Performance of a Stabilized Aggregate Base Subject to Different Durability Procedures

Abstract

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°C for 24 h and thawing them at 21.7°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 (MR) and unconfined compressive strength (UCS) values. Results showed that the MR values of 28-day cured specimens increased as FT-1 cycles increased up to 12, beyond which a reduction in MR values was observed. For 3-day cured specimens the MR 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 MR with FT-1 cycles. In addition, the specimens subject to 30 FT-2 cycles exhibited a higher reduction in MR 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 MR -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 MR values of stabilized aggregate bases.