Crystalline Shotcrete Revitalizes Croatia’s Dujmovača Tunnel

The Dujmovača Tunnel, a vital artery on the M604 suburban railway line, required a comprehensive upgrade to address persistent water seepage and structural performance issues. Original plans for a dimpled membrane system proved impractical after supply chain disruptions for composite drainage materials and poor adhesion test results forced a design pivot. Theodor Mentzikofakis, Managing Director of Penetron Hellas, oversaw the shift to a system that paired reinforcement mesh with specialized shotcrete layers.

The revised strategy utilized a 3+8 cm and 10 cm shotcrete configuration treated with the crystalline admixture, which functions by reacting with moisture to self-seal cracks. This chemical approach provided waterproofing capabilities equivalent to dual-layer sprayed membranes. The simplification of the application process allowed crews to work within tight 6.5-hour daily windows, ultimately recovering two months of lost time. Validation testing confirmed the effectiveness of the modification, showing an 83 percent reduction in water penetration depth over ten cycles. The project also employed PENEPLUG, a rapid-setting compound, to stabilize active leaks in the tunnel walls.