As landfill space becomes scarce and disposal costs increase, alternative uses for foundry sand are sought to avoid landfilling. Many research projects have shown that foundry sand can successfully be used as a fine aggregate in geotechnical applications. Controlled low strength material, or flowable fill, is a slurry backfill used to fill trenches, abandoned pipelines, underground voids and to replace poor quality soil. Flowable fill is composed predominantly of fine aggregate, making it an attractive application for foundry sand reuse. However, since foundry sand composition varies from one generator to the next, its properties and behavior in flowable fill must be characterized.
Current practice calls for evaluating each foundry sand on an individual basis.
If foundry sands can instead be grouped into categories based on performance in flowable fill, generators and users can eliminate costly mix design and thus enhance the marketability of this by-product. A number of different foundry sands, representative of the foundry sands used in Wisconsin, were mixed with portland cement, fly ash, and water to create flowable fill. First, components were mixed in various proportions until a minimum flow was achieved. Second, mixes were tested for strength and strength gain over time with unconfined compression tests. Achieving some minimum strength is required to accept loads such as pavement and traffic.