SCANNING ELECTRON MICROSCOPE (SEM) STUDIES TO DETERMINE 'GEL' DEVELOPMENTS AS DISTRESS MECHANISMS IN CONCRETE

摘要

The paper discuss four different type of "gel" that may be present in concrete, three distress mechanisms caused by chemical reactions of particular elements in concrete, and the characteristic features observed by using an SEM equipped for X-ray elemental analysis. The three destructive mechanisms are: the formation of magnesium hydroxide, silica gel and ettringite. Using low magnification, all of these may be observed as gel-like materials. Since these formations may involve expansive volume change of the paste that is responsible for destructive cracking and failure of concrete structures, a determination of the expansive mechanism is necessary to ascertain its cause and to develop remedial actions.