Concrete remains the backbone of modern construction because of its durability and cost-effectiveness. However, increasing demand and the depletion of natural aggregates have heightened sustainability concerns, especially in Nigeria, where large volumes of tested concrete cubes and construction debris are disposed of in landfills. Although recycling construction waste has great potential, the effective use of recycled coarse aggregates (RCA) in structural concrete, especially when properly treated, remains underexplored in developing regions. This study investigated the compressive strength of treated recycled coarse aggregate concrete (TRAC) compared to conventional concrete and untreated recycled aggregate concrete (URAC). The aims include quantifying the amount of usable aggregate that can be recovered from waste concrete and analyzing the effects of treating RCA with 0.1 M concentrated sulfuric acid (H2SO4) and a cement slurry on physical properties. Discarded concrete cubes and cylinders were crushed and sieved to produce 4–35 mm RCA. The aggregates were treated by soaking in 0.1 M H2SO4 and coated with a cement slurry. Three concrete mixes were prepared: TRAC, URAC, and normal concrete. Results indicated that about 78% by weight of usable coarse aggregates could be recovered from crushed waste concrete. Treatment decreased RCA water absorption from 5.2% to 2.2% and increased aggregate density from 2350 kg/m3 to 2480 kg/m3. The 28-day compressive strength tests showed that TRAC reached 24.02 MPa, outperforming URAC at 23.28 MPa and performing similarly to normal concrete at 24.23 MPa. These results showed that treated RCA can produce structural-grade concrete, providing environmental and economic benefits by reducing landfill waste and saving natural resources. The study supports SDG 12 and offers practical insights for engineers and policymakers working toward sustainable and circular construction practices.