Orlando – October 16, 2026 -- A crystalline waterproofing admixture removed roughly 60 days of planned waterproofing work from the rehabilitation of the Dujmovača Tunnel in Split, Croatia, and cut water penetration depth by 83% after ten test cycles, according to Penetron Group.
Redesign followed material shortage and failed adhesion tests
The Dujmovača Tunnel (M604) is part of the Split suburban railway line and is one of two railway tunnels beneath the city center. The rehabilitation targeted waterproofing and drainage to control water ingress. The original design specified a dimpled membrane system to channel inflows through drains and half-pipes into a drainage channel.
Two problems forced a rethink. The specified composite drainage material was no longer available, and shotcrete adhesion tests returned values below the required threshold, said Theodor Mentzikofakis, Managing Director and Partner of Penetron Hellas.
Third design option combined mesh with two extra shotcrete layers
Of three alternatives, two required more implementation steps and raised total construction costs. The third paired reinforcement mesh with two additional waterproofing shotcrete layers: 8 cm over the base layer and a new 10 cm layer on untreated surfaces. The design is meant to create a static arch effect that improves mechanical resistance.
PENETRON ADMIX was proposed for the shotcrete layers and incorporated in late 2025. PENETRON, a topical crystalline waterproofing material, and PENEPLUG, a rapid-setting crystalline compound, were specified to stop active leaks and repair surface cracking in the tunnel walls.
Thicker shotcrete passes shorten work inside a 61⁄2-hour daily window
Penetron says the admixture delivers waterproofing performance comparable to two layers of a sprayed membrane system. It reacts with water and moisture to self-seal cracks.
Crews could apply the shotcrete in a 3+8 cm configuration rather than the original 3+3+4 cm sequence. That change eliminated about 60 days originally allocated for waterproofing works. It also allowed faster rehabilitation within a daily work window limited to 61⁄2 hours.
Testing shows 83% lower water penetration depth
Testing and validation of PENETRON ADMIX SB showed water penetration depth fell by 83% after ten cycles. Mentzikofakis described the admixture as "a cost-effective and time-efficient alternative" to traditional PVC sheet membranes and sprayed waterproofing systems. He added that combining reinforcement mesh with crystalline-enhanced shotcrete also improved mechanical resistance.