Hybrid effect of carbon nanotubes and silica aerogel on mechanical, durability, and thermal properties of concrete

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. 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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