Effect of the Proportion of Bamboo Scraps on the Properties of Bamboo Scraps/Magnesium Oxychloride Composites

This study was designed to solve the problem of large waste volume from bamboo processing residues in recent years. Using magnesium oxychloride (MO) cementitious material as the main material and bamboo residue (BR) as the reinforcing material, a BR/MO composite material was prepared. The effects of BR amount on the molding properties, mechanical strength, and water resistance of BR/MO composites were examined and discussed. Scanning electron microscopy (SEM), X-ray diffractometry (XRD), and thermogravimetric analysis were used to characterize composite microscopic morphology, crystalline structure, and heat resistance. The results showed that, when the BR content was 1.00% (by wt), the flowability of MO paste was beneficial to composite molding. Composite mechanical properties and water resistance were greatly affected by BR addition. When the BR content was 1.00%, composite compressive and bending strengths and softening coefficient all reached maximum values. Meanwhile, increases in water absorption by 24 h and decreases of contact angle were small. These results suggested that, when the BR content was 1.00%, composite mechanical properties and water resistance were the best and the mechanical strength also improved with extended composite storage time. SEM analysis indicated that BR played the role of a reinforcing phase in MO matrices. However, when the BR content exceeded 1.00%, interfacial bonding between BR and MO became less. XRD analysis showed that, with 1.00% BR content, composites showed more 5-phase crystals with high strength. This further explained the reason why this composite's mechanical properties were the best and the heat resistance not deteriorated due to BR, which was easily decomposed.