This paper proposes an estimation method of flexural capacity of RC-beams having corroded re-bars, and the method is based on non-destructive inspections. Observing crack width and the drop of wave velocity associated with the re-bars corrosion, the flexural capacity of RC-beams is calculated by substitutions of the reduced re-bar areas estimated from the non-destructive inspections into the formula shown in the Standard Specifications for Concrete Structures of the Japan Society of Civil Engineers. The calculated flexural capacity is checked with results of loading test, and some statistical procedures are studied to obtain conservative flexural capacity overcoming scattered results of the non-destructive inspections.
Imitating reinforced concrete structures received external chloride induced damage located in the coastal area, the exposure test has been carried out for several years. The specimens have been exposed to 10% aqueous solution of sodium chloride on their upper surface. Two kinds of cure conditions are performed to the specimens. The test data have shown that the corrosion rate of reinforcement is increased with the content of chloride ions and the temperature. They also have shown that the corrosion rate is dependent on the quality of concrete. Based on the test data, we have carried out neural network analyses and constructed the equation to evaluate corrosion rate from apparent chloride diffusion coefficient, chloride contents close to reinforcement, and temperature. We applied the equation to upper structures of actual piers. The simulation results coincided with the actual data.
This study is to develop an analysis method to estimate corrosion process that includes initial corrosion and onset of corrosion-induced crack in concrete. The method shall be applied to rationalize durability verification for salt-damaged RC structures. This study illustrates computing corrosion deterioration with consideration of a coupled analysis between structure and reinforcement corrosion. This article also proposes calculation method of macro-cell corrosion with consideration of macro-cell corrosion density and its allocation, focusing on cathode elements. This article validates the proposed analytical method by dry-wet cyclic tests with salt solution to simulate macro-cell corrosion. We conclude the method is accurate by confirming non-uniformity of concrete before the crack, coupled analysis of structure analysis, expansion rate of corrosion products and diffusion factor affect how corrosion start period, initial corrosion crack period and chloride ions density and corrosion amount.
This study first discusses the mechanism of severe deterioration found in RC slab in a cold mountainous region. Based on the discussion, laboratory tests were conducted to clarify the mechanism of composite deterioration caused by ASR and frost attack. The tests investigated the effects of ASR expansion, types of alkali used for accelerating ASR, air content in concrete, and presence or absence, or position, of reinforcement in cross section. The test results showed that repeated cycles of freezing and thawing would cause very severe surface scaling on ASR-deteriorated concrete and continued expansion of concrete despite the low temperature. The deterioration process could not be slowed down by entrained air. The types of alkali used in the tests for accelerating ASR, or whether or not reactive aggregate was used only for the coarse aggregate, had no apparent impact on the degree of degradation.