Performance of a Stabilized Aggregate Base Subject to Different Durability Procedures

This study examined the effects of two freeze-thaw (FT) laboratory procedures, FT-1 and FT-2, on stabilized aggregate specimens. Cylindrical specimens were stabilized with 10% Class C fly ash (CFA) cured for selected periods and then subjected to either FT-1 or FT-2 cycles. FT-1 and FT-2 procedures consisted of freezing specimens at -25 degrees C for 24 h and thawing them at 21.7 degrees C for another 24 h with a high relative humidity; the only difference was that FT-1 required a membrane around each specimen, while FT-2 required no membranes during freezing and thawing. After being subject to freezing and thawing actions, specimens were then tested for resilient modulus (M-R) and unconfined compressive strength (UCS) values. Results showed that the M-R values of 28-day cured specimens increased as FT-1 cycles increased up to 12, beyond which a reduction in M-R values was observed. For 3-day cured specimens the M-R increased with FT-1 cycles up to 30. The UCS values of 28- and 3-day stabilized specimens also exhibited the same trend as the M-R with FT-1 cycles. In addition, the specimens subject to 30 FT-2 cycles exhibited a higher reduction in M-R values than the specimens subject to FT-1. This behavior is explained by the moisture increase in the specimens subject to FT-2 cycles which caused an ice lens formation in the fine matrix and destruction in the particle matrix. The study also showed that the M-R-stress model recommended by the new mechanistic-empirical pavement design guide for unbound pavement materials could be a statistically good and a reliable predictor of the M-R values of stabilized aggregate bases.