Developing Sustainable Ultra High Strength Concrete Mixtures Using Spent Foundry Sand

This study presents the development of ultra high strength concrete (UHSC) that has been made more sustainable by usingboth local materials from central Texas and spent foundry sand (FS) from the metal casting industry, which has also been obtainedlocally. This study first describes various trial mixtures tested as well as the specimen preparation techniques investigated that led to thefinal UHSC-FS mixtures. The developed mixtures were proportioned with local constituents to increase the sustainable impact of thematerial by reducing emissions due to shipping as well as making UHSC more affordable to a wider variety of applications. The finalmixture design constituents were: river sand, locally available type I/II cement, silica fume, and spent FS, which was obtained from alocal steel casting company. Multiple variables were investigated, such as the aggregate type and size, concrete age (7, 14, and 28-days),the curing regimen, and the water-to-cement ratio (w/cm) to optimize a UHSC mixture that used local materials and FS. This systematicdevelopment revealed that heat curing the specimens in a water bath at 50 ºC (122 ºF) after demolding and then dry curing at 200 ºC(392 ºF) two days before testing with a w/cm of 0.20 at 28-days produced the highest compressive strengths. Once an optimum UHSCmixture was identified a partial replacement of the fine aggregate with FS was completed at 10%, 20%, and 30%. The results showed anincrease of compressive strength performance at 10% replacement, followed by no change at 20%, and finally a slight decrease at 30%.Developing this innovative material with local materials and FS ultimately produces a novel sustainable construction material, reducesthe costs, and produces mechanical performance similar to prepackaged, commercially, available construction building materials.