J. Pallavi, S. Mandal
Texas State University,
United States
Keywords: ceramic powder, metallic waste, sustainable concrete, mechanical properties, workability
Summary:
Cement production is one of the leading sources of global CO₂ emissions and resource depletion. As one of the most expensive components of concrete, reducing cement usage is a key priority in sustainable construction. This study investigates the potential of ceramic powder (CP), an industrial waste rich in silica, alumina, and calcium oxide, as a partial replacement for Portland cement. Due to its pozzolanic nature, CP reacts with calcium hydroxide during hydration to form additional calcium silicate hydrate (C–S–H) gel, improving concrete strength and durability. Cement was replaced with CP at levels of 0%, 4%, and 6% using a standard concrete mixer, and the resulting mixes were evaluated for workability and compressive strength. The concrete with 4% ceramic powder replacement achieved a strength of 31.65 MPa, compared to 28.78 MPa for the control mix, showing an increase of about 9.97%. Hence, replacing cement with 4% CP produced the optimal concrete strength compared to normal concrete. Workability with 4% CP was better than the control and 6% mix. It retained the same compaction factor (0.97) as the control, but with acceptable workability as illustrated by the Vee-Bee time of 16 seconds, which is slightly stiffer but still workable concrete. Though the slump value (20 mm) was small compared to the control (48 mm), it indicates that there was better cohesion and less segregation. 4% CP is the ideal balance between workability and strength. To further improve sustainability and multifunctionality, this study proposes the incorporation of hydrochar and recycled metallic waste into CP-modified concrete. Hydrochar, derived from biomass through hydrothermal carbonization, is a carbon-rich, porous material that can enhance internal curing, reduce water permeability, and improve thermal insulation due to its low thermal conductivity. Moreover, it acts as a partial carbon sink, thereby offsetting part of the CO₂ footprint of cement production. On the other hand, incorporating recycled metallic wastes, such as aluminium or copper shavings, can increase the thermal reflectivity and radiative heat dissipation of the concrete surface. These metals reflect incident solar radiation, reducing heat absorption and surface temperature, which in turn can decrease indoor air-conditioning loads in buildings. Additionally, metallic inclusions may enhance the microstructural integrity and crack resistance of the concrete through mechanical interlocking effects. Hence, the combination of hydrochar, and recycled metallic waste presents a novel pathway toward the development of eco-reflective, thermally efficient, and low carbon concrete that not only preserves natural resources like limestone and clay but also contributes to energy-efficient and sustainable infrastructure.