Abstract
When the rock involved in the alkali-aggregate reaction (AAR) is volcanic, the matter present in the interstices of the grains, called mesostasis is considered responsible for the expansions. Mesostasis is a residue which consists of mineral phases rich in silica and alkalis (K and Na) and in optical microscopy looks like amorphous matter. By means of scanning electron microscopy (SEM) and with the aid of energy dispersive spectroscopy (EDS), the presence of well-crystallized mineral phases in mesostasis can be observed. The objective of this study was to evaluate the amount, the chemical composition and the degree of crystallinity of mesostasis on the reactive potentiality of volcanic rocks.
Highlights
Mesostasis originates from the abrupt cooling of magma when volcanic rocks form
The name microcrystalline mesostasis was given to the matter of low crystallinity, rich in silica and alkalis, and accompanied by small grains of hematite and needles of apatite, since optical microscopy cannot individualize grains of quartz or feldspar
The mesostasis with better crystalized grains is the one where there is dissemination of quartz grains that can be visualized in optical microscopy, associated to the matter that consists of feldspar, clay minerals and apatites
Summary
Mesostasis originates from the abrupt cooling of magma when volcanic rocks form. It consists of micro-tocryptocrystalline phases, which in optical microscopy look like amorphous matter and is often confused with volcanic glass. In an alkali-aggragate reaction with basic rocks being used, alkalireactive phases appear to be in mesostasis state. Alkaliaggregate reaction develops when the silica present in aggregates reacts with the alkali hydroxides coming from cement. There seems to be no direct relationship between the amount of microcrystalline, or amorphous matter present in the rocks and the expansions resulting from the alkali-aggregate reaction (AAR) [2].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
