International Concrete Abstracts Portal

Efficiency of repairs conducted for a jetty damaged by chloride salt attack in Toyko Bay was investigated by field and laboratory tests after five years of repair. Investigation results on durability of surface coatings, chloride ion concentration in concrete, and corrosion of reinforcing bars are presented. Visual inspection, and elasticity or crack bridging ability and adhesion strength to concrete indicated that the durability of surface coatings is sufficient. There is no significant difference in distribution of chloride ion concentration in coated concrete before and after repairing. Dispersion of chloride ion in surface coated concrete was numerically analyzed and the results show that the surface coatings decrease the existing chloride content in surface area as the chloride ions disperse into deeper area by degrees. Reinforcing steels in the coated concrete were found predominantly to be in sound condition, except some did show corrosion where the chloride ion content exceeds a critical value. This investigation also demonstrates the importance of maintenance after repair.

Introduces a typical repair case of chemically attacked reinforced concrete structure. At the present time, the maintenance of reinforced concrete structures is a common and a serious problem for industry in Korea. The structure examined is in a chemical plant that processes sulfates. The repair procedures are described by the following five basic steps: 1) how to find the deterioration, 2) how to determine the causes of deterioration, 3) how to evaluate the strength of the existing structure, 4) how to decide the repair needed, and 5) what kind of repair method and material should be selected. This paper also suggests the future research direction of repair techniques of reinforced concrete structures in Korea

The island of Guam is located in the Mariana Islands chain in the Pacific, approximately 3800 miles west of Hawaii. This small island played an important role in World War II, when it was occupied by the Japanese and recaptured by American forces. In 1978, the war in the Pacific National Historical Park was established to commemorate those involved in the assault and defense of the island as well as Guam's residents during the war. Approximately 100 extant military structures are located within park boundaries. As part of a National Park Service program to preserve the site and its features as an historic park, a survey was made of 12 structures including four pillboxes, four gun emplacements, two bridges, one masonry wall, and one partially submerged latrine foundation. The surveyed structures are all partially or totally constructed of concrete. Some local materials were used in construction, including coral sand, seawater, coconut logs for formwork, and chain link fence for reinforcing in some structures. An on-site investigation conducted in February, 1990, included documentation and assessment of existing conditions, preparation of measure drawings, and removal of samples for laboratory analysis. Observed deterioration included cracks, water leakage, surface erosion, corrosion of embedded steel, spalls, growth of vegetation, soil subsidence, war damage, and adverse effects from visitors. Based on the results of visual inspection and testing, the structures were evaluated and categorized in terms of deterioration and level of required intervention. This information is being used to develop recommendations for repair, stabilization, and restoration.

A six-story reinforced concrete military school building in Ankara, Turkey was severely damaged as a result of a steam boiler explosion in the basement. Damage was localized to the first and second stories. Upper floors survived the explosion with minor cracks even though three basement- and two first-floor columns, together with the connecting beams and slabs, were totally demolished. The building was repaired in 1988 in accordance with the procedure and specifications prepared by the two senior authors. The most critical decision was to allow workers into the damaged building to clear the debris and to set up temporary shoring for final repair. Extensive analyses revealed that nonload-bearing partition walls prevented the collapse of the structure by acting as compression struts and thus providing the reserve strength. The rehabilitation of the building was done at a minimum cost by making intermittent openings in existing partition walls to provide continuity in the slabs that had to be recast and by the utilization of the existing reinforcement.

Strengthening of concrete structures in situ by bonding steel plates to concrete surfaces through epoxy-resin adhesives is now recognized as an effective and convenient method of improving their performance under service loads and increasing their ultimate strength. This paper presents a critical review of the structural behavior of the plated beams with emphasis on the effects of plating on serviceability and ultimate limit states. Problems of premature bond failure are described, and methods of overcoming such failures and insuring full flexural capacity, ductility, and composite action are reported. Resistance to fire hazards and other relevant design considerations are discussed.