Abstract
The criteria, with which one should be guided at the assessment of the
binding properties of bentonites used for moulding sands, are
proposed in the paper. Apart from the standard parameter which is the active
bentonite content, the unrestrained growth indicator should be taken into
account since it seems to be more adequate in the estimation of the sand
compression strength. The investigations performed for three kinds of
bentonites, applied in the Polish foundry plants, subjected to a high
temperature influences indicate, that the pathway of changes of the
unrestrained growth indicator is very similar to the pathway of changes of
the sand compression strength. Instead, the character of changes of the
montmorillonite content in the sand in dependence of the temperature is
quite different. The sand exhibits the significant active bentonite
content, and the sand compression strength decreases rapidly. The
montmorillonite content in bentonite samples was determined by the modern
copper complex method of triethylenetetraamine (Cu(II)-TET). Tests were
performed for bentonites and for sands with those bentonites subjected to
high temperatures influences in a range: 100-700ºC.
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