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A part of the Statpipe Development Project is a landfill for two gas pipelines on the exposed western coast of Norway. The pipelines are placed inside a submerged concrete tunnel that acts as an underwater protecting bridge over the rocky sea bed. The 590 m long tunnel was cast in five separate elements produced in two dry docks. The tunnel starts at a water depth of 30 m and ends up at water level. The tunnel elements were produced and placed during the summer of 1982. The splash zone element encompassed the following characteristics; 400 kg ordinary portland cement and 32.5 kg silica fume per m3 concrete. The water-cement-sand ratio was 0.36, the slump value was approximately 200 mm, and the 28-day cube strength was approximately 78 Mpa. After 7 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 seawater and cement paste will fill up the original low porosity and tighten the concrete so that the ingress of chlorides will cease. For concrete exposed to seawater, ingress of clorides and risk of reinforcing bar corrosion represents the most severe problem. The tightening effect of seawater in such a high-performance concrete seems to reduce this problem to a minimum.

A survey was conducted of failures of prestressing steel in bridge members exposed to potentially aggressive environments. It appears that the main cause of corrosion of prestressing tendons is the ingress of moisture laden with corrosion-inducing agents. Moisture can make its way to the prestressing steel by penetrating through leaking joints from a deck slab, or by diffusion from the underside of a bridge. Moisture may penetrate through concrete cover, sheathing and grout (or grease in unbonded tendons), as well as through anchorage systems. The rate of penetration of moisture depends primarily on permeability of concrete, type of sheath employed for protection of a tendon, and condition of grout or grease inside the sheath. Brittle fracture of reinforcing steel can occur due to pitting corrosion and/or stress corrosion cracking (SCC). Two types of SCC have been identified in prestressing steel in bridges: hydrogen embrittlement and fatigue corrosion. The rate of corrosion in prestressed concrete components can be minimized by using proper preventive and remedial measures.

Discusses the findings from the study of bond that forms a part of a major laboratory evaluation of the characteristics of repair materials carried out in the Building Research Centre. The important properties of repair patching materials that can affect the bond of a repair, such as shrinkage, thermal movement, compressive, shear, and tensile strength, are evaluated. The importance of surface preparation is also discussed.

The task of providing durable concrete for the construction of industrial structures is complex, not only because the service environment, which is man-made, varies from one industry to another, but quite often because of a combination of a large number of causative, promoting, and accelerating factors. Results of a condition survey conducted on a large number of concrete structures in chemical, fertilizer, and petrochemical industries in India are presented. A multidisciplinary approach to investigating the causes of deterioration involving laboratory and in situ tests, is described, with the help of care studies. Since no specific guidance is available in the relevant codes of practice, a broad classification both in terms of the mechanism and kinetics of deterioration is suggested for such created environments for the design and construction specifications of concrete structures. Methods of protection through structural detailing, workmanship, and materials technology are also outlined.

The Arthur Laing Bridge was constructed in 1975. At a relatively early age of about 6 years it began to suffer damage due to corrosion of the deck reinforcement. A major rehabilitation and resurfacing program was implemented in 1987, which included the installation of a cathodic protection system on about 45 percent of the 21,200 mý deck. This is one of the largest installations of cathodic protection on a reinforced concrete bridge deck. The original deck was milled to a depth of 15 to 25 mm to remove chloride-contaminated concrete. A catalyzed titanium wire mesh anode system was installed on the milled surface after delaminations had been patched. Finally a 50 mm thick low-slump dense concrete overlay was placed. This paper describes the design and construction of the cathodic protection system. Technical details of the cathodic protection and overlay system and construction costs are also presented.