Improved resistance to water erosion and self-healing capacity of earthen-based 3D printed elements using enzyme-induced carbonate precipitation (EICP)

Abstract Cracking in earth-based construction materials poses significant durability challenges, necessitating sustainable solutions. 3D printing offers efficient, scalable construction with earthen materials, but requires durable, eco-friendly matrices. This study explores enzymatic-induced carbonate precipitation (EICP) using urease to improve water resistance and self-healing in earthen-based 3D printed elements containing cement and rice husk fibers. Urease catalyzes urea hydrolysis, forming calcium carbonate ( $${\text {CaCO}}_{3}$$ CaCO 3 ) to fill pores and seal cracks. EICP was applied as a soil additive for water resistance and as a surface treatment for crack repair. The optimized formulation (1 M $${\text {CaCl}}_{2}$$ CaCl 2 -urea 4 U/L urease, Mod. B1-E4) achieved 25.5% less mass loss than 24. 7% for nonenzymatic controls after 60 min of immersion in water and sealed cracks up to 0.45 mm wide within 48 h. SEM, EDS, and XRD analysis confirmed a reduction in porosity 15% through $${\text {CaCO}}_{3}$$ CaCO 3 formation, which improved resistance to erosion. The formulation yielded 0.75 g of $${\text {CaCO}}_{3}$$ CaCO 3 per reaction cycle, demonstrating efficient biocementation. EICP offers a low carbon alternative for improving the durability of 3D printed earthen structures as a pore-filler and crack-sealer, with potential for sustainable and scalable repairs in construction.