Reuse of Waste Foundry Sand from its Interaction with the Bonding Agent Sodium Silicate

Green sand molds are used in metal casting process. However, after heating, activated bentonite present in green sand loses the binding properties, and part of the foundry sand has to be discarded from the process. The ABNT NBR 15.984/2011 standard establishes the management of waste foundry sand (WFS) avoiding disposal in landfills. The objective of this work was to investigate the possibility of reusing the WFS from the study of its interaction with sodium silicate binder. Studies with silica sand and new green sand were performed in order to compare the results obtained with the WFS. The characterization of the samples was performed by measuring compressive strength, by X-ray diffraction, by optical microscopy and by scanning electron microscopy. The results showed that there is an interaction of the sodium silicate with the WFS as well as with the silica sand and green sand.