Response-surface optimization of air-dried alkali-treated structural bamboo for enhanced flexural strength, elastic modulus and creep resistance.

Bamboo is a promising bio-based construction material owing to its rapid renewability, lightweight characteristics, and high specific strength. However, its application in load-bearing structures is still limited by inadequate mechanical performance and creep deformation under sustained loading. Herein, an air-dried alkali treatment strategy without hot pressing was developed to regulate the lignocellulosic macromolecular network and improve the mechanical properties and creep resistance performance of bamboo. Five alkaline solutions combined with air drying were used to select the optimal alkali. NaOH treatment showed the most balanced improvement by partially removing amorphous hemicellulose/lignin components, increasing cellulose crystallinity, and promoting cellulose microfibril rearrangement and hydrogen-bond reconstruction during air drying. These changes led to a more compact cell-wall structure and enhanced load-bearing performance. Subsequently, response surface methodology (RSM) was employed to investigate the effects of NaOH concentration, reaction temperature, and reaction time, on the mechanical properties of bamboo. The results indicated that the elastic modulus and maximum stress of BN-V increased to 14.36 GPa and 182.87 MPa, respectively, under the optimized conditions of 10.25% NaOH, 41.5 °C, and 2.55 h, while the relative creep was 20.23%. The experimental results were in good agreement with the model predictions, with an error of less than 5%. This work provides a scalable and low-energy strategy for improving the mechanical properties and creep resistance through mild regulation of the native lignocellulosic macromolecular network.