The sustainable management of high-water-content dredged clay represents a major environmental and geotechnical challenge in coastal engineering and waterway maintenance. Traditional chemical stabilization relies heavily on ordinary Portland cement to solidify water-rich sediment; however, excessive free water dilutes hydration ions and weakens mechanical strength development while generating substantial carbon emissions. In the publication appearing in Materials, authors Wenrui Xu, Zichen Zhang, Zhicheng Dong, Hao Li, and Gaofeng Xie investigated corn straw biochar as a functional co-binder to replace a portion of ordinary Portland cement in simulated water-rich dredged clay. By converting agricultural waste into a high-capacity internal curing agent, the research team sought to regulate excessive free water, optimize microstructural evolution, and lower the overall carbon footprint of sediment treatment.

The experimental results revealed that the carbonization temperature and residence timeResidence time refers to the duration that the biomass is heated during the pyrolysis process. The residence time can influence the properties of the biochar produced.   More play a pivotal role in dictating the physical structure and water absorption performance of biochar. When corn straw was pyrolyzed at seven hundred degrees Celsius for thirty minutes, the resulting material developed a honeycomb-like interconnected carbon skeleton with high internal porosityPorosity of biochar is a key factor in its effectiveness as a soil amendment and its ability to retain water and nutrients. Biochar’s porosity is influenced by feedstock type and pyrolysis temperature, and it plays a crucial role in microbial activity and overall soil health. Biochar More. This optimized biochar achieved an exceptional water absorption capacity of nearly fifteen hundred percent of its dry weight. When incorporated into simulated dredged clay prepared at an initial water content of eighty percent, the biochar rapidly sequestered excess free water from the surrounding clay matrix. This immediate water intake reduced the effective water-to-cement ratio around hydration sites, thereby preventing ion dilution and accelerating early cementitious reactions.

Long-term mechanical evaluations demonstrated that replacing thirty percent of ordinary Portland cement with this optimized biochar yielded superior compressive strength compared to cement-only controls. Over a twenty-eight-day curing period, the biochar-amended specimens achieved unconfined compressive strength values reaching one hundred thirty-seven kilopascals, whereas the control specimens stabilized solely with cement reached approximately one hundred two kilopascals. Microstructural analysis via electron microscopy confirmed that the absorbed water within the porous biochar was gradually released as internal curing water during later curing stages. This sustained internal moisture supply promoted continuous cement hydration, resulting in abundant calcium silicate hydrate gels that filled structural pores and coated biochar surfaces.

Beyond mechanical enhancements, the biochar-cement composite demonstrated strong environmental and structural synergies. The physical presence of biochar particles facilitated local clay consolidation through interfacial moisture uptake, creating tightly bound interfaces between biochar, clay, and hydration products. Maintenance of an alkaline matrix environment further supported the formation of stable calcium-rich hydration networks. Life-cycle assessment metrics confirmed that replacing thirty percent of conventional cement with corn straw biochar significantly lowered embodied carbon emissions while improving strength performance. The findings indicate that properly pyrolyzed crop residue can serve as an effective internal curing agent and low-carbon co-binder for sustainable sediment stabilization.

Source: Xu, W., Zhang, Z., Dong, Z., Li, H., & Xie, G. (2026). Corn straw biochar–OPC composites for sustainable treatment of water-rich dredged clay: Internal curing mechanisms, pore-structure evolution, and mechanical–environmental performance. Materials, 19(16), Article 3369.