PROJECT DESCRIPTION
BACKGROUND
There are around 3 000 active foundry operations in Europe that annually generate over 9 million tonnes of waste sand, with ferrous industries the major generators. Only 25% of this Spent Foundry Sand (SFS) is recycled for a few applications, mainly by the cement industry, but these sectors are unable to absorb the total amount of sand generated so the remaining 75% is landfilled. The global warning potential of sand extraction (quarrying and dredging) and processing is between 92-120 g CO2 eq. per 1 kg of dry silica sand obtained. Air pollutants are emitted by the extracting equipment (usually diesel), and noise is a common occurrence due to extraction and transportation. Sand extraction involves considerable land take and loss of soil (estimated at 0.4 ha per tonne of sand extracted), with associated loss of wildlife habitat. The re-use of foundry sand would minimise these impacts.
OBJECTIVES
The LIFE ECO-SANDFILL project aimed to demonstrate the technical and economic feasibility of using Spent Foundry Sand (SFS) as an eco-friendly fine aggregate in construction applications. The goal was to reduce the large volume of foundry sand annually sent to landfills. The mechanical process, demonstrated for the first time in Europe, would treat up to 1 500 tonnes of SFS in a pilot plant integrated into a foundry in the Spanish Basque Country. The new product was intended to be used as fine aggregate for three different construction applications: embankments, mortars and as Controlled Low Strength Material (CLSM). The proposed technology would perform better than existing technologies in terms of sand impurity removal, and from an economic perspective it is expected to reduce foundry sand management costs by 40% and construction industry raw material costs by 30%, while establishing a green economic activity with potential for job creation. The ECO-SANDFILL technique is suitable for all type of sands and moulding systems, and it has high replicability potential. The projects objective of reusing a waste stream to divert it from landfill is in line with the Roadmap to a Resource Efficient Europe and the 7th Environment Action Programme (EAP).
The specific objectives were to:
- Demonstrate that SFS correctly pre-processed can be re-used in construction applications with a high demand for fine aggregates;
- Obtain non-hazardous sand as a safe by-product from waste;
- Contribute to close to zero main solid waste from foundries being sent to landfill and to reverse the trend of new sand excavation from virgin land; and
- Stimulate industrial activity and increase competitiveness in several sectors (e.g. casting, construction and waste management).
RESULTS
The LIFE ECO-SANDFILL project team constructed a prototype of a novel mechanical Spent Foundry Sand (SFS) reclamation system, based on attrition of sand grains by means of centrifugal force. This prototype was integrated in the moulding sand circuit of ESTANDA steel foundry located in the Basque Country (Spain).
Preparatory project actions established the optimal operating conditions of the prototype, by reconciling minimal environmental impact of the reclamation process with the necessary properties required for the reclaimed sand.
The SFS generated in the foundry in the de-moulding step was treated in the prototype to remove impurities from binders and from the casting process, enabling the reclaimed sand to reach the required quality for reuse in various applications. However, the planned three full-scale demonstrations of construction applications could not be performed (due to authorisation to use railway infrastructure being withdrawn).
Testing in three mould-casting trials confirmed the viability of the ECO-SANDFILL reclaimed SFS as a substitute for the thermally-reclaimed SFS that ESTANDA uses as facing sand in moulds for high-end castings. However, supplementary addition of resins was needed and mould-making time increased.
Two demonstrations were carried out in buildings under construction, to validate the use of the reclaimed SFS as a partial substitute for natural fine aggregates in screed mortars for two different applications (6 t SFS valorised). The monitoring of the demonstration mortars over 1 year revealed no sign of mechanical deterioration for the sand substitution of up to 20% of the original material. Laboratory results indicated that even 35% substitution could ensure durability, if aggregates grading is observed.
The project team produced guidelines for the use of the reclaimed sand as a secondary aggregate in construction applications, to guarantee quality and environmental safety, based on the lessons learnt from the project demonstrations and research on the performance of SFS as aggregate.
Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).
