OCCURRENCE OF THAUMASITE IN LINING CONCRETE OF OLD-TUNNEL STRUCTURE

摘要

The sampling examination on the lining concrete of a 70-year-old tunnel structure was carried out. The compressive strength and RCPT test on the core samples were also performed. In order to identify product formed in the lining concrete, microstructural observations were conducted on the samples obtained from the lining concrete using x-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. From the results of the examination, it was confirmed the presence of thaumasite formation as well as ettringite formation induced by sulfate attack. Especially, thaumasite solid solution led to a low compressive strength showing cracks and delamination on the surface part of the core samples.