In this work, the experimental data of four eco-friendly soil stabilizers—recycled concrete aggregate (RCA), recycled aggregate concrete (RAC), Class F fly ash, and nano-MgO— used for low plasticity clay (CL) are synthesized in a comparative manner. A well-organized secondary database was developed for OMC and MDD, UCS, soaked CBR, ultimate bearing capacity, and settlement. Differences between studies were controlled by limiting the data to similar test conditions and calculating changes from each source study’s respective untreated control. OMC was raised by the fly ash from 17.2% to 20.2%, while MDD was decreased from 1.80 g/cm3 (3% dosage) to 1.69 g/cm3 (9% dosage). RCA and RAC yielded maximum dry density (MDD) of 1.86 and 1.89 g/cm3, respectively. At 28 days, nano-MgO exhibited the highest UCS (520 kPa) and soaked CBR (11.6%) at 1% dosage. Fly ash at 6% led to the highest ultimate bearing capacity for the non-nano cases (3,434 kPa), while the highest bearing capacity (4,120 kPa) and the lowest settlement (3.8 mm) were reached by nano-MgO. Based on UCS, CBR, bearing capacity, and settlement control, an equal-weight min-max index placed the tested conditions in this order: nano-MgO, RAC, fly ash at 9%, fly ash at 6%, and RCA. Pearson r for CBR versus UCS was 0.98 indicating very strong correlation, while r for MDD versus ultimate bearing capacity was −0.02 indicating no clear linear relation between ultimate bearing capacity and MDD. The conclusions are limited to short-term laboratory data for CL soils; cost, life-cycle impacts, durability, and field performance require separate evaluation.
