科研之友
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摘要
A durability investigation has been conducted on the actual tunnels locating at Kunming Section of Chengkun railway line. Appearance of concrete deterioration was recorded by a Nikon camera. In some representative locations, concrete cores were taken from Shot-concrete or bulk concrete with a hand-held coring rig. The eroded residuals and water around the coring site were collected for further investigations in laboratory. XRD and EPMA analyses were conducted to identify the facts of destructive course. Site investigation shows the lining concrete is subjected to a serious deterioration including salt crystallisation, leaking, surface powdered and flaked, etc. Further investigations in laboratory corroborate the major deterioration, i.e. carbonisation, the chemical erosion and physical attack by sulphate ions, etc. Elements distributions declare that carbonisation has notable evolvement of concrete properties and leads to the movements of sulphur and sodium elements. The sulphur migrates from neutralised area to alkaline area while the sodium moves along the opposite direction. EPMA analysis identifies that the aggressive sulphur ions are sourced from the external environment.
