This study evaluated the use of fines obtained from demolished concrete structures to stabilize clayey subgrade soil. Laboratory tests were conducted on the virgin clayey soil and soil mixed with 4-15% fines. Results showed that mixing fines up to 10% by weight of dry soil increased the maximum dry density and California Bearing Ratio (CBR) values of the soil, both unsoaked and soaked. The highest CBR values were obtained at 10% fines addition. Specifically, the unsoaked CBR increased 86.9% and soaked CBR increased 276.6% compared to the virgin soil, indicating the fines are effective at improving the engineering properties of clayey subgrade soil.