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During the mid-1970s, there was a boom in the construction industry in Saudi Arabia. To meet the housing requirements, and to furnish the infrastructure needed for a growing industry, construction had to be carried out at a pace unprecedented in the country's history. In the absence of guidelines, concrete specifications from other industrialized countries were used. However, when the structures started to show signs of deterioration within a short fraction of their design life, it was realized that specifications developed for temperate conditions cannot be used in this region. Field and laboratory studies carried out at King Fahd University of Petroleum and Minerals at Dhahran, Saudi Arabia, showed that concrete in this region should not only be designed for strength, but also for durability. Since permeability is one of the most important properties that control the durability of concrete, much emphasis should be given to the production of dense and impermeable concrete. This paper reports the results of an investigation carried out on a number of reinforced concrete structures exposed to underground and seawater conditions that showed serious signs of deterioration within less than 10 years after construction. The paper recommends repair procedures for the damaged structures and future practices to extend their service life.

It has been reported recently that there exists early-stage deterioration in many concrete structures due to salt injury, alkali-silica reaction, freezing-thawing action, and their combined actions. Thus, it will be important to assess the change in quality of the surface layer of concrete because the deterioration often appears on the surface of the concrete by way of cracking or scaling. In this paper, the authors describe the results of field investigations on the state and the cases of deterioration in three seaside concrete bridges located in Aomori prefecture, in the most northern districts of the mainland. Various tests were performed on surface layers of concrete incorporating conventional nondestructive methods. A large amount of chloride ion, in excess of 1 kg/m3 in soluble chloride, had accumulated at the depth of cover, and severe corrosion of reinforcing bars was observed in all bridges. In the case of a reinforced concrete bridge that had been in service for more than 50 years, not only the depth of carbonation and penetration of chloride, but also sulfate intrusion, were deeper than the cover depth. The severe damage caused by alkali-silica reaction was also observed in the pier of a prestressed concrete bridge and newel post of a reinforced concrete bridge. It was possible that the penetration of chloride greatly affected the degree of deterioration due to alkali-silica reaction. The change in quality of the surface layers of concrete brought about by deterioration was assessed successfully by in situ tests based on the pulloff tensile strength, rapid air permeability, and depth of carbonation.

The work described in this paper is part of a research program aimed at quantifying and, if possible, modelizing, the contribution of metallic glass fibers to the durability of thin concrete repairs (about 5 cm) cast on horizontal surfaces. The tests that have been carried out up to now on fresh concrete overlays (0 to 24 hr) indicate that metallic glass fibers can decrease the magnitude of swelling during the first hours after casting. The tests carried out on hardened concrete overlays (on composite specimens kept under Toulouse natural climatic conditions) indicate significant differences between fiber reinforced concrete overlays and plain concrete overlays. Replicas examined with a scanning electron microscope show that microcracks near the interface between the overlay and the base concrete are less numerous when fiber reinforced concrete is used as a repair material instead of plain concrete. Ultrasonic pulse velocity test results are in agreement with these microscopic examinations. A field experiment was also carried out in Quebec, Canada. This experiment proved that normal mixing procedures are sufficient to disperse these fibers if a proper mixing sequence is used (no balling problems occurred). In spite of correct curing conditions, cracks developed after only 2 weeks in the plain concrete overlays, but the fiber concrete overlays are still uncracked after more than 6 months of exposure.

This paper describes repairs on two prestressed concrete pipelines (inverted siphons) that were found to have distressed areas. The distressed areas included disbonded mortar coating, and corroded and broken prestressing wires. The siphons were dewatered, during January and part of February 1991, for repairs and inside inspection. Repairs in areas of major corrosion and broken prestressed wires consisted of removing the earth cover, excavating a limited-length trench under a pipe unit, and completely removing the mortar coating and prestressing wire around the pipe for 360 deg. High-strength steel tendons were placed around the pipe and stressed to the initial prestressing force. Shotcrete was placed over the tendons and anchors, followed by backfilling. The two siphons were returned to service on Feb. 15, 1991. The repairs appear to be successful in restoring the concrete pipe to its initial design strength.

Injection methods for repairing concrete to maintain the integrity of structural members were studied. As a general rule, the lower is the viscosity of epoxy, the longer the setting time and the deeper the grout goes. Further, the deeper the placing, the better the result will be. In the actual case, splitting tension test of core cylinders from repaired sections show that the repair method that adopts a specially designed injector will do better work than that using a conventional one.