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This study presents the hydration reactivity and alkali silica reaction (ASR) of ultrahigh strength concrete (UHSC) that has been made more sustainable by using spent foundry sand. Spent foundry sand not only is sustainable but has supplementary cementitious material (SCM) characteristics. Two series of UHSC mixtures were prepared using a nonreactive and reactive sand (in terms of ASR) to investigate both the impact of a more reactive aggregate and the use of spent foundry sand. Conduction calorimetry was used to monitor the heat of hydration maintained under isothermal conditions, while ASR was investigated using the accelerated mortar bar test (AMBT). Additionally, the compressive strengths were measured for both series of mixtures at 7, 14, and 28 days to confirm high strength requirements. The compressive strengths ranged from 85 MPa (12,345 psi) to 181.78 MPa (26,365 psi). This result demonstrates that a UHSC mixture was produced. The calorimetry results revealed a slight acceleration in the heat of hydration flow curve compared to the control from both aggregates indicating increased hydration reactivity from the addition of foundry waste. The combination of foundry sand and reactive sand was found to increase ASR reactivity with increasing additions of foundry sand up to 30% replacement.

The ferrous and non-ferrous foundry industry produces approximately 6 million tons of foundry sand (FS) waste annually in the United States and estimates have shown that only 15% of the waste is being recycled. This study utilized FS waste in the production of Ultra High Strength Concrete (UHSC) as a partial replacement for natural sand. Natural sand was replaced with FS at the replacement levels of 0%, 10%, 20%, and 30% by volume. UHSC mixtures produced were tested to determine the compressive strength, splitting tensile strength, flexural strength, elastic modulus, and Poisson’s ratio at 7, 14, and 28 days. The results showed an increase in mechanical performance up to 10% FS replacement. The results also indicate an insignificant decrease in mechanical performance at 20% replacement levels. FS had no significant impact on the Poisson’s ratio of UHSC.