Timber and wood waste biochar in cementitious composites: a circular economy approach to performance and sustainability: a review

Abstract

Timber biochar, derived from wood waste, has emerged as a promising alternative for partially replacing cement and aggregates in cementitious composites, offering both environmental and performance benefits. This review systematically analyzes the influence of biochar properties and dosages on cement composites through data synthesis and the development of contour plots for property optimization. Incorporating optimal biochar dosages (1–5%) achieves compressive strength improvements of up to 45% at 28 days and reduces shrinkage up to 25% through effective water retention. Fine biochar particles (< 50 µm) enhance the interfacial transition zone, promoting a denser microstructure and improved load transfer. Pre-soaked biochar performs better than dry biochar, particularly in low-moisture environments, by enhancing hydration and strength development. Economically, low-temperature biochar (300 °C) reduces cement composite costs by up to 1.6% while sustainably managing wood waste. Combining biochar with silica fume enhances resilience at high temperatures (500 °C), reducing internal damage and maintaining durability. Despite its potential, challenges remain in optimizing pre-treatment methods, addressing leaching risks, and ensuring long-term durability. This review highlights the transformative potential of timber biochar for sustainable construction, carbon capture and utilization, while demonstrating its ability to balance economic viability with environmental responsibility.