Crushing character of sand-sodium-silicate mixtures structured by steam-microwave treatment

Abstract

At the present, from among the known methods of sand-sodium-silicate mixtures structuring, the least studied, but the most promising, is the method of steam-microwave solidification. Among unexplored elements of steam-microwave solidification method is nature of mixtures destruction. This is especially important for determining the ways to increase the sand-sodium-silicate casting molds and cores strength before pouring and lowering their strength by the time when casting should be knocked out the mold and the core from cast product. Knowledge about mixture destruction nature is also necessary for appropriate technical solutions elaboration concerning sand regeneration. In this regard, the purpose of the present work has to be nature of sand-sodium-silicate mixtures structured by steam-microwave solidification method destruction establishing. Quartz sand cladded with sodium-silicate solute has been used in the present investigation. Mixture (cladded sand) structuring has been carried out by microwave radiation at nominal magnetron power of 700 W and radiation frequency of 2.45 GHz in area of standing waves. To cladded sand structuring, 1 g water portion has been added, which has been placed in bottom of container in which mixture has been microwave treated. To make decision on mixture destruction nature, images of structured mixtures destruction places within one grain (sand grain), which are typical for adhesive and cohesive character of destruction, obtained with scanning electron microscope have been used. It has been found that with sodium-silicate solute for quartz sand cladding mass content from 0.5 to 6 % (by weight) increasing, as well as with mixture processing by the method of steam-microwave solidification duration increasing, mixture compression ultimate strength increases according to dependence closed to exponential. Character of structured mixture destruction, in this case, is not depend on sodium-silicate solute used for quartz sand cladding content, but depends on steam-microwave solidification duration. With its time increasing it changes from adhesive to mix or from adhesive to mixed and cohesive.