Hydrophobic kenaf straw core for biomass-based cement mortar with excellent mechanical properties

Abstract

High moisture uptake of lignocellulosic biomass is one of the primary reasons for poor mechanical properties of biomass-based building materials that limit its wide applications. Herein, hydrophobic kenaf straws core (HKC) was fabricated by a convenient sol-gel method, and was used to produce biomass-based cement mortar (CM) with excellent mechanical properties. Characteristic analysis shown that silane-based coating successfully blocked the hydroxyl groups on surface of the natural straw core (NKC), and endowed HKC with stable hydrophobic properties, thereby reducing water consumption during the preparation of cement mortar, providing larger space for C–S–H to growth, and improving the strength development of CMs. In the strength test, HKC-CM exhibited flexural and compressive strength up to 5.7 MPa and 16.43 MPa at 28 d with HKC dosage of 6 wt%, which was significantly improved compared with NKC-CM, and even when the HKC addition was doubled these properties were not obviously reduced. These results proved feasibility to add lignocellulosic biomass in quantity into building materials, providing ideas for both the industrial utilization of agricultural wastes and green materials design in construction industry.