Thermal impacts on eco-friendly ultra-lightweight high ductility geopolymer composites doped with low fiber volume

Engineered geopolymer composites (EGC) have garnered significant attentions as an eco-friendly building material with high ductility. However, their mechanical behavior under thermal exposure remains rarely-known. This study investigated the macroscopic mechanical properties, pore structure, and thermal conductivity of ultra-lightweight high ductility engineered geopolymer composite (ULHD-EGC) subjected to various exposure temperatures. The ultrasonic pulse velocity (UPV), scanning electron microscopy (SEM), and X-ray diffraction (XRD) were used to decouple the mechanisms affected by thermal exposure. The results indicate that as the exposure temperature increased, the compressive strength of EGC evidently decreased from 48.25 MPa at 20 degrees C to 4.56 MPa at 600 degrees C. The ULHD-EGC exhibited high ductility with tensile strain exceeding 5.95 % between 20 degrees C and 140 degrees C, and a tensile strain-to-fiber content ratio of over 8 %. At 20 degrees C to 140 degrees C, the first crack strength and tensile strength tend to decrease, with cracks becoming denser and finer as the temperature increased. Additionally, the ULHD-EGC demonstrated an exceptionally low thermal conductivity of 0.31 W/(m & sdot;K), offering valuable insights for practical applications in thermal insulation. Compared with classical cement-based fiber- reinforced composites (M45-ECC), the energy consumption, carbon emissions, and costs of ULHD-EGC are reduced by 52.7 %, 75.8 %, and 61.9 %, respectively, demonstrating significant economic and environmental benefits.