Performance evaluation of thermochromic pigment-Functionalized jute and polypropylene fiber-based cement composites for energy-efficient building applications

This study investigates the thermochromic fiber-reinforced cement composites as a promising solution for enhancing building energy efficiency and structural performance. Jute (JF) and polypropylene (PF) fibers were chemically treated and coated with a thermochromic pigment-acrylic adhesive formulation using a dip-and-dry method, producing thermochromic-jute (TJF) and polypropylene (TPF) fibers. Scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDX) revealed a denser thermochromic coating on TJF than on TPF fibers. Moreover, thermochromic fibers exhibited temperature-responsive thermal conductivity and solar reflectance, enabling seasonal thermal regulation. Various cement composites incorporating plain fibers (JCM, PCM) and thermochromic fibers (TJCM, TPCM) were prepared and systematically evaluated for their physical, mechanical, thermal regulation, and microstructural properties. TJCM (45 MPa) and TPCM (47.10 MPa) showed slightly reduced compressive strength after 28 days compared to JCM (46.55 MPa) and PCM (49.10 MPa), with flexural strengths of 8.89 and 10.08 MPa, respectively, along with reduced water absorption and porosity, due to the thermochromic fibers. Semi-quantitative Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses corroborate the adequate bonding of thermochromic fibers within the cement matrix. Furthermore, SEM-EDX provided detailed observations of the microstructural characteristics, including the interfacial transition zone (ITZ), the presence of voids, and the formation of strength-contributing products. TJCM and TPCM composites exhibited modulated solar reflectance, with values of 85.45 % (TJCM) and 83.83 % (TPCM) at 36 °C, decreasing to 72.14 % and 75.61 % at 10 °C, respectively, outperforming JCM and PCM. Thermal conductivity also significantly reduced in TJCM at 0.191/0.168 W/m·K and TPCM at 0.210/0.178 W/m·K (heating/cooling cycles), compared to higher values for JCM (0.240/0.23) and PCM (0.250/0.243). The results suggest that thermochromic fibers provide an effective multifunctional strategy for passive thermal regulation in building composites. Overall, this study demonstrates that thermochromic fibers offer superior performance over direct pigment incorporation, promoting thermally adaptive and energy-efficient building envelopes.