PRETEC NC-Bolt and Pc-Bolt

The combination bolt may be used for most ground conditions, but excluding ground subjected to strain bursting and very large contour convergence. The injected grout improves the corrosion protection provided by the plastic grout pipe and the Pc-Coat. Such bolts are therefore highly attractive for very corrosive environments like subsea tunnels. The end-anchorage with tensioning of the rebar, plastic grouting pipe and the cementitious mortar embedment creates a very stiff system offering extended durability. Any tunnel may cross zones of variable need of corrosion protection for bolts, but to classify the exposure level may be difficult. One mitigation strategy may be to use the well protected Combination Bolt along all of the tunnel length.