Spent Foundry Sand (SFS) generation is intrinsic to metal casting processes. Most of the foundries use sand moulds and cores for casting, which are discarded after pouring. That generates large amounts of waste sand,... [ view full abstract ]
Spent Foundry Sand (SFS) generation is intrinsic to metal casting processes. Most of the foundries use sand moulds and cores for casting, which are discarded after pouring. That generates large amounts of waste sand, representing approximately 60-85% of total solid waste from the foundry industry. Landfill of foundry sand remains a severe environmental problem in Europe due to its significant quantity. Besides, it is a lost opportunity, as it represents a huge amount of available material with very interesting properties (valuable silica mineral) for potential recycling that is missed.
Use of SFS as secondary fine aggregates in a material intensive sector such as construction offers promising valorisation options. The sand must meet relevant technical specifications for each application and, additionally, fulfil several environmental conditions for unbound uses, where the sand is directly in contact with the soil. The LIFE ECO-SANDFILL project is investigating the use of SFS as fine aggregate in construction applications, specifically for geotechnical applications (embankments) and for flowable mortars and Controlled Low Strength Material (CLSM).
To this end, a prototype of a novel mechanical SFS reclamation system, based on attrition of the sand grains by means of centrifugal force, has been constructed and integrated in the moulding sand circuit of a steel foundry located in the Basque Country (ES). The SFS generated in the foundry, after metal parts casting and de-moulding, is being treated in the prototype to remove impurities from binders and the casting process and to make the reclaimed sand reach the required quality for the different applications envisaged in the project. The environmental, technical and economic performance of the solution will be validated in three full-scale case studies to be executed in the construction works for the High-Speed Train Madrid-Irun in the vicinity of the foundry (distance = 20 km) and through a pilot casting trial of steel parts in the foundry itself, using reclaimed sand in the manufacture of the moulds.
This paper describes the preparatory activities carried out before executing the three construction demos, focused on dosage studies and characterisation tests of sand samples and construction products specimens manufactured using SFS (untreated and reclaimed) in their formulations. From the chemical analysis results, it has been concluded that the reclaimed sand obtained in the integrated prototype coupled to the chemical sand circuit of the foundry fulfils environmental conditions for construction applications and could be safely used in mortar, CLSM and embankment demos. Further physical-chemical tests are in progress to evaluate if they meet UNE EN 13139 technical requirements for mortar aggregates and/or PG-3 specifications as tolerable soil for embankments. Considering the preliminary results, it is expected that in mortars the substitution of natural aggregate is up to 50%, and in the case of CLSM around 100%. Promising results are also being obtained regarding the properties of reclaimed SFS as filling material for embankment.
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