Mechanical and thermoelectric properties of high ductility geopolymer composites with nano zinc oxide and red mud

Building surface temperatures rise because of urban development, resulting in a heat island effect. Thermoelectric cementitious composites (TECCs) can transform a building's indoor-outdoor temperature difference into electrical energy; however, when used in civil buildings, TECCs are prone to tensile cracking due to eccentric pressures. High-ductility cementitious composites (HDCCs) can alleviate the brittleness and cracking susceptibility of ordinary concrete while enhancing deformation ability. In a bid to reduce cement usage, alternative low-carbon cementitious materials are employed to prepare high-ductility geopolymer composites (HDGCs) with superior tensile capabilities, which is in accordance with the green sustainable strategy than HDCCs. For the first time, TE-HDGCs with red mud (RM), high tensile ductility, and thermoelectric energy conversion are developed in this study. The results show that the compressive strength, tensile strength, and tensile strain of the HDGCs are 48.7 MPa, 2.40 MPa, and 3.51 %, respectively, with an RM dosage of 30 % by mass of fly ash and no nanomaterials. The compressive strength of the TE-HDGCs is increased by adding 0.5 %-2.0 % nano ZnO. The thermoelectric properties of the HDGCs are considerably enhanced upon adding nano ZnO, first increasing the Seebeck coefficient and later decreasing it, reducing the heat conductivity while raising the electrical conductivity and figure of merit (ZT). TE-HDGCs with compressive strength of >40 MPa, tensile ductility of >2.0 %, and ZT of >10(-7)mu V/degrees C are obtained. They exhibit potential civil engineering applications and can provide technical references for development of more efficient thermoelectric materials than the current ones.