Utilization of industrial and hazardous waste materials to formulate energy-efficient hygrothermal bio-composites

Construction industry is one of the major factor contributing to deleption of natural resources and global warming. Therefore, development and search for the alternative building materials has prerequisite of sustainable development. In this study, energy-efficient and sustainable bio-composites were produced exploiting the hazardous and industrial wastes, e.g. red mud, fly ash and ground granulated blast furnace slag. Magnesium phosphate cement was employed as main binder to prepare the control bio-composites. In the other bio-composites, magnesium phoshphate cement was replaced by red mud, fly ash and ground granulated blast furnace slag at high proportion of 50%. Bio-composites were prepared by mixing the binder and corn stalk aggregates. A wide range of properties were investigated including the hygroscopic, thermal, mechanical, microstructure and heat transfer. Thermal conductivity of bio-composites was in the range of 0.147–0.221 Wm⁻¹K⁻¹ at 25°C. Thermal properties showed direction relationship with the increase in temperature from 20°C to 50°C. Capillary uptake and water absorption of bio-composites containing waste materials were higher than that of control mixture and were in range of 1.0–4.8 kgm⁻²h^−1/2 and 30.4–49.4% respectively. Flexural and compressive strength of bio-composites varied from 1.41 to 2.15 MPa and 2.92–4.26 MPa respectively. Porosity of bio-composites was in the range of 56–63% showing that influence of type of binder on the porosity of bio-composites was not significant. Microstructure revealed the strong interlacing between the binder and plant aggregates which confirmed their chemical compatibility. Finally, bio-composites were classified into structural and thermal insulation grade concretes as per RILEM functional classifications.