Abstract
Recently, alkali aggregate reaction, one type of concrete deterioration, has been found frequently throughout the world.
In this work, in order to elucidate the reaction mechanism, scanning electron microscopic observation and electron probe microanalysis were carried out on reaction products on the fracture surfaces of aggregate in concrete. The results clarified that these reaction products are classified into the following three types, i.e.,
(1) Na2O-K2O-SiO2 system,
(2) Na2O-K2O-Ca0-SiO2 system, and
(3)(Na2O)-K2O-CaO-SiO2 system,
based on the chemical compositions. Products of (1) and (2) types are jelly-like materials probably caused by, the alkali-silica reaction, but that of (3) type is rosette-like one probably caused by taking K off layered silicate. From these facts, it is indicated that the latter material is one of the alkali-silicate reaction products, and that this material is characterized by the presence of mica or mica clay mineral in aggregate.
Furthermore, mineralogical compositions of above aggregates were investigated by means of X-ray diffraction technique, giving the results that they had still a little amount of reactive minerals.
