This study compares Enzyme-Induced Calcium Carbonate Precipitation (EICP) and Microbially Induced Calcium Carbonate Precipitation (MICP) for repairing external cracks in cement-based materials. Cracks in cement-base members can compromise structural integrity and increase maintenance costs. Thus, cement-base specimens with controlled cracks were treated using EICPs and MICP, with organic and non-organic additives to enhance calcium carbonate formation. Results show that both methods were effective in sealing cracks smaller than 0.35 mm. While incorporated additives improved the overall precipitation effectiveness, influence the crystallite size and altern the morphology of precipitated calcium carbonate. MICP generated more consistent crystal structures, while EICPs resulted in diverse crystal shapes influenced by enzyme sources and additives. Both methods offer promising, sustainable solutions for crack repair, with EICP providing greater flexibility and easier preparation. Presented research gives the comprehensive insights into the field of crack repair via bio-based methods reveals its potential in this area.

The near-surface structural and chemical changes were investigated for pure copper against a tungsten carbide (WC) sphere during high tribological loading. Fundamental stages are identified in the Cu-WC tribo-system: (i) high tribological stress promotes grain refinement to the ultra-fine grains regime in the very beginning; (ii) nucleation of extremely fine (~3 nm) oxygen–enriched Cu nano particles in the near-surface layer and subsequent growth of the Cu ₂O oxide; (iii) formation of continuous nanostructured mixing layer with heterogeneous Cu and O distribution in the late stage. Near-surface mechanical mixing is presumably the main contribution to chemical modifications under high tribological loading. Our findings shed atomic-insights into intricate tribochemical modifications, one of the most intriguing phenomena in material-oriented tribology.