The influence of hydrothermal pre-treatment of hemp hurds on the compatibility and performance of cement-bonded boards with GU, white, and CSA cements

The adoption of locally sourced materials in the building industry is witnessing a significant increase, driven by the demand for construction practices with lower embodied carbon. Wood wool cement boards are gaining popularity in proportion to low-carbon building materials. However, the availability of wood for their mass production is rapidly reducing. A solution to the problem lies in its substitution by hemp hurds. This study aims to assess the performance of the cement-bonded boards incorporating hemp hurds. It compares the Physico-mechanical properties and microstructures of boards made from nontreated and hydrothermally pre-treated hemp hurds, about their compatibility with General Use (GU), White and Calcium sulfoaluminate (CSA) cements, using isothermal calorimetry and scanning electron microscopy. The study found that pre-treated hemp hurds improved cement hydration kinetics and increased board strength significantly across all cement types. CSA cement boards with pe-treated hemp hurds achieved a flexural strength of 2.7 MPa, surpassing White and GU cement boards by 48% and 50%, respectively, after 28 days of curing. Moreover, the formation of uniform interfacial transition zone (ITZ) between hemp hurds and CSA cement enhances matrix connections, while hydrothermal treatment boosts compatibility and mechanical strength by removing hindering compounds. In addition, the hydrothermal treatment increased the crystallinity index of hemp hurds by 10.88%, reducing the amorphous regions and thereby improving their compatibility with different cement matrices. However, at a water-to-cement ratio of 1, board strength decreased by 58%. Additionally, CSA cement boards had lower swelling and water absorption rates compared to White and GU cement boards. • Hydrothermal pre-treatment significantly enhances hemp hurd performance • CSA cement exhibited the best compatibility with hemp hurd. • Thermal conductivity remained low and acceptable for insulation • Microstructural analysis confirmed better ITZ with pre-treated hemp hurd • Water absorption and thickness swelling were significantly reduced by pre-treatment.