CO2 curing and fibre reinforcement for green recycling of contaminated wood into high-performance cement-bonded particleboards

- CO2 curing enhances strength, reduces leachability, and abates carbon footprint.
- Wood particles are suitable for CO2 diffusion and accelerated carbonation.
- Moisture content plays an important role in CO2 curing and cement hydration.
- Basalt fibre reinforces mechanical strength and fracture energy.
- Contaminated wood can be upcycled into high-performance particleboards.

To alleviate disposal burden of contaminated wood at landfills, construction wood waste can be recycled into cement-bonded particleboards, however, their qualities are often compromised by organic extractives and preservative chemicals in wood. In contrast to traditional approaches using phenol formaldehyde resin or chloride accelerator, this study proposed the use of eco-friendly CO2 curing and fibre reinforcement to accelerate carbonation and enhance physical properties of the particleboards. Cement chemistry and microstructure characteristics were evaluated by using quantitative X-ray diffraction, mercury intrusion porosimetry, and scanning electron microscopy analyses. The 24-h CO2 curing significantly facilitated cement hydration (i.e., more than 63 wt% amorphous cement hydrate) and accelerated Ca(OH)2 transformation into CaCO3, which contributed to strength development and carbon sequestration (as high as 9.2 wt%) in the particleboards. Consequently, the total pore area was reduced from 12.2 to 10.3 m2 g−1 and porosity from 34.8 to 29.7%. A subsequent 7-d air curing allowed cement rehydration and densified micropore structure, especially for capillary pores. As a result, mechanical strength, dimensional stability, and contaminants sequestration were enhanced to fulfil the requirement of International Standards. The results also illustrated the vital role of moisture content of particleboards in cement hydration and accelerated carbonation, for which the moisture content ranging from 16.7% to 17.9% was considered optimal. The addition of grid basalt fibre (0.5% by wood volume) enhanced the fracture energy of the particleboards by 6.5 times. This study presents a low-carbon and environmentally-friendly technology to upcycle construction wood waste into value-added materials in a sustainable way.

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