Development of Method for Measuring Residual Expansion of Cores Taken from Concrete Structures Affected by ASR

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This study developed an accelerated test method to judge the residual expansivity of concrete affected by ASR at the early stage. The current method, which measures the residual expansion of the concrete core, does not correspond to environments where seawater deicing salts, etc. penetrate concrete and promote ASR. Therefore, we addressed this problem by examining an accelerated test method with which the concrete cores were immersed in an NaOH or NaCl solution.The following results were obtained:1. Effect of Storage TemperatureASR expansion became small when the storage temperature rose excessively in the low solution concentration, but it increased with rising storage temperature in the high solution concentration.2. Effects of Kind of Solution and its ConcentrationASR expansion became small when the solution concentration rose excessively at low storage temperature, but it increased with rising solution concentration at high storage temperature. The core immersed in the NaOH solution generated larger expansion at the early stage than the core in the NaCl solution.3. Effect of Initial Alkali Content of ConcreteASR expansion of the core with a higher initial alkali content before immersion in the NaOH solution was larger.4. Effect of Degree of Concrete Deterioration due to ASRFor the concrete immersed in the NaOH solution, when the deterioration of the concrete had progressed more before the start of the test, the ASR expansion of the core after the start of the test became smaller.5. Proposal of Accelerated Curing ConditionBased on the results obtained within the range of this study, an acclerated curing condition was proposed to judge the residual expansivity of concrete at the early stage.