Valorization of hydrophobic wood waste in concrete mixtures: Investigating the micro and macro relations

This study investigates the effect of partially replacing fine aggregate with wood waste in concrete mixes in order to preserve natural resources (i.e., sand) and reduce the disposal of wood waste into landfill. A total of 81 specimens were prepared and divided into two groups based on their w/c ratio, namely: Group 1 with w/c = 0.46, and Group 2 with w/c = 0.42. Each group has two different percentages of replacement of fine aggregates (i.e., 5% and 7%). And each percentage was tested in two batches; namely raw wood waste and Silane-treated wood waste. The absorption, compressive strength, and tensile strength were measured for all the specimens. In addition, morphological and interfacial bonding analyses were implemented by running SEM and FTIR tests. The results show that replacing the fine aggregate with wood waste increases the absorption of the concrete mix up to 300% in certain mixes. The tensile strength was affected depending on the wood waste percentages. However, incorporating wood waste in concrete mixes reduced its compressive strength up to 65.5%. The Silane treatment of the wood waste improves the mechanical properties, as well as, the impermeability of the produced mix when compared with the raw wood waste specimens. The microstructural and interaction mechanism analyses revealed the formation of high content of ettringite and air voids in concrete with raw chippings, which negatively affect the mechanical properties of the mixture. It is recommended to avoid using raw wood waste in concrete mixes since it significantly harms its mechanical properties