Evaluation and Repair of Concrete Structure in Urban Environment: Case Study

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Title: Evaluation and Repair of Concrete Structure in Urban Environment: Case Study

Author(s): D. Bjegovic, V. Ukraincik, and Z. Beus

Publication: Special Publication

Volume: 122

Issue:

Appears on pages(s): 427-450

Keywords: carbon dioxide; concrete durability; damage; environments; evaluation; mortars (material); plasticizers; quality control; reinforced concrete; repairs; serviceability; shotcrete; silica fume; stadiums; Construction

Date: 6/1/1990

Abstract:
A characteristic example of reinforced concrete structural damage in an urban environment after 25 years' service is the east end of a stadium in Zagreb, Yugoslavia, for 11,000 spectators. This paper presents research works that served as a basis for the design of repairs to prolong the structure's service life. The damage is classified by types. The basic causes of the damage are explained with a detailed description of the influence of carbon dioxide from the air on the concrete. The repair design is described. The basic principle in repairing the upper and lower surface of the stand was that the materials and construction methods must be compatible with the existing concrete and also meet durability criteria. The repair design prescribes conditions for the materials, construction methods, and durability criteria. The paper presents preliminary investigations to select the optimum composition of a mortar that complies with the criteria required by the design. The influence of two polymer dispersions based on acryl and latex, as well as the influence of silica fume added to the mortar, are investigated. To repair the stand slab, the selected mortar applied was the cement mortar modified by added silica fume and superplasticizer to obtain a dense and compact composition and increased chemical resistance. The proposed solution for the lower surface was shotcrete improved by special admixtures. In designing the overlay, care was exercised that the additional load should not require strengthening of the stand structure. Acceptance of the repair work performed is outlined.