Performance Evaluation of Locally Available Alternative Materials and Industrial By-Products for Sustainable Concrete Production in Sudan

Following the conflict that began in 2023, Sudan faces substantial reconstruction needs, while demolition debris, steel slag, sawdust and quarry fines accumulate with little reuse. This study screened six locally sourced materials—recycled coarse aggregate (RCA), natural pozzolana, air-cooled steel slag (ACSS), sawdust (SD), sawdust ash (SDA) and quarry dust (QD)—as partial substitutes for aggregate or cement in five experimental series, each evaluated against its own control mixture. Slump and compressive strength were measured at 7, 14 and 28 days, and ultrasonic pulse velocity (UPV) was measured in the RCA series. Full replacement of natural coarse aggregate with RCA reduced the 28-day strength by 27% (from 26.0 to 19.0 MPa). Replacing 10% of the cement in this concrete with natural pozzolana restored the strength to 25.3 MPa and increased the UPV from 3.2 to 3.7 km/s. When the strengths were normalised by cement content, the pozzolana gave 1.4–1.5 times the strength expected from dilution alone, Algabaleen QD behaved as an inert filler (ratio 0.99), and SDA performed worse than an inert filler (ratio 0.65–0.83). Soaking the sawdust increased the 28-day strength of concrete with 10% SD from 10.0 to 18.0 MPa, although SD concrete remained non-structural. A consistency screen identified anomalous or inconsistent records in four series, which were excluded from the mechanistic interpretation. The results define source-specific replacement windows for Sudanese materials and the data required before structural use.