and silica aerogel on mechanical, durability, and thermal properties of concrete Hybrid effect of carbon nanotubes and silica aerogel on mechanical, durability, and thermal properties of concrete 0000-0002-4590-8552 Ehsani Armin arminehsani97@gmail.com 0000-0001-5939-3257 Nasimi Shahin shahin.nasimi@yahoo.com 0000-0003-2272-7473 Shambina Svetlana Lvovna shambina-sl@rudn.ru Peoples' Friendship University of Russia Moscow, Russia 01 01 2026 37 1 37 3703 3703

Silica aerogel improves the thermal insulation of concrete but typically reduces its compressive strength. Carbon nanotubes (CNTs) were incorporated to compensate for this strength loss. Sixteen concrete mixtures containing 0–8% silica aerogel (by volume) and 0–0.5% CNTs (by weight of cement) were tested for compressive strength, electrical resistivity, chloride ion penetration, and heat transfer coefficient. The object of the research is to investigate the hybrid effect of carbon nanotubes (CNTs) and silica aerogel (SA) on the mechanical (compressive strength), durability (electrical resistivity, chloride ion penetration, permeable porosity), and thermal (heat transfer coefficient) properties of concrete. Additionally, the study aims to determine the optimal dosages of these two materials to balance strength, durability, and thermal insulation. Method. An experimental study was conducted with 16 concrete mix designs containing different amounts of silica aerogel (0, 4, 6, 8% by volume of concrete) and carbon nanotubes (0, 0.2, 0.3, 0.5% by weight of cement). Cubic specimens (15 cm) and cylindrical specimens (10 cm diameter × 5 cm height) were prepared. The following tests were performed: 1. Compressive strength at 7 and 28 days (according to EN 12390-3 standard); 2. Electrical resistivity (two-point method with 2 kHz frequency), 3. Chloride ion penetration (according to ASTM C1202), 4. Permeable porosity (saturation method), 5. Heat transfer coefficient (using a thermal sensor device). Results. The results demonstrate that the hybrid combination of CNTs and silica aerogel simultaneously enhances durability, mechanical strength, and thermal insulation. The optimal mixture (0.3% CNTs + 4% silica aerogel) increased 28-day compressive strength by 21% and reduced the heat transfer coefficient by 73% relative to control concrete. The highest compressive strength (58 MPa, 35% increase) was recorded for 0.3% CNTs with 6% silica aerogel, while the lowest thermal conductivity (0.451 W/m·K) was achieved with 0.2% CNTs and 8% silica aerogel. CNTs effectively mitigated the aerogel-induced increase in porosity and chloride ion permeability, producing a high-performance concrete suitable for energy-efficient construction.

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