Possibilities of waste binder reclamation using the example of moulding sands with water glass hardened by the conventional drying process

The article presents the results of preliminary studies on the possible application of innovative activation treatments of inorganic binders during the reclamation of waste water glass moulding sands hardened by conventional drying. The test moulding mixture based on silica sand and selected sodium water glass in grade 145 was subjected to the following processing steps: mixing of components, compaction, drying at 100°C for hardening, cooling, thermal loading of mould up to a temperature of 800°C, cooling to ambient temperature, knocking out, and dry or wet mechanical reclamation to restore the sand mixture binding properties. Several waste sand processing techniques were chosen; they use, among other things, various surface phenomena usually accompanying the mechanical reclamation combined with dedusting of the thermally reacted binder separated from the base silica sand grains. Studies also covered possible use of some elements of the wet reclamation process to rehydrate the thermally reacted binder. To check the effectiveness of the proposed methods of activation, after their implementation, selected strength parameters were measured. Studies disclosed, moreover, the importance of the type of device used for the activation and dust removal during the preliminary reclamation of moulding sand. The possibility of restoring partially the binder ability to bond the waste and properly processed moulding sand containing sodium silicate has been confirmed, providing physical methods which are applied for its hardening. The results of conducted tests, including examination of the surface of sand grains in the reclaimed mixture, allowed selecting the best method that can be used for the waste moulding sand treatment in an innovative process of the periodical sand rebonding. The results of tests highlight the possibility to use an eco-innovative method of rebonding the moulding sands with inorganic binders hardened by physical means and make them an alternative technology for the traditional system sands.

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