Partial Replacement of Fine aggregates with Pozzocrete Foundry sand and Cement with Hypo Sludge

The disposal or potential recycling of foundry sand constitutes a major economic and environmental problem for the paper and board industry. In the India approximately 1 metric tonnes of foundry sand are produced annually. Whilst the main alternatives to land filling are the use of the sand as a fuel and its land-spreading as agricultural fertilizer, further outlets for this waste (or by-product) material are needed. The presented research investigated the use of foundry sand produced by the incineration of the sand, as a partial fine aggregates replacement for pozzocrete production. OPC production is responsible for approximately 10 % of the global carbon dioxide emission caused by anthropogenic activity. Therefore the need to use alternative, less energy intensive cementitious materials for concrete is imminent. In the present study a series of tests were performed on pozzocrete mixes in which aggregates was partially replaced by Foundry Sand, in order to identify the best mixes that could also allow for the highest OPC replacements. Mixes were also made in which in addition to PSA other constituent binders such as Ground Granulated Blast Furnace Slag (GGBS), or metakaolin were used to prevent potential deleterious reactions and the production of expansive products by consumption of CaO, leading to concrete unsoundness. The tests investigated a number of fresh and hardened concrete properties including workability, density, compressive and tensile strength as well as the soundness of the resulting cement. The results showed that the sand can partially replace Pozzocrete and that when used at modest Pozzocrete replacement levels it can actually improve the concrete strength compared to regular concrete. It can therefore be concluded that the foundry sand can be used to partially replace aggregates with overall environmental advantages (discussed in the paper) and at the same time have a beneficial effect on properties of the resulting concrete.