Mixture Design and Reaction Sequence for Recycling Construction Wood Waste into Rapid-Shaping Magnesia-Phosphate Cement Particleboard

This study has elucidated the roles of hydration chemistry and reaction sequence of magnesia-phosphate cement (MPC) in the upcycling of construction wood waste into rapid-shaping cement-bonded particleboards. The mineralogy and microstructure were evaluated using thermogravimetry, quantitative X-ray diffraction, scanning electron microscopy, and mercury intrusion porosimetry. The results showed that the magnesia-to-phosphate (M/P) ratio controlled the formation of magnesium potassium phosphate hexahydrate (MgKPO4·6H2O, MKP) for strength development. Low M/P ratios gave ill-formed MKP, whereas high M/P ratios resulted in unreacted magnesia. The optimal M/P ratio of 7 led to a much shorter setting time and greater compatibility with wood waste than for ordinary Portland cement. Wood waste can provide a platform for cement hydration and porosity for harboring crystalline MKP and also regulate water release to maintain a moderate MPC reaction. We also highlight the importance of reaction sequence for promoting matrix homogeneity and MKP crystallinity. Our approach enables fast production of value-added construction products from wood waste.