Studying the Compressive Strength and Thermal Conductivity Properties of Metakaolin-based Geopolymer Concrete by Using Natural Perlite

The building industry must investigate sustainable alternatives due to the environmental impact of traditional construction methods and the growing depletion of natural resources. Using perlite (3–5 mm) to partially replace natural coarse aggregates in concrete production is one possible strategy. However, concerns remain regarding the performance of perlite in structural applications, particularly its effect on mechanical behavior and durability. This study examines the structural performance of concrete incorporating graphene and partially substituting perlite for coarse aggregates. Perlite was used at replacement levels of 5%, 10%, and 15%, and graphene was added at 0.1%, 0.3%, and 0.5% by cement mass. Cubic samples (100 × 100 × 100 mm) were produced for thermal conductivity and compressive strength testing under controlled curing conditions. The lowest thermal conductivity, 0.5063 W/(m· K), was obtained at 15% perlite. The 5% P + 0.3% G mixture exhibited the highest compressive strength (54.8 MPa) with a thermal conductivity of 0.9261 W/(m· K), indicating a practical balance between strength and insulation performance for sustainable structural concrete.