Quality Inspection of Shore Approach High-Strength Concrete

A part of the Statpipe Development Project is a landfall for two gas pipelines on the exposed western coast of Norway. The pipelines are placed inside a submerged concrete tunnel which acts as an underwater protecting bridge over the rocky sea bed. The 590 m long tunnel was cast in five separte elements produced in two dry docks. The tunnel starts at a water depth of 30 m and ends up at water level. After seven years in service, cores were drilled from the splash zone element. The testing of the cores included compressive strength, capillary absorption, chloride profile, thin section analyses, X-ray diffraction, scanning electron microscopy and element analysis. The results indicate that in such a low porous concrete, the reaction products between sea water and cement paste will fill up the original low porosity and tighten the concrete so that the ingress of chlorides will cease.