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

Author

Lei Wang, Iris K. M. Yu, Daniel C. W. Tsang* , Shuang Li, and Chi Sun Poon

Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China

Ind. Eng. Chem. Res., 2017, 56 (23), pp 6645–6654

DOI: 10.1021/acs.iecr.7b01175

Publication Date (Web): May 19, 2017

Copyright © 2017 American Chemical Society

*E-mail: dan.tsang@polyu.edu.hk.

Abstract

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.

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http://pubs.acs.org/doi/abs/10.1021/acs.iecr.7b01175