Effect of foundry waste on the mechanical properties of Portland Cement Concrete

Approximately 6-10 million tons of waste is produced annually by the ferrous and non-ferrous foundry industry in the United States and estimates have shown that only 15% of the waste produced is being recycled. The increasing scarcity of landfill space and disposal cost has fashioned a need for an alternative disposal method of this large industrial waste. Foundry waste can consist of many products such as used-foundry sand, slag, ash, refractory, coagulant, baghouse dust, pattern shop waste, and debris. Past researchers have presented an alternative disposal method by using spent sand and slag as constituents in concrete with positive results. This paper generalizes the foundry waste for use in Portland Cement Concrete (PCC) in order to increase the recycling percentage, by reducing processing time/cost and using all the waste produced by the foundry industry. This was done by partially replacing both fine aggregate and coarse aggregate of concrete with lightly processed foundry waste. Since foundry waste contains both fine and coarse materials, the as-received foundry waste was lightly processed and sieved to match the control concrete mixtures coarse and fine aggregate distribution. Both virgin coarse and fine aggregate were replaced by mass at 10%, 20%, and 30%. Two mixture groups replaced individual constituents separately (coarse and fine), and one mixture group replaced both coarse and fine in the same mixture. The compressive strength, splitting-tensile strength, flexural strength, and modulus of elasticity were measured for all groups at 7, 14, and 28 days. The results indicated that general foundry waste as either coarse, fine, or combined by mass replacement of natural aggregate has no impact on the mechanical performance of PCC up to 30% for individual replacement or 20% combined. This result not only demonstrates a possible avenue to increase the amount of foundry waste recycled annually, but it also reduces the demand for virgin aggregates for PCC.