Mechanical and Thermal Properties of an Energy-Efficient Cement Composite Incorporating Silica Aerogel

The thermal performance of the building envelope is significant in energy-efficient construction. Because concrete is widely used in civil engineering, options to reduce its R-value should be considered. This study explores the thermal and structural properties of aerogel-enhanced concrete. Silica aerogel powder was mixed with fine-grained concrete at 15 vol.%. Two series of samples were prepared to identify the preferred technology. The first series of samples were mixed without isopropyl alcohol; for the second series, the alcohol was mixed with silica aerogel before mixing into the dry mix. The thermal conductivity, compressive strength, and bending resistance of the specimens were measured. The presence of silica aerogel admix resulted in a decrease in the compressive strength of the specimens by 30% compared with that of the reference samples and a reduction in the bending strength of the samples by 9% compared with that of the reference samples. For the first and second series of samples, the K-values of the aerogel-enhanced specimens varied in the range from 0.83 W/(m·K) to 1.13 W/(m·K), respectively. To further decrease the thermal conductivity, gypsum putty was then added to the specimens, resulting in the K-values further decreasing to 0.64 W/(m·K) and 0.84 W/(m·K), respectively. The calculation of heat losses through 1 m2 of the aerogel-enhanced concrete wall was performed. It has been shown that energy expenses for heating can be lowered by 30%. The calculation of the greenhouse gas emissions from the combustion of fuel required for heating was also considered. The emissions decreased by 30.2% compared with the reference sample. Microscopic examination of the face and section surfaces of the sample revealed a significant number of pores compared with conventional fine-grain concrete.

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