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• Silica aerogel granules were replaced by quartz sand of 0 to 4.5 wt% to produce lightweight cement-based composite mortars. • SAG has increased the water absorption and porosity of the mortar, while reduced compressive strength and hardened density. • Pores increased with increase in aerogel, SAG tend to agglomerate, and pores accumulate around the aerogel particles. • SAG significantly decreased thermal conductivity from 0.772 to 0.155 W/mK. • SAG also reduced thermal diffusivity and heat storage, and increased specific heat. It has been discovered in recent years that the use of silica aerogel in cement-based materials contributes to the thermal insulation properties of the materials, and studies on this subject have gained importance. However, it was determined that the studies mostly remained at the level of the thermal conductivity coefficient and the main physical and mechanical properties of the materials. In this study, a comprehensive research was carried out with the replacement of micro-sized aerogel particles with quartz sand in different ratios (0, 1, 1.6, 2.4, 3.2, 4 and 4.5 wt%) in lightweight cement-based composite mortar (LCCM) combinations. Specifically, the effect of silica aerogel granules (SAG) on flowability, fresh and hardened densities, porosity, water absorption, compressive strength, macro/microstructural properties (by optic microscope, SEM, XRD analysis), thermal conductivity, specific heat, thermal diffusivity and heat storage capability of LCCMs were investigated. While SAG could increase the flowability (up to 8.4 %) at low using rates, it decreased it at higher rates. It is very effective in reducing fresh and hardened densities. However, it highly increased porosity and water absorption, and greatly decreased compressive strength. On the other hand, generally the poor interfacial properties of the cement matrix and the aerogel were moderately improved in this study. The lowest thermal conductivity was determined as 0.155 W/mK in the highest SAG usage. SAG increased specific heat, decreased thermal diffusivity and decreased heat storage capability of LCCMs up to 45.23 %, 63.49 % and 46.32 %, respectively. As a result of the study, aerogel has been identified as a very suitable material that can be used to highly improve thermal properties in LCCMs. [ABSTRACT FROM AUTHOR]

• Properties of alkali-excited fly ash aerogel foam concrete were studied. • The microstructure of alkali-excited fly ash aerogel foamed concrete was analyzed. • Test variable included aerogel particles, fly ash, foam and polypropylene fiber. • Developed concrete exhibited excellent thermal performance and mechanical strength. • Aerogel used in concrete had excellent thermal insulation performance. With increasing focus on low-carbon energy conservation and environmental protection, there is a need to consider all aspects of life in future developments. To meet the concept and requirements of energy conservation and environmental protection in the building industry, we have developed alkali-excited aerogel-foamed concrete that exhibits excellent thermal insulation performance and mechanical strength. The variables involved in its production include fly ash, foam, aerogels, and polypropylene fibres. In this study, the microstructure and mechanical and thermal properties of alkali-excited fly ash aerogel foam concrete was analysed. The results indicated that fly ash can replace a portion of the cement, resulting in a reduction in the thermal conductivity of the concrete. The addition of aerogels and foams to the concrete can significantly decrease its thermal conductivity. Specifically, when the aerogel content reaches 12 % and the foam content reaches 75 %, the thermal conductivity of the concrete decreases from 0.498 W/m·K to 0.183 W/m·K and 0.19 W/m·K, respectively. However, this decrease in thermal conductivity comes at a cost of approximately 50 % reduction in the flexural and compressive strengths of the concrete. The findings reveal that the aerogel has excellent thermal insulation performance similar to that of the foam, but it has little influence on the mechanical properties of the concrete. Additionally, an increase in the polypropylene fibre content significantly improves the mechanical properties of alkali-excited fly ash aerogel concrete, but the thermal properties of the concrete remain mostly unaffected. [ABSTRACT FROM AUTHOR]