Our specialities


Rock support – combination bolts with long service life


We produce and offer to the market rock anchor bolts with particularly long service life using PC-CoatTM corrosion protection (hot dip galvanizing, zinc manganese phosphating and epoxy powder coating). In order to fully control product quality to very high standards, manufacturing is completely done in our own premises, both mechanical production as well as all steps of corrosion protection.

We are producing two types of combination bolts, NC-Bolt and PC-BoltTM. Combination bolts are effective for immediate work protection at the face after torque tensioning, and when later fully grouted, can be classified as permanent support. Workers are installing rock bolts in the face area while grouting of the bolts takes place at a convenient time and distance behind the face (typically about 50m). Combination bolts contribute to efficient tunnel advance and when needed, we also offer self drilling anchors (SDA), either HDG- or PC-CoatTM protected.

Our rebar combination bolts (NC-Bolt) are produced from HRB-500E steel quality, which has uniform homogenous properties throughout the cross section of the steel bar. Most rebar steel is of the so-called TempCore type, which means that the outer part of the cross section has higher strength than the core. When threads are applied to a rebar, the strength of TempCore rods will be more influenced negatively than our NC-Bolt, as demonstrated by tests at SINTEF in Trondheim, Norway.

The main benefit of using our combination bolts is still that all immediate support can be made part of the permanent support when combined with sprayed concrete. For hard rock tunnels, typically more than 90% of the tunnel length can be permanently lined this way, replacing temporary sprayed concrete and the additional permanent in-situ concrete lining. For D&B tunnels, the use of concrete materials can be reduced by about 2/3, which represents a major reduction of CO2- footprint for a tunnel. The likely and significant reduction of construction time and cost should also be considered.

Presentation of combination bolts for download: PowerPoint or PDF.
Installation video of PC-BoltTM and NC-Bolt.

For further information, please contact our sales team:
Erik A. Karlsen, erik@pretec.no, +47 977 13 810 (UTC +1)
Even A. Karlsen, even@pretec.no, +47 908 45 246 (UTC +1)
Tony Tang, tony@chinapretec.com, +86 139 6735 8765 (UTC +8)

Catalogues relevant for the Rock Support segment using Combination Bolts with long service life.

NC-Bolt Catalogue

NC-Bolt Catalogue

Pc-Bolt Catalogue

Pc-Bolt Catalogue

Pc-Coat catalogue

Pc-Coat catalogue

Grouting Catalogue

Grouting Catalogue

Testing Catalogue

Testing Catalogue


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