Resumen
Waste foundry sand (WFS) is a ferrous and non-ferrous foundry industry by-product, produced in the amount of approximately 700 thousand tons annually in Poland and it is estimated that only a small percentage of this waste is recycled. The study used WFS to produce ultra-high performance concrete (UHPC) as a partial substitute for quartz sand. It was replaced with WFS levels of 0%, 5%, 10%, and 15% by weight of quartz sand content. The UHPC mixtures were produced and tested to determine the compressive strength, flexural strength, splitting tensile strength as well as the modulus of elasticity at 28, 56, and 112 days. Scanning electron microscope (SEM) analysis was done to identify the presence of various compounds and micro-cracks in UHPC with WFS. The results revealed an increase as well as an insignificant decrease in the mechanical properties up to 5% and 10% WFS replacement, respectively. These studies also prove improvement in the microstructure of UHPC up to a 5% WFS level. In all the tested properties in this work, 5% WFS was found to be an apt substitute for quartz sand.