Filling Research Gaps in Thermal Performance and Structural Behaviour of Phase-Change Material-Embedded Concrete Panels for Building Envelopes in Hot-Dry Climate Zones

Phase-change materials embedded in building envelope panels offer dual functionality, providing latent heat thermal storage that reduces building cooling loads while being incorporated within the structural fabric of the envelope. While phase-change material research has grown substantially in temperate climates, data on the structural implications of phase-change material inclusion in concrete panels used in hot-dry building envelopes representative of Nigeria's North West and North East geopolitical zones are scarce. This study investigates both the thermal performance and structural behaviour of microencapsulated phase-change material-embedded concrete panels fabricated with a paraffin-based phase-change material at dosage levels of 5, 10, and 15 percent by concrete volume, using an n-octadecane phase-change material with a melting range of 24 to 28 degrees Celsius applicable to the diurnal temperature cycle in Sokoto and Maiduguri. Thermal flux measurements were conducted in a hot-box apparatus simulating peak ambient temperatures of 42 degrees Celsius, and structural tests including flexural strength, compressive strength, and impact resistance were performed on panels and companion cube specimens. Results indicate that 10 percent phase-change material dosage reduced peak heat flux through the panel by 37 percent relative to the plain concrete control during the cooling cycle, while retaining 84 percent of the reference compressive strength. At 15 percent dosage, structural strength degraded to 71 percent of the control, falling below the C20 threshold for structural applications. A 10 percent dosage formulation is identified as the optimum for the hot-dry climate context, meeting both thermal and structural requirements. Keywords: phase-change materials, thermal performance, concrete panels, hot-dry climate, building envelope.