Developing High-strength, Flowable Sand Concrete by Adding Combined Industrial Ceramic and Granite Waste with Seashell Bio-waste as Fine Aggregates

Due to its large consumption of raw materials and high construction work rates, the building industry presents one of the most effective potentials for the use of recycled materials. In an attempt to maximize landfill waste valorization and enhance concrete properties, this study investigates the combined use of industrial ceramic waste (CW) and granite waste (GW) with seashell bio-waste (SW) and their effect on the physical and mechanical properties of flowable sand concrete (FSC). For this, seven FSC mixtures were manufactured by partially replacing natural sand with different amounts of CW, GW, and SW combinations (0, 5, 10, 15, 20, 25, and 30 wt%). The results showed that up to 30% recycled aggregates could be utilized while maintaining the fresh properties of all FSC mixes. Compressive and flexural strengths as well as ultrasonic pulse velocity were significantly improved by 40%, 90%, and 6%, respectively. Both water absorption and porosity were reduced by 20% with the simultaneous addition of 30% recycled aggregates, compared to the reference concrete. Furthermore, the scanning electron microscopy analysis of some FSC mixes showed that the microstructure of FSC was enhanced with a stronger bond between the cement paste and aggregates when the three recycled aggregates were included in amounts of up to 30%. Finally, the results are encouraging when CW and GW are used simultaneously with SW in developing high-strength FSC, allowing the replacement of up to 30% of fine aggregates for sustainable construction.