Our specialities


Rock support – combination bolts with long service life


Project: New Slussen, Sweden (Bus terminal, one of the largest urban transformation projects in Sweden) Product: Rock Support with combination bolt with long service life  -  PC-Bolt R27/12, PC-Coat. Builder: Stockholm City Contractor: Implenia

Project: New Slussen, Sweden (Bus terminal, one of the largest urban transformation projects in Sweden) Product: Rock Support with combination bolt with long service life - PC-Bolt R27/12, PC-Coat. Builder: Stockholm City Contractor: Implenia

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 standard rebar combination bolts (NC-Bolt) are produced from steel quality HRB-500E according to GB/T 1499.2: 2018, 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 standard NC-Bolt, as demonstrated by tests at SINTEF in Trondheim, Norway. We also offer NC-Bolt in rebar material B500NC according to NS3576-3 and class C according to EN1992-1-1+A1+NA. Both standards fulfil demands according to EN 10080.

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)

Learn more


Learn more about Norwegian Tunneling
See under “Elements of Norwegian Tunneling”:
Temporary and permanent rock bolts in Norway

Other areas


Video introduction to Pretec China – top modern facilities for production of rock support bolts and accessories with long service life. The company is 100% owned by Pretec Group AS.

About Pretec Group

The group companies are manufacturing and supplying products for rock support and water & frost proofing of tunnels, slope stabilization, products for the precast industry, like cast in sleeves, lifting systems, sandwich/connections, welding plates, anchor channels, release agents etc. We also have a program for steel builders and mechanical workshops including tie rods, tension rods, foundation bolts, structural bolts, expansion bolts, hollow bolts, dowels, etc. Our network of dealers offers full on-site service to the general building industry.

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