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This study documents the current practices for overlaying horizontal concrete surfaces as a first phase in the development of performance criteria for concrete overlays. The case histories presented were typically for overlays completed within the last 10 years and located at Corps of Engineers civil works projects. Overlays documented included bonded conventional, low-slump, fly-ash, silica-fume, polymer-modified, and fiber-reinforced concretes. Unbonded overlays were also documented. Although the information obtained for each case history varied and was sometimes limited, an attempt was made to provide the following basic information for each repair: (a) project description, (b) cause and extent of damage, (c) description of repair materials and procedures, (d) cost, and (e) performance of repair. The extension of service life resulting from using one type of overlay in lieu of another was not evident in the case histories examined, with the exception of where fiber-reinforced concrete was used to resist abrasion erosion (repair failed). Shrinkage and reflective cracks that develop in polymer-modified concrete overlays and overlays containing polypropylene fibers are more likely to be smaller in width and length than those of similiar cracks in conventional and low-slump concrete overlays. Cracks in concretes containing fibers are generally smallest.
This study was conducted to identify methods that have been used in the repair and rehabilitation of concrete dams. Information was obtained through literary searches, discussions with project personnel, and visits to project sites. Each case history includes a background of the project, the deficiency that necessitated repair or rehabilitation, and descriptions of materials and methods used in the repair or rehabilitation. When available, the cost of the repair project and the performance of the repair to date have been included. Case histories included in this report cover a range of deficiencies in concrete structures, including cracking, spalling, erosion, leakage, inadequate PMF capacity, expansion resulting from alkali-aggregate reaction, instability, and insufficient storage capacity.
Presented are the results of a program conducted to identify the repair methods and materials currently being used to repair and rehabilitate concrete structures deteriorating as a result of cracking and spalling. These repair methods and materials were evaluated for their applicability to the in situ repair of concrete hydraulic structures. From this evaluation, the following three repair techniques were identified as best suited for in situ repair procedures: pressure injection, polymer impregnation, and addition of reinforcement. Case histories illustrating the application of each technique are presented. Recommendations are made for work to be performed to make these systems more applicable to the repair of hydraulic structures. Keywords: Concrete, Cracking, Hydraulic structures, In situ repair, Polymer impregnation, Post reinforcement, Pressure injection, Spalling.
The surfaces of many of the Corps' concrete structures are subject to deterioration due to freezing and thawing, weathering, chemical attack, erosion, and other destructive mechanisms. Surface treatment of the concrete with a material to retard action of the forces is one way to reduce the rate of or eliminate deterioration. In the past, various surface treatments have been applied to concrete; some were successful, while others failed. In most cases the failures were due to either selection of the wrong surface treatment material or improper application. There is a need to evaluate various surface treatments to determine which would offer the best protection and what would be the proper ways to apply them. The objective of this study was to obtain information on the types of current surface treatment materials available, chemical compositions, and properties, and the performance of these materials in service conditions. Keywords: Abrasion, Erosion, Coating, Hydraulic structures, Concrete deterioration, Sealers, Surface treatments, Stone consolidants, Vapor transmittance.
This manual provides guidance on evaluating the condition of the concrete in a structure, relating the condition of the concrete to the underlying cause or causes of that condition, selecting an appropriate repair material and method for any deficiency found, and using the selected materials and methods to repair or rehabilitate the structure. Guidance is also included on maintenance of concrete and on preparation of concrete investigation reports for repair and rehabilitation projects. Considerations for certain specialized types of rehabilitation projects are also given.