Silica fume-superplasticiser synergy mitigates concrete bioreceptivity to Aspergillus spp

Fungal biodeterioration of concrete infrastructure, particularly by Aspergillus species, poses a significant durability challenge in moisture-exposed environments. This study investigates the mitigation of concrete bioreceptivity through microstructural densification using 15% silica fume (SF) replacement and polycarboxylate-based superplasticizers (PCE). Specimens were characterised using scanning electron microscopy, X-ray diffraction, and capillary porosity measurements, then subjected to controlled inoculation with Aspergillus strains for 28 days. Results demonstrated a synergistic effect of SF and PCE, reducing capillary porosity by 40.6% (down to 4.39%) and significantly enhancing mechanical properties. Critically, while control specimens exhibited robust biofilm development, the modified concrete remained completely free of colonisation throughout the experimental period. This resistance is mechanically attributed to pore refinement, which restricts hyphal penetration (<5–10 μm) and reduces internal water activity. These findings establish that optimising microstructure through mineral and chemical admixtures provides a durable, passive defence against fungal attack in sanitary and hydraulic structures, offering a viable alternative to antimicrobial treatments.