Assessment of blended cement containing waste basalt powder: physicomechanical and electrochemical impedance spectroscopy investigations.

Basalt powder (BP) is the residue of a plant that crushes basalt stones. This work deals with the effect of waste BP on the properties of cement mortars and the physical properties of hardened mortars. Modified concrete was prepared by partial replacement of BP in amount of 5, 10, 20% by weight of cement. Physico-mechanical properties and corrosion resistance were investigated. Electrochemical impedance spectroscopy (EIS) was used to examine the corrosion behavior of cement pastes with a partial addition of basalt powder in aggressive solutions of 5% NaCl and 5% MgCl₂ for up to 270 days. Infrared spectroscopy (IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were also performed to investigate the hydration process and microstructure formation of the basalt blended paste. Results indicate that the addition of basalt powder as a partial replacement of cement influences the microstructure of the interfacial transition zone (ITZ), which is denser and stronger than in cement paste without basalt powder. The filler effect of the basalt powder improves the compressive strength of cement paste. Also, comparing BP0 and BP20 in 5% NaCl after 270 days, the partial substitution of cement with BP resulted in a higher compressive strength of 671 and 895 kg/cm², respectively. The EIS results also showed the highest values of R_p 953 ohms cm² after 270 days. This high corrosion resistance might indicate the binding by high Al₂O₃ that reduced the free aggressive chloride ions in the solution. Article Highlights: The addition of basalt powder as a partial replacement of cement, improved the compressive strength of the concrete. The physicochemical and mechanical investigations showed that the basalt addition led to physical densification and more ITZ robust of cement matrix. EIS measurements showed that BP20 sample in 5% NaCl had a high R_p, 953 ohms cm² after 270 days indicated higher corrosion resistance. [ABSTRACT FROM AUTHOR]